Rabu, 03 April 2013
Prosedur bedah Gyn Mayor-2
1 Middle rectal artery,2 Internal pudendal artery,3 Inferior gluteal artery,4 Superior gluteal artery,5 Lateral sacral artery,6 Iliolumbar artery,7 Aorta,8 Common iliac artery,9 Internal iliac artery,10 External iliac artery,11 Uterine artery,12 Circumflex liliac artery,13 Obturator artery,14 Inferior epigastric artery,15 Superior vesical
A Transverse level, umbilicus,B Transverse level, arcuate line
1 Obturator internus, 2 Puborectalis, 3 Piriformis,
4 Pubococcygeal muscle, 5 Iliococcygeal muscle,
6 Coccygeus, 7 Rectus abdominis, 8 Platysmus,
9 Sternocleidomastoid muscle, 10 Anterior scalene muscle, 11 Trapezius
THE PELVIC FASCIA AND PELVIC SPACES 21
11 T rapez ius,12 Deltoid,13 Pectoralis major,
14 Psoas,15 Iliacus,16 Pectineus,17 Sartorius,
18 Rectus femoris,19 Add uctor brevis,
20 Adductor longus,21 Vastus lateralis,22 Gracilis,
23 Anterior superior iliac spine
4.Incisi pada bedah ginekologi:
Mediana :insisi diantara simfisis pubis dan umbilikus pada garis tengah atau di linea alba. Insisi diteruskan sampai mencapai fascia muskulus rektus. Fascia dibuka secara tajam dan diperlebar sampai tampak aponeurosis muskulus rektus, otot disisihkan sampai tampak aponeurosis muskulus rektus dan peritoneum dan fascia transversalis. Angkat peritoneum menggunakan pinset kanan dan kiri lalu dibuka secara tajam menggunakan gunting. Angkat peritoneum dengan memasukkan jari tengah dan telunjuk agar tidak mengenai usus lalu gunting kearah bawah dengan memperhatikan jangan sampai mengenai vesica. Lebarkan kearah atas dengan cara yang sama.
Paramediana :insisi dibuat ± 2 cm kelateral dari garis tengah. Muskulus rektus disisihkan ke lateral lakukan seperti insisi mediana.
Insisi Joel Cohen:
INSISI PFANNENSTIEL:
1. Insisi kulit tranversal semilunar 2 cm suprasimfisis.
2. Insisi diperdalam sampai fascia rectus dan fascia rectus dibuka secara tranversal dengan gunting “Mayo” atau “scalpel”.
3. Tepi atas fascia rectus dijepit dengan “kocher” dan dipisahkan dari m.rectus abdominalis serta m.pyramidalis secara tumpul dan waspada terhadap trauma pembuluh darah disekitar garis tengah.
4. Setelah pemisahan diatas sudah lengkap – tepi bawah fascia rectus dijepit dengan “kocher” dan dipisahkan dari m.pyramidalis secara tumpul sampai mencapai simfsis pubis.
5. m.Rectus kiri dan kanan dipisahkan kearah lateral sehingga fascia tranversal dan peritoneum terpapar.
6. Lapisan tersebut dijepit dengan 2 buah klem dan diangkat.
7. Hati-hati agar tidak mencederai vesica urinaria.
8. Hati-hati agar tidak mencederai omentum atau usus terutama pada pasca pembedahan intra abdominal – endometriosis atau infeksi intra abdominal.
9. Lapisan tersebut dibuka kearah kranial dengan gunting “Metzenbaum”.
10. Lapisan tersebut dibuka lebih lanjut ke kaudal secara tajam.
11. Hati-hati mencederai vesica urinaria.
12. Lakukan pemeriksaan “transilluminasi” untuk menghindari cedera pada kandung kemih
13. Untuk pemapaparan bidang operasi m.pyramidalis perlu dipisahkan digaris tengah.
14. Bila langkah-langkah ditas sudah dilakukan, operator dapat masuk ke rongga abdomen.
15. Bila pemaparan masih kurang optimal maka lakukan insisi CHERNEY (jangan melakukan insisi Maylard !!!! )
. INSISI MAYLARD
1. Insisi melintang kulit 2 – 3 cm diatas simfisis pubis dan diperdalam sampai fascia rectus (seperti pada PFANNENSTIEL)
2. Identifikasi fascia rectus – dijepit – dibuka secara tajam bilateral.
3. Perbedaan dengan PFANNENSTIEL : m.rectus abdominalis tidak perlu dipisahkan dari fascia rectus.
4. Identifikasi arteria epigastrica inferior – sisihkan dari jaringan ikat sepanjang tepi lateral m.rectus :
o Identifikasi dengan palpasi dan pemisahan secara tumpul
o Setelah identifikasi – ikat secara ganda dan potong
5. Transeksi secara “zig-zag” m.rectus abdominalis kira-kira 3 – 5 cm diatas origo di simfsis pubis.
6. Bila perlu elevasi masing-masing m.rectus abdominalis dengan “penrose drain” untuk memudahkan transeksi dan melindungi jaringan dibawah otot.
7. Setelah transeksi – m.rectus disisihkan ke kranial dan kaudal dan peritoneum dibuka secara TRANVERSAL (seperti insisi pada kulit) dengan tehnik yang sama.
8. Saat menutup luka operasi: m.rectus tidak perlu didekatkan dengan menjahit oleh karena akan sembuh secara spontan.
Cherney:
1. Insisi kulit sampai fascia musculus rectus dilakukan dengan cara yang sama dengan insisi Pfannestiel atau insisi Cherney
2. Fascia m.rectus dijepit di garis tengah kemudian dilakukan insisi tranversal
3. Potongan inferior fascia m.rectus dijepit dengan “kocher Clamps” – di elevasi dan dibebaskan dari m.rectus abdominalis dan m.pyramidalis secara tumpul dan tajam ke arah simfisis pubis sehingga apponeurosis m.rectus dan m.pyramidalis dapat di identifikasi
4. Tendon dipotong dengan gunting “MAYO” untuk membebaskan otot dari origo pada simfisis pubis
5. M.rectus abdominalis mengalami rektraksi ke superior
6. Fascia tranversalis serta peritoneum dibuka dengan cara yang sama
7. Penutupan luka : tendon m.rectus abdominalis dan m.pyramidalis didekatkan denfgan jahitan terputus permanen
8. Bila pada insisi Pfannenstiel bidang pembedahan kurang luas – dapat dilakukan perubahan ke arah insisi CHERNEY tanpa menggangu intergritas muskulatur di garis tengah.
5.Histerektomi menurut Richardson:
1.setelah rongga peritoneum dibuka dilakukan eksplorasi; 2masukkan kassa besar basah & psg retraktor; 3menjepit, memotong mengikat lig rotundum kanan kiri; 4membuka plica vesikouterina & menyisihkan kd kemih ke bwh; 5menembus lig latum kanan kiri dgn jari dari arah belakang; 6menjepit memotong mengikat lig infundibulopelvikum kanan kiri; 7menjepit memotong mengikat vasa uterina kanan kiri; 8membuka fasia pubovesikoservikalis & fasia rektovaginalis;9menjepit memotong mengikat lig sakrouterina & jaringan paraservikal kanan kiri; 10menjepit puncak vagian dgn klem 90 & memancung vagina setinggi porsio; 11menjahit sudut tunggul vagina; 12menjahit puncak vagina; 13menyatukan sudut tunggul vagina dgn tunggul lig rotundum dan tunggul lig infundibulopelvikum ; 14retroperitonealisasi; 15eksplorasi ulang dengan memeriksa perdarahan setelah diyakini tidak ada perdarahan lalu rongga perut dicuci; 16mengangkat kasa di perut, retraktor perut & membersihkan rongga perut; 17menutup dinding perutlapis demi lapis
6.TEKNIK PENJEPITAN A.UTERINA:
• Klem ochsner terendah dipasang pertama kali
• Klem pertama ini ditempatkan setinggi OUI
• Klem dipasang tegak lurus terhadap SBR
Tujuannya:
7.KULDOPLASTI:
Usaha untuk mengatasi kemungkinan prolaps puntung vagina atau enterokel beberapa tahun setelah dilakkukan TAH dengan cara menggantungkan dinding posterior puntung vagina dengan lig.sacrouterina
Tujuan: mencegah prolaps puntung vagina atau enterokel pasca TAH
Teknik: dengan menggunakan benang polydioxanon, puntung vagina satu sisi dijahitkan pada ligamentum sakrouterina,
8.PADA WANITA PREMENOPOUSE histerektomi terbaik dilakukan pada ........ karena......
9TEKNIK AMPUTASI UTERUS SVH:
serviks di pancung dengan bentuk huruf “V” dengan titik terendah pada garis lipatan endocerviks
tujuan:
• mengangkat seluruh endometrium dan sebanyak mungkin endoserviks sehingga tidak lagi terjadi perdarahan saat menstruasi.
• Mengurangi resiko Ca tunggul serviks
• Mempermudah penutupan tunggul serviks.
10.TINDAKAN SETELAH SVH (mencegah ca tunggul):
• PAP’s Smear sebelum dan setelah SVH
• Lakukan koagulasi dengan termokauter serviks : menurunkan resiko dari 0,4 – 19% menjadi 0,11%
• Terapi dini bila ada abnormalitas PAP’S Smear.
11MANFAAT SVH:
• Waktu operasi singkat
• Psikologis dan fungsi seksual tidak terlalu terganggu dengan masih adanya serviks
• Komplikasi pasca operasi kecil
• Menurunkan resiko gangguan diuresis
• Waktu perawatan lebih singkat karena mobilisasi boleh lebih cepat.
RESIKO SVH:
• Infeksi yang sulit sembuh karena serviks merupakan sumber leukorea
• Tunggul serviks dapat terjadi keganasan : 0,4% - 19%
• Penanganan terhadap Ca tunggul serviks lebih sulit karena ada peerubahan anatomi dan sirkulasi darah dan limfe.
12.Komplikasi Histerektomi totalis ab dominalis perdarahan, cedera kandung kemih, cedera ureter, cedera usus, infeksi, granulasi vagina, prolaps vagina, komplilaksi lain seperi gangguan penyembuhan luka.
13. Penanganan tubo ovarial abses lihat gambar
14. penanganan abses pelvis.pengobatan dengan antibiotik yg efektif terhadap bakteri aerob dan anaerob; paseien dievaluasi adakah keterlibatan peritoneum ke dlm septum rektovaginal intervensi pembedahan dilakukan drainase vagina dgn kateter pezar berukuran besar diikuti dgn irigasi bertekanan rendah dgn salin steril setiap 6 jam sampai rongga tertutup; jika tetap terjadi demam meskipun sudah diberi AB, drainase irigasi cul de sac per kutaneus. Jika keaadaan melemah, lakukan laparotomi eksplorasi. Pembedahan ditentukan oleh umur, paritas, keadaan tuba,ovarium & keinginan mempunyai anak lagi.
Prosedur bedah Gyn Mayor
1 Middle rectal artery,2 Internal pudendal artery,3 Inferior gluteal artery,4 Superior gluteal artery,5 Lateral sacral artery,6 Iliolumbar artery,7 Aorta,8 Common iliac artery,9 Internal iliac artery,10 External iliac artery,11 Uterine artery,12 Circumflex liliac artery,13 Obturator artery,14 Inferior epigastric artery,15 Superior vesical
A Transverse level, umbilicus,B Transverse level, arcuate line
1 Obturator internus, 2 Puborectalis, 3 Piriformis,
4 Pubococcygeal muscle, 5 Iliococcygeal muscle,
6 Coccygeus, 7 Rectus abdominis, 8 Platysmus,
9 Sternocleidomastoid muscle, 10 Anterior scalene muscle, 11 Trapezius
THE PELVIC FASCIA AND PELVIC SPACES 21
11 T rapez ius,12 Deltoid,13 Pectoralis major,
14 Psoas,15 Iliacus,16 Pectineus,17 Sartorius,
18 Rectus femoris,19 Add uctor brevis,
20 Adductor longus,21 Vastus lateralis,22 Gracilis,
23 Anterior superior iliac spine
4.Incisi pada bedah ginekologi:
Mediana :insisi diantara simfisis pubis dan umbilikus pada garis tengah atau di linea alba. Insisi diteruskan sampai mencapai fascia muskulus rektus. Fascia dibuka secara tajam dan diperlebar sampai tampak aponeurosis muskulus rektus, otot disisihkan sampai tampak aponeurosis muskulus rektus dan peritoneum dan fascia transversalis. Angkat peritoneum menggunakan pinset kanan dan kiri lalu dibuka secara tajam menggunakan gunting. Angkat peritoneum dengan memasukkan jari tengah dan telunjuk agar tidak mengenai usus lalu gunting kearah bawah dengan memperhatikan jangan sampai mengenai vesica. Lebarkan kearah atas dengan cara yang sama.
Paramediana :insisi dibuat ± 2 cm kelateral dari garis tengah. Muskulus rektus disisihkan ke lateral lakukan seperti insisi mediana.
Insisi Joel Cohen:
INSISI PFANNENSTIEL:
1. Insisi kulit tranversal semilunar 2 cm suprasimfisis.
2. Insisi diperdalam sampai fascia rectus dan fascia rectus dibuka secara tranversal dengan gunting “Mayo” atau “scalpel”.
3. Tepi atas fascia rectus dijepit dengan “kocher” dan dipisahkan dari m.rectus abdominalis serta m.pyramidalis secara tumpul dan waspada terhadap trauma pembuluh darah disekitar garis tengah.
4. Setelah pemisahan diatas sudah lengkap – tepi bawah fascia rectus dijepit dengan “kocher” dan dipisahkan dari m.pyramidalis secara tumpul sampai mencapai simfsis pubis.
5. m.Rectus kiri dan kanan dipisahkan kearah lateral sehingga fascia tranversal dan peritoneum terpapar.
6. Lapisan tersebut dijepit dengan 2 buah klem dan diangkat.
7. Hati-hati agar tidak mencederai vesica urinaria.
8. Hati-hati agar tidak mencederai omentum atau usus terutama pada pasca pembedahan intra abdominal – endometriosis atau infeksi intra abdominal.
9. Lapisan tersebut dibuka kearah kranial dengan gunting “Metzenbaum”.
10. Lapisan tersebut dibuka lebih lanjut ke kaudal secara tajam.
11. Hati-hati mencederai vesica urinaria.
12. Lakukan pemeriksaan “transilluminasi” untuk menghindari cedera pada kandung kemih
13. Untuk pemapaparan bidang operasi m.pyramidalis perlu dipisahkan digaris tengah.
14. Bila langkah-langkah ditas sudah dilakukan, operator dapat masuk ke rongga abdomen.
15. Bila pemaparan masih kurang optimal maka lakukan insisi CHERNEY (jangan melakukan insisi Maylard !!!! )
. INSISI MAYLARD
1. Insisi melintang kulit 2 – 3 cm diatas simfisis pubis dan diperdalam sampai fascia rectus (seperti pada PFANNENSTIEL)
2. Identifikasi fascia rectus – dijepit – dibuka secara tajam bilateral.
3. Perbedaan dengan PFANNENSTIEL : m.rectus abdominalis tidak perlu dipisahkan dari fascia rectus.
4. Identifikasi arteria epigastrica inferior – sisihkan dari jaringan ikat sepanjang tepi lateral m.rectus :
o Identifikasi dengan palpasi dan pemisahan secara tumpul
o Setelah identifikasi – ikat secara ganda dan potong
5. Transeksi secara “zig-zag” m.rectus abdominalis kira-kira 3 – 5 cm diatas origo di simfsis pubis.
6. Bila perlu elevasi masing-masing m.rectus abdominalis dengan “penrose drain” untuk memudahkan transeksi dan melindungi jaringan dibawah otot.
7. Setelah transeksi – m.rectus disisihkan ke kranial dan kaudal dan peritoneum dibuka secara TRANVERSAL (seperti insisi pada kulit) dengan tehnik yang sama.
8. Saat menutup luka operasi: m.rectus tidak perlu didekatkan dengan menjahit oleh karena akan sembuh secara spontan.
Cherney:
1. Insisi kulit sampai fascia musculus rectus dilakukan dengan cara yang sama dengan insisi Pfannestiel atau insisi Cherney
2. Fascia m.rectus dijepit di garis tengah kemudian dilakukan insisi tranversal
3. Potongan inferior fascia m.rectus dijepit dengan “kocher Clamps” – di elevasi dan dibebaskan dari m.rectus abdominalis dan m.pyramidalis secara tumpul dan tajam ke arah simfisis pubis sehingga apponeurosis m.rectus dan m.pyramidalis dapat di identifikasi
4. Tendon dipotong dengan gunting “MAYO” untuk membebaskan otot dari origo pada simfisis pubis
5. M.rectus abdominalis mengalami rektraksi ke superior
6. Fascia tranversalis serta peritoneum dibuka dengan cara yang sama
7. Penutupan luka : tendon m.rectus abdominalis dan m.pyramidalis didekatkan denfgan jahitan terputus permanen
8. Bila pada insisi Pfannenstiel bidang pembedahan kurang luas – dapat dilakukan perubahan ke arah insisi CHERNEY tanpa menggangu intergritas muskulatur di garis tengah.
5.Histerektomi menurut Richardson:
1.setelah rongga peritoneum dibuka dilakukan eksplorasi; 2masukkan kassa besar basah & psg retraktor; 3menjepit, memotong mengikat lig rotundum kanan kiri; 4membuka plica vesikouterina & menyisihkan kd kemih ke bwh; 5menembus lig latum kanan kiri dgn jari dari arah belakang; 6menjepit memotong mengikat lig infundibulopelvikum kanan kiri; 7menjepit memotong mengikat vasa uterina kanan kiri; 8membuka fasia pubovesikoservikalis & fasia rektovaginalis;9menjepit memotong mengikat lig sakrouterina & jaringan paraservikal kanan kiri; 10menjepit puncak vagian dgn klem 90 & memancung vagina setinggi porsio; 11menjahit sudut tunggul vagina; 12menjahit puncak vagina; 13menyatukan sudut tunggul vagina dgn tunggul lig rotundum dan tunggul lig infundibulopelvikum ; 14retroperitonealisasi; 15eksplorasi ulang dengan memeriksa perdarahan setelah diyakini tidak ada perdarahan lalu rongga perut dicuci; 16mengangkat kasa di perut, retraktor perut & membersihkan rongga perut; 17menutup dinding perutlapis demi lapis
6.TEKNIK PENJEPITAN A.UTERINA:
• Klem ochsner terendah dipasang pertama kali
• Klem pertama ini ditempatkan setinggi OUI
• Klem dipasang tegak lurus terhadap SBR
Tujuannya:
7.KULDOPLASTI:
Usaha untuk mengatasi kemungkinan prolaps puntung vagina atau enterokel beberapa tahun setelah dilakkukan TAH dengan cara menggantungkan dinding posterior puntung vagina dengan lig.sacrouterina
Tujuan: mencegah prolaps puntung vagina atau enterokel pasca TAH
Teknik: dengan menggunakan benang polydioxanon, puntung vagina satu sisi dijahitkan pada ligamentum sakrouterina,
8.PADA WANITA PREMENOPOUSE histerektomi terbaik dilakukan pada ........ karena......
9TEKNIK AMPUTASI UTERUS SVH:
serviks di pancung dengan bentuk huruf “V” dengan titik terendah pada garis lipatan endocerviks
tujuan:
• mengangkat seluruh endometrium dan sebanyak mungkin endoserviks sehingga tidak lagi terjadi perdarahan saat menstruasi.
• Mengurangi resiko Ca tunggul serviks
• Mempermudah penutupan tunggul serviks.
10.TINDAKAN SETELAH SVH (mencegah ca tunggul):
• PAP’s Smear sebelum dan setelah SVH
• Lakukan koagulasi dengan termokauter serviks : menurunkan resiko dari 0,4 – 19% menjadi 0,11%
• Terapi dini bila ada abnormalitas PAP’S Smear.
11MANFAAT SVH:
• Waktu operasi singkat
• Psikologis dan fungsi seksual tidak terlalu terganggu dengan masih adanya serviks
• Komplikasi pasca operasi kecil
• Menurunkan resiko gangguan diuresis
• Waktu perawatan lebih singkat karena mobilisasi boleh lebih cepat.
RESIKO SVH:
• Infeksi yang sulit sembuh karena serviks merupakan sumber leukorea
• Tunggul serviks dapat terjadi keganasan : 0,4% - 19%
• Penanganan terhadap Ca tunggul serviks lebih sulit karena ada peerubahan anatomi dan sirkulasi darah dan limfe.
12.Komplikasi Histerektomi totalis ab dominalis perdarahan, cedera kandung kemih, cedera ureter, cedera usus, infeksi, granulasi vagina, prolaps vagina, komplilaksi lain seperi gangguan penyembuhan luka.
13. Penanganan tubo ovarial abses lihat gambar
14. penanganan abses pelvis.pengobatan dengan antibiotik yg efektif terhadap bakteri aerob dan anaerob; paseien dievaluasi adakah keterlibatan peritoneum ke dlm septum rektovaginal intervensi pembedahan dilakukan drainase vagina dgn kateter pezar berukuran besar diikuti dgn irigasi bertekanan rendah dgn salin steril setiap 6 jam sampai rongga tertutup; jika tetap terjadi demam meskipun sudah diberi AB, drainase irigasi cul de sac per kutaneus. Jika keaadaan melemah, lakukan laparotomi eksplorasi. Pembedahan ditentukan oleh umur, paritas, keadaan tuba,ovarium & keinginan mempunyai anak lagi.
Kamis, 03 Mei 2012
Misteri Pasir Pemangsa atau Pasir Hisap
Pasir hidup adalah mekanisme paling unik alam semesta, ia mungkin terpendam di pantai tepi sungai atau bahkan mungkin di halaman belakang sekitarnya, dengan tenang menunggu orang-orang mendekat, membuat orang sulit maju ataupun mundur.
Pada tahun 1692,
di pelabuhan Jamaika, pernah terjadi pasir hidup yang terbentuk dari larutan tanah akibat gempa,
belakangan menyebabkan 1/3 kota hilang, dan tragedi yang menewaskan 2000 jiwa manusia.
Bagaimana menyelamatkan diri dari perangkap
Sebenarnya sebagian besar pasir hisap tidak jauh berbeda dengan pasir pada umumnya, tidak menyeramkan sebagaimana yang dilukiskan dalam film. Secara prinsipal, ia hanya pasir yang telah diresapi air, karena friksi (gaya gesek) antar butiran pasir berkurang, sehingga menjadi campuran pasir dan air setengah cair yang sulit mendukung. Pasir hidup biasanya dijumpai di sekitar pantai.
Menurut Benn, bahwa hanya ada satu keadaan pasir hisap dapat menenggelamkan manusia (mati tenggelam), yaitu ketika bagian kepala lebih dulu masuk ke dalam, namun kemungkinan terperosok dengan cara demikian sangat kecil. Orang yang terperosok ke dalam pasir hisap hanya merasakan sedikit tekanan pada bagian dada, agak sulit bernapas, tidak akan mengancam jiwa. Air pasang di dekat pasir hidup barulah musuh yang menakutkan bagi korban yang terperangkap.
Orang-orang keliru menafsirkan bahwa dengan menggoyangkan kaki bisa melonggarkan pasir di sekitar badan, sehingga dengan demikian dapat membantu anggota badan untuk keluar dari dalam pasir. Ilmuwan terkait menuturkan, sebetulnya bukan begitu, gerakan demikian hanya akan mempercepat endapan tanah liat, memperkuat viskositas (sifat merekat) pasir hisap, meronta membabi buta hanya akan membuat korban terperosok lebih dalam.
Benn mengatakan, “cara untuk terlepas dari pasir hisap tetap ada, yaitu korban yang terperangkap harus menggerakkan secara perlahan kedua kakinya, agar air dan pasir semaksimal merembes masuk ke daerah hampa, dengan begitu akan dapat mengurangi tekanan badan si korban, sekaligus membuat pasir agar perlahan-lahan menggembur.
Selain itu, sang korban juga harus berusaha agar anggota badannya terpisah, sebab jika area permukaan pasir yang disentuh badan semakin besar, maka daya apung yang didapat akan semakin besar. Asalkan korban memiliki kesabaran yang cukup, dengan gerakan yang cukup tenang dan santai, maka secara perlahan pasti akan terbebas dari perangkap pasir hisap.
Selain itu hasil penelitian juga mendapati, saat suatu obyek terperosok ke dalam pasir hisap, kecepatan terbenamnya ditentukan oleh densitas obyek tersebut. Densitas pasir hidup umumnya 2 g/milliliter, sedangkan densitas manusia adalah 1g/milliliter. Di bawah densitas demikian, tubuh manusia yang terbenam ke pasir hidup tidak akan mati tenggelam, kerap akan berhenti sampai sebatas pinggang.
Selain itu peneliti juga mendapati, bahwa meskipun sejumlah obyek yang berdensitas lebih besar dari pasir hidup, tapi tetap bisa mengapung di atas pasir hidup. Dalam percobaan terkait, mereka kemudian meletakkan bola aluminium yang berdensitas 2.7g/mililiter di atas permukaan pasir hisap.
Dan meskipun densitasnya lebih besar dari pasir hidup. Namun karena mendapat pengaruh daya apung pasir hisap dan tegangan pasir, maka bola aluminium tetap bisa dengan tenang berada di permukaan pasir hidup. Bola tersebut tidak tenggelam hingga para peneliti menggetarkan pasir hisap dan membuat gerakan yang menyebabkan campuran lebih cair. Ketika melakukan hal ini, bola aluminium benar-benar seluruhnya tenggelam.
Namun saat menggunakan bola aluminium yang memiliki kerapatan sama dengan manusia yang berarti lebih rendah daripada kerapatan pasir hisap, bola tersebut tidak pernah tenggelam walaupun campuran diperlakukan dengan kasar.
Jatuhnya objek ke pasir hisap menyebabkan pastikel pasir bercampur air kehilangan kestabilan. Jika terus diberi tekanan, campuran tersebut akan berubah menjadi lebih cair di permukaan dan sangat padat di dasarnya.
“Semakin besar tekanannya, semakin banyak cairan yang terbentuk di pasir hisap sehingga gerakan korban membuatnya terperosok semakin dalam,” kata Daniel Bonn, pemimpin penelitian dari University of Amsterdam sebagaimana ditulis dalam jurnal Nature.
Berdasarkan pengukuran terhadap peralatan aluminium ini, meningkatkan tekanan fisik ke partikel sebesar 1 persen menyebabkan kecepatan tenggelamnya naik sejuta kali. Bonn menambahkan bahwa menarik benda dari pasir pada tahap ini membutuhkan kekuatan setara mengangkat mobil berukuran menengah.
Danau yang tampak tenang di selatan Inggris, fyord atau teluk sempit di Alaska yang indah tapi berbahaya dan daerah lainnya pernah terjadi peristiwa manusia terperangkap ke dalam pasir hidup.
Namun, sebagian besar orang kerap tidak pernah menjumpai pasir hidup, apalagi menyaksikan sendiri orang terperosok ke dalam pasir hidup atau mengalaminya sendiri. Kesan orang-orang terhadap pasir hidup terutama berdasarkan berbagai film yang ditontonnya. Suasana atau pemandangan yang diciptakan dalam film melukiskan pasir hidup adalah suatu momok yang dapat menghisap manusia ke lubang tak berdasar.
Akan larut jika permukan pasir hisap terganggu
Seorang ilmuwan dari Universitas Amsterdam, Belanda yakni Daniel Bonn pernah menemui seorang gembala setempat. Sang gembala menunjuk pasir hisap sambil berkata pada Bonn, bahwa pernah ada unta terperosok ke dalam kemudian lenyap tak berbekas.
Lalu segera ia melakukan penyelidikan terkait setelah kembai ke negaranya. Ia membawa sampel pasir ke Belanda dan menganalisis komposisinya. Setelah menemukan bahwa campuran tersebut terdiri atas pasir berkualitas tinggi, tanah liat, dan air garam, Bonn bersama timnya membuat tiruan pasir hisap dalam jumlah besar.
Ia mengamati dan menganalisa dengan cermat puluhan film yang melukiskan pemandangan pasir hisap yang menelan manusia itu, dan mendapati bahwa gambaran yang dilukiskan film-film ini sepenuhnya salah dan keliru.
Kemudian, di dalam laboratoriumnya, Bonn mencampurkan pasir, tanah liat dan air garam, membentuk sebuah maket pasir hidup dalam ruangan kecil untuk diteliti. Setelah percobaan secara berulang-ulang, personel peneliti yang dipimpin Bonn mendapati, bahwa perlu waktu beberapa hari untuk membuat pasir menjadi lengket.
Sebaliknya sangat mudah kalau hendak menghilangkan viskositasnya (sifat merekat), yakni cukup diberi tekanan yang pas di permukaannya. Permukaannya akan segera “larut” dengan cepat jika mendapat gangguan gerak, pasir di permukaan akan menjadi gembur (lembek), dan pasir di lapisan yang dangkal juga akan merosot ke bawah dengan cepat.
Gerakan perpindahan ini membuat benda yang bergerak di permukaan pasir tenggelam ke bawah, kemudian seiring dengan meningkatnya kedalaman penenggelaman tersebut, pasir yang jatuh ke bawah melalui gerakan perpindahan dari lapisan atas perlahan-lahan akan menyatu, lalu akan menciptakan endapan yang tebal, sehingga viskositas atau sifat merekat pasir bertambah cepat, mencegah obyek terperosok lebih jauh.
Butuh kekuatan mengangkat sebuah mobil
Menurut hasil penelitian, bahwa orang yang terperosok ke dalam pasir hisap umumnya tidak bisa bergerak, densitas pasir yang meningkat kemudian merekat di bagian anggota badan bawah yang terperosok dalam pasir hisap tersebut, membentuk tekanan yang sangat besas pada tubuh, membuat kita sangat sulit mengeluarkan tenaga.
Orang yang sangat besar tenaganya sekalipun juga sulit dalam waktu singkat bisa mengeluarkan korban yang terperangkap dalam pasir hisap tersebut. Setelah di kalkulasi peneliti terkait, bahwa untuk mengeluarkan satu kaki korban yang terperangkap dengan kecepatan 1 cm/ detik saja butuh kekuatan 100 ribu Newton, atau kurang lebih setara dengan kekuatan mengangkat sebuah mobil ukuran sedang.
Kecuali dibantu dengan mobil Derek, jika tidak sulit sekali mengeluarkan korban yang terperangkap dalam pasir hisap tersebut dalam waktu singkat. Hasil penelitian terkait juga menunjukan, menurut hitungan kekuatan ini, jika secara paksa menyeret korban, maka sebelum pasir hisap “melepaskan” korban yang terperangkap, tubuh korban sudah putus tertarik oleh kekuatan yang besar itu.
Resiko yang diakibatkan tindakan demikian jauh lebih berbahaya dibanding membiarkan korban tetap berada dalam pasir hisap tersebut untuk sementara waktu.
Sabar dan tenang
“Yang paling berbahaya adalah apabila pasir hisap cenderung menarik dengan cepat,” katanya. Tapi, kesabaran dapat menyelamatkan Anda. Jika ditunggu dengan sabar, partikel pasir lambat laun akan stabil sehingga daya apung campuran tersebut akan mengangkat Anda ke atas.
Kami mengetahui bahwa lapisan pasir di bawahnya lebih rapat sedangkan air lebih banyak di lapisan atas. Lapisan pasir yang sangat pekat di bawah sangat sedikit mengandung air sehingga sulit melepas kaki yang terperosok ke dalamnya,” lanjut Bonn.
Sarannya, tetaplah tenang dan biasanya Anda akan terapung. Luruskan punggung Anda untuk memperluas area yang bebas dan tunggu hingga kaki bebas dari pasir. Bonn juga menyarankan agar kaki bergerak untuk mengendalikan air sehingga Anda terapung. “Anda harus memasukkan air ke dalam pasir dan cara yang paling mudah adalah memutar-mutar sekitar kaki di dalam pasir hisap,” tambahnya.
Saran tersebut kemungkinan besar benar. Buktinya, bola aluminium kedua dalam percobaan ini tidak tenggelam lebih dari setengah bagian. Meskipun bola tersebut hanya empat milimeter diameternya, kerapatannya sama dengan manusia sehingga bisa digunakan sebagai model manusia.
Jumat, 13 Januari 2012
For turbidity, color and microbiological control
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 9
uniform. Small systems are the most frequent violators of federal regulations.
Microbiological violations account for the vast majority of cases, with failure to
monitor and report. Among others, violations exceeding SDWA maximum
contaminant levels (MCLs) are quite common. Bringing small water systems into
compliance requires applicable technologies, operator ability, financial resources,
and institutional arrangements. The 1986 SDWA amendments authorized USEPA
to set the best available technology (BAT) that can be incorporated in the design for
the purposes of complying with the National Primary Drinking Water Regulations
(NPDWR). Current BAT to maintain standards are as follows:
For turbidity, color and microbiological control in surface water treatment:
filtration. Common variations of filtration are conventional, direct, slow sand,
diatomaceous earth, and membranes.
For inactivation of microorganisms: disinfection. Typical disinfectants are
chlorine, chlorine dioxide, chloramines, and ozone.
For organic contaminant removal from surface water: packed-tower aeration,
granular activated carbon (GAC), powdered activated carbon (PAC), diffused
aeration, advanced oxidation processes, and reverse osmosis (RO).
For inorganic contaminants removal: membranes, ion exchange, activated
alumina, and GAC.
10 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
For corrosion control: typically, pH adjustment or corrosion inhibitors. The
implications of the 1986 amendments to the SDWA and new regulations have
resulted in rapid development and introduction of new technologies and equipment
for water treatment and monitoring over the last two decades. Biological processes
in particular have proven effective in removing biodegradable organic carbon that
may sustain the regrowth of potentially harmful microorganisms in the distribution
system, effective taste and odor control, and reduction in chlorine demand and DBP
formation potential. Both biologically-active sand or carbon filters provide cost
effective treatment of micro-contaminants than do physicochernical processes in
many cases. Pertinent to the subject matter cover in this volume, membrane
technology has been applied in drinking water treatment, partly because of
affordable membranes and demand to removal of many contaminants.
Microfiltration, ultrafiltration, nanofiltration and others have become common
names in the water industry. Membrane technology is experimented with for the
removal of microbes, such as Giardia and Cryptosporidium and for selective
removal of nitrate. In other instances, membrane technology is applied for removal
of DBP precursors, VOCs, and others.
Other treatment technologies that have potential for full-scale adoption are
photochemical oxidation using ozone and UV radiation or hydrogen peroxide for
destruction of refractory organic compounds. One example of a technology that
was developed outside North America and later emerged in the U.S. is the Haberer
process. This process combines contact flocculation, filtration, and powdered
activated carbon adsorption to meet a wide range of requirements for surface water
and groundwater purification.
Utilities are seeking not only to improve treatment, but also to monitor their
supplies for microbiological contaminants more effectively. Electro-optical sensors
are used to allow early detection of algal blooms in a reservoir and allow for
diagnosis of problems and guidance in operational changes. Gene probe technology
was first developed in response to the need for improved identification of microbes
in the field of clinical microbiology. Attempts are now being made by radiolabeled
and nonradioactive gene-probe assays with traditional detection methods for enteric
viruses and protozoan parasites, such as Giardia and Cryptosporidium. This
technique has the potential for monitoring water supplies for increasingly complex
groups of microbes.
In spite of the multitudinous regulations and standards that an existing public water
system must comply with, the principles of conventional water treatment process
have not changed significantly over half a century. Whether a filter contains sand,
anthracite, or both, slow or rapid rate, constant or declining rate, filtration is still
filtration, sedimentation is still sedimentation, and disinfection is still disinfection.
What has changed, however, are many tools that we now have in our engineering
arsenal. For example,, a supervisory control and data acquisition (SCADA) system
can provide operators and managers with accurate process control variables and
operation and maintenance records. In addition to being able to look at the various
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 11
options on the computer screen, engineers can conduct pilot plant studies of the
multiple variables inherent in water treatment plant design. Likewise, operators and
managers can utilize an ongoing pilot plant facility to optimize chemical feed and
develop important information needed for future expansion and upgrading.
Technology and ultimately equipment selection depends on the standards set by the
regulations. Drinking water standards are regulations that EPA sets to control the
level of contaminants in the nation's drinking water. These standards are part of the
Safe Drinking Water Act's "multiple barrier" approach to drinking water
protection, which includes assessing and protecting drinking water sources;
protecting wells and collection systems; making sure water is treated by qualified
operators; ensuring the integrity of distribution systems; and making information
available to the public on the quality of their drinking water. With the involvement
of EPA, states, tribes, drinking water utilities, communities and citizens, these
multiple barriers ensure that tap water in the U.S. and territories is safe to drink.
In most cases, EPA delegates responsibility for implementing drinking water
standards to states and tribes. There are two categories of drinking water standards:
* A National Primary Drinking Water Regulation (NPDWR or primary
standard) is a legally-enforceable standard that applies to public water
systems. Primary standards protect drinking water quality by limiting the
levels of specific contaminants that can adversely affect public health and
are known or anticipated to occur in water. They take the form of
Maximum Contaminant Levels (MCL) or Treatment Techniques (TT).
9 A National Secondary Drinking Water Regulation (NSDWR or secondary
standard) is a non-enforceable guideline regarding contaminants that may
cause cosmetic effects (such as skin or tooth discoloration) or aesthetic
effects (such as taste, odor, or color) in drinking water. EPA recommends
secondary standards to water systems but does not require systems to
comply. However, states may choose to adopt them as enforceable
standards. This information focuses on national primary standards.
Drinking water standards apply to public water systems (PWSs), which provide
water for human consumption through at least 15 service connections, or regularly
serve at least 25 individuals. Public water systems include municipal water
companies, homeowner associations, schools, businesses, campgrounds and
shopping malls. EPA considers input from many individuals and groups throughout
the rule-making process. One of the formal means by which EPA solicits the
assistance of its stakeholders is the National Drinking Water Advisory Council
(NDWAC). The 15-member committee was created by the Safe Drinking Water
Act. It is comprised of five members of the general public, five representatives of
state and local agencies concerned with water hygiene and public water supply, and
five representations of private organizations and groups demonstrating an active
interest in water hygiene and public water supply, including two members who are
associated with small rural public water systems.
12 WATERA ND WASTEWATER TREATMENT TECHNOLOGIES
NDWAC advises EPA's Administrator on all of the agency's activities relating to
drinking water. In addition to the NDWAC, representatives from water utilities,
environmental groups, public interest groups, states, tribes and the general public
are encouraged to take an active role in shaping the regulations, by participating in
public meetings and commenting on proposed rules. Special meetings are also held
to obtain input from minority and low-income communities, as well as
representatives of small businesses.
The 1996 Amendments to Safe Drinking Water Act require EPA to go through
several steps to determine, first, whether setting a standard is appropriate for a
particular contaminant, and if so, what the standard should be. Peer-reviewed
science and data support an intensive technological evaluation, which includes many
factors: occurrence in the environment; human exposure and risks of adverse health
effects in the general population and sensitive subpopulations; analytical methods
of detection; technical feasibility; and impacts of regulation on water systems, the
economy and public health. Considering public input throughout the process, EPA
must (1) identify drinking water problems; (2) establish priorities; and (3) set
standards.
EPA must first make determinations about which contaminants to regulate. These
determinations are based on health risks and the likelihood that the contaminant
occurs in public water systems at levels of concern. The National Drinking Water
Contaminant Candidate List (CCL), published March 2, 1998, lists contaminants
that (1) are not already regulated under SDWA; (2) may have adverse health
effects; (3) are known or anticipated to occur in public water systems; and (4) may
require regulations under SDWA. Contaminants on the CCL are divided into
priorities for regulation, health research and occurrence data collection.
In August 2001, EPA selected five contaminants from the regulatory priorities on
the CCL and determined whether to regulate them. To support these decisions, the
Agency determined that regulating the contaminants presents a meaningful
opportunity to reduce health risk. If the EPA determines regulations are necessary,
the Agency must propose them by August 2003, and finalize them by February
2005. In addition, the Agency will also select up to 30 unregulated contaminants
from the CCL for monitoring by public water systems serving at least 100,000
people. Currently, most of the unregulated contaminants with potential of occurring
in drinking water are pesticides and microbes. Every five years, EPA will repeat
the cycle of revising the CCL, making regulatory determinations for five
contaminants and identifying up to 30 contaminants for unregulated monitoring. In
addition, every six years, EPA will re-evaluate existing regulations to determine if
modifications are necessary. Beginning in August 1999, a new National
Contaminant Occurrence Database was developed to store data on regulated and
unregulated chemical, radiological, microbial and physical contaminants, and other
such contaminants likely to occur in finished, raw and source waters of public water
systems.
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 13
After reviewing health effects studies, EPA sets a Maximum Contaminant Level
Goal (MCLG), the maximum level of a contaminant in drinking water at which no
known or anticipated adverse effect on the health of persons would occur, and
which allows an adequate margin of safety. MCLGs are non-enforceable public
health goals. Since MCLGs consider only public health and not the limits of
detection and treatment technology, sometimes they are set at a level which water
systems cannot meet. When determining an MCLG, EPA considers the risk to
sensitive subpopulations (infants, children, the elderly, and those with compromised
immune systems) of experiencing a variety of adverse health effects.
Non-Carcinogens (excluding microbial contaminants): For chemicals that can
cause adverse non-cancer health effects, the MCLG is based on the reference dose.
A reference dose (RFD) is an estimate of the amount of a chemical that a person
can be exposed to on a daily basis that is not anticipated to cause adverse health
effects over a person's lifetime. In RFD calculations, sensitive subgroups are
included, and uncertainty may span an order of magnitude. The RFD is multiplied
by typical adult body weight (70 kg) and divided by daily water consumption (2
liters) to provide a Drinking Water Equivalent Level (DWEL). Note that the
DWEL is multiplied by a percentage of the total daily exposure contributed by
14 WATERA ND WASTEWATER TREATMENT TECHNOLOGIES
drinking water to determine the MCLG. This empirical factor is usually 20 percent,
but can be a higher value.
Chemical Contaminants (Carcinogens): If there is evidence that a chemical may
cause cancer, and there is no dose below which the chemical is considered safe, the
MCLG is set at zero. If a chemical is carcinogenic and a safe dose can be deter
mined, the MCLG is set at a level above zero that is safe.
Microbial Contaminants: For microbial contaminants that may present public
health risk, the MCLG is set at zero because ingesting one protozoa, virus, or
bacterium may cause adverse health effects. EPA is conducting studies to determine
whether there is a safe level above zero for some microbial contaminants. So far,
however, this has not been established.
Once the MCLG is determined, EPA sets an enforceable standard. In most cases,
the standard is a Maximum Contaminant Level (MCL), the maximum permissible
level of a contaminant in water which is delivered to any user of a public water
system. The MCL is set as close to the MCLG as feasible, which the Safe Drinking
Water Act defines as the level that may be achieved with the use of the best
available technology, treatment techniques, and other means which EPA finds are
available(after examination for efficiency under field conditions and not solely
under laboratory conditions) are available, taking cost into consideration. When
there is no reliable method that is economically and technically feasible to measure
a contaminant at particularly low concentrations, a Treatment Technique (TT) is
set rather than an MCL. A treatment technique (TT) is an enforceable procedure
or level of technological performance which public water systems must follow to
ensure control of a contaminant. Examples of Treatment Technique rules are the
Surface Water Treatment Rule (disinfection and filtration) and the Lead and Copper
Rule (optimized corrosion control). After determining a MCL or TT based on
affordable technology for large systems, EPA must complete an economic analysis
to determine whether the benefits of that standard justify the costs. If not, EPA may
adjust the MCL for a particular class or group of systems to a level that "maximizes
health risk reduction benefits at a cost that is justified by the benefits."
WHAT THE CURRENT DRINKING WATER STANDARDS ARE
The following matrices provide you with a summary of the NPDWRs or primary
standards. You should visit the EPA Web site (www.epa.gov) and become familiar
with the various documents that are publically available. You will not only find
these regulations there, but detailed information that explains the reasoning behind
each MCLG. You will also find the entire legislation on this site and can become
familiar with all of the subtleties of this piece of complex environmental legislation.
Tables 1 through 5 are derived from EPA Web site- www.epa.gov/safewater.
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 15
Table 1. NPDW Regulations for Microorganisms.
Microorganisms MCLG 1
(mg/L) z
: Cryptosporidium
I
Giardia lamblia
Heterotrophic n/a
l MCL or Potential Health Effects Sources of [
TT 1 from Ingestion of Water Contaminant in
. (mg/L) z . . Drinking Water .
as of Gastrointestinal illness Human and
(e.g., diarrhea, vomiting, animal fecal wastel
cramps) I
9 . !
01/01/02:
TT 3
TT 3
TT 3
Gastrointestinal illness
(e.g., diarrhea, vomiting,
cramps)
Human and
animal fecal waste l
HPC has no health effects, HPC measures a
plate count but can indicate how
effective treatment is at
controlling
microorganisms.
Legionella
Total Coliforms
(including fecal
coliform and E.
Coli)
TT 3
5.0% 4
Legionnaire's Disease,
commonly known as
.pneumonia
Used as an indicator that
other potentially harmful
bacteria may be present s
range of bacteria
that are naturally
present in the
environment
Found naturally in
water; multiplies
]in heating systems
Coliforms are
naturally present
in the
environment;
fecal coliforms
and E. coli come
from human and
animal fecal
waste.
Turbidity n/a TT 3 Turbidity, a measure of
water cloudiness, is used
to indicate water quality
and filtration effectiveness
(e.g., whether diseasejcausing
organisms are
ipresent). Higher turbidity
!is associated with higher J
levels of microorganisms
such as viruses, parasites
and some bacteria. These
organisms can cause
symptoms such as nausea,
cramps, diarrhea, and
associated headaches.
Soil runoff
Viruses (enteric)
i
TT s Gastrointestinal illness
(e.g.~ diarrhea/vomiting)
Human and
animal fecal waste l
uniform. Small systems are the most frequent violators of federal regulations.
Microbiological violations account for the vast majority of cases, with failure to
monitor and report. Among others, violations exceeding SDWA maximum
contaminant levels (MCLs) are quite common. Bringing small water systems into
compliance requires applicable technologies, operator ability, financial resources,
and institutional arrangements. The 1986 SDWA amendments authorized USEPA
to set the best available technology (BAT) that can be incorporated in the design for
the purposes of complying with the National Primary Drinking Water Regulations
(NPDWR). Current BAT to maintain standards are as follows:
For turbidity, color and microbiological control in surface water treatment:
filtration. Common variations of filtration are conventional, direct, slow sand,
diatomaceous earth, and membranes.
For inactivation of microorganisms: disinfection. Typical disinfectants are
chlorine, chlorine dioxide, chloramines, and ozone.
For organic contaminant removal from surface water: packed-tower aeration,
granular activated carbon (GAC), powdered activated carbon (PAC), diffused
aeration, advanced oxidation processes, and reverse osmosis (RO).
For inorganic contaminants removal: membranes, ion exchange, activated
alumina, and GAC.
10 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
For corrosion control: typically, pH adjustment or corrosion inhibitors. The
implications of the 1986 amendments to the SDWA and new regulations have
resulted in rapid development and introduction of new technologies and equipment
for water treatment and monitoring over the last two decades. Biological processes
in particular have proven effective in removing biodegradable organic carbon that
may sustain the regrowth of potentially harmful microorganisms in the distribution
system, effective taste and odor control, and reduction in chlorine demand and DBP
formation potential. Both biologically-active sand or carbon filters provide cost
effective treatment of micro-contaminants than do physicochernical processes in
many cases. Pertinent to the subject matter cover in this volume, membrane
technology has been applied in drinking water treatment, partly because of
affordable membranes and demand to removal of many contaminants.
Microfiltration, ultrafiltration, nanofiltration and others have become common
names in the water industry. Membrane technology is experimented with for the
removal of microbes, such as Giardia and Cryptosporidium and for selective
removal of nitrate. In other instances, membrane technology is applied for removal
of DBP precursors, VOCs, and others.
Other treatment technologies that have potential for full-scale adoption are
photochemical oxidation using ozone and UV radiation or hydrogen peroxide for
destruction of refractory organic compounds. One example of a technology that
was developed outside North America and later emerged in the U.S. is the Haberer
process. This process combines contact flocculation, filtration, and powdered
activated carbon adsorption to meet a wide range of requirements for surface water
and groundwater purification.
Utilities are seeking not only to improve treatment, but also to monitor their
supplies for microbiological contaminants more effectively. Electro-optical sensors
are used to allow early detection of algal blooms in a reservoir and allow for
diagnosis of problems and guidance in operational changes. Gene probe technology
was first developed in response to the need for improved identification of microbes
in the field of clinical microbiology. Attempts are now being made by radiolabeled
and nonradioactive gene-probe assays with traditional detection methods for enteric
viruses and protozoan parasites, such as Giardia and Cryptosporidium. This
technique has the potential for monitoring water supplies for increasingly complex
groups of microbes.
In spite of the multitudinous regulations and standards that an existing public water
system must comply with, the principles of conventional water treatment process
have not changed significantly over half a century. Whether a filter contains sand,
anthracite, or both, slow or rapid rate, constant or declining rate, filtration is still
filtration, sedimentation is still sedimentation, and disinfection is still disinfection.
What has changed, however, are many tools that we now have in our engineering
arsenal. For example,, a supervisory control and data acquisition (SCADA) system
can provide operators and managers with accurate process control variables and
operation and maintenance records. In addition to being able to look at the various
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 11
options on the computer screen, engineers can conduct pilot plant studies of the
multiple variables inherent in water treatment plant design. Likewise, operators and
managers can utilize an ongoing pilot plant facility to optimize chemical feed and
develop important information needed for future expansion and upgrading.
Technology and ultimately equipment selection depends on the standards set by the
regulations. Drinking water standards are regulations that EPA sets to control the
level of contaminants in the nation's drinking water. These standards are part of the
Safe Drinking Water Act's "multiple barrier" approach to drinking water
protection, which includes assessing and protecting drinking water sources;
protecting wells and collection systems; making sure water is treated by qualified
operators; ensuring the integrity of distribution systems; and making information
available to the public on the quality of their drinking water. With the involvement
of EPA, states, tribes, drinking water utilities, communities and citizens, these
multiple barriers ensure that tap water in the U.S. and territories is safe to drink.
In most cases, EPA delegates responsibility for implementing drinking water
standards to states and tribes. There are two categories of drinking water standards:
* A National Primary Drinking Water Regulation (NPDWR or primary
standard) is a legally-enforceable standard that applies to public water
systems. Primary standards protect drinking water quality by limiting the
levels of specific contaminants that can adversely affect public health and
are known or anticipated to occur in water. They take the form of
Maximum Contaminant Levels (MCL) or Treatment Techniques (TT).
9 A National Secondary Drinking Water Regulation (NSDWR or secondary
standard) is a non-enforceable guideline regarding contaminants that may
cause cosmetic effects (such as skin or tooth discoloration) or aesthetic
effects (such as taste, odor, or color) in drinking water. EPA recommends
secondary standards to water systems but does not require systems to
comply. However, states may choose to adopt them as enforceable
standards. This information focuses on national primary standards.
Drinking water standards apply to public water systems (PWSs), which provide
water for human consumption through at least 15 service connections, or regularly
serve at least 25 individuals. Public water systems include municipal water
companies, homeowner associations, schools, businesses, campgrounds and
shopping malls. EPA considers input from many individuals and groups throughout
the rule-making process. One of the formal means by which EPA solicits the
assistance of its stakeholders is the National Drinking Water Advisory Council
(NDWAC). The 15-member committee was created by the Safe Drinking Water
Act. It is comprised of five members of the general public, five representatives of
state and local agencies concerned with water hygiene and public water supply, and
five representations of private organizations and groups demonstrating an active
interest in water hygiene and public water supply, including two members who are
associated with small rural public water systems.
12 WATERA ND WASTEWATER TREATMENT TECHNOLOGIES
NDWAC advises EPA's Administrator on all of the agency's activities relating to
drinking water. In addition to the NDWAC, representatives from water utilities,
environmental groups, public interest groups, states, tribes and the general public
are encouraged to take an active role in shaping the regulations, by participating in
public meetings and commenting on proposed rules. Special meetings are also held
to obtain input from minority and low-income communities, as well as
representatives of small businesses.
The 1996 Amendments to Safe Drinking Water Act require EPA to go through
several steps to determine, first, whether setting a standard is appropriate for a
particular contaminant, and if so, what the standard should be. Peer-reviewed
science and data support an intensive technological evaluation, which includes many
factors: occurrence in the environment; human exposure and risks of adverse health
effects in the general population and sensitive subpopulations; analytical methods
of detection; technical feasibility; and impacts of regulation on water systems, the
economy and public health. Considering public input throughout the process, EPA
must (1) identify drinking water problems; (2) establish priorities; and (3) set
standards.
EPA must first make determinations about which contaminants to regulate. These
determinations are based on health risks and the likelihood that the contaminant
occurs in public water systems at levels of concern. The National Drinking Water
Contaminant Candidate List (CCL), published March 2, 1998, lists contaminants
that (1) are not already regulated under SDWA; (2) may have adverse health
effects; (3) are known or anticipated to occur in public water systems; and (4) may
require regulations under SDWA. Contaminants on the CCL are divided into
priorities for regulation, health research and occurrence data collection.
In August 2001, EPA selected five contaminants from the regulatory priorities on
the CCL and determined whether to regulate them. To support these decisions, the
Agency determined that regulating the contaminants presents a meaningful
opportunity to reduce health risk. If the EPA determines regulations are necessary,
the Agency must propose them by August 2003, and finalize them by February
2005. In addition, the Agency will also select up to 30 unregulated contaminants
from the CCL for monitoring by public water systems serving at least 100,000
people. Currently, most of the unregulated contaminants with potential of occurring
in drinking water are pesticides and microbes. Every five years, EPA will repeat
the cycle of revising the CCL, making regulatory determinations for five
contaminants and identifying up to 30 contaminants for unregulated monitoring. In
addition, every six years, EPA will re-evaluate existing regulations to determine if
modifications are necessary. Beginning in August 1999, a new National
Contaminant Occurrence Database was developed to store data on regulated and
unregulated chemical, radiological, microbial and physical contaminants, and other
such contaminants likely to occur in finished, raw and source waters of public water
systems.
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 13
After reviewing health effects studies, EPA sets a Maximum Contaminant Level
Goal (MCLG), the maximum level of a contaminant in drinking water at which no
known or anticipated adverse effect on the health of persons would occur, and
which allows an adequate margin of safety. MCLGs are non-enforceable public
health goals. Since MCLGs consider only public health and not the limits of
detection and treatment technology, sometimes they are set at a level which water
systems cannot meet. When determining an MCLG, EPA considers the risk to
sensitive subpopulations (infants, children, the elderly, and those with compromised
immune systems) of experiencing a variety of adverse health effects.
Non-Carcinogens (excluding microbial contaminants): For chemicals that can
cause adverse non-cancer health effects, the MCLG is based on the reference dose.
A reference dose (RFD) is an estimate of the amount of a chemical that a person
can be exposed to on a daily basis that is not anticipated to cause adverse health
effects over a person's lifetime. In RFD calculations, sensitive subgroups are
included, and uncertainty may span an order of magnitude. The RFD is multiplied
by typical adult body weight (70 kg) and divided by daily water consumption (2
liters) to provide a Drinking Water Equivalent Level (DWEL). Note that the
DWEL is multiplied by a percentage of the total daily exposure contributed by
14 WATERA ND WASTEWATER TREATMENT TECHNOLOGIES
drinking water to determine the MCLG. This empirical factor is usually 20 percent,
but can be a higher value.
Chemical Contaminants (Carcinogens): If there is evidence that a chemical may
cause cancer, and there is no dose below which the chemical is considered safe, the
MCLG is set at zero. If a chemical is carcinogenic and a safe dose can be deter
mined, the MCLG is set at a level above zero that is safe.
Microbial Contaminants: For microbial contaminants that may present public
health risk, the MCLG is set at zero because ingesting one protozoa, virus, or
bacterium may cause adverse health effects. EPA is conducting studies to determine
whether there is a safe level above zero for some microbial contaminants. So far,
however, this has not been established.
Once the MCLG is determined, EPA sets an enforceable standard. In most cases,
the standard is a Maximum Contaminant Level (MCL), the maximum permissible
level of a contaminant in water which is delivered to any user of a public water
system. The MCL is set as close to the MCLG as feasible, which the Safe Drinking
Water Act defines as the level that may be achieved with the use of the best
available technology, treatment techniques, and other means which EPA finds are
available(after examination for efficiency under field conditions and not solely
under laboratory conditions) are available, taking cost into consideration. When
there is no reliable method that is economically and technically feasible to measure
a contaminant at particularly low concentrations, a Treatment Technique (TT) is
set rather than an MCL. A treatment technique (TT) is an enforceable procedure
or level of technological performance which public water systems must follow to
ensure control of a contaminant. Examples of Treatment Technique rules are the
Surface Water Treatment Rule (disinfection and filtration) and the Lead and Copper
Rule (optimized corrosion control). After determining a MCL or TT based on
affordable technology for large systems, EPA must complete an economic analysis
to determine whether the benefits of that standard justify the costs. If not, EPA may
adjust the MCL for a particular class or group of systems to a level that "maximizes
health risk reduction benefits at a cost that is justified by the benefits."
WHAT THE CURRENT DRINKING WATER STANDARDS ARE
The following matrices provide you with a summary of the NPDWRs or primary
standards. You should visit the EPA Web site (www.epa.gov) and become familiar
with the various documents that are publically available. You will not only find
these regulations there, but detailed information that explains the reasoning behind
each MCLG. You will also find the entire legislation on this site and can become
familiar with all of the subtleties of this piece of complex environmental legislation.
Tables 1 through 5 are derived from EPA Web site- www.epa.gov/safewater.
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 15
Table 1. NPDW Regulations for Microorganisms.
Microorganisms MCLG 1
(mg/L) z
: Cryptosporidium
I
Giardia lamblia
Heterotrophic n/a
l MCL or Potential Health Effects Sources of [
TT 1 from Ingestion of Water Contaminant in
. (mg/L) z . . Drinking Water .
as of Gastrointestinal illness Human and
(e.g., diarrhea, vomiting, animal fecal wastel
cramps) I
9 . !
01/01/02:
TT 3
TT 3
TT 3
Gastrointestinal illness
(e.g., diarrhea, vomiting,
cramps)
Human and
animal fecal waste l
HPC has no health effects, HPC measures a
plate count but can indicate how
effective treatment is at
controlling
microorganisms.
Legionella
Total Coliforms
(including fecal
coliform and E.
Coli)
TT 3
5.0% 4
Legionnaire's Disease,
commonly known as
.pneumonia
Used as an indicator that
other potentially harmful
bacteria may be present s
range of bacteria
that are naturally
present in the
environment
Found naturally in
water; multiplies
]in heating systems
Coliforms are
naturally present
in the
environment;
fecal coliforms
and E. coli come
from human and
animal fecal
waste.
Turbidity n/a TT 3 Turbidity, a measure of
water cloudiness, is used
to indicate water quality
and filtration effectiveness
(e.g., whether diseasejcausing
organisms are
ipresent). Higher turbidity
!is associated with higher J
levels of microorganisms
such as viruses, parasites
and some bacteria. These
organisms can cause
symptoms such as nausea,
cramps, diarrhea, and
associated headaches.
Soil runoff
Viruses (enteric)
i
TT s Gastrointestinal illness
(e.g.~ diarrhea/vomiting)
Human and
animal fecal waste l
HANDBOOK OF WATER AND WASTEWATER TREATMENT TECHNOLOGIES
HANDBOOK OF WATER AND WASTEWATER TREATMENT TECHNOLOGIES
Chapter I
AN OVERVIEW OF
WATER AND WASTEWATER
TREATMENT
INTRODUCTION
We may organize water treatment technologies into three general areas: Physical
Methods, Chemical Methods, and Energy Intensive Methods. Physical methods of
wastewater treatment represent a body of technologies that we refer largely to as
solid-liquid separations techniques, of which filtration plays a dominant role.
Filtration technology can be broken into two general categories - conventional and
non-conventional. This technology is an integral component of drinking water and
wastewater treatment applications. It is, however, but one unit process within a
modern water treatment plant scheme, whereby there are a multitude of equipment
and technology options to select from depending upon the ultimate goals of
treatment. To understand the role of filtration, it is important to make distinctions
not only with the other technologies employed in the cleaning and purification of
industrial and municipal waters, but also with the objectives of different unit
processes.
Chemical methods of treatment rely upon the chemical interactions of the
contaminants we wish to remove from water, and the application of chemicals that
either aid in the separation of contaminants from water, or assist in the destruction
or neutralization of harmful effects associated with contaminants. Chemical
treatment methods are applied both as stand-alone technologies, and as an integral
part of the treatment process with physical methods.
Among the energy intensive technologies, thermal methods have a dual role in
water treatment applications. They can be applied as a means of sterilization, thus
providing high quality drinking water, and/or these technologies can be applied to
the processing of the solid wastes or sludge, generated from water treatment
applications. In the latter cases, thermal methods can be applied in essentially the
same manner as they are applied to conditioning water, namely to sterilize sludge
contaminated with organic contaminants, and/or these technologies can be applied
to volume reduction. Volume reduction is a key step in water treatment operations,
2 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
because ultimately there is a tradeoff between polluted water and hazardous solid
waste.
Energy intensive technologies include electrochemical techniques, which by and
large are applied to drinking water applications. They represent both sterilization
and conditioning of water to achieve a palatable quality.
All three of these technology groups can be combined in water treatment, or they
may be used in select combinations depending upon the objectives of water
treatment. Among each of the general technology classes, there is a range of both
hardware and individual technologies that one may select from. The selection of not
only the proper unit process and hardware from within each technology group, but
the optimum combinations of hardware and unit processes from the four groups
depends upon such factors as:
1. How clean the final water effluent from our plant must be;
2. The quantities and nature of the influent water we need to treat;
3. The physical and chemical properties of the pollutants we need to remove
or render neutral in the effluent water;
4. The physical, chemical and thermodynamic properties of the solid wastes
generated from treating water; and
5. The cost of treating water, including the cost of treating, processing and
finding a home for the solid wastes.
To understand this better, let us step back and start from a very fundamental
viewpoint. All processes are comprised of a number of unit processes, which are
in turn made up of unit operations. Unit processes are distinct stages of a
manufacturing operation. They each focus on one stage in a series of stages,
successfully bringing a product to its final form. In this regard, a wastewater
treatment plant, whether industrial, a municipal wastewater treatment facility, or
a drinking water purification plant, is no different than, say, a synthetic rubber
manufacturing plant or an oil refinery. In the case of a rubber producing plant,
various unit processes are applied to making intermediate forms of the product,
which ultimately is in a final form of a rubber bale, that is sold to the consumer.
The individual unit processes in this case are comprised of: (1) a catalyst reparation
stage - a pre-preparation stage for monomers and catalyst additives; (2)
polymerization - where an intermediate stage of the product is synthesized in the
form of a latex or polymer suspended as a dilute solution in a hydrocarbon diluent;
(3) followed by finishing - where the rubber is dried, residual diluent is removed
and recovered, and the rubber is dried and compressed into a bale and packaged for
sale. Each of these unit process operations are in turn comprised of individual unit
operations, whereby a particular technology or group pf technologies are applied,
which, in turn, define a piece of equipment that is used along the production line.
Drinking water and wastewater treatment plants are essentially no different. There
are individual unit processes that comprise each of these types of plants that are
applied in a succession of operations, with each stage aimed at improving the
quality of the water as established by a set of product-performance criteria. The
criteria focuses on the quality of the final water, which in the case of drinking water
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 3
is established based upon legal criteria (e.g., the Safe Drinking Water Act, SDWA),
and if non-potable or process plant water, may be operational criteria (e.g., nonbrackish
waters to prevent scaling of heat exchange equipment).
The number and complexity of unit processes and in turn unit operations
comprising a water purification or wastewater treatment facility are functions of the
legal and operational requirements of the treated water, the nature and degree of
contamination of the incoming water (raw water to the plant), and the quantities of
water to be processed. This means then, that water treatment facilities from a
design and operational standpoints vary, but they do rely on overlapping and even
identical unit processes.
If we start with the first technology group, then filtration should be thought of as
both a unit process and a unit operation within a water treatment facility. As a
separate unit process, its objective is quite clear: namely, to remove suspended
solids. When we combine this technology with chemical methods and apply
sedimentation and clarification (other physical separation methods), we can extend
the technology to removing dissolved particulate matter as well. The particulate
matter may be biological, microbial or chemical in nature. As such, the operation
stands alone within its own block within the overall manufacturing train of the
plant. Examples of this would be the roughening and polishing stages of water
treatment. In turn, we may select or specify specific pieces of filtration equipment
for these unit processes.
The above gives us somewhat of an idea of the potential complexity of choosing the
optimum group of technologies and hardware needed in treating water. To develop
a cost-effective design, we need to understand not only what each of the unit
processes are, but obtain a working knowledge of the operating basis and ranges
for the individual hardware. That, indeed, is the objective of this book; namely, to
take a close look at the equipment options available to us in each technology group,
but not individually. Rather, to achieve an integrated and well thought out design,
we need to understand how unit processes and unit operations complimem each
other in the overall design.
This first chapter is for orientation purposes. Its objectives are to provide an
overview of water treatment and purification roles and technologies, and to
introduce terminology that will assist you in understanding the relation of the
various technologies to the overall schemes employed in waster treatment
applications. Recommended resources that you can refer to for more in-depth
information are included at the end of each chapter. The organization of these
resources are generally provided by subject matter. Also, you will find a section for
the student at the end of each chapter that provides a list of Questions for Thinking
and Discussing. These will assist in reinforcing some of the principles and concepts
presented in each chapter, if the book is used as a primary or supplement textbook.
We should recognize that the technology options for water treatment are great, and
quite often the challenge lies with the selection of the most cost-effective
combinations of unit processes and operations. In this regard, cost-factors are
examined where appropriate in our discussions within later chapters.
4 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
WHAT WE MEAN BY WATER PURIFICATION
When we refer to water purification, it makes little sense to discuss the subject
without first identifying the contaminants that we wish to remove from water. Also,
the source of the water is of importance. Our discussion at this point focuses on
drinking water. Groundwater sources are of a particular concern, because there are
many communities throughout the U.S. that rely on this form. The following are
some of the major contaminants that are of concern in water purification
applications, as applied to drinking water sources, derived from groundwater.
Heavy Metals - Heavy metals represent problems in terms of groundwater
pollution. The best way to identify their presence is by a lab test of the water or by
contacting county health departments. There are concerns of chronic exposure to
low levels of heavy metals in drinking water.
T u r b i d i t y - Turbidity refers to suspended solids, i.e. muddy water, is very turbid.
Turbidity is undesirable for three reasons:
aesthetic considerations,
solids may contain heavy metals, pathogens or other contaminants,
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 5
9 turbidity decreases the effectiveness of water treatment techniques by
shielding pathogens from chemical or thermal damage, or in the case of
UV (ultra violet) treatment, absorbing the UV light itself.
Organic Compounds - Water can be contaminated by a number of organic
compounds, such as chloroform, gasoline, pesticides, and herbicides from a variety
of industrial and agricultural operations or applications. These contaminants must
be identified in a lab test. It is unlikely groundwater will suddenly become
contaminated, unless a quantity of chemicals is allowed to enter a well or
penetrating the aquifer. One exception is when the aquifer is located in limestone.
Not only will water flow faster through limestone, but the rock is prone to forming
vertical channels or sinkholes that will rapidly allow contamination from surface
water. Surface water may show great variations in chemical contamination levels
due to differences in rainfall, seasonal crop cultivation, and industrial effluent
levels. Also, some hydrocarbons (the chlorinated hydrocarbons in particular) form
a type of contaminant that is especially troublesome. These are a group of
chemicals known as dense nonaqueous phase liquids, or DNAPLs. These include
chemicals used in dry cleaning, wood preservation, asphalt operations, machining,
and in the production and repair of automobiles, aviation equipment, munitions, and
electrical equipment. These substances are heavier than water and they sink quickly
into the ground. This makes spills of DNAPLs more difficult to handle than spills
of petroleum products. As with petroleum products, the problems are caused by
groundwater dissolving some of the compounds in these volatile substances. These
compounds can then move with the groundwater flow. Except in large cities,
drinking water is rarely tested for these contaminants. Disposal of chemicals that
have low water solubility and a density greater than water result in the formation
of distinct areas of pure residual contamination in soils and groundwater. These
chemicals are typically solvents and are collectively referred to as Dense Non-
Aqueous Phase Liquids (DNAPLs). Because of their relatively high density, they
tend to move downward through soils and groundwater, leaving small amounts
along the migratory pathway, until they reach an impermeable layer where they
collect in discrete pools. Once the DNAPLs have reached an aquitard they tend to
move laterally under the influence of gravity and to slowly dissolve into the
groundwater, providing a long-term source for low level contamination of
groundwater. Because of their movement patterns DNAPL contamination is
difficult to detect, characterize and remediate.
Pathogens - These include protozoa, bacteria, and viruses. Protozoa cysts are the
largest pathogens in drinking water, and are responsible for many of the waterborne
disease cases in the U.S. Protozoa cysts range is size from 2 to 15 #m (a micron
is one millionth of a meter), but can squeeze through smaller openings. In order to
insure cyst filtration, filters with a absolute pore size of 1 #m or less should be used.
The two most common protozoa pathogens are Giardia lamblia (Giardia) and
Cryptosporidium (Crypto). Both organisms have caused numerous deaths in recent
years in the U.S. and Canada, the deaths occurring in the young and elderly, and
the sick and immune compromised. Many deaths were a result of more than one of
6 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
these conditions. Neither disease is likely to be fatal to a healthy adult, even if
untreated. For example in Milwaukee in April of 1993, of 400,000 who were
diagnosed with Crypto, only 54 deaths were linked to the outbreak, 84 % of whom
were AIDS patients. Outside of the U.S. and other developed countries, protozoa
are responsible for many cases of amoebic dysentery, but so far this has not been
a problem in the U.S., due to the application of more advanced wastewater
treatment technologies. This could change during a survival situation. Tests have
found Giardia and/or Crypto in up to 5 % of vertical wells and 26 % of springs in
the U.S.
Bacteria are smaller than protozoa and are responsible for many diseases, such as
typhoid fever, cholera, diarrhea, and dysentery. Pathogenic bacteria range in size
from 0.2 to 0.6 ~m, and a 0.2 ~m filter is necessary to prevent transmission.
Contamination of water supplies by bacteria is blamed for the cholera epidemics,
which devastate undeveloped countries from time to time. Even in the U.S., E. coli
is frequently found to contaminated water supplies. Fortunately, E. coli is relatively
harmless as pathogens go, and the problem isn't so much with E. coli found, but
the fear that other bacteria may have contaminated the water as well. Never the
less, dehydration from diarrhea caused by E. coli has resulted in fatalities.
One of hundreds of strains of the bacterium Escherichia coli, E. coli O157:H7 is
an emerging cause of food borne and waterborne illness. Although most strains of
E. coli are harmless and live in the intestines of healthy humans and animals, this
strain produces a powerful toxin and can cause severe illness. E. coli 0157:H7 was
first recognized as a cause of illness during an outbreak in 1982 traced to
contaminated hamburgers. Since then, most infections are believed to have come
from eating undercooked ground beef. However, some have been waterborne. The
presence of E. coli in water is a strong indication of recent sewage or animal waste
contamination. Sewage may contain many types of disease-causing organisms.
Since E. coli comes from human and animal wastes, it most often enters drinking
water sources via rainfalls, snow melts, or other types of precipitation, E. coli may
be washed into creeks, rivers, streams, lakes, or groundwater. When these waters
are used as sources of drinking water and the water is not treated or inadequately
treated, E. coli may end up in drinking water. E. coli 0157 :H7 is one of hundreds
of strains of the bacterium E. coli. Although most strains are harmless and live in
the intestines of healthy humans and animals, this strain produces a powerful toxin
and can cause severe illness. Infection often causes severe bloody diarrhea and
abdominal cramps; sometimes the infection causes non-bloody diarrhea.
Frequently, no fever is present. It should be noted that these symptoms are common
to a variety of diseases, and may be caused by sources other than contaminated
drinking water. In some people, particularly children under 5 years of age and the
elderly, the infection can also cause a complication, called hemolytic uremic
syndrome, in which the red blood cells are destroyed and the kidneys fail. About
2%-7% of infections lead to this complication. In the U.S. hemolytic uremic
syndrome is the principal cause of acute kidney failure in children, and most cases
of hemolytic uremic syndrome are caused by E. coli O157:H7. Hemolytic uremic
AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 7
syndrome is a life-threatening condition usually treated in an intensive care unit.
Blood transfusions and kidney dialysis are often required. With intensive care, the
death rate for hemolytic uremic syndrome is 3 %-5 %. Symptoms usually appear
within 2 to 4 days, but can take up to 8 days. Most people recover without
antibiotics or other specific treatment in 5-10 days. There is no evidence that
antibiotics improve the course of disease, and it is thought that treatment with some
antibiotics may precipitate kidney complications. Antidiarrheal agents, such as
loperamide (Imodium), should also be avoided. The most common methods of
treating water contaminated with E. coli is by using chlorine, ultra-violet light, or
ozone, all of which act to kill or inactivate E. coli. Systems, using surface water
sources, are required to disinfect to ensure that all bacterial contamination is
inactivated, such as E. coll. Systems using ground water sources are not required
to disinfect, although many of them do. According to EPA regulations, a system
that operates at least 60 days per year, and serves 25 people or more or has 15 or
more service connections, is regulated as a public water system under the Safe
Drinking Water Act (SDWA). If a system is not a public water system as defined
by EPA's regulations, it is not regulated under the SDWA, although it may be
regulated by state or local authorities. Under the SDWA, EPA requires public
water systems to monitor for coliform bacteria. Systems analyze first for total
coliform, because this test is faster to produce results. Any time that a sample is
positive for total coliform, the same sample must be analyzed for either fecal
coliform or E. coli. Both are indicators of contamination with animal waste or
human sewage. The largest public water systems (serving millions of people) must
take at least 480 samples per month. Smaller systems must take at least five samples
a month, unless the state has conducted a sanitary survey - a survey in which a
state inspector examines system components and ensures they will protect public
health- at the system within the last five years.
Viruses are the 2nd most problematic pathogen, behind protozoa. As with protozoa,
most waterborne viral diseases don't present a lethal hazard to a healthy adult.
Waterborne pathogenic viruses range in size from 0.020-0.030/~m, and are too
small to be filtered out by a mechanical filter. All waterborne enteric viruses
affecting humans occur solely in humans, thus animal waste doesn't present much
of a viral threat. At the present viruses don't present a major hazard to people
drinking surface water in the U.S., but this could change in a survival situation as
the level of human sanitation is reduced. Viruses do tend to show up even in remote
areas, so a case can be made for eliminating them now.
THE DRINKING WATER STANDARDS
When the objective of water treatment is to provide drinking water, then we need
to select technologies that are not only the best available, but those that will meet
local and national quality standards. The primary goals of a water treatment plant
8 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
for over a century have
remained practically the same:
namely to produce water that is
biologically and chemically
safe, is appealing to the
consumer, and is noncorrosive
and nonscaling. Today, plant
design has become very
complex from discovery of
seemingly innumerable
chemical substances, the
multiplying of regulations, and
trying to satisfy more
discriminating palates. In
addition to the basics, designers must now keep in mind all manner of legal
mandates, as well as public concerns and en-vironmental considerations, to provide
an initial prospective of water works engineering planning, design, and operation.
The growth of community water supply systems in the United States started in the
early 1800s. By 1860, over 400, and by the turn of the century over 3000 major
water systems had been built to serve major cities and towns. Many older plants
were equipped with slow sand filters. In the mid 1890s, the Louisville Water
Company introduced the technologies of coagulation with rapid sand filtration.
The first application of chlorine in potable water was introduced in the 1830s for
taste and odor control, at that time diseases were thought to be spread by odors. It
was not until the 1890s and the advent of the germ theory of disease that the
importance of disinfection in potable water was understood. Chlorination was first
introduced on a practical scale in 1908 and then became a common practice.
Federal authority to establish standards for drinking water systems originated with
the enactment by Congress in 1883 of the Interstate Quarantine Act, which
authorized the Director of the United States Public Health Services (USPHS) to
establish and enforce regulations to prevent the introduction, transmission, or
spread of communicable diseases.
Today resource limitations have caused the United States Environmental Protection
Agency (USEPA) to reassess schedules for new rules. A 1987 USEPA survey
indicated there were approximately 202,000 public water systems in the United
States. About 29 percent of these were community water systems, which serve
approximately 90 percent of the population. Of the 58,908 community systems that
serve about 226 million people, 51,552 were classified as "small" or "very small."
Each of these systems at an average serves a population of fewer than 3300 people.
The total population served by these systems is approximately 25 million people.
These figures provide us with a magnitude of scale in meeting drinking water
demands in the United States. Compliance with drinking water standards is not
8 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
for over a century have
remained practically the same:
namely to produce water that is
biologically and chemically
safe, is appealing to the
consumer, and is noncorrosive
and nonscaling. Today, plant
design has become very
complex from discovery of
seemingly innumerable
chemical substances, the
multiplying of regulations, and
trying to satisfy more
discriminating palates. In
addition to the basics, designers must now keep in mind all manner of legal
mandates, as well as public concerns and en-vironmental considerations, to provide
an initial prospective of water works engineering planning, design, and operation.
The growth of community water supply systems in the United States started in the
early 1800s. By 1860, over 400, and by the turn of the century over 3000 major
water systems had been built to serve major cities and towns. Many older plants
were equipped with slow sand filters. In the mid 1890s, the Louisville Water
Company introduced the technologies of coagulation with rapid sand filtration.
The first application of chlorine in potable water was introduced in the 1830s for
taste and odor control, at that time diseases were thought to be spread by odors. It
was not until the 1890s and the advent of the germ theory of disease that the
importance of disinfection in potable water was understood. Chlorination was first
introduced on a practical scale in 1908 and then became a common practice.
Federal authority to establish standards for drinking water systems originated with
the enactment by Congress in 1883 of the Interstate Quarantine Act, which
authorized the Director of the United States Public Health Services (USPHS) to
establish and enforce regulations to prevent the introduction, transmission, or
spread of communicable diseases.
Today resource limitations have caused the United States Environmental Protection
Agency (USEPA) to reassess schedules for new rules. A 1987 USEPA survey
indicated there were approximately 202,000 public water systems in the United
States. About 29 percent of these were community water systems, which serve
approximately 90 percent of the population. Of the 58,908 community systems that
serve about 226 million people, 51,552 were classified as "small" or "very small."
Each of these systems at an average serves a population of fewer than 3300 people.
The total population served by these systems is approximately 25 million people.
These figures provide us with a magnitude of scale in meeting drinking water
demands in the United States. Compliance with drinking water standards is not
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