Pengolahan limbah domestik sistem Aerob-Anaerob

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Pengolahan Air Limbah Dengan Proses Aerasi Kontak

           Proses ini merupakan pengembangan dari proses lumpur aktif dan proses biofilter. Pengolahan air limbah dengan proses aerasi kontak ini terdiri dari dua bagian yakni pengolahan primer dan pengolahan sekunder.

Pengolahan Primer

           Pada pengolahan primer ini, air limbah dialirkan melalui saringan kasar (bar screen) untuk menyaring sampah yang berukuran besar seperti sampah daun, kertas, plastik dll. Setelah melalui screen air limbah dialirkan ke bak pengendap awal, untuk mengendapkan partikel lumpur, pasir dan kotoran lainnya. Selain sebagai bak pengendapan, juga berfungasi sebagai bak pengontrol aliran.

Pengolahan sekunder

           Proses pengolahan sekunder ini terdiri dari bak kontaktor anaerob (anoxic) dan bak kontaktor aerob. Air limpasan dari bak pengendap awal dipompa dan dialirkan ke bak penenang, kemudian dari bak penenang air limbah mengalir ke bak kontaktor anaerob dengan arah aliran dari bawah ke atas (Up Flow). Di dalam bak kontaktor anaerob tersebut diisi dengan media dari bahan plastik atau kerikil/batu split. Jumlah bak kontaktor anaerob ini bisa dibuat lebih dari satu sesuai dengan kualitas dan jumlah air baku yang akan diolah. Air limpasan dari bak kontaktor anaerob dialirkan ke bak aerasi. Di dalam bak aerasi ini diisi dengan media dari bahan pasltik (polyethylene), batu apung atau bahan serat, sambil diaerasi atau dihembus dengan udara sehingga mikro organisme yang ada akan menguraikan zat organik yang ada dalam air limbah serta tumbuh dan menempel pada permukaan media. Dengan demikian air limbah akan kontak dengan mikro-orgainisme yang tersuspensi dalam air maupun yang menempel pada permukaan media yang mana hal tersebut dapat meningkatkan efisiensi penguraian zat organik. Proses ini sering di namakan Aerasi Kontak (Contact Aeration).

           Dari bak aerasi, air dialirkan ke bak pengendap akhir. Di dalam bak ini lumpur aktif yang mengandung massa mikro-organisme diendapkan dan dipompa kembali ke bagian inlet bak aerasi dengan pompa sirkulasi lumpur. Sedangkan air limpasan (over flow) dialirkan ke bak khlorinasi. Di dalam bak kontaktor khlor ini air limbah dikontakkan dengan senyawa khlor untuk membunuh micro-organisme patogen. Air olahan, yakni air yang keluar setelah proses khlorinasi dapat langsung dibuang ke sungai atau saluran umum. Dengan kombinasi proses anaerob dan aerob tersebut selain dapat menurunkan zat organik (BOD, COD), cara ini dapat menurunkan konsentrasi nutrient (nitrogen) yang ada dalam air limbah. Dengan proses ini air limbah rumah sakit dengan konsentrasi BOD 250 -300 mg/lt dapat di turunkan kadar BOD nya menjadi 20 -30 mg/lt. Skema proses pengolahan air limbah rumah sakit dengan sistem aerasi kontak dapat dilihat pada gambar III.5. Surplus lumpur dari bak pengendap awal maupun akhir ditampung ke dalam bak pengering lumpur, sedangkan air resapannya ditampung kembali di bak penampung air limbah.


Gambar III.5 : Diagram proses pengolahan air limbah dengan proses aerasi kontak.

Keunggulan Proses Aerasi Kontak

  • Pengelolaannya sangat mudah.
  • Biaya operasinya rendah.
  • Dibandingkan dengan proses lumpur aktif, Lumpur yang dihasilkan relatif sedikit.
  • Dapat menghilangkan nitrogen dan phospor yang dapat menyebabkan euthropikasi.
  • Suplai udara untuk aerasi relatif kecil.
  • Dapat digunakan untuk air limbah dengan beban BOD yang cukup besar.

4.2.4. Pengolahan Air Limbah Dengan Proses Biofilter “Up Flow”

           Proses pengolahan air limbah dengan biofilter “up flow” ini terdiri dari bak pengendap, ditambah dengan beberapa bak biofilter yang diisi dengan media kerikil atau batu pecah, plastik atau media lain. Penguraian zat-zat organik yang ada dalam air limbah dilakukan oleh bakteri anaerobik atau facultatif aerobik Bak pengendap terdiri atas 2 ruangan, yang pertama berfungsi sebagai bak pengendap pertama, sludge digestion (pengurai lumpur) dan penampung lumpur sedangkan ruang kedua berfungsi sebagai pengendap kedua dan penampung lumpur yang tidak terendapkan di bak pertama, dan air luapan dari bak pengendap dialirkan ke media filter dengan arah aliran dari bawah ke atas.

           Setelah beberapa hari operasi, pada permukaan media filter akan tumbuh lapisan film mikro-organisme. Mikro-organisme inilah yang akan menguraikan zat organik yang belum sempat terurai pada bak pengendap. Air luapan dari biofilter kemudian dibubuhi dengan khlorine atau kaporit untuk membunuh mikroorganisme patogen, kemudian dibuang langsung ke sungai atau saluran umum. Skema proses pengolahan air limbah dengan biofilter “Up Flow” dapat dilihat seperti terlihat dalam Gambar III.6.

           Biofilter “Up Flow” ini mempunyai 2 fungsi yang menguntungkan dalam proses pengolahan air buangan yakni antara lain :

  • Adanya air buangan yang melalui media kerikil yang terdapat pada biofilter lama kelamaan mengakibatkan timbulnya lapisan lendir yang menyelimuti kerikil atau yang disebut juga biological film. Air limbah yang masih mengandung zat organik yang belum teruraikan pada bak pengendap bila melalui lapisan lendir ini akan mengalami proses penguraian secara biologis. Efisiensi biofilter tergantung dari luas kontak antara air limbah dengan mikro-organisme yang menempel pada permukaan media filter tersebut. Makin luas bidang kontaknya maka efisiensi penurunan konsentrasi zat organiknya (BOD) makin besar. Selain menghilangkan atau mengurangi konsentrasi BOD cara ini dapat juga mengurangi konsentrasi padatan tersuspensi atau suspended solids (SS) dan konsentrasi total nitrogen dan posphor.

  • Biofilter juga berfungsi sebagai media penyaring air limbah yang melalui media ini. Sebagai akibatnya, air limbah yang mengandung suspended solids dan bakteri E.coli setelah melalui filter ini akan berkurang konsentrasinya. Efesiensi penyaringan akan sangat besar karena dengan adanya biofilter up flow yakni penyaringan dengan sistem aliran dari bawah ke atas akan mengurangi kecepatan partikel yang terdapat pada air buangan dan partikel yang tidak terbawa aliran ke atas akan mengendapkan di dasar bak filter. Sistem biofilter Up Flow ini sangat sederhana, operasinya mudah dan tanpa memakai bahan kimia serta tanpa membutuhkan energi. Poses ini cocok digunakan untuk mengolah air limbah dengan kapasitas yang tidak terlalu besar.


Gambar III.6. : Diagram proses pengolahan air limbah dengan sisten biofilter “Up Flow”.

4.2.5. Kriteria Perencanaan

Kriteria Perencanaan Bak Pengendap

Bak pengendap harus memenuhi persyaratan tertentu antara lain:

  • Bahan bangunan harus kuat terhadap tekanan atau gaya berat yang mungkin timbul dan harus tahan terhadap asam serta harus kedap air.
  • Jumlah ruangan disarankan minimal 2 (dua) buah.
  • Waktu tinggal (residence time) 1s/d 3 hari.
  • Bentuk Tangki empat persegi panjang dengan perbandingan panjang dan lebar 2 s/d 3 : 1.
  • Lebar Bak minimal 0,75 meter dan panjang bak minimal 1,5 meter.
  • Kedalaman air efektif 1-2 meter, tinggi ruang bebas air 0,2-0,4 meter dan tinggi ruang
  • Untuk penyimpanan lumpur 1/3 dari kedalaman air efektif (laju produksi lumpur sekitar 0,03 – 0,04 M3/orang /tahun ).
  • Dasar bak dapat dibuat horizontal atau dengan kemiringan tertentu untuk memudahkan pengurasan lumpur.
  • Pengurasan lumpur minimal dilakukan setiap 2 – 3 tahun.

Kriteria Perencanaan Biofilter “Up Flow”

Untuk merencanakan biofilter “Up Flow” harus memenuhi beberapa persyaratan, yakni :

  • Bak biofilter terdiri dari 1 (satu) ruangan atau lebih.
  • Media filter terdiri dari kerikil atau batu pecah atau bahan plastik dengan ukuran diameter rata-rata 20 -25 mm , dan ratio volume rongga 0,45.
  • Tinggi filter (lapisan kerikil) 0,9 -1,2 meter.
  • Beban hidrolik filter maksimum 3,4 M3/m2/hari.
  • Waktu tinggal dalam filter 6 -9 jam (didasarkan pada volume rongga filter).

           Salah satu contoh hasil uji coba pengolahan air limbah dengan proses air limbah dengan biofilter Up Flow ditunjukkan seperti pada Tabel III.1.

4.2.6. Proses Pengolahan Dengan Sistem Biofilter Anaerob-Aerob

           Proses ini pengolahan dengan biofilter anaerob-aerob ini merupakan pengembangan dari proses proses biofilter anaerob dengan proses aerasi kontak Pengolahan air limbah dengan proses biofilter anaerob-aerob terdiri dari beberapa bagian yakni bak pengendap awal, biofilter anaerob (anoxic), biofilter aerob, bak pengendap akhir, dan jika perlu dilengkapi dengan bak kontaktor khlor.

           Air limbah yang berasal dari rumah tangga dialirkan melalui saringan kasar (bar screen) untuk menyaring sampah yang berukuran besar seperti sampah daun, kertas, plastik dll. Setelah melalui screen air limbah dialirkan ke bak pengendap awal, untuk mengendapkan partikel lumpur, pasir dan kotoran lainnya. Selain sebagai bak pengendapan, juga berfungasi sebagai bak pengontrol aliran, serta bak pengurai senyawa organik yang berbentuk padatan, sludge digestion (pengurai lumpur) dan penampung lumpur.

           Air limpasan dari bak pengendap awal selanjutnya dialirkan ke bak kontaktor anaerob dengan arah aliran dari atas ke dan bawah ke atas. Di dalam bak kontaktor anaerob tersebut diisi dengan media dari bahan plastik atau kerikil/batu split. Jumlah bak kontaktor anaerob ini bisa dibuat lebih dari satu sesuai dengan kualitas dan jumlah air baku yang akan diolah. Penguraian zat-zat organik yang ada dalam air limbah dilakukan oleh bakteri anaerobik atau facultatif aerobik Setelah beberapa hari operasi, pada permukaan media filter akan tumbuh lapisan film mikro-organisme. Mikro-organisme inilah yang akan menguraikan zat organik yang belum sempat terurai pada bak pengendap

           Air limpasan dari bak kontaktor anaerob dialirkan ke bak kontaktor aerob. Di dalam bak kontaktor aerob ini diisi dengan media dari bahan kerikil, pasltik (polyethylene), batu apung atau bahan serat, sambil diaerasi atau dihembus dengan udara sehingga mikro organisme yang ada akan menguraikan zat organik yang ada dalam air limbah serta tumbuh dan menempel pada permukaan media.

           Dengan demikian air limbah akan kontak dengan mikro-orgainisme yang tersuspensi dalam air maupun yang menempel pada permukaan media yang mana hal tersebut dapat meningkatkan efisiensi penguraian zat organik, deterjen serta mempercepat proses nitrifikasi, sehingga efisiensi penghilangan ammonia menjadi lebih besar. Proses ini sering di namakan Aerasi Kontak (Contact Aeration).

           Dari bak aerasi, air dialirkan ke bak pengendap akhir. Di dalam bak ini lumpur aktif yang mengandung massa mikro-organisme diendapkan dan dipompa kembali ke bagian inlet bak aerasi dengan pompa sirkulasi lumpur. Sedangkan air limpasan (over flow) dialirkan ke bak khlorinasi. Di dalam bak kontaktor khlor ini air limbah dikontakkan dengan senyawa khlor untuk membunuh micro-organisme patogen.

           Air olahan, yakni air yang keluar setelah proses khlorinasi dapat langsung dibuang ke sungai atau saluran umum. Dengan kombinasi proses anaerob dan aerob tersebut selain dapat menurunkan zat organik (BOD, COD), ammonia, deterjen, padatan tersuspensi (SS), phospat dan lainnya. Skema proses pengolahan air limbah rumah tangga dengan sistem biofilter anaerob-aerob dapat dilihat pada Gambar III.7.

Tabel III.1 : Efisiensi pengoalahan air limbah dengan proses biofilter “Up Flow”


CONTOH AIR

BOD

COD

SS

T-N

MBAS

COLI

 

 

mg/lt

%

mg/lt

%

mg/lt

%

mg/lt

%

mg/lt

%

MPN/

100 ml

%

Air

Limbah

(1)

235,93

 

483,43

 

249

 

68,87

 

11,52

 

17.670

 

 

(2)

76,73

67,48

173,38

64,14

79,75

67,97

49,90

27,54

9,45

17,97

11.500

34,92

Air

(3)

68,49

70,87

145,82

69,84

55,25

77,81

43,49

36,85

8,03

30,29

6.130

65,31

Olahan

(4)

62,54

73,49

137,97

71,47

44,06

82,33

39,79

42,22

6,66

42,19

4.500

74,53

 

(5)

45,01

80,92

108,61

77,53

33

86,75

32,2

53,24

5,26

54,33

3.100

82,46


Keterangan : (1), (2) … (5) adalah titik pengambilan contoh air seperti pada gambar (7).
Sumber : Said, N.I., “Sistem Pengolahan Air Limbah Rumah Tangga Skala Individual Tangki
Septik Filter Up Flow”, Majalah Analisis Sistem Nomor 3, Tahun II, 1995.


Gambar III.7 : Diagram proses pengolahan air limbah rumah tangga (domistik)
dengan proses biofilter anaerob-aerob .

Peoses dengan Biofilter “Anaerob-Aerob” ini mempunyai beberapa keuntungan yakni :

  • Adanya air buangan yang melalui media kerikil yang terdapat pada biofilter mengakibatkan timbulnya lapisan lendir yang menyelimuti kerikil atau yang disebut juga biological film. Air limbah yang masih mengandung zat organik yang belum teruraikan pada bak pengendap bila melalui lapisan lendir ini akan mengalami proses penguraian secara biologis. Efisiensi biofilter tergantung dari luas kontak antara air limbah dengan mikro-organisme yang menempel pada permukaan media filter tersebut. Makin luas bidang kontaknya maka efisiensi penurunan konsentrasi zat organiknya (BOD) makin besar. Selain menghilangkan atau mengurangi konsentrasi BODdan COD, cara ini dapat juga mengurangi konsentrasi padatan tersuspensi atau suspended solids (SS) , deterjen (MBAS), ammonium dan posphor.

  • Biofilter juga berfungsi sebagai media penyaring air limbah yang melalui media ini. Sebagai akibatnya, air limbah yang mengandung suspended solids dan bakteri E.coli setelah melalui filter ini akan berkurang konsentrasinya. Efesiensi penyaringan akan sangat besar karena dengan adanya biofilter up flow yakni penyaringan dengan sistem aliran dari bawah ke atas akan mengurangi kecepatan partikel yang terdapat pada air buangan dan partikel yang tidak terbawa aliran ke atas akan mengendapkan di dasar bak filter. Sistem biofilter anaerob-aerb ini sangat sederhana, operasinya mudah dan tanpa memakai bahan kimia serta tanpa membutuhkan energi. Poses ini cocok digunakan untuk mengolah air limbah dengan kapasitas yang tidak terlalu besar

  • Dengan kombinasi proses “Anaerob-Aerob”, efisiensi penghilangan senyawa phospor menjadi lebih besar bila dibandingankan dengan proses anaerob atau proses aerob saja. Phenomena proses penghilangan phosphor oleh mikroorganisne pada proses pengolahan anaerob-aerob dapat diterangkan seperti pada Gambar III.8. Selama berada pada kondisi anaerob, senyawa phospor anorganik yang ada dalam sel-sel mikrooragnisme akan keluar sebagi akibat hidrolosa senyawa phospor. Sedangkan energi yang dihasilkan digunakan untuk menyerap BOD (senyawa organik) yang ada di dalam air limbah. Efisiensi penghilangan BOD akan berjalan baik apabila perbandingan antara BOD dan phospor (P) lebih besar 10. (Metcalf and Eddy, 1991). Selama berada pada kondisi aerob, senyawa phospor terlarut akan diserap oleh bakteria/mikroorganisme dan akan sintesa menjadi polyphospat dengan menggunakan energi yang dihasik oleh proses oksidasi senyawa organik (BOD). Dengan demikian dengan kombinasi proses anaerob-aerob dapat menghilangkan BOD maupun phospor dengan baik. Proses ini dapat digunakan untuk pengolahan air limbah dengan beban organik yang cukup besar.

Keunggulan Proses Biofilter “Anaerob-Aerob”

Beberapa keunggulan proses pengolahan air limbah dengan biofilter anaerb-aerob antara lain yakni :

  • Pengelolaannya sangat mudah.
  • Biaya operasinya rendah.
  • Dibandingkan dengan proses lumpur aktif, Lumpur yang dihasilkan relatif sedikit.
  • Dapat menghilangkan nitrogen dan phospor yang dapat menyebabkan euthropikasi.
  • Suplai udara untuk aerasi relatif kecil.
  • Dapat digunakan untuk air limbah dengan beban BOD yang cukup besar.
  • Dapat menghilangan padatan tersuspensi (SS) dengan baik.


Gambar III.8 : Proses penghilangan phospor oleh mikroorganisme
di dalam proses pengolahan “Anaerob-Aerob”.


V. RANCANG BANGUN UNIT PENGOLAHAN AIR LIMBAH RUMAH SAKIT DENGAN SISTEM BIOFILTER ANAEROB-AEROB

5.1.Proses Pengolahan

           Seluruh air limbah yang dihasilkan oleh kegiatan rumah sakit, yakni yang berasal dari limbah domistik maupun air limbah yang berasal dari kegiatan klinis rumah sakit dikumpulkan melalui saluran pipa pengumpul. Selanjutnya dialirkan ke bak kontrol. Fungsi bak kontrol adalah untuk mencegah sampah padat misalnya plastik, kaleng, kayu agar tidak masuk ke dalam unit pengolahan limbah, serta mencegah padatan yang tidak bisa terurai misalnya lumpur, pasir, abu gosok dan lainnya agar tidak masuk kedalam unit pengolahan limbah.

           Dari bak kontrol, air limbah dialirkan ke bak pengurai anaerob. Bak pengurai anaerob dibagi menjadi tiga buah ruangan yakni bak pengendapan atau bak pengurai awal, biofilter anaerob tercelup dengan aliran dari bawah ke atas (Up Flow), serta bak stabilisasi. Selanjutnya dari bak stabilisai, air limbah dialirkan ke unit pengolahan lanjut. Unit pengolahan lanjut tersebut terdiri dari beberapa buah ruangan yang berisi media untuk pembiakan mikro-organisme yang akan menguraikan senyawa polutan yang ada di dalan air limbah.

           Setelah melalui unit pengolahan lanjut , air hasil olahan dialirkan ke bak khlorinasi. Di dalam bak khlorinasi air limbah dikontakkan dengan khlor tablet agar seluruh mikroorganisme patogen dapat dimatikan. Dari bak khlorinasi air limbah sudah dapat dibuang langsung ke sungai atau saluran umum.

5.2. Bentuk Dan Prototipe Alat

           Rancangan prototipe alat dirancang yang digunakan untuk uji coba pegolahan air limbah rumah sakit ditunjukkan seperti pada Gambar IV.1. Prototipe alat ini secara garis besar terdiri dari bak pengendapan/pengurai anaerob dan unit pengolahan lanjut dengan sistem biofilter anaerob-aerob. Bak pengurai anaerob dibuat dari bahan beton cor atau dari bahan fiber glas (FRP), disesuaikan dengan kondisi yang ada. Ukuran bak pengurai anaerob yakni panjang 160 cm, lebar 160 cm, dan kedalaman efektif sekitar 200 cm, dengan waktu tinggal sekitar 8 jam.

           Unit pengolahan lanjut dibuat dari bahan fiber glas (FRP) dan dibuat dalam bentuk yang kompak dan langsung dapat dipasang dengan ukuran panjang 310 cm, lebar 100 cm dan tinggi 190 cm. Ruangan di dalam alat tersebut dibagi menjadi beberapa zona yakni rungan pengendapan awal, zona biofilter anaerob, zona biofilter aerob dan rungan pengendapan akhir.

           Media yang digunakan untuk biofilter adalah batu apung atau batu pecah dengan ukuran 1-2 cm, atau ari bahan lain misalnya zeolit, batubara (anthrasit), palstik dan lainnnya. Selain itu, air limbah yang ada di dalam rungan pengendapan akhir sebagian disirkulasi ke zona aerob dengan menggunakan pompa sirkulasi.

5.3. Kapasitas Alat

           Prototipe alat ini dirancang untuk dapat mengolah air limbah sebesar 10 -15 m3/hari, yang dapat melayani rumah sakit dengan 30 –50 bed.

5.4. Waktu Tinggal (Retention Time)

A. Bak Pengurai Anaerob

Debit Air Limbah = 15 m3/hari = 625 lt/jam = 0,625 m3/jam
Dimensi = 1,6 m X 1,6 X 2,2 m
Volume Efektif = 5 m3
Waktu Tinggal = 8 Jam
Gambar penampang bak pengurai awal ditunjukan seperti pada gambar IV.2.

B. Unit Pengolahan Lanjut

1. Ruang Pengendapan Awal

Debit Air Limbah (Q) = 15 m3/hari = 625 lt/jam = 0,625 m3/jam
Volume Efektif = 1,6 m x 1,0 m x 0,6 m = 0,96 M3
Waktu Tinggal di dalam ruang pengendapan awal (T1) = 0,96 m3/0,625 m3/jam
T1 = 1,5 jam

2. Zona Biofilter Anaerob

Volume Total Ruang efektif = 1,6 m x 1,0 m x 1,2 m = 1,92 m3
Volume Total Unggun Medium = 2 x [1,2 m x 1 m x 0,6 m] = 1,44 m3
Porositas Mediun = 0,45
Volume Medium tanpa rongga = 0,55 x 1,44 m3 = 0,79 m3
Total Volume Rongga dalam Medium = 0,45 x 1,44 m3 = 0,65 m3
Volume Air Limbah Efektif di dalam zona Anareob = 1,92 m3 – 0,79 m3 = 1,13 m3
Waktu Tinggal di dalam Zona Anaerob (T2) = 1,13 m3/0,625 m3/jam = 1,8 jam
Waktu Kontak di dalam medium zona Anaerob = 0,65 m3/0,625 m3/jam = 1.04 jam

3. Zona Aerob

Volume Efektif = 1,5 m x 1 m x 0,7 m = 1,05 m3
Volume Unggun Medium = 1,1 m x 0,6 m x 1 m = 0,66 m3
Porositas Medium = 0,45
Volume Rongga = 0,45 x 0,66 m3 = 0,3 m3
Volume Medium Tanpa Rongga = 0,66 m3- 0,3 m3 = 0,36 m3
Waktu Tinggal Total di dalam zona aerob (T3) = [1,05 – 0,36] m3/0,625 m3/jam = 1,1 jam
Waktu Kontak di dalam medium zona aerob = 0,3 m3/0,625 m3/jam = 0,48 jam

4. Ruangan Pengendapan Akhir

Volume Efektif = 1,5 m x 0,6 m x 1 m = 0,9 m3
Waktu Tinggal (T4) = 0,9 m3/0,625 m3/jam = 1,44 jam
Waktu Tinggal Total di dalam Unit Pengolahan Lanjut = [1,5+1,13+1,1+1,44] jam = 5,17 jam

Gambar penampang bak pengolahan lanjut ditunjukkan seperti pada gambar IV.3.

Gambar IV.1 : Diagram proses pengolahan air limbah rumah sakit.


5.5. Bak Kontaktor Khlorine

           Unit prototipe alat pengolahan air limbah rumah tangga tersebut dapat dilengkapi dengan bak khlorinasi (bak kontaktor) yang berfungsi untuk mengkontakan khlorine dengan air hasil pengolahan. Air limbah yang telah diolah sebelum dibuang ke saluran umum dikontakkan dengan khlorine agar mikroorganisme patogen yang ada di dalam air dapat dimatikan. Senyawa khlor yang digunakan adalah kaporit dalam bentuk tablet. Penampang bak kontaktor adalah seperti pada gambar IV.4. Bak kontaktor ini dipasang atau disambungkan pada pipa pengeluaran air olahan.

5.6. Lokasi Uji Coba

           Uji coba prototipe alat pengolah air limbah rumak sakit dilakukan Rumah Sakit “Makna”, Ciledug, Tangerang. Air yang diolah adalah seluruh limbah cair yang dihasilkan oleh kegiatan rumah sakit, yakni baik yang berasal dari limbah domistik maupun limbah yang berasal dari limbah klinis.


Gambar IV.2 : Penampang bak pengurai Anaerob.

PENAMPANG MELINTANG

Keterangan : gambar tidak menurut skala
Gambar IV.3 : Rancangan prototipe alat pengolahan air limbah domistik dengan sistem biofilter anaerob-aerob.

Gambar IV.4 : Penampang bak khlorinator.

VI. PEMBANGUNAN ALAT PENGOLAHAN AIR LIMBAH RUMAH SAKIT DENGAN PROSES BIOFILTER ANAEROB-AEROB KAPASITAS 10 – 15 M3/HARI

Penggalian tanah untuk pemasangan unit alat pengolahan limbah

Konstruksi bak pengurai anaerobik

Lantai penyangga berlubang-lubang

Bak penenang pada bak pengurai anaerob

Unit alat pengolahan air limbah yang sedang dipasang.

Konstruksi reaktor alat pengolahan air limbah dari bahan fiber glass.

Konstruksi bak pengurai atau bak pengendapan awal pada proses pengolahan lanjut

Konstruksi bagian dalam reaktor pada proses pengolahan lanjut.

Konstruksi bagian dalam reaktor (sebelum diisi dengan media).

Konstruksi bagian dalam reaktor zona aerobik (sebelum diisi dengan media).

Konstruksi bagian dalam reaktor zona pengendapan akhir.

Konstruksi bak pengurai anaerob

Unit reaktor pengolahan lanjut yang telah dipasang.

Media plastik sarang tawon untuk pembiakan mikro-organisme untuk menguraikan zat organik.

Media plastik yang telah dipasang pada bak pengurai anaerob.

Media plastik yang telah dipasang pada bak pengolahan lanjut.

Blower dan pompa sirkulasi yang digunakan untuk proses pengolahan.

Konstruksi bak kontrol pertama.

Konstruksi bak kontrol kedua.

Air di bak penenang pada bak pengurai anaerob.

Unit pengolahan air limbah rumah sakit dengan proses Biofilter Anaerob-Aerob.

VII. UJI COBA ALAT PENGOLAHAN AIR LIMBAH RUMAH SAKIT “KOMBINASI BIOFILTER ANAEROB-AEROB”

7.1. Hasil Pengamatan Fisik

           Berdasarkan pengamatan secara fisik (dengan mata), pada awal proses yakni pengamatan setelah dua hari operasi, proses pengolahan belum berjalan secara baik. Hal ini karena mikroorganisme yang ada di dalam reaktor belum tumbuh secara optimal, walupun demikian air yang keluar dari reaktor sudah relatif bersih dibandingkan dengan air limbah yang masuk. Setelah proses berjalan berjalan sekitar dua minggu, mikroorganisme sudah mulai tumbuh atau berkembang biak di dalam reaktor. Di dalam bak pengendapan awal sudah mulai terlihat lapisan mikro organisme yang menempel pada permukaan media. Mikro orgnisme tersebut sangat membantu menguraikan senyawa organik yang ada di dalam air limbah.

           Dengan berkembang-biaknya mikro orgnisme atau bakteri pada permukaan media maka proses penguraian senyawa polutan yang ada di dalam air limbah menjadi lebih efektif. Selain itu, setelah proses berjalan beberapa minggu pada permukaan media kontaktor (media plastik sarang tawon dan batu pecah) yang ada di dalam zona anaerob maupun zona aerob, telah diselimuti oleh lapisan mikroorganisme. Dengan tumbuhnya lapisan mikroorganisme tersebut maka proses penyaringan padatan tersuspensi (SS) maupun penguraian senyawa polutan yang ada di dalam air limbah menjadai lebih baik. Hal ini secara fisik dapat dilihat dari air limpasan yang keluar dari zona anaerob sudah cukup jernih, dan buih atau busa yang terjadi di zona aerob (bak aerasi) sudah sangat berkurang. Sedangkan air olahan yang keluar secara fisik sudah sangat jernih.

lapisan mikroorganisme yang telah tumbuh dan menempel pada permukaan media biofilter.

Air limbah sebelum diolah (kanan) dan air hasil olahan (kiri).


           Berdasarkan pengamatan secara fisik (dengan mata), dapat dilihat dari air limpasan yang keluar dari zona anaerob sudah cukup jernih, dan buih atau busa yang terjadi di zona aerob (bak aerasi) sudah sangat berkurang. Sedangkan air olahan yang keluar secara fisik sudah sangat jernih.

7.2. Hasil Analisa Kualitas Air

           Berdasarkan hasil analisa kualitas air limbah sebelum dan sesudah pengolahan setelah proses berjalan selama 4 (empat) bulan menunjukkan bahwa konsentrasi BOD turun dari 419 mg/l menjadi 16,5 mg/l, konsentrasi COD di dalam air limbah 729 mg/l turun menjadi 52 mg/l, konsentrasi zat padat tersuspensi dari 825 mg/l turun menjadi 10 mg/l, konsentrasi ammonia dalam air limbah 33,86 mg/l turun menjadi 8 mg/l dan konsentrasi deterjen (MBAS) 12 mg/l turun menjadi 2,6 mg/l.

           Dengan demikian efisiensi penghilangan BOD 96 %, COD 92,8 %, Total zat padat tersuspensi (SS) 98,8 %, Ammonia 76,2 % dan deterjen (MBAS) 78 %. Hasil anailasa kualitas air limbah sebelum dan sesudah pengolahan seperti terlihat pada tabel berikut.


Hasil analisa kualitas air limbah sebelum dan sesudah pengolahan.



No


PARAMETER

KONSENTRASI AIR LIMBAH (mg/l)

KONSENTRASI AIR LOAHAN (mg/l)

EFISIENSI
PENGHILANGAN (%)

1

BOD

419

16,5

96

2

COD

729

52

92,8

3

Total SS
(suspended solids)

825

10

98,8

4

NH4-N

33,68

8

76,2

5

MBAS (deterjen)

12

2,6

78

6

pH

7,3

7,9

-


Catatan ; Setelah operasi berjalan 4 bulan.


VIII. PENUTUP

           Berdasarkan hasil pengamatan selama lebih dari empat bulan opersi, pengolahan air limbah rumah sakit dengan sistem kombinasi proses biofilter Anaerob-Aerob mempunyai beberapa keunggulan antara lain yakni :

  • Efisiensi pengolahan cukup tinggi.
  • Pengelolaannya sangat mudah.
  • Biaya operasinya rendah.
  • Dibandingkan dengan proses lumpur aktif, Lumpur yang dihasilkan relatif sedikit. (selama empat bulan operasi belum terjadi ekses lumpur.
  • Suplai udara untuk aerasi relatif kecil.
  • Dapat digunakan untuk air limbah dengan beban BOD yang cukup besar.
  • Dapat menghilangan padatan tersuspensi (SS) dengan baik.
  • Tahan terhadap perubahan beban pengolahan secara mendadak.

Water Treatment di Boiler

Rangkuman Diskusi Proses di Mailing List Migas untuk bulan September 2006, membahas mengenai water treatment di Boiler.

Apa saja yang diukur untuk water boiler, feed water boiler dan condensate boiler dan apa saja parameter-parameternya, dibahas lebih lanjut dalam file berikut:

Pertanyaan :

Dear all,
Sehubungan saya akan mengadakan kontrak dengan supplier Boiler, Mohon pencerahannya untuk Water Treatment di Boiler, Working pressure 8 Bar dan Design Pressure 10 Bar.
1. Parameter yang di ukur untuk water boiler, feed water boiler dan condensate boiler.
2. Bisa memberikan parameter‐parameter std tersebut.
Atas percercahaannya saya ucapkan terima kasih.

Tanggapan 1 :

Dear,

menarik sekali issue yang dilontarkan, memang setelah boiler nya sendiri urusan feed water ada di top list decision beli boiler atau beli listrik nya. berikut parameter yang harus anda lihat dengan jeli.:

a. scaling tendensi dr feed water, kalau membentuk scale anda harus treat dulu.
b. korosion tendensi
c. foaming tendensi
d. oxigen content, makin tinggi corosif
e. silika, jadi scale di boiler tube, in the long run low efficiency, hot spot, bisa juga tube failure.
f. ada nya volatile material di wtr, menyebabkan carry over, kadang kadang menimbulkan erosi
g. PH,Hardness, CO2, silicate,disolved solid.

Untuk itu significant amount dr capital invesment harus anda taruh di water treatment untuk menghasilkan suitable ʺboiler feed waterʺ misalnya saja via ion exchange,reverse osmosis, chemical dosing, dearation, condensate recicle dll.
agak terlalu ruwet interaksinya, tapi advise saya hire a profesional consultant, atau yang anda anggap tahu untuk menuliskan beberapa lembar persyaratan water quality dan water treatment anda. water treatment itu sebaiknya made to purpose, tergantung raw water nya, jadi agak beda beda dari satu area ke area lain. saya kira millis lain akan share pengalaman nya.

Tanggapan 2 :
Salam,
Pada saat mulai kontrak baru sebuah plant dengan supplier chemical untuk treatment boiler, sangat sensitif sekali krena menyangkut kenyamanan Pihak Plant dari service yang diberikan Pihak Suplier.
Hal itu menyangkut baik Teknis maupun Harga yang competitif yang diberikan, maksudnya adalah agar biaya yang dikeluarkan oleh Pabrik untuk beli chemical harus seimbang dengan hasil treatmentnya dan dapat save biaya maintenance. Kenapa seperti itu?

Jawabnya:
Kita perlu ketahui bahwa permasalahan water treatment mencakup 2 problem besar:
Suspended Solid
bahan solid yang msh terlihat oleh mata; lumpur, lumut, pasir, dll
Dissolved Solid
bahan solid yang tidak terlihat lagi oleh mata karena berupa ion2 yang terlarut dalam air.

Penanganan Suspended Solid biasanya dengan melakukan treatment raw water dengan proses sedimentasi dan filterisasi. Alat yang digunakan juga bermacam2; sedimentasi bisa dengan Klarifier dgn diinjeksikan Alum (koagulan), NaOH (control pH) dan Polimer (floculant). Untuk Polimer (floculant) biasanya Supplier merekomendasikan produknya.
Alat Filter juga banyak macamnya. Sebagian telah di sebutkan diatas. Bisa dengan tangki yang berisi pasir silika dan antrasit, bisa filter dari membran (RO) dan banyak lagi. Pak Agung bisa Tanya Langsung dengan Suppliernya.
Parameternya; Turbidity biasanya<1, pH 6,5 ‐ 7,5 agar menghasilkan Clear water yang bagus untuk Feed Water for Boiler. Anjuran Saya, Bapak minta kepada Suplier itu untuk analisa kualitas air juga (disamping pihak Laboratorium Bapak) secara periodik (1 bulan 1x atau 1 bulan 2x). Tujuannya to Make sure that we get good quality of clear water that fit with supplier control limit and supplier recommendation for feed water of boiler.

Penanganan Dissolved Solid
Setelah pretreatment bagus maka belum berarti kualitas air aman bagi boiler, karena masih ada ion2 yang terkandung dalam clear water (tak kasat mata) yang dapat menyebabkan 3 problem besar pada pipa, tubing, dan drum boiler, yaitu Korosi, Deposite, dan carry over.
Untuk itu perlu adanya demin plant atau softener (pemakaiannya depend on raw water quality). Demin Plant biasanya ada 2 tangki (Tangki Anoda dan Katoda). Didalam tangki terdapat Resin, Resin katoda menangkap ion positif dan Anoda nangkap ion negatif. Ion2 yang saya maksud biasanya adalah Ca+2, Mg+2, Fe+2, SiO2‐2, Cl‐1 dll.
dan ion2 tersbut menjadi parameter yang harus diukur untuk menentukan high quality of feed water. Biasanya setiap Parameter punya limit control yang beda2 untuk kondisi sumber air atau clear water yang dihasilkan. Dibawah ini yang umumnya jadi panduan untuk Demin water.

pH = 8, Conduktivity<10 micromhos, Total Hardness = Trace, Silica<2.5, Fe<1

Parameter diatas juga bisa berlaku untuk air hasil Softener. Bedanya hanya pada tangki, Softener hanya Tangki katoda saja. Satu lagi Pak, untuk mengurangi O2 yang terlarut maka air umpan itu perlu dipanasi hingga 100 C untuk memastikan removenya O2 didalam alat Deaerator. Nah, apabila sudah dipastikan kualitas air umpan boiler (feed water) sdh OK, maka perlu penanganan lagi.

Perisai pertama: PreTreatment yang baik (lebih kurang seperti penjelasan di atas)
Perisai kedua: Chemical Khusus untuk menangkap kembali ion2 yang lolos dari demin/softener atau deaerator di dalam Drum boiler.biasanya chemical ini direcommendasikan oleh supplier.
Tujuan injeksi Chemical Boiler
1. menangkap lolosnya ion2 penyebab deposit (deposite inhibitor) atau bisa dengan (deposit dispersant) untuk boiler yang sudah mulai berkerak. komponen kimianya mengandung PO4 (phosphate base), ini jadi parameter yang diukur dalam air boiler selain parameter yang pada pretreatment. Chemical ini sangat penting juga untuk mengikat silika yang dapat ikut ke jalur steam agar tidak terjadi Carry Over dan terjadi deposit after boiler equipment (spt Turbin)
2. menangkap Oksigen yang masih terlarut after Deaerator Tank agar tigak terjadi Korosi dalam Drum boiler (korosi inhibitor), Chemical ini terbagi 2 yaitu Food Grade dan Non Food Grade. Kemudian ada chemical yang perannya sama namun di menetralisir asam yg sebabkan korosi pada kondensate line.

Diakhir teknis ini saya hanya menjawab pertanyaan diawal Bahwa semua hal di atas perlu diawasi secara seksama baik oleh pihak Pabrik dan PASTINYA juga Pihak Suplayer sebagai service after salenya. Dan minta Inspeksi juga saat setelah Running Boiler 6 bulan atau 1 Tahun. Shg Ongkos yang kita keluarkan untuk treatment lebih efektif dan efisien.
Nah, mungkin masih ada yang belum tertuangkan di tulisan ini, saya mohon maaf dan rekan‐rekan lain dari milis bisa menyempurnakannya lagi.

Tanggapan 3 : novianto.fitriawan@power.alstom.com
Halo,
Apa kabar pak ? Tanpa bermaksud menggurui, saya mencoba sedikit menambahkan. Saya yakin pasti ada teman‐teman lain bisa menambahkan lebih komplit dan jelas lagi. Sebelumnya, mungkin Bapak bisa lebih spesifik menjelaskan: boiler‐nya type, steam yang diproduksi superheated atau saturated, penggunaan steamnya.
Kadang‐kadang user mempunyai steam purity target yang spesifik. Steam purity target ini akan dimintakan kepada boiler manufacturer untuk digaransi dan ujung‐ujungnya boiler manufaturer akan meminta syarat untuk pemenuhan steam purity target terhadap feedwater quality.

Tujuan water treatment adalah 1. Untuk meminimisasi akumulasi produk korosi seperti metal oxides (iron, copper, atau nickel dari pre‐boiler piping system), 2. Mengontrol impurities seperti calcium, magnesium dan silica yang terkandung di feedwater atau make up water yang bisa menyebabkan scale, 3. mencegah carryover dari partikel solid ke superheater atau downstream equipment seperti turbine atau process, 4. untuk mencegah korosi.

Berdasarkan tekanan operasi 8 bar (low pressure), kira‐kira ʺstandardʺ (mungkin tepatnya rekomendasi atau suggestion ‐ user boleh mengadop atau menolaknya) yang diperlukan adalah sebagai berikut (berdasarkan reference yang digunakan) :

ABMA, ʺBoiler Water Limits and Achievable Steam Purity For Water Tube Boilerʺ.
Boiler Water : Maximum boiler water solid adalah 3500 ppm, maximum suspended solid 15 ppm, maximum total alkalinity adalah 20% dari boiler water solid (700 ppm) as CaCO3, Maximum Fractional carryover adalah 0.0003.

ASME, ʺConsensus on Operating Practises for the Control of Feedwater and Boiler Water Quality in Modern Industrial Boilerʺ
a. Water Quality as per ASME Table 1
Boiler Type : Industrial water tube, high duty, primary fuel fired, drum type with superheaters and turbines drives and/or process restriction on steam purity.
Make up water percentage : up to 100% feedwater
Conditions: includes superheater, turbine drives or process restriction on steam purity.

Feedwater :
DO before oxygen scavenger addition (max), ppm = < 0.04
Total Iron (Max), ppm = 0.1
Total Cooper (max), ppm = 0.05
Total Hardness (CaCO3), ppm = 0.3
pH range @ 25 deg C = 7.5 ‐ 10
Non Volatile TOC (max), ppm = < 1
Oily Matter (max), ppm = < 1

Boiler Water :
Silica (SiO2), ppm = < 150
Total Alkalinity (CaCO3), ppm = < 350
Free Hydroxide Alkalinity (CaCO3), ppm = Not specified
Specification Conductance @ 25 deg C w/o Neutralization (max), micro mho/cm = < 3500

b. Suggested Water Quality Limits as per ASME table 2
Boiler Type : Industrial water tube, high duty, primary fuel fired, drum type
Make up water percentage : up to 100% feedwater
Conditions: no superheater, turbine drives or process restriction on steam purity.
Saturated Steam Purity Target : 1 ppm TDS maximum

Feedwater :
Total Hardness (CaCO3), ppm = < 0.5
DO before oxygen scavenger addition (max), ppm = < 0.04
DO measured afetr oxygen scavenger addition (max), ppm = < 0.07
Total Cooper (max), ppm = 0.05
Total Iron (Max), ppm = 0.1
Non Volatile TOC (max), ppm = < 1
Oily Matter (max), ppm = < 1
pH range @ 25 deg C = 7.5 ‐ 10.5

Boiler Water :
Silica (SiO2), ppm = < 150
Total Alkalinity (CaCO3), ppm = < 1000
Free Hydroxide Alkalinity (CaCO3), ppm = Not specified
Specification Conductance @ 25 deg C w/o Neutralization (max),
micro mho/cm = < 8000
JIS B8223, ʺThe quality of boiler water feedwater and boiler waterʺ.

Feedwater :
pH (25 deg C) = 7 ‐ 9
Hardness as CaCO3 (mg/L) = below 1
Oil and Fat = possibly keep 0
Dissolved oxygen (mg/L) = keep low
Boiler Water (treatment method : Caustic Treatment)
pH (25 deg C) = 11 ‐ 11.8
M Alkalinity (mg CaCO3 / L) = 100 ‐ 800
P Alkalinity (mg CaCO3 / L) = 80 ‐ 600
Electrical conductivity (micro S/cm) = below 4000
Chloride Ion (mg ion Cl / L) = below 400
Phosphate Ion (mg ion PO4 / L) = 20 ‐ 40
Sulphite Ion ( mg ion SO3 / L) = 10 ‐ 20
Hydrazine (mg N2H4 / L) = 0.1 ‐ 0.5

Semoga membantu dan berharap rekan‐rekan lain bisa menambahkan.
Thanks.

BOILER CHEMICAL TREATMENT

Tirta Alam Abadi (Head Office) North Jakarta
Tel: +62 (21) 6457-334
Fax: +62 (21) 6456-256

Written by :
Sunardi., ST
H. 0852 1615 1255
C. 0888 834 1568
E. suntzu2107@gmail.com

TREATMENT KIMIAWI PADA SISTEM BOILER

Fungsi utama boiler adalah mentransfer energi dari bentuk gas panas yang diciptakan melalui bahan bakar hingga mengubah air menjadi uap. Uap panas atau air panas kemudian digunakan pada proses produksi. Air umpan seringkali mengandung unsur pengotor, yang menggangu kinerja & efisiensi pada sistem boiler. Aditif kimia dapat digunakan untuk mengatasi masalah yang diakibatkan oleh unsur pengotor tersebut. Untuk meningkatkan kualitas air umpan, dan uap yang baik, bahan kimiawi dapat di-injeksikan secara langsung ke air umpan yang digunakan.

Keuntungan treatment secara kimiawi.

• Meningkatkan kinerja boiler;

• Menghemat bahan bakar dan biaya perawatan menjadi lebih murah;

• Menurunkan waktu downtime mesin; dan

• Melindungi aset produksi dari kerusakan dan meningkatkan daya pakai alat produksi.

TREATMENT KIMIAWI UNTUK BOILER TIPE WATER-TUBE

Air umpan terdiri atas air baku (make-up water) dan air kondensat (uap balik).  Air baku umumnya mengandung pengotor, yang menyebabkan deposit pada boiler. Zat pengotor yang umum dijumpai termasuk alkalinitas, silika, besi, oksigen terlarut, kalsium & magnesium (hardness). Blowdown, secara periodik ataupun otomatis adalah proses pembuangan air pada boiler, untuk membatasi konsentrasi zat pengotor dan mineral-2 lain yang terkandung pada air boiler. Blowdown penting sebagai penunjang treatment kimiawi.

Masalah-Masalah yang disebabkan oleh Zat Pengotor pada Boiler


Kerak. adalah deposit mineral yang biasa terjadi. Kerak adalah padatan terjadi akibat reaksi dari zat pengotor dan permukaan pipa logam. Kerak berperan sebagai insulator memperlambat transfer panas, yang menyebabkan efisiensi menurun dan pemakaian bahan bakar jadi meningkat. Efek yang lebih serius adalah overheating dan penyebab kerusakaan pada pipa-2 boiler.

Korosi. Korosi disebabkan oleh kandungan oksigen terlarut pada air umpan. Reaksi oksidasi menjadi semakin agresif bila mendapat energi panas menciptakan korosi pada permukaan logam. Kerusakaan akibat korosi dapat terjadi pada drum boiler, header, dan pipa-2 kondensat.

Asam. adalah juga penyebab korosi pada logam. Air dikatakan asam bila pH air umpan berada dibawah kisaran 8,5. Alkali karbonat diubah menjadi CO2 oleh panas dan tekanan pada boiler. CO2 terbawa sepanjang uap air diproduksi. Ketika uap air mengembun, CO2 menjadi larut dalam air membentuk asam karbonat (H2CO3) dan secara langsung menurunkan pH pada air kondensat.  Asam tersebut juga akan merusak pipa kondensat.

PERSYARATAN TREATMENT KIMIA BOILER

Produk Treatment. Faktanya adalah biasanya program treatment memerlukan prosentase relatif kecil dari keseluruhan biaya operasi pada boiler. Akan tetapi, kinerja treatment yang buruk menyebabkan efek domino yang meningkatkan biaya operasi maupun pemeliharaan boiler. Untuk hasil terbaik, seluruh chemical untuk treatment internal harus digunakan secara kontinyu dengan dosis yang cukup. Chemicals dapat diumpan langsung ke tangki air umpan. Kimia tertentu boleh dicampur penggunaannya pada waktu bersamaan. Posisi injeksi chemical biasanya diletakkan lebih tinggi dari posisi sirkuit boiler.  Untuk posisi feeder chemical dibawah pompa air umpan, pompa harus disesuaikan dengan tekanan boiler.

Skema Dasar Boiler. Seperti pada gambar, sistem pembangkitan uap terdiri atas 3 komponen utama; deaerator, boiler, dan sistem kondensat. Oxygen scavenger diumpankan pada tangki deaerator. treatment internal diumpankan pada pompa air umpan atau drum boiler.

Treatment Kimiawi

Lime Softening dan Soda Ash. Lime dicampurkan ada air baku untuk mengendapkan kalsium, magnesium, dan silika pada air. Soda ash dicampurkan untuk mengendapkan hardness non-bicarbonate. Proses ini terjadi pada tangki clarifier diikuti oleh proses pertukaran ion melalui demineralization. Kedua bahan kimiawi ini dalam bentuk cair, juga granular.

Oxygen Scavengers. deaerator menghilangkan oksigen pada air umpan; akan tetapi, oksigen yang masih trace masih ada dan menyebabkan masalah korosi. Oxygen scavengers dicampurkan pada air umpan. Bentuk umum oxygen scavenger adalah sodium sulfite. Sodium sulfite murah, efektif, dan mudah diukur kandungannya pada air.

Sulfite (Oxygen Scavenger)

Uncatalyzed sodium sulfite may be mixed with other chemicals. The preferred location for sulfite injection is a point in the storage section of the deaerating heater where the sulfite will mix with the discharge from the deaerating section. If sulfite is fed alone, the following basic equipment is

needed:

  • skid mounted dual metering pumps (duty/stand-by) with stainless steel wet end/trim
  • pulsation dampener
  • stainless steel relief valve
  • stainless steel check valve
  • stainless steel Y-strainer
  • stainless steel tubing, valves, and fittings
  • flowmeter
  • calibration cylinder
  • pressure gauge with diaphragm seals
  • electrical junction boxes
  • dilution water line c/w static mixer (optional)
  • drip pan (optional)
  • In all cases, an injection quill should be used.

Sulfite shipped as liquid concentrate is usually acidic and, when fed neat, corrodes stainless steel tanks at the liquid level. Sulfite storage tanks must be fiberglass, or polyethylene. Lines may be PVC or 316 stainless steel.

 

Catalyzed Sulfite (Oxygen Scavenger)

Catalyzed sulfite must be fed alone and continuously. Mixing of catalyzed sulfite with any other chemical impairs the catalyst. For the same reason, catalyzed sulfite must be diluted with only condensate or demineralized water. To protect the entire preboiler system, including any economizers, catalyzed sulfite should be fed to the storage section of the deaerating heater. Caustic soda may be used to adjust the pH of the day tank solution; therefore, a mild steel tank cannot be used. Materials of construction for feed equipment are the same as those required for regular sulfite.

Hydrazine (Oxygen Scavenger)

Hydrazine is compatible with all boiler water treatment chemicals except organics, amines, and nitrates. However, it is good engineering practice to feed hydrazine alone. It is usually fed continuously into the storage section of the deaerating heater. Because of handling and exposure concerns associated with hydrazine, closed storage and feed systems have become standard. Materials of construction are the same as those specified for sulfite.

Organic Oxygen Scavengers

Many organic compounds are available, including hydroquinone and ascorbic acid. Some are catalyzed. Most should be fed alone. Like sulfite, organic oxygen scavengers are usually fed continuously into the storage section of the deaerating heater. Materials of construction are the same as those specified for sulfite.

Neutralizing Amines

Neutralizing amines are high pH chemicals that neutralize the carbonic acid formed in the condensate (acid attack). The three most commonly used neutralizing amines are morpholine, diethyleminoethanal (DEAE) and cyclohexylamine. Neutralizing amines cannot protect against oxygen attack; however, it helps keep oxygen less reactive by maintaining an alkaline pH. Neutralizing amines may be fed to the storage section of the deaerating heater, directly to the boiler with the internal treatment chemicals, or into the main steam header. Some steam distribution systems may require more than one feed point to allow proper distribution. An injection quill is required for feeding into a steam distribution line. Neutralizing amines are usually fed based on condensate system pH and measured corrosion rates. These amines may be fed neat, diluted with condensate or demineralized water, or mixed in low concentrations with the internal treatment chemicals. A standard packaged pump skid and tank can be used for feeding.

Filming Amines

Filming amines are various chemicals that form a protective layer on the condensate piping to protect it from both oxygen and acid attack. The two most common filming amines are octadecylamine (ODA) and ethoxylated soya amine (ESA). Combining neutralizing and filming amine is a successful alternative to protect against both acid and oxygen attack. The filming amines should be continuously fed into steam headers at points that permit proper distribution. A single feed point is satisfactory for some systems. In every case, the steam distribution should be investigated and feed points established to ensure that all parts of the system receive proper treatment. Filming amines must be mixed with condensate or demineralized water. Water containing dissolved solids cannot be used, because the solids would contaminate the steam and could produce unstable amine emulsions. The use of stainless steel tanks is recommended. Equipment specifications are the same as those for regular sulfite, except that a vapor-type injection nozzle or quill is required.

 

Internal Treatment Chemicals

There are three major classifications of chemicals used in internal treatment: phosphates, chelants, and polymers. These chemicals may be fed either separately or in combination; in most balanced treatment programs, two or three chemicals are fed together. The preferred feed point varies with the chemical specified. For example, when caustic soda is used to maintain boiler water alkalinity, it is fed directly to the boiler drum. When caustic is used to adjust the feedwater pH, it is normally injected into the storage section of the deaerating heater.

Phosphate

Mono-, di- or trisodium phosphate and sodium polyphosphate can be added to treat boiler feedwater. Phosphate buffers the water to minimize pH fluctuation. It also precipitates calcium or magnesium into a soft deposit rather than a hard scale. Additionally, it helps to promote the protective layer on boiler metal surfaces. However, phosphate forms sludge as it reacts with hardness; blowdown or other procedures should be established to remove the sludge during a routine boiler shutdown. Phosphates are usually fed directly into the steam drum of the boiler, although they may be fed to the feedwater line under certain conditions. Treatments containing orthophosphate may produce calcium phosphate feed line deposits; therefore, they should not be fed through the boiler feed line. Orthophosphate should be fed directly to the boiler steam drum through a chemical feed line. Polyphosphates must not be fed to the boiler feedwater line when economizers, heat exchangers, or stage heaters are part of the preboiler system. If the preboiler system does not include such equipment, polyphosphates may be fed to the feedwater piping provided that total hardness does not exceed 2 ppm. In all cases, feed rates are based on feedwater hardness levels. Phosphates should be fed neat or diluted with condensate or high-purity water. Mild steel tanks, fittings, and feed lines are appropriate. If acidic phosphate solutions are fed, stainless steel is recommended.

Chelants

Nitrilotriacetic acid (NTA) and ethylenediamine tetraacetic acid (EDTA) are the most commonly used chelants. Chelants combine with hardness in water to form soluble compounds. The compounds can then be eliminated by blowdown.

  • • Chelants treatment is not recommended for feedwater with high hardness concentration
  • • Chelants should not be fed if the feedwater contains a significant level of oxygen.
  • • Chelants should never be fed directly into a boiler

The preferred feed location for chelants is downstream of the feedwater pump. All chelant treatments must be fed to the boiler feedwater line by means of a stainless steel injection nozzle at a point beyond the discharge of the boiler feed pumps. If heat exchangers or stage heaters are present in the boiler feed line, the injection point should be at their discharge. Care should be exercised in the selection of metals for high-temperature injection quills.

At feed solution strength and elevated temperatures, chelating agents can corrode mild steel and copper alloys; therefore, 304 or 316 stainless steel is recommended for all feed equipment. Equipment specifications are the same as those for regular sulfite. Chelant products may be fed neat or diluted with condensate. Chelant feed rates must be carefully controlled based on feedwater hardness, because misapplication can have serious consequences.

 

Polymeric Dispersants. In most applications, polymeric dispersants are provided in a combined product formulation with chelants and/or phosphates. Dilution and feed recommendations for chelants should be followed for chelant-dispersant and chelant-phosphate-dispersant programs. Dilution and feed recommendations for phosphates should be followed for phosphate-dispersant programs. These combination programs typically have the best results with respect to boiler cleanliness.

 

Neutralizing Amines

Neutralizing amines are high pH chemicals that neutralize the carbonic acid formed in the condensate (acid attack). The three most commonly used neutralizing amines are morpholine, diethyleminoethanal (DEAE) and cyclohexylamine. Neutralizing amines cannot protect against oxygen attack; however, it helps keep oxygen less reactive by maintaining an alkaline pH.

Neutralizing amines may be fed to the storage section of the deaerating heater, directly to the boiler with the internal treatment chemicals, or into the main steam header. Some steam distribution systems may require more than one feed point to allow proper distribution. An injection quill is required for feeding into a steam distribution line. Neutralizing amines are usually fed based on condensate system pH and measured corrosion rates.

These amines may be fed neat, diluted with condensate or demineralized water, or mixed in low

concentrations with the internal treatment chemicals. A standard packaged pump skid and tank can be used for feeding.

Filming Amines

Filming amines are various chemicals that form a protective layer on the condensate piping to protect it from both oxygen and acid attack. The two most common filming amines are octadecylamine (ODA) and ethoxylated soya amine (ESA). Combining neutralizing and filming amine is a successful alternative to protect against both acid and oxygen attack.

The filming amines should be continuously fed into steam headers at points that permit proper

distribution. A single feed point is satisfactory for some systems. In every case, the steam distribution should be investigated and feed points established to ensure that all parts of the system receive proper treatment. Filming amines must be mixed with condensate or demineralized water. Water containing dissolved solids cannot be used, because the solids would contaminate the steam and could produce unstable amine emulsions.

The use of stainless steel tanks is recommended. Equipment specifications are the same as those for regular sulfite, except that a vapor-type injection nozzle or quill is required.

Computerized Boiler Chemical Feed Systems

Computerized boiler chemical feed systems are being used to improve program results and cut operating costs. These systems can be used to feed oxygen scavengers, amines, and internal treatment chemicals. A typical system incorporates a metering pump, feed verification equipment, and a microprocessor-based controller. These systems are often linked to personal computers, which are used to monitor program results, feed rates, system status, and plant operating conditions. Trend graphs and management reports can then be produced to provide documentation of program results and help in troubleshooting. In many cases, these systems can be programmed to feed boiler treatment chemicals according to complex customized algorithms. For example, chelant feed can be adjusted automatically, based on analyzer or operator hardness test results, boiler feedwater flow, and minimum/maximum allowable product feed rates. Thus, chemical feed precisely matches system demand, virtually eliminating the possibility of underfeed or overfeed. Feed verification is another important facet of some computerized feed systems. The actual output of the pump is continuously measured and compared to a computer-calculated setpoint. If the output doesn’t match the set point, the speed or stroke length is automatically adjusted. The benefits of this technology include the elimination of time-consuming drawdown measurements, the ability to feed most chemicals directly from bulk tanks, precise chemical residual control, and minimal manpower requirements.

 

Statements and suggestions herein are based upon the best information and practices known to

us. However, it should not be assumed either that information is complete on the subjects covered or that all possible circumstances, safety measures, precautions, etc. have been included. These statements and suggestions are not intended to reflect provincial, municipal or insurance requirements or national safety codes; where applicable, those sources must be considered directly.

Since the conditions of use are beyond our control, Hayward Gordon makes no guarantee of results and assumes no liability in connection with the information contained herein. When dealing with installation, operation or maintenance of specific pumps, the Hayward Gordon manuals and instructions pertaining to that product should be followed carefully.

Tel: +62 (21) 6457-334 Fax: +62 (21) 6456-256 BOILER SYSTEM CHEMICAL TREATMENT The primary function of a boiler is to transfer heat from hot gases generated by the combustion of fuel into water until it becomes hot or turns to steam. The steam or hot water can then be used in building or facility processes. Boiler feedwater often contains impurities, which impairs boiler operation and efficiency. Chemical additives can be used to correct the problems caused by these impurities. To improve feedwater quality, and steam purity, these chemicals can be injected directly into the feedwater or steam. Benefits of Chemical Treatments • Increase boiler efficiency; • Reduce fuel, operating and maintenance costs; • Minimize maintenance and downtime; and • Protect equipment from corrosion and extend equipment lifetime. CHEMICAL TREATMENTS FOR WATERSIDE OF BOILER TUBES The feedwater is composed of makeup water (usually city water from outside boiler room/ process) and condensate (condensed steam returning to the boiler). The feedwater normally contains impurities, which can cause deposits and other related problems inside the boiler. Common impurities in water include alkalinity, silica, iron, dissolved oxygen and calcium and magnesium (hardness). Blowdown, a periodic or continuous water removal process, is used to limit the concentration of impurities in boiler water and to control the buildup of dissolved solid levels in the boiler. Blowdown is essential in addition to chemical treatments. List of Problems Caused By Impurities in Water Boiler Waterside Fouling Scale is one of the most common deposit related problems. Scale is a buildup of solid material from the reactions between the impurities in water and tube metal, on the water-side tube surface. Scale acts as an insulator that reduces heat transfer, causing a decrease in boiler efficiency and excessive fuel consumption. More serious effects are overheating of tubes and potential tube failure (equipment damage). Oxygen Attack Oxygen attack is the most common causes of corrosion inside boilers. Dissolved oxygen in feedwater can become very aggressive when heated and reacts with the boiler’s internal surface to form corrosive components on the metal surface. Oxygen attack can cause further damage to steam drums, mud dams, boiler headers and condensate piping. Acid Attack Acid attack is another common cause of corrosion. Acid attack happens when the pH of feedwater drops below 8.5. The carbonate alkalinity in the water is converted to carbon dioxide gas (CO2) by the heat and pressure of the boilers. CO2 is carried over in the steam. When the steam condenses, CO2 dissolves in water to form carbonic acid (H2CO3) and reduces the pH of the condensate returning to the boilers. Acid attack may also impact condensate return piping throughout the facility. BOILER SYSTEM CHEMICAL TREATMENTS AND FEED EQUIPMENT REQUIREMENTS Product Feed Considerations An often-overlooked fact is that the water treatment program usually represents a small percentage of the overall costs of a boiler operation. However, poor treatment or equipment performance can create domino effects increasing operating and maintenance costs. For best results, all chemicals for internal treatment of a steam generating facility must be fed continuously and at proper injection points. Chemicals may be fed directly from the storage tank (neat) or may be diluted in a day tank with high-purity water. Certain chemicals may be mixed together and fed from the same day tank. Chemical feed points are usually selected as far upstream in the boiler water circuit as possible. For chemical feed beyond the feedwater pump or into the steam drum, the pump must be matched to the boiler pressure. For high-pressure boilers, proper pump selection is critical. Basic Boiler System Schematic As shown in the figure, a steam generating system includes three major components for which treatment is required: the deaerator, the boiler, and the condensate system. Oxygen scavengers are usually fed to the storage section of the deaerator. The boiler internal treatment is fed to the feedwater pump suction or discharge, or to the steam drum. Condensate system feed points also vary, according to the chemical and the objective of treatment. Typical feed points include the steam header or other remote steam lines. Chemical Treatments Lime Softening and Soda Ash Lime is added to hard water to precipitate the calcium, magnesium and, to some extent, the silica in the water. Soda ash is added to precipitate non-bicarbonate hardness. The process typically takes place in a clarifier followed by a hydrogen cycle cation exchange and a hydroxide cycle anion exchange demineralization. Both hydrated lime and soda ash can be purchased as a liquid, a slurry or in a dry granular form. Specialized handling and preparation systems are required for dry storage and makedown. Oxygen Scavengers A deaerator removes most of the oxygen in feedwater; however, trace amounts are still present and can cause corrosion-related problems. Oxygen scavengers are added to the feedwater, preferably in the storage tank of the feedwater, to remove the trace mount of oxygen escaped from the deaerator. The most commonly used oxygen scavenger is sodium sulfite. Sodium sulfite is cheap, effective and can be easily measured in water. Sulfite (Oxygen Scavenger) Uncatalyzed sodium sulfite may be mixed with other chemicals. The preferred location for sulfite injection is a point in the storage section of the deaerating heater where the sulfite will mix with the discharge from the deaerating section. If sulfite is fed alone, the following basic equipment is needed: • skid mounted dual metering pumps (duty/stand-by) with stainless steel wet end/trim • pulsation dampener • stainless steel relief valve • stainless steel check valve • stainless steel Y-strainer • stainless steel tubing, valves, and fittings • flowmeter • calibration cylinder • pressure gauge with diaphragm seals • electrical junction boxes • dilution water line c/w static mixer (optional) • drip pan (optional) • In all cases, an injection quill should be used. Sulfite shipped as liquid concentrate is usually acidic and, when fed neat, corrodes stainless steel tanks at the liquid level. Sulfite storage tanks must be fiberglass, or polyethylene. Lines may be PVC or 316 stainless steel. Catalyzed Sulfite (Oxygen Scavenger) Catalyzed sulfite must be fed alone and continuously. Mixing of catalyzed sulfite with any other chemical impairs the catalyst. For the same reason, catalyzed sulfite must be diluted with only condensate or demineralized water. To protect the entire preboiler system, including any economizers, catalyzed sulfite should be fed to the storage section of the deaerating heater. Caustic soda may be used to adjust the pH of the day tank solution; therefore, a mild steel tank cannot be used. Materials of construction for feed equipment are the same as those required for regular sulfite. Hydrazine (Oxygen Scavenger) Hydrazine is compatible with all boiler water treatment chemicals except organics, amines, and nitrates. However, it is good engineering practice to feed hydrazine alone. It is usually fed continuously into the storage section of the deaerating heater. Because of handling and exposure concerns associated with hydrazine, closed storage and feed systems have become standard. Materials of construction are the same as those specified for sulfite. Organic Oxygen Scavengers Many organic compounds are available, including hydroquinone and ascorbic acid. Some are catalyzed. Most should be fed alone. Like sulfite, organic oxygen scavengers are usually fed continuously into the storage section of the deaerating heater. Materials of construction are the same as those specified for sulfite. Neutralizing Amines Neutralizing amines are high pH chemicals that neutralize the carbonic acid formed in the condensate (acid attack). The three most commonly used neutralizing amines are morpholine, diethyleminoethanal (DEAE) and cyclohexylamine. Neutralizing amines cannot protect against oxygen attack; however, it helps keep oxygen less reactive by maintaining an alkaline pH. Neutralizing amines may be fed to the storage section of the deaerating heater, directly to the boiler with the internal treatment chemicals, or into the main steam header. Some steam distribution systems may require more than one feed point to allow proper distribution. An injection quill is required for feeding into a steam distribution line. Neutralizing amines are usually fed based on condensate system pH and measured corrosion rates. These amines may be fed neat, diluted with condensate or demineralized water, or mixed in low concentrations with the internal treatment chemicals. A standard packaged pump skid and tank can be used for feeding. Filming Amines Filming amines are various chemicals that form a protective layer on the condensate piping to protect it from both oxygen and acid attack. The two most common filming amines are octadecylamine (ODA) and ethoxylated soya amine (ESA). Combining neutralizing and filming amine is a successful alternative to protect against both acid and oxygen attack. The filming amines should be continuously fed into steam headers at points that permit proper distribution. A single feed point is satisfactory for some systems. In every case, the steam distribution should be investigated and feed points established to ensure that all parts of the system receive proper treatment. Filming amines must be mixed with condensate or demineralized water. Water containing dissolved solids cannot be used, because the solids would contaminate the steam and could produce unstable amine emulsions. The use of stainless steel tanks is recommended. Equipment specifications are the same as those for regular sulfite, except that a vapor-type injection nozzle or quill is required. Internal Treatment Chemicals There are three major classifications of chemicals used in internal treatment: phosphates, chelants, and polymers. These chemicals may be fed either separately or in combination; in most balanced treatment programs, two or three chemicals are fed together. The preferred feed point varies with the chemical specified. For example, when caustic soda is used to maintain boiler water alkalinity, it is fed directly to the boiler drum. When caustic is used to adjust the feedwater pH, it is normally injected into the storage section of the deaerating heater. Phosphate Mono-, di- or trisodium phosphate and sodium polyphosphate can be added to treat boiler feedwater. Phosphate buffers the water to minimize pH fluctuation. It also precipitates calcium or magnesium into a soft deposit rather than a hard scale. Additionally, it helps to promote the protective layer on boiler metal surfaces. However, phosphate forms sludge as it reacts with hardness; blowdown or other procedures should be established to remove the sludge during a routine boiler shutdown. Phosphates are usually fed directly into the steam drum of the boiler, although they may be fed to the feedwater line under certain conditions. Treatments containing orthophosphate may produce calcium phosphate feed line deposits; therefore, they should not be fed through the boiler feed line. Orthophosphate should be fed directly to the boiler steam drum through a chemical feed line. Polyphosphates must not be fed to the boiler feedwater line when economizers, heat exchangers, or stage heaters are part of the preboiler system. If the preboiler system does not include such equipment, polyphosphates may be fed to the feedwater piping provided that total hardness does not exceed 2 ppm. In all cases, feed rates are based on feedwater hardness levels. Phosphates should be fed neat or diluted with condensate or high-purity water. Mild steel tanks, fittings, and feed lines are appropriate. If acidic phosphate solutions are fed, stainless steel is recommended. Chelants Nitrilotriacetic acid (NTA) and ethylenediamine tetraacetic acid (EDTA) are the most commonly used chelants. Chelants combine with hardness in water to form soluble compounds. The compounds can then be eliminated by blowdown. • Chelants treatment is not recommended for feedwater with high hardness concentration • Chelants should not be fed if the feedwater contains a significant level of oxygen. • Chelants should never be fed directly into a boiler The preferred feed location for chelants is downstream of the feedwater pump. All chelant treatments must be fed to the boiler feedwater line by means of a stainless steel injection nozzle at a point beyond the discharge of the boiler feed pumps. If heat exchangers or stage heaters are present in the boiler feed line, the injection point should be at their discharge. Care should be exercised in the selection of metals for high-temperature injection quills. At feed solution strength and elevated temperatures, chelating agents can corrode mild steel and copper alloys; therefore, 304 or 316 stainless steel is recommended for all feed equipment. Equipment specifications are the same as those for regular sulfite. Chelant products may be fed neat or diluted with condensate. Chelant feed rates must be carefully controlled based on feedwater hardness, because misapplication can have serious consequences. Polymeric Dispersants. In most applications, polymeric dispersants are provided in a combined product formulation with chelants and/or phosphates. Dilution and feed recommendations for chelants should be followed for chelant-dispersant and chelant-phosphate-dispersant programs. Dilution and feed recommendations for phosphates should be followed for phosphate-dispersant programs. These combination programs typically have the best results with respect to boiler cleanliness. Neutralizing Amines Neutralizing amines are high pH chemicals that neutralize the carbonic acid formed in the condensate (acid attack). The three most commonly used neutralizing amines are morpholine, diethyleminoethanal (DEAE) and cyclohexylamine. Neutralizing amines cannot protect against oxygen attack; however, it helps keep oxygen less reactive by maintaining an alkaline pH. Neutralizing amines may be fed to the storage section of the deaerating heater, directly to the boiler with the internal treatment chemicals, or into the main steam header. Some steam distribution systems may require more than one feed point to allow proper distribution. An injection quill is required for feeding into a steam distribution line. Neutralizing amines are usually fed based on condensate system pH and measured corrosion rates. These amines may be fed neat, diluted with condensate or demineralized water, or mixed in low concentrations with the internal treatment chemicals. A standard packaged pump skid and tank can be used for feeding. Filming Amines Filming amines are various chemicals that form a protective layer on the condensate piping to protect it from both oxygen and acid attack. The two most common filming amines are octadecylamine (ODA) and ethoxylated soya amine (ESA). Combining neutralizing and filming amine is a successful alternative to protect against both acid and oxygen attack. The filming amines should be continuously fed into steam headers at points that permit proper distribution. A single feed point is satisfactory for some systems. In every case, the steam distribution should be investigated and feed points established to ensure that all parts of the system receive proper treatment. Filming amines must be mixed with condensate or demineralized water. Water containing dissolved solids cannot be used, because the solids would contaminate the steam and could produce unstable amine emulsions. The use of stainless steel tanks is recommended. Equipment specifications are the same as those for regular sulfite, except that a vapor-type injection nozzle or quill is required. Computerized Boiler Chemical Feed Systems Computerized boiler chemical feed systems are being used to improve program results and cut operating costs. These systems can be used to feed oxygen scavengers, amines, and internal treatment chemicals. A typical system incorporates a metering pump, feed verification equipment, and a microprocessor-based controller. These systems are often linked to personal computers, which are used to monitor program results, feed rates, system status, and plant operating conditions. Trend graphs and management reports can then be produced to provide documentation of program results and help in troubleshooting. In many cases, these systems can be programmed to feed boiler treatment chemicals according to complex customized algorithms. For example, chelant feed can be adjusted automatically, based on analyzer or operator hardness test results, boiler feedwater flow, and minimum/maximum allowable product feed rates. Thus, chemical feed precisely matches system demand, virtually eliminating the possibility of underfeed or overfeed. Feed verification is another important facet of some computerized feed systems. The actual output of the pump is continuously measured and compared to a computer-calculated setpoint. If the output doesn’t match the set point, the speed or stroke length is automatically adjusted. The benefits of this technology include the elimination of time-consuming drawdown measurements, the ability to feed most chemicals directly from bulk tanks, precise chemical residual control, and minimal manpower requirements.

Statements and suggestions herein are based upon the best information and practices known to us. However, it should not be assumed either that information is complete on the subjects covered or that all possible circumstances, safety measures, precautions, etc. have been included. These statements and suggestions are not intended to reflect provincial, municipal or insurance requirements or national safety codes; where applicable, those sources must be considered directly. Since the conditions of use are beyond our control, Hayward Gordon makes no guarantee of results and assumes no liability in connection with the information contained herein.

Mengenal Boiler

Boiler Fittings
The minimum fittings required are:
•Safety valves.
•Water Level indicators.
•Low water alarm and shut down.
•Main Stop valve
•Feed Cheek valves
•Pressure Gauge
•Salinometer Valve
•Blow Down Valve
•Manhole

HSE Rules
9  Water level controls and the first low water alarm which also extinguishes the burner may be housed in the same external chamber or internal protection tube. Additionally a separate chamber or internal protection tube with an independent electrical control circuit is required for an overriding second low water alarm and fuel cut out; this should be a lock‑out type requiring manual reset (para 17(c)).
Automatic firing controls so arranged that they effectively control the supply of fuel to the burners on oil or gas fired boilers, or air to solid fuel fired boilers, and effectively shut off the supply in the event of any one or more of the following circumstances:
(iv)when the water level falls to a predetermined point below the normal operating level. When the water level is restored the burner may be automatically refired;
Note: In the case of (i) (ii) and (v), these controls should be of the lock out type requiring manual resetting. In the case of (iv) this control should cut off the fuel/air supply and cause an audible alarm to sound.

Exhaust Gas Boiler

Manhole Door
Water Tube Boiler Components
Evaporator


Turbine Generator Boiler

Drain Hole Boiler

Steam Boiler Valve

Valve Component

Modified Valve Component

Drain Component

Boiler Operation Flowchart

Uptake Fires

Initial Boiler Entry
•Permit to Work.
•Isolate all fires by shutting off the burner fuel inlets. Close feed inlets
•Let the boiler cool down until about 3‑4 bar steam pressure remains
•Open the blowdown line to empty the boiler drum.
•When about 2 bar pressure remains in the boiler drum open the air vent and leave open
•Prepare to open the manhole doors by loosening nuts and breaking seal when the steam drum pressure has reduced to atmospheric (22.5.1)
•Remove top doors first, and then bottom after ensuring contents drained. Thoroughly ventilate.
•Personnel should not enter boiler, furnace or flue until the unit has cooled sufficiently. (22.5.2)
•Ensure all connections to drum are either blanked off, removed or valves locked in closed position with posted notices. (22.5.3)
•All personnel working on boiler require PPE. (22.5.4)
•Treat the boiler as an enclosed space, so ventilate and test atmosphere for oxygen content (22.5.5)
Oil Contamination Of Boiler
•Change feed to an uncontaminated supply.
•Do not blow down the boiler from the bottom; just surface blow (scum) several times. If you bottom blow the boiler, it will become totally covered in oil.
•The boiler should be shut down and released from pressure and the venting valve opened.
•Drain the boiler slowly until water stops flowing from the loosened, upper manhole door before opening up the manhole for inspection. The oil will now only cover the boiler in the normal water level range and can be manually removed.
•Hot or cold water high-pressure jet equipment together with oil dispersive additives would be efficient for removal of the oil.
•In case the boiler is completely oily inside, the cleaning work should be turned over to a cleaning company specialised in such work. A full alkaline wash of the inside and complete structural inspection would be required.

Boiler Inspection
FIRESIDE
•Loss or refractory
•Condition of the refractory around the burner and the back wall, as these areas suffer from high temperature cracking.
•Distortion to any metal surfaces including the furnace and the tube plates
•Condition of the furnace floor looking for signs of oil contamination
•Signs of overheating at the burner assembly.
•Tube ends for signs of leakage, creep cracking.

WATERSIDE
•Integrity of the bottom blow down pipe and other internal fittings.
•Boiler bottom plate (furnace top‑fire tube boiler), furnace wall for steam bubble pitting
•Mechanical grooving of boilerplates at internal supports
•Oxygen pitting of shell at the water line
•Thinning or necking of the tubes
•Pitting of the boiler tubes
•Feed and scum pipe integrity
•Oxygen pitting in the steam space
•Condition of manhole opening, joint faces, welds, corrosion
•Steam space stay condition.
•Scale deposits
•Condition of welds
•Blockages in pipes for mountings

SHELL
•Condition of lagging
•Signs of leakage
•Fit of manhole door and condition of securing device
•Overhaul all valve and fittings;
•Check for corrosion. All parts should be made from non-corrodable material
•Check valve seat faces free from defects and face width not excessive
•Check valve bodies for corrosion and cracks
•Hang all components and check free from cracks by NDT inspection
•For safety valves
•Check spring length, and carry out NDT inspection
•Check valve spindle straight
•Cheek valve body drain clear
•Check easing gear operation and condition

Refilling And Raising Steam
•Replace all mountings, ensuring correct fitting and direction of flow.
•Replace inspection covers, ensuring securing devices not overightened.
•Refill boiler water, adding correct chemical dosage. Level should be just above Low Level alarm.
•Check operation of level alarms, feed controls, automation pressure switches.
•Ensure all valves are in their working positions, test gauge glasses.
•Check burner controls and cut outs.
•With the vent open, start to warm the boiler. Firing should initially be for short periods (5 mins) with a break (15 mins) to allow the boiler to warm through evenly.
•When steam is coming out of the vent, (2 bar pressure), close vent and bring boiler to working pressure.
•Set safety valves.
•Test all alarms and shutdowns.
•Check tightness of glands and bolts.
•Check tightness of manhole and inspection covers.

Adjustment Of Safety Valves.
•Calibrate pressure gauge and check pipes clear                                           
•Raise steam
•Steam outlet closed
•Gag one valve
•Raise pressure and adjust valve to open at required pressure
•Check blowdown
•Change over gag
•Repeat 5 & 6
•Remove gag
•Lock valve adjusters / make and fit spacers
•Recheck opening pressure
•Check easing gear and seal covers
•Check alarms and burner operation

Soot Fires

Hydrogen Fires
Conditions Required
•Tube metal temperatures of over 705°C
•Tubes with some steam content (poor circulation)
•The presence of a catalyst in the form of a carbon ash.
Prevention.
•Regular sootblowing to prevent build up of carbon ash
•Ensure circulation of boiler
•If boiler to be run dry, drain and vent to eliminate possibility of steam presence
Fighting.
•Shut of air by gagging turbo blowers – wet canvass over intakes, ensure exhaust valves closed
•Boundary cool
Water Analysis
Scale Forming Salts
Magnesium Chloride
Decomposes to form hydroxide and hydrochloric acids. The former will produce hard scale and the later lowers the pH.
MgCl2 + 2H2O  ®  2HCl + Mg(OH)2
Magnesium Sulphate
Forms a hard scale on the heating surfaces
Calcium Sulphate
Forms a hard scale on the heating surfaces
Calcium Bi-carbonate
Decomposes at a low temperature when CO2 is liberated. Remaining Calcium carbonate deposits on the heating surface as a soft scale.
Ca(HCO3)2  ®  CaCO3 + CO2 + H2O

Boiler Treatment
ALKALIS
Sodium Carbonate (soda ash).
Reacts with non‑alkaline hardness salts by either precipitating them, or converting into sodium salts, which stay in solution. Excess Sodium carbonate remains in solution to provide an alkalinity to reduce corrosion.
Na2CO3 + CaSO4  ®  CaCO3 + Na2SO4
Sodium Hydroxide. (caustic soda)
Reacts with magnesium chloride producing a harmless precipitant and sodium chloride, which remains in solution.
It is not suitable for pre‑mixing with other chemicals. But can be used in conjunction with other chemical treatments.
2NaOH  +  MgCl2  ®  2NaCl  +  Mg(OH)2

PHOSPHATES
Disodium Phosphate
Dissolves in water and forms a neutral solution. Reacts with magnesium and calcium sulphates and precipitates them as phosphates, or converts them to sodium salts, which will remain in solution.
Na2HPO4  +  MgSO4   Þ MgHPO4   +  Na2SO4
Trisodium Phosphate
Dissolves in water to produce disodium phosphate and sodium hydroxide, an alkaline solution.
Na3PO4     +    H2O    Þ Na2HPO4   + NaOH
• The function of both these chemicals is to prevent scale formation by  precipitating the salts of magnesium and calcium as a soft sludge.

Coagulants (Starch, Tannin, Sodium aluminate)
These chemicals attract the sludges which float in the boiler water. They keep the sludge in suspension and so avoid any build up of sludge on the heating surfaces. Can also help in the reduction of foaming and also keep any oil present in an emulsified form.

OXYGEN SCAVENGERS
Presence of oxygen in the boiler water will result in serious corrosion.
To reduce the amount of oxygen present in the boiler water oxygen scavengers are used.
These are Hydrazine or Sodium Sulphite
Hydrazine N2H4 + O2 ® 2H2O + N2
Sodium Sulphite 2NaSO3 + O2 ® 2NaSO4

Water Systems: Water Conditioning for Process and Boiler Use

Introduction

Industrial water

Process water: Water that is used for, or comes in contact with an end product or the materials used in an end product.

Boiler feed water

Water that serves in any level of the manufacturing process

Common contaminants: Ca, Mg, Fe, Al, Silica, salt, oil

Treatment Methods

  • External Treatment
  • Internal Treatment

External methods of conditioning

  • Clarification
  • Filtration
  • Ion exchange
  • Membrane separation

Clarification

•Removes all types of solids & large particles – sediments, oil, natural org. matter, colour etc.
•Consists of 4 steps – screening, coagulation-flocculation, sedimentation, fine filtration.
•Screening protects downstream units from large, easily separable objects.
•Three types:
–Fine screening (spacing < 10 mm)
–Medium screening (spacing 10 – 40 mm)
–Coarse screening (spacing > 40 mm)
•Coagulation-flocculation removes suspended solids & colloidal particles.

•Important factors – velocity gradient, time, pH
•Flotation – to separate particles having density lesser than water.
•Three types:
–Natural
–Aided
–Induced
•Induced flotation facilitated through bubbling of air; 2 types –
–Dissolved air flotation (DAF) (bubbles of 40 – 70 mm)
–Mechanical flotation (bubbles of 0.2 – 2 mm)

Filtration

•Separates undissolved solids from water by means of a filter – porous substance, membrane or permeable fabric.
•Three types of filtration:
–Micro filtration (pore size 0.1 – 10 µm)
–Ultra filtration (pore size 1-100nm)
–Nano filtration (pore size < 1 nm)
•Micro filtration – removes bacteria; used for biological wastewater treatment, effluent treatment, separation of oil-water emulsions.
•Ultra filtration – separation of suspended solids, colloids, bacteria, virus.

•2 ultra filtration module configurations:
–Pressurized system or pressure-vessel configuration
–Immersed system
•Nano filtration – water softening, decolouring, micro-pollutant removal (org. matter, heavy metals, pesticides).
•Ultra & nano filtration – pressure driven processes.
•Pre-treatment – protects filtration membranes; microfiltration – pre-filter for ultra filtration and so on.

Ion Exchange

•Resins – acidic/basic radicals with ions fixed on them; exchanged with ions present in water.
•Theoretically removes 100 % of salts; does not remove organics, virus or bacteria.
•2 types of resins – gel type (microporous) and macroporous or loosely cross-linked type.
•3 systems of resin beds:
–Strong acid cation + Strong base anion
–Strong acid cation + weak base anion + Strong base anion
–Mixed-bed Deionization
•Ion exchange plant – softens water, removes heavy metals, produces demineralized water.

Reverse Osmosis (RO)

•By applying pressure greater than osmotic pressure, water flows from the higher concentration solution to lower one.
•Mostly used for desalination; also for waste water treatment.
•Applied pressure depends on the type and salinity of water.
•Working pressure:
– < 15 bar for tap water (< 1500 ppm)
–15 – 25 bar for brackish water (< 8000 ppm)
–50 – 75 bar for sea water (35000 – 45000 ppm)
•RO plant preceded by pretreatment to avoid membrane fouling by sediments, bacteria, metal oxides & chlorine.
•RO permeate water more acidic than the feed water due to dissolved CO2. Common post-treatment are pH neutralization and remineralization.
 

Electrodionization

•Combines membrane separation and ion-exchange to provide high efficiency demineralization process.
•Electric potential transports & segregates charged aqueous species.
•Electric current continuously regenerates resin; no need for periodical regeneration.
•Deionization chamber – ion exchange resin, packed between cationic & anionic exchange membranes.

•Advantages
–continuous operation
–eliminates use of chemicals for regeneration
–low power consumption
•Disadvantages
–Not used for water with hardness > 1
–requires purification pretreatment
–Pre-removal of CO2

Internal Treatment methods

•Deaerators:
•Dissolved non-condensibles: O2 and CO2
•Pitting and corrosion
•Mechanical deaeration: reducing solubility of gases
–Increased temperature
–Decreased partial pressure over the water
–Commonly used purge gas: steam
–Advantages:
–No added impurities
–Easily available
–Also provides heat
–Pressure/Vacuum operation, ~98% of total and free is removed
•Coupled with chemical scavengers for complete deaeration

Corrosion control

•pH control
–Different for different components, different alloys
–CS : optimum pH = 9.2 to 9.6 at feed water temperatures
–MS : optimum pH = 8.5 to 12.7 in boilers
–Cu and CS : 8.8 to 9.2
–Maintained by addition of amines or small amount of caustic soda
–Avoidance of addition of ammonia

•Oxygen control: during operation
–Chemical Scavengers added to feedwater and condensates
•Sodium sulfite, bisulfite, hydrazine
•Quinone, ascorbate
–Common entry: between deaerator and storage
Sodium sulfite: easy to handle, safe, for pressures of < 70 bar, solid addition to system, decomposition to corrosive gases
Hydrazine: no solid addition, high pressures, but toxic, handling issues, Ammonia liberation, slower reaction
–Constant sampling and monitoring

•Control: downtime and storage
–Oxygen in-leakage and pH lowering
–Dry storage: long downtime, month or more
•Completely dried
•Applied dessicants like quicklime, silica gel, activated alumina
–Wet storage: short downtime
•Cleaning, inspection and filling with deaerated feedwater
•Addition of scavenger, heat addition

Deposits

•Scaling/deposition from carryover
•Carbonate/Phosphate control
–Addition of certain amounts of carbonate/phosphate for ensuring precipitate in the form of salts. Prevention of Sulphates
–For removal of hardness, Ca and Mg
–Precipitation in bulk instead of at walls, non-adherent
•Organic supplements: fluid sludge formation (polymer addition)
–Bottom blowdown removes sludge
•Chelant control
•Combination of additives
•Blowdown

Case study -Boiler tube failure

Failure mode :Oxygen corrosion
Result: 3-5 shutdowns.
Reasons
-Improper deaeration.
-High level of dissolved oxygen.
-Leakage in recirculator pump.

Best practices

Maintain the equipment properly .
Control the composition of the boiler feed water
Identify optimal chemicals for the prevention of biological growth
Electrically powered water conditioning units

Pretreatment of makeup water
Materials of construction
Optimize the frequency of cleaning boilers.
Recent techniques
- Magnetic water treatment.

COOLING WATER TREATMENT

ABSTRACT

Traditionally, chemical water treatment has involved adding corrosion inhibitor and then periodically testing for the residual.  However to be effective, these programs must also include the control of scale and biological growth.  Controlling the 3 sides of the cooling water triangle will drastically increase the effectiveness of your water treatment program.  Failure to control any one component of the triangle will lead to probable failure of your water treatment program and repair or replacement of your valuable capital equipment.

THE COST OF FAILURE

TERMINOLOGY

  • Conductivity- the measurement of how much electrical current  water is carrying.  Used to measure Cycles of Concentration (CoC)
  • Cycles of Concentration- The number of times minerals have been concentrated in a system due to evaporation
  • pH- measurement of free hydrogen in the water.  Represents how acid or alkaline the water is.
  • Blowdown- the removal of water from a cooling tower system to reduce or limit the Cycles of Concentration
  • Corrosion Coupon Rack- piping assembly that is a slip stream from the main system used to hold corrosion coupons.  Flow through the coupon rack should be regulated to 3-5 g.p.m.
  • Pot Feeder- feeder used to introduce chemical into a closed system.
  • Chemical Residual- the amount of chemical measured in a particular system
  • White Rust- the formation of zinc hydroxide deposits in a galvanized cooling tower.  Caused by inadequate cooling tower passivation at start up.
  • Evaporation Credits- a program by-which a city will give you a credit on your water bill for the water evaporated from your cooling system.

pH

pH can tell us whether the water has corrosive or scaling tendencies.  High pH tells us that the water is more likely to cause scale or mineral deposits.  Low pH tells us that the water is more likely to cause corrosion

CONDUCTIVITY

Conductivity gives us an approximate idea of what the mineral content of the water is based on the water source used to supply the cooling tower.  High conductivity is critical and can cause rapid scaling and mineral deposition on heat exchange surfaces (cooling tower fill and condenser tubes).

  • Cooling tower conductivity should run between 2500-3500 umhos.
  • Conductivity above 3500 umhos an cause scaling
  • Conductivity below 2500 indicates water/chemical waste.

ASPECTS OF WATER TREATMENT

Looking at a water treatment program for a condenser water system it is easy to focus on the traditional areas, such as:

  • Corrosion control
  • Microbial control
  • Deposition/scale control

While these are important, they do not take into account the broader scope of what needs to be done to ensure the maximum lifespan of these systems.  In designing a system consideration needs to be given to each of the following aspects:

 

  1. Is it a new or existing system?
  2. If it is existing, are there corrosion products in it?
  3. Is there a risk of organic contamination?
  4. What level of monitoring can be expected (plant or supplier personnel)?
  5. How extensive is the fluid distribution piping?
  6. What are the typical blowdown rates?
  7. What is the metallurgy of the cooling tower?
  8. Does the system run constantly or intermittently?
  9. Are the tubes enhanced?

The objective of a treatment program is to minimize damage and allow the system

to operate as efficiently as possible.  This means that:

 

  • The corrosion inhibitors need to be able to get to the metal surfaces
  • Deposits are not present that can interfere with fluid circulation
  • Microbes are not present that can compromise the corrosion protection

CORROSION INHIBITORS

NOT ALL CHEMICALS ARE THE SAME!!  organic corrosion Inhibitors using polymers and phosphonates are the most effective program. Phosphates are used-good corrosion protection, but can form mineral deposits.

  • Zinc can be used, is not environmentally friendly and can CAUSE corrosion at pH over 8.5
  • Molybdate is often used but is VERY expensive at useful levels
  • New technology-organic base, safer to handle, lower liability, potentially improved performance.

BIOCIDES

Approximately 70 % of the cooling water chemical programs that fail do so as a result of poor biological control. The key to effective biological control is applying the proper amount of chemical with the proper frequency.  A vigorous biocide program will utilize 2-alternating products.

  • Water with pH > 8.0, chlorine is not acceptable
  • Quaternary biocides neutralize most corrosion inhibitors
  • Sulfur based biocides do not perform well in alkaline water
  • Swimming pool floaties do not count as biocide

SYSTEM MONITORING

Considering the liabilities of improperly treating any system, monitoring is one of the simplest ways of ensuring that performance criteria are being met.  The low cost combined with the confirmation of due diligence makes monitoring virtually mandatory.

  • Corrosion coupons (mild steel < 2.0/copper < 0.2)
  • Real time corrosion monitoring
  • Mineral balance
  • Regular evaluation of system water conditions
  • DAILY testing and log sheets
  • Electronic reporting from your controller

CONTROL EQUIPMENT

Water treatment control equipment has evolved significantly over the past 10 years.  Controllers can do everything from notifying designated people of a problem, to emailing service reports and other information daily, weekly, or monthly.

At a minimum, your cooling tower controller should control blowdown, chemical feed, 2 biocides, and have an integrated flow switch.

FILTRATION

The use of any means of filtration can help any condenser water system.  Filtration is particularly important if your chiller has enhanced tubes on either the condenser or the evaporator side

  • Filtration maintains low water turbidity allowing more economical and effective chemical treatment
  • Filtration removes organic matter that can feed biological life in the cooling water
  • Filtration removes environmental debris that can be a breading ground for Legionella Pnumophelia .

CLEANING

Chemical water treatment is only an adjunct to proper maintenance of a cooling water program.   C.T.I. (Cooling Tower Institute) recommends that cooling towers be cleaned twice a year.

Annual inspection and brushing of condenser tubes is also an important part of a good PM program.  Enhanced tube heat exchangers are especially vulnerable to corrosion from even small amounts of sludge, oxidation, or environmental debris.

WATER TREATMENTS MYTHS

  1. Only the”Big Companies “ can offer the latest technology-FALSE
  2. All chemicals are the same-FALSE
  3. If you have soft water you do not need chemical treatment-FALSE
  4. If the tubes are clean, the chemicals are working-FALSE, FALSE, FALSE,
  5. All chemicals are hazardous-FALSE
  6. Magnets-FALSE
  7. Panther Unit-FALSE
  8. Ozone-FALSE
  9. “If it scales up we will clean it for free” FALSE AND DECEPTIVE
  10. Concentrated products that are mixed on site-FALSE
  11. A little white rust can not be prevented-FALSE

“NOT ACCEPTABLE” MAINTENANCE BEHAVIOUR

EXPECTATIONS

From : Various Source Document

Drinking Water Treatment

Public Water Systems

Public Water Systems (PWSs) come in all shapes and sizes, and no two are exactly the same. They may be publicly or privately owned and maintained. While their design may vary, they all share the same goal – providing safe, reliable drinking water to the communities they serve. To do this, most water systems must treat their water. The types of treatment provided by a specific PWS vary depending on the size of the system, whether they use ground water or surface water, and the quality of the source water.

Tapping a Source of Water

Large-scale water supply systems tend to rely on surface water sources, while smaller systems tend to rely on ground water. Around 35 percent of the population served by community water systems (CWSs) drink water that originates as ground water. Ground water is usually pumped from wells ranging from shallow to deep (50 to 1,000 feet). The remaining 65 percent of the population served by CWSs receive water taken primarily from surface water sources like rivers, lakes, and reservoirs.

Treating Raw Water

The amount and type of treatment applied by a PWS varies with the source type and quality. Many ground water systems can satisfy all Federal requirements without applying any treatment, while others need to add chlorine or additional treatment. Because surface water systems are exposed to direct wet weather runoff and to the atmosphere and are therefore more easily contaminated, federal and state regulations require that these systems treat their water.

Water suppliers use a variety of treatment processes to remove contaminants from drinking water. These individual processes may be arranged in a “treatment train” (a series of processes applied in sequence). The most commonly used processes include filtration, flocculation and sedimentation, and disinfection for surface water. Some treatment trains also include ion exchange and adsorption. Water utilities select a combination of treatment processes most appropriate to treat the contaminants found in the raw water used by the system.

Types of Treatment

Flocculation/Sedimentation
Flocculation refers to water treatment processes that combine or coagulate small particles into larger particles, which settle out of the water as sediment. Alum and iron salts or synthetic organic polymers (used alone or in combination with metal salts) are generally used to promote coagulation. Settling or sedimentation occurs naturally as flocculated particles settle out of the water.

Filtration
Many water treatment facilities use filtration to remove all particles from the water. Those particles include clays and silts, natural organic matter, precipitates from other treatment processes in the facility, iron and manganese, and microorganisms. Filtration clarifies water and enhances the effectiveness of disinfection.

Ion Exchange
Ion exchange processes are used to remove inorganic contaminants if they cannot be removed adequately by filtration or sedimentation. Ion exchange can be used to treat hard water. It can also be used to remove arsenic, chromium, excess fluoride, nitrates, radium, and uranium.

Adsorption
Organic contaminants, unwanted coloring, and taste-and-odor-causing compounds can stick to the surface of granular or powder activated carbon and are thus removed from the drinking water.

Disinfection (chlorination/ozonation)
Water is often disinfected before it enters the distribution system to ensure that potentially dangerous microbes are killed. Chlorine, chloramines, or chlorine dioxide are most often used because they are very effective disinfectants, not only at the treatment plant but also in the pipes that distribute water to our homes and businesses. Ozone is a powerful disinfectant, and ultraviolet radiation is an effective disinfectant and treatment for relatively clean source waters, but neither of these are effective in controlling biological contaminants in the distribution pipes.

Monitoring Water Quality

Water systems monitor for a wide variety of contaminants to verify that the water they provide to the public meets all federal and state standards. Currently, the nation’s community water systems (CWSs) and nontransient non-community water systems (NTNCWSs) must monitor for more than 83 contaminants. The major classes of contaminants include volatile organic compounds (VOCs), synthetic organic compounds (SOCs), inorganic compounds (IOCs), radionuclides, and microbial organisms (including bacteria). Testing for these contaminants takes place on varying schedules and at different locations throughout the water system.

Transient non-community water systems may monitor less frequently and for fewer contaminants than CWSs. Because these types of systems serve an ever-changing population, it is most important for them to monitor for contaminants such as microbiologicals and nitrate that can cause an immediate, acute public health effect.

Water systems also monitor for a number of contaminants that are currently not regulated. This monitoring data provides the basis for identifying contaminants to be regulated in the future.

Distribution to Customers

An underground network of pipes typically delivers drinking water to the homes and businesses served by the water system. Small systems serving just a handful of households may be relatively simple. Large metropolitan water systems can be extremely complex – sometimes with thousands of miles of piping serving millions of people. Although water may be safe when leaving the water treatment plant it is important to ensure that this water does not become contaminated in the distribution system because of such things as water main breaks, pressure problems, or growth of microorganisms.

The Water Cycle

Drinking water can come from both surface water and ground water. The water cycle begins with rainwater and snow melt that gathers in lakes and rivers which interact with ground water.

Water Treatment Plant

Follow a drop of water from the source through the treatment process. Water may be treated differently in different communities depending on the quality of the water which enters the plant. Groundwater is located underground and typically requiresless treatment than water from lakes, rivers, and streams.