dasar – dasar Teknik pengolahan air

1. dasar – dasarTeknikpengolahan air

2. PermasalahandanTujuan Permasalahan: • Air bakutidakmemenuhi standard • Faktorekonomi (biayatinggi) • Faktorsosial (kurangnyakesadarandanpengetahuan) Tujuan: • Menjadikan air baku yang kurang/tidakmemenuhi standard menjadi air bersih yang memenuhi standard sesuaidenganperuntukannyaberdasarkan standard peraturan yang berlaku.

3. Standard Kualitas Air PeraturanPemerintahRepublik Indonesia No. 82 Tahun 2001 tentangPengelolaanKualitas Air danPengendalianPencemaran Air

4. KarakteristikSumber Air

5. MetodaPengolahan Air Perubahankualitas air terjadiakibatprosesfisik PengolahanFisika Perubahankualitas air terjadiakibatreaksi-reaksikimiawi Pengolahan Kimia Perubahankualitas air terjadiakibatkehadiranmakhlukhidup PengolahanBiologi

6. PengolahanFisik

7. Penapisan (Screening) : “Screening may be defined as consisting of those processes used to remove grit, heavy solids and floatable material from wastewater by using grit settling, coarse screening (bar racks), medium screening and comminution/grinding” Screening is a preliminary treatment system that used to protect pumps, valves, pipelines and other appurtenances from damage or clogging by large solids or high density materials. It will also remove large particulate material, thus reducing loadings on following processes

8. Clarifier : “Clarifiers are used for solids removal from wastewater, such as raw sewage or highly contaminated raw water supplies. The process provides for removal of settleable solids and floating material while reducing suspended solids concentrations to levels suitable for subsequent treatment” There are usually two types of clarifier, those are rectangular primary clarifier and circular primary clarifier. Not only removing settleable solids and floating materials, clarifier is also used to reduce Total Suspended Solids (TSS) and Biochemical Oxygen Demand (BOD) and to treat raw water with high turbidity

9. Filtration : “Filtration is a treatment used for removal of solids and turbidity with high degree of efficiency in the case of raw water with low turbidity and color (turbidity up to 50 NTU and color up to 30 units). Taste and odor are also removed in this process. The slower the filtration process, the greater the efficiency of removal process” There are many types of filter: Slow sand filter Rapid sand filter Membrane filter Vacuum rotation filter

10. PengolahanKimia

11. Coagulation : “Coagulation is a process of adding coagulant into raw water that aimed to separate colloidal (particle size ranges 1 – 100 nm) from water. Many kinds of coagulant are frequently used in the coagulation process, such as aluminium sulfate, ferrous sulfate, ferric chloride, chlorinated copperas and coagulant aid” Flocculation : “The objective of flocculation is to provide an increase in the number of contacts among coagulating particles suspended in water by gentle and longed agitation. Flocculation follows chemical addition. During agitation, particles collide, producing larger and more easily removed flocs” There are many different types of flocculators currently in use. Some of them are gravel, baffled and horizontal and vertical mechanical flocculators

12. Disinfection : “Disinfection is conducted when the raw water contains patogenic bacteria. Disinfection can be done through heating process, chlorination, UV radiation and Ozone radiation. Of those techniques, chlorination in the most popular method employed in disinfection process.” UV Disinfection : “UV radiation is used to disinfect drinking water as well as wastewater on an increasingly frequent basis as reliable equipment become more available. UV radiation is generated from special low pressure mercury-vapor lamp that produce UV radiation as a result of an electron flow between the electrodes in an ionized mercury vapor. The inactivation of microorganisms by UV radiation is based on photochemical reactions in the DNA molecule that produce reproductive system errors”

13. Ozone Disinfection : “Ozone is an effective agent for deactivating common forms of bacteria, bacterial spores and vegetative microorganisms, as well as eliminating harmful viruses. Ozone can also reduce BOD5 and COD. Ozone injection into wastewater flow is accomplished by mechanical mixing devices, countercurrent or co-current flow columns, porous diffusers or jet injectors. Ozone acts quickly and consequently, requires a relatively short contact time.”

14. Chlorination : Chlorination is the most commonly used water and wastewater disinfection process worldwide. This process involves the addition of elemental chlorine or hypochloringe, either calcium or sodium to the wastewater. Chlorine is supplied as a liquified gas under high pressure in containers as well as tank cars of large sizes. Precaution should be taken when handling chlorine gas : Chlorine gas is both very poisonous and very corrosive, adequate exhaust ventilation at floor level should be provided since chlorine gas is heavier than air. Chlorine-containing liquid and gas can be handled in black qrought iron piping, but chlorine solution is highly corrosive and should be handled in rubber-lined or resistant plastic piping with hard rubber parts where necessary Disinfection is used to kill harmful organisms, and generally does not result in sterile water (free of all microorganisms)

15. Granular Activated Carbon Adsorption : “Granular activated carbon (GAC) adsorption is generally utilized for the removal of suspended and or colloidal matter in wastewater and the removal of tastes and odors in water supplies. Generally, applications for water supply use powdered activated carbon (PAC). GAC can also be used either as a tertiary treatment process in advanced wastewater treatment plants or as a secondary treatment process.”

16. PengolahanBiologi

17. Activated Sludge : “Activated sludge treatment is used to remove dissolved and colloidal biodegradable organics. The technology is a continuous flow, stirred, biological treatment process with recycling of the biomass. The process is characterized by a suspension of aerobic microorganisms maintained in a relatively homogeneous state by mixing and turbulence-induced or diffused aeration.” Activated Sludge systems are classified generally as high rate, conventional or extended aeration (low rate), based on organic loading. In the conventional activated sludge plant, the wastewater is commonly aerated for a period of 4 – 8 hours.

18. Facultative Lagoon : “Facultative lagoons are low cost, highly efficient alternatives for wastewater treatment in tropical and subtropical climates. Lagoons are of intermediate depth ponds in which the wastewater is stratified into three zones. These zones consist of an anaerobic bottom layer, aerobic lsurface layer and an intermediate zone. Stratification is a result of solids settling and temperature-water density variations.” In general, the aerobic surface layer serves to reduce odors while providing treatment of soluble organic by products by means of anaerobic processes operating at the bottom. Sludge at the bottom of the facultative lagoons will undergo anaerobic digestion producing largely carbon dioxide and methane. The photosynthetic activity in the anaerobic lagoon surface produces oxygen diurnally, increasing the dissolved oxygen during daylight hours, while surface oxygen is depleted at night.

19. PemilihanMetodaPengolahan Air Kualitas air baku • Kandunganunsur-unsur yang ada • Bahan-bahanpencemar yang terkandungdidalamnya Kualitas air olahan • Air Minum • Kegiatanrumahtangga • Pertanian • Perikanan • Peternakan • Dll

20. Karakteristik air limbah Suhu: Suhubergunadalammelihatkecenderunganaktivitas-aktivitaskimiawidanbiologis, pengentalan, tekananuap, teganganpermukaandannilai-nilaipenjenuhanbenda-bendapadatdan gas. Pengentalanmengatursedimentasi; semakintinggisuhu, pengentalanberkurangdanmengakibatkanpeningkatansedimentasi. Aktivitasbiologismeningkatpadasuhukira-kira 60 ºC.. Tingkat oksidasizatorganikjauhlebihbesarpadamusimpanasdibandingkanpadamusimdingin. Nitrifikasidariamoniaksecarakasardilipatgandakandengannaiknyasuhusampai 10 ºC. Pembusukananaerobikjarangterjadipadatitikbeku. Pembusukanpadasuhu 27 ºC empat kali lebihbesardibandingkanpembusukanpadasuhu 8 ºC.

21. Kekeruhan: Kekeruhanterjadiumumnyadisebabkanadanyazat-zatkoloidyaituzat yang terapungsertateruraisecarahalussekali. Hal inidisebabkanolehkehadiranzatorganik, lumpur, tanahliatdanzatkoloid. Meskikekeruhantidakdapatdigunakansebagaiukuranmengenaijumlahbenda-bendapadat yang terapung, namunsemakintinggitingkatkekeruhan, semakinkuatlimbahitu. Warna Warnapada air jugamenunjukkankekuatanlimbah. Air limbah yang baruberwarnaabu-abu. Air limbah yang sudah lama/busukberwarnagelap. Meskidemikianwarnatidakdapatmenunjukkansecarategasbahaya yang dikandungnya. Artinya, semakingelapwarna air limbahbelumtentulebihberbahayadibandingkandengan yang lebihjernih.

22. Bau Bau air limbahmemberikangambaran yang jelasmengenaikeadaan. Baudapatmenunjukkanapakah air limbahmasihbaruatausudahmembusuk. Air limbahdomestik yang masihbaruhampirtidakberbau. Kebanyakanbautidaksedapdihasilkanolehcampuran nitrogen, sulfur, fosfor, protein danbahanorganiklainnya. Bau yang paling menyerangadalahbaudarihidrogensulfida (H2S). Konsentrasisuatuzatdapatditelusuridaribaunya. Konsentrasikira-kira 0.037 mg/l amoniakdapatmenimbulkanbauamoniak yang sedikitmenyengat. Konsentrasi 0.0011 mg/l H2S menyebarkanbaukhastelurbusuk; 0.0026 mg/l karbondisulfidamenimbulkanbau yang tidakenak. Meskidemikianbau yang tidakmenyenangkantersebuttidaksendirinyamengganggukesehatanmasyarakat, kecualiapabilabau-bautersebutkeluardari gas beracun.

23. Nitrogen Dalam air limbahkebanyakan nitrogen padadasarnyaterdapatdalambentukorganikatau nitrogen protein danamoniak. Setingkatdemisetingkat nitrogen organikdiubahmenjadiamoniakdanpadakondisiaerobik, oksidasiamoniakmenjadinitritdannitrat. AmoniakBebas Amoniakbebasdisebutjuga nitrogen amoniakdihasilkanolehpembusukansecarabakterialzat-zatorganik. Air limbah yang masihbaruberkadaramoniakbebasrendahdanberkadar nitrogen organiktinggi. Nitrogen amoniakberkurangkadarnyaketika air limbahdiolahsedangkankeseimbangannyatercapai.

24. Nitrit Nitritmerupakansuatutingkatperalihandalamprosesperubahanzatorganikkedalambentuk yang tetap. Nitrit, dengandemikian, tidakdapatdiketemukandalam air limbahbarukecualidalamjumalhkecilsekali. Akantetapidalam air limbah yang sudahmembusuk, nitritdapatsajalebihbanyakditemukan. Nitritjarangterjadidalamkonsentrasi yang lebihbesardari 1 mg/l dalam air limbah. Pengaturanpembagian air limbah yang salahdapatmeningkatkankadarnitritdisampingjugakarenamenurunnyanitrat (NO3) menjadinitri (NO2). Keberadaannitritmenunjukkanadanya air limbah yang pengolahannyatidaksempurna. Nitrat Nitratmewakiliprodukakhirdaripengoksidasianzat yang bersifat nitrogen. Penentuannitratmenjadipentingdalampengolahan air limbah. Air limbah yang diolahsecarasempurnamenunjukkankadarnitrat yang tinggi. Padamusimpanas/kemarau, dimanaberpotensihilangnyaoksigenterlarutdalam air karenaprosespenguapan, nitratdapatmenyalurkanoksigengabungannyauntukmencegahdanmenghambatterjadinyakondisianaerobikdanbaubusuk. Meskipunnitratmerupakanpenunjukstabilitas, kehadirannya yang terlalutinggipadasaluran air limbahdanbak-bakpenampungmaupunpadadanautidakdiinginkankarenadapatmeningkatkanpertumbuhantanaman air secaradrastis.

25. Khlorida Kotoranmanusia, khusunya urine, mengandungsejumlahkhloridaolehkarenasebagiandarigaram yang terdapatdidalammakanandanminumanturutdibuang. Olehsebabitu, air limbahmengandungkadarkhlorida yang lebihtinggidaripadadidalampersediaan air kota. Olehkarenakhloridamerupakanzat-zatanorganik yang larut, merekatidakdipengaruhiolehsedimentasiatauolehproses-prosesbiologis. Khloridatetaptidakberubahselamapengolahansampahdanolehkarenaitunilai yang kuranglebihsamaharusdiperolehpadaberbagaitahappengolahan. SulfatdanSulfida Penentuansulfatjarangsekalidiperlukan, kecualiapabiladitemuimasalah-masalah yang menyangkutberkaratnyabeton. Sulfidamerupakanhasil-hasilpembusukanzat-zatorganikdanjugaakibatpenurunankadarbelerang. Pembusukananaerobikberbagaizat yang mengandungbelerangdanpenurunankadarcampuranbelerangmenjadisulfidamenghasilkanbau yang tidakmenyenangkan.

26. BOD Pengujian BOD merupakanpengujian yang pentingdalammenentukankekuatanataudayacemar air limbah. BOD mengukurjumlahzatorganik yang kemungkinanakandioksidasiolehkegiatan-kegiatanbakteriaerobik. Nilai BOD air limbahkasarsangatberbeda-beda, berkisar 100 mg/l untuk air limbah yang sangatencersampai 600 mg/l ataulebihuntuk air limbahterpadu yang berisibeberapajenislimbah. Pengujian BOD dibatasiolehbeberapakondisi. Apabilaterdapatsedikitsajajumlah ion logamberacundalam air limbah, tampaklahnilai BOD rendah yang menyesatkan yang disebabkanolehaktivitasbakteri yang terhambat. Beberapaobatpembasmibakteriseperti phenol, khlorbebas, cyanida, formaldehyde jugamempunyaiakibat yang menekan BOD. Pengujian BOD tidakmembedakanantarakebutuhanoksigen yang disebabkankarenanitrifikasi. Air limbah yang beradadalamkeadaannitrifikasiaktifcenderungmemperlihatkan BOD tinggi yang menyesatkan.

27. COD Pengujian COD digunakansecaraluassebagaisuatuukurankekuatanpencemaranlimbahdomestikmaupunindustri. Pengujiantersebutdirencanakanuntukmengukuroksigen yang dibutuhkanuntukmengoksidasizat-zatorganikpada air limbah. Pengujianinisangatbernilaiterutamajikapengujian BOD tidakdapatditentukankarenaterdapatnyabahan-bahanberacun. Selain itu, uji COD sangat singkat yaitu kira-kira 3 jam. Pengujian COD tidakmengadakanperbedaanantarazatorganik yang stabildan yang tidakstabil. Iatidakdapatmemberikanpetunjuktentangtingkatdimanabahan-bahan yang aktifsecarabiologisdapatdiseimbangkan.

28. DO Pengujianoksigenterlarut (DO) pentinguntukmenjaminkeadaan-keadaanaerobikdalamdaerahperairan yang menampungzat-zatpencemardalambentuk air limbah yang berasaldariinstalasipengolahan. Dalamsuatuinstalasipengolahan, kehadiranoksigenterlarutmerupakanpetunjukbahwasuatuoksidasi yang amatberartitelahtercapaidenganpengolahan yang digunakan.. Apabilaoksigenterlarutterdapatpadaperairan yang menampunghasilpengolahan air limbah, haliniberartidiperairantersebuthanyaterdapatsedikitgangguan. Faktor-faktor yang mempengaruhikadaroksigenterlarutdalam air alamiahadalah: pergolakanpermukaan air, luasnyadaerahpermukaan air yang terbukabagiatmosfer, tekananatmosferdanprosentaseoksigendalamudaradisekelilingnya. Dayalarutoksigenlebihrendahdidalam air lautdibandingkandengandayalarutnyadidalam air tawar, dayalarutnyadalam air limbahkuranglebih 95% dibandingkandayalarutnyadidalam air tawar. Oksidasibiologismeninggibersamaandenganmeningkatnyasuhudankebutuhanakanoksigenjugabertambah. Kondisiinimembawamasalahkarenaoksigenjadi paling sedikitdapatdilarutkandidalamkeadaan yang demikian. Dengandemikiankeadaan yang gawatterjadipadamusimkemaraudimanasuhulebihtinggidandayalarutoksigenmenjadirendah.

29. pH pH menyatakanintensitaskemasamanataualkalinitasdarisuatucairanencerdanmewakilikonsentrasi ion hidrogen. Skala pH adalahskalalogaritma, bukanskalailmu-hitung. Apabila pH bertambahdengansatu unit, perubahanitumewakilipengurangansepuluh kali lipatdalamkonsentrasi ion hidrogen.