PENGOLAHAN LIMBAH SECARA KIMIAWI
Six chemical processes :
1. Reaction to produce an insoluble solid 2. Reaction to produce an insoluble gas 3. Reduction of surface charge to produce coagulation of a colloidal suspension 4. Reaction to produce a biologically degradable substance
from a nonbiodegradable subs. 5. Reaction to destroy or deactivate a chelating agent 6. Oxidation or reduction
1. Reaction to produce an insoluble solid
• Removing metals alkaline precipitations, precipitation
of the metal as the
sulfide,
precipitation as the phosphate, precipitation as the carbonate, or co-precipitation with another metal
hydroxide,
carbonate.
sulfide,
phosphate,
or
1. Reaction to produce an insoluble solid
Chemical substances Chemical
Application
Lime
Heavy metals, fluoride, phosporus
Soda Ash
Heavy metals
Sodium sulfide
Heavy metals
Hydrogen sulfide
Heavy metals
Phosporic acid
Heavy metals
Fertilizer grade phosphate
Heavy metals
Ferric sulfate
Arsenic, sulfide
Ferric chloride
Arsenic, sulfide
Alum
Arsenic, fluoride
Sodium sulfate
Barium
Schematic for Removal by forming an insoluble substances
Conditioning Raw Waste
Oxidation or chelating agent destruct
pH adjust Steps
pH adjust or Chem addition
Floc
Sed
Filt
Return For Seed
Sludge Dewater, Dry
2. Reactions to Produce an Insoluble Gas
• If produce insoluble gas it will remove itself from solution as it is formed • Ex : 2 NO2- + Cl2 + 8 H+ N2 + 4H2O + 2 Cl• Chlorine added in the form of chlorine gas or hypochlorite, or another chloride compound that dissolves in water
2. Reactions to Produce an Insoluble Gas
Chemical substances CHEMICAL TREATMENT SUBSTANCE TECHNOLOGY Chlorine gas or other (1). Breakpoint chlorination to chlorine compound remove ammonia (hypochlorite, or chlorine dioxide) (2). Alkaline chlorination of cyanide Sulfuric or hydrochloric Removal of sulfide as acids (technical grade or hydrogen sulfide gas waste acids)
3. Reduction of surface charge to produce coagulation of a colloidal suspension
• Industrial wastewater consists of colloidal suspensions
• Destabilized industrial wastewater by chemical coagulation allow separation of destabilized colloidal material from water
4. Reaction to produce a biologically degradable substance from a nonbiodegradable subs.
• Unbiodegradable substances altered to biodegradable materials
• Hydrolysis (acid or alkaline) break up large organic molecules into smaller segments • Ex: Substances from cellulose or derivatives acid hydrolysis + heat
5. Reaction to destroy or deactivate a chelating agent • Chelating agents : organic materials (EDTA) or inorganic
materials (polyphosphates) • ORGANIC CHELATING AGENTS : – Destroy by acid hydrolysis – Destroy by hydroxyl free radical oxidation : • • • •
Fenton’s reagent (H2O2 + ferrous ions) Hydrogen peroxide + UV light Ozone + hydrogen peroxide Ozone + UV light
– Destroy by adding potassium permanganate + heating – Pass the wastewater through granular activated carbon
6. Oxidation or reduction to produce a non objectionable subs.
• Senyawa yg tidak diijinkan dapat dioksidasi secara kimia, menjadi CO2 dan H2O • Contoh : – Menghilangkan chromium reducing hexavalent chrome ions (soluble in water & highly toxic) menjadi bentuk trivalent
• Reducing agents :
SO2, sodium/potasium bisulfit, or metabisulfit, and sodium or potasium bisulfit plus hydrazine.
• pH acid range
Chemical treatment
• Kelebihan pengolahan secara kimia: – Efisiensi tinggi (dapat mencapai angka yang diinginkan) – Waktu dentensi relatif singkat sehingga volume reaktor/unit pengolahan relatif lebih kecil
• Kekurangan – Ada penambahan zat aditif sehingga meningkatkan konsentrasi Total Dissolved Solid (TDS). Penyisihan TDS relatif sulit dan mahal: membran atau destilasi – Meningkatkan beban pengolahan – Biaya bahan kimia cukup mahal = biaya untuk energi
Water Softening I. Introduction
A. Reasons to Soften 1. Reduce Soap Consumption 2. Improve Aesthetics of Water 3. Hot Water Heaters last longer B. Reasons not to Soften 1. Expensive Process 2. May be less healthy 3. Competes with health related costs
Water Softening II. What is Hardness? A. Hardness Classifications a. Soft Water = 0 to 70 mg/L b. Moderate Hardness = 71 to 150 mg/L c. Hard Water = > 150 mg/L B. T. Hardness, mg/L, as CaCO3 = (Ca X 2.5) + (Mg X 4.12) (MW=100) (40 X 2.5 = 100) (24.3 X 4.12 = 100) C. Carbonate Hardness as CaCO3 = T. Alkalinity as CaCO3
a. Removed by Boiling b. Removed by Lime D. Non-Carbonate Hardness = T. Hardness – T. Alkalinity
a. Unaffected by boiling b. Removed by Soda Ash
Water Softening III. Methods of Softening
A. Lime-Soda Ash Chemistry 1. 1st Stage Treatment (Lime only) a. Carbon Dioxide Removal (< 8.3 pH) * CO2 + Ca(OH)2
CaCO3 + H2O
b. Carbonate Hardness Removal * Ca + 2HCO3 + Ca(OH)2 * Mg + 2HCO3 + Ca(OH)2
2CaCO3 + 2H2O(pH 8.3-9.4) CaCO3 + Mg + CO3 + 2H2O(pH >10.8)
c. Magnesium Hardness Removal (>pH 10.8) * Mg + CO3 + Ca(OH)2
CaCO3 + Mg(OH)2
* Mg + SO4 + Ca(OH)2
Ca + SO4 + Mg(OH)2
2. 2nd Stage Treatment (Soda Ash) * Ca + SO4 + Na2CO3
* Ca + Cl2 + Na2CO3
Na2SO4 + CaCO3
CaCO3 + 2NaCl
PENGOLAHAN LIMBAH SECARA BIOLOGI
Pengolahan limbah secara biologi • Proses yang menggunakan bahan organik sebagai makanan bagi bakteri atau m.o lain bakteri, fungi, rotifera • O2 dibutuhkan baik dalam bentuk yg larut ataupun anion spt sulfat dan nitrat (aerobik) • Produk akhir : penurunan jumlah polutan organik, meningkatnya jumlah m.o, CO2, H2O, by-products
• Sebagai pengolahan sekunder, pengolahan secara biologi dipandang sebagai pengolahan yang paling murah dan efisien. • Proses secara biologi berlangsung selama 1-7 hari
Pengolahan limbah secara biologi
Aerobik
• • • •
Membutuhkan O2 Perlu energi besar u/ BOD < 400 mg/l u/ COD < 2000 ppm
Anaerobik
• • • •
Tidak membutuhkan O2 Perlu energi kecil u/ BOD > 4000 mg/l u/ COD < 2000 ppm
AEROBIK • Jika bakteri berasal dari limbah maka yang tumbuh bermacam-macam jenis bakteri dari mulai yang bersifat patogen maupun probiotik. • Dalam kondisi semacam ini maka proses hanya dapat berlangsung secara aerobik.
Organic Matter
M.O
O2
M.O
CO2
H2O
Oxidized Organic Material
Mikroorganisme
Microbial Metabolism
• General nutritional requirements -: • Carbon Substrate (Org. Or Inorg.) • Electron Donor • Energy Source
• Need for molecular oxygen. • Basic elements required-C,O ,N,H, P,S • Inorganic elements: K,Mg,Ca,Fe,Na,Cl
Mikroorganisme
-
O2 consumption
GROWTH - CELL DIVISION INCREASE IN BIOMASS (assimilation)
2.0m
ORGANIC POLLUTANT AND NUTRIENTS (C,P,N,O,Fe,S…) SINGLE BACTERIUM
Controlled release of energy Slow Burning!
CO2 evolved (dissimilation)
Mikroorganisme obligate aerobes: need oxygen, use it as terminal electron acceptor
obligate anaerobes: cannot grow in the presence of oxygen
facultative anaerobes: under certain conditions can grow in the absence of oxygen
Mikroorganisme
• Bakteri
• Fungi
• Algae
• Nemotodes
• Protozoa
• Rotifera
Pengaruh kondisi lingkungan
Nutrients
Subs conc
Temp
pH
D.O.
Mikroba
mixing
Bioreaktor (untuk pengolahan limbah)
1. Reaktor pertumbuhan tersuspensi (suspended growth reactor)
2. Reaktor pertumbuhan lekat (attached growth reactor)
Suspended Growth
• Terdiri dari berbagai jenis mikroba • Mikroba tersuspensi dalam limbah • Jumlah mikroba dapat terkontrol dengan baik mudah diuji di lab • Contoh: Activated sludge : proses aerobik
termasuk oksidasi karbon dan nitrifikasi • Disertai flokulasi mikroba diikuti filtrasi dan sedimentasi
Raw water
screens
Grit chamber
Primary Settling tank
aeration
Secondary Settling tank
Reareation
chlorination
Activated Sludge return
Activated Sludge Pump Effluent to disposal Sludge Thickener
Sludge Digestion
To Sludge Drying
Flow Diagram of ASP
Lumpur aktif • Screening and Grit Units : to remove large objects and to reduce particle size
• Primary Settling Tanks : to remove particles from water sedimentation – Particulates suspended size : 10-1 to 10-7 mm – ( > 10-4 : turbidity ; < 10-4 : color & taste) – 70% of the solids and 30% of the BOD can be removed
• Aeration Tanks : provides 6 to 24 hours retention – The contents mixed liquor, and the solids are called mixed liquor suspended solids (MLSS), living and dead microbial cells – microorganisms kept in suspension 4 to 8 hr (by mechanical mixers and/or diffused air), – M.o concentration maintained by the continuous return of the settled biological floc from a secondary settling tank to the aeration tank.
Lumpur aktif • Final Settling Tanks : provide longer detention (2h) and lower overflow rates (30 to 50 m3/m2.day) • the sludge settles to the bottom of the tank still active and able to remove more BOD from the waste water maintains and increases the microorganism concentration in the aeration chamber – key factor to increase BOD removal from the waste water
• << 24 hr in the aerobic process BOD concentration should not exceed about 2,000 mg/l on the effluent
• Thickener : part of the separation of the activated sludge from the mixed liquor in the secondary clarifiers – Type of thickeners Gravity Thickening, Thickening by Flotation, and Centrifugal Thickening – reduce sludge volume by 50 - 70%
Suspended Growth Advantages • Diverse; can be used for one household up a huge plant
• Removes organics • Oxidation and Nitrification achieved • Biological nitrification without adding chemicals • Biological Phosphorus removal • Solids/ Liquids separation • Stabilization of sludge • Capable of removing ~ 97% of suspended solids • The most widely used wastewater treatment process
Suspended Growth
Disadvantages • Does not remove color from industrial wastes and may increase the color through formation of highly colored intermediates through oxidation • Does not remove nutrients, tertiary treatment is necessary • Problem of getting well settled sludge • Recycle biomass keeps high biomass concentration in aeration tanks allowing it to be performed in technologically acceptable detention times
Attached Growth
trickling filter cakram biologi reaktor fludisasi RBC (rotating biological contactor)
Seluruh modifikasi ini dapat menghasilkan efisiensi penurunan BOD sekitar 80%-90%.
Attached Growth
• All microbes attached to the medium batu, plastik, dll
• The microbes able to access the organis matter in the waste water
• Trickling filter, RBC, Fluidized bed
Penyaring Trikel
• Terdiri dr lapisan batu dan kerikil dgn tinggi 90 cm-3 m • Air limbah dialirkan secara perlahan melalui lapisan ini. • Bakteri akan terkumpul & berkembang biak pd batu dan kerikil mengkonsumsi bahan organik yg terdapat dlm air limbah
Penyaring Trikel
RBC Flow Scheme
INFLUENT
Primary Treatment
Pretreatment
Rotating Biological Contactors
Disinfection
Solids Handling
Secondary Clarifiers
EFFLUENT
RBC Secondary Treatment Rotating
Plastic Media
1.6 rpm
Provides Large Surface Area
40 % Submerged
Microorganisms “Treat” the Wastewater by Using Organics
RBC COMPONENTS
CONTACTOR
Discs
Individual Disc
Shaft
Anaerobic digestion
• Anaerobic digestion is widely used to treat wastewater sludges and organic wastes because it provides volume and mass reduction of the input material. • Anaerobic digestion is a renewable energy source because the process produces a methane and carbon dioxide rich biogas suitable for energy production helping replace fossil fuels. Also, the nutrient-rich solids left after digestion can be used as fertiliser.
Anaerobic digestion • The digestion process begins with bacterial hydrolysis of the input materials in order to break down insoluble organic polymers such as carbohydrates and make them available for other bacteria. • Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. • Acetogenic bacteria then convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide. • Methanogens, finally are able to convert these products to methane and carbon dioxide.
The key process stages of anaerobic digestion There are four key biological and chemical stages of anaerobic digestion
Hydrolysis Acidogenesis Acetogenesis Methanogenesis A simplified generic chemical equation for the overall processes outlined above is as follows: C6H12O6 → 3CO2 + 3CH4
Anaerobic digestion
• Slow rate process required long times retention • For waste of high organic strength --? COD > 2000 ppm • Capable treating some substances cellulosic materials, aromatic compounds,
chlorinated solvents
Aerobic vs Anaerobic
Apa akibat dari proses biologi yang tidak tepat pada pengolahan limbah cair ? • Pengolahan secara biologi yang tidak tepat akan menyebabkan timbulnya bau busuk dan penggumpalan bahan berlemak. Jika tidak diatasi segera maka akan sangat mengganggu. • Untuk menghindari proses pengolahan limbah yang tidak efektif dilakukan terlebih dahulu pre-treatment dengan tujuan agar tidak terjadi over load COD, diusahakan agar COD maksimal 2000 ppm. • Tujuan pre-treatment adalah agar beban COD lebih rendah dan limbah lebih homogen.
TERIMA KASIH
