pengolahan limbah secara kimiawi

PENGOLAHAN LIMBAH

SECARA KIMIAWI

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

Six chemical processes :

• 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, sulfide, phosphate, or carbonate.

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

1. Reaction to produce an insoluble solid

Raw Waste

pH adjust

Oxidation or chelating

agent destruct

pH adjust Chem or addition

Floc Sed Filt

Sludge Dewater, Dry

Conditioning

Steps

Return For Seed

Schematic for Removal by forming an insoluble substances

• If produce insoluble gas  it will remove itself from solution as it is formed

• Ex :

2 NO

₂^-

+ Cl

₂

+ 8 H

⁺

N

₂

+ 4H

₂

O + 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 SUBSTANCE

TREATMENT TECHNOLOGY Chlorine gas or other

chlorine compound

(hypochlorite, or chlorine dioxide)

(1). Breakpoint chlorination to remove ammonia

(2). Alkaline chlorination of cyanide

Sulfuric or hydrochloric acids (technical grade or waste acids)

Removal of sulfide as hydrogen sulfide gas 2. Reactions to Produce an Insoluble Gas

• Industrial wastewater consists of colloidal suspensions

• Destabilized industrial wastewater by

chemical coagulation  allow separation of destabilized colloidal material from

water

3. Reduction of surface charge to produce coagulation of a colloidal suspension

• 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

4. Reaction to produce a biologically degradable substance from a nonbiodegradable subs.

• 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

5. Reaction to destroy or deactivate a chelating agent

• Senyawa yg tidak diijinkan  dapat

dioksidasi secara kimia, menjadi CO

₂

dan H

₂

O

• 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

6. Oxidation or reduction to produce a non objectionable subs.

• 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

Chemical treatment

I. Introduction

A. Reasons to Soften

1. Reduce Soap Consumption 2. Improve Aesthetics of Water

B. Reasons not to Soften 1. Expensive Process 2. May be less healthy

3. Hot Water Heaters last longer

Water Softening

3. Competes with health related costs

II. What is Hardness?

C. Carbonate Hardness as CaCO₃ = T. Alkalinity as CaCO₃

D. Non-Carbonate Hardness = T. Hardness – T. Alkalinity

Water Softening

a. Removed by Boiling b. Removed by Lime

a. Unaffected by boiling b. Removed by Soda Ash

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) 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

Water Softening

III. Methods of Softening

A. Lime-Soda Ash Chemistry

1. 1^st Stage Treatment (Lime only)

* CO₂ + Ca(OH)₂ CaCO₃ + H₂O

* Ca + 2HCO₃+ Ca(OH)₂ 2CaCO₃+ 2H₂O(pH 8.3-9.4)

* Mg + 2HCO₃+ Ca(OH)₂ CaCO₃+ Mg + CO₃+ 2H₂O(pH >10.8)

a. Carbon Dioxide Removal (< 8.3 pH)

b. Carbonate Hardness Removal

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

* Ca + SO₄+ Na₂CO3 Na₂SO₄ + CaCO₃ 2. 2^nd Stage Treatment (Soda Ash)

* Ca + Cl₂ + Na₂CO₃ CaCO₃ + 2NaCl

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

Pengolahan limbah secara biologi

• Membutuhkan O₂

• Perlu energi besar

• u/ BOD < 400 mg/l

• u/ COD < 2000 ppm

Aerobik

• Tidak membutuhkan O₂

• Perlu energi kecil

• u/ BOD > 4000 mg/l

• u/ COD < 2000 ppm

Anaerobik

• 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.

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

-

SINGLE

BACTERIUM 2.0m

ORGANIC POLLUTANT

AND NUTRIENTS (C,P,N,O,Fe,S…)

GROWTH - CELL DIVISION INCREASE IN BIOMASS

(assimilation)

CO₂ evolved (dissimilation)

O

₂

consumption

Controlled release of energy Slow Burning!

Mikroorganisme

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

• Bakteri ^{• Fungi}

• Nemotodes

• Algae

• Protozoa • Rotifera

Mikroorganisme

Pengaruh kondisi lingkungan

Mikroba

pH

Temp

Nutrients Subs conc

D.O.

mixing

Bioreaktor (untuk pengolahan limbah)

1. Reaktor pertumbuhan

tersuspensi (suspended growth reactor)

2. Reaktor pertumbuhan lekat

(attached growth reactor)

• 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

Suspended Growth

screens Grit

chamber

Primary Settling

tank

aeration chlorination

Raw water

Secondary Settling

tank

Effluent to disposal Reareation

Activated Sludge Pump

Activated Sludge return

Sludge Thickener

Sludge

Digestion To Sludge Drying

Flow Diagram of ASP

• 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%

Lumpur aktif

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 Suspended Growth

Seluruh modifikasi ini dapat menghasilkan efisiensi penurunan BOD sekitar 80%-90%.

trickling filter

cakram biologi reaktor fludisasi

RBC (rotating biological contactor)

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

Attached Growth

• 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

Penyaring Trikel

Pretreatment

Primary Treatment

Rotating Biological Contactors

Secondary Clarifiers

Solids Handling INFLUENT

Disinfection

EFFLUENT

RBC Flow Scheme

RBC Secondary Treatment

Plastic Media

1.6 rpm

40 % Submerged

Microorganisms “Treat” the Wastewater by Using Organics

Provides Large Surface Area Rotating

CONTACTOR

Shaft

Individual Disc

Discs

RBC COMPONENTS

• 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.

Anaerobic digestion

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

• 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

Anaerobic digestion

Aerobic vs Anaerobic

• 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.

Apa akibat dari proses biologi yang tidak tepat pada pengolahan limbah cair ?

TERIMA KASIH