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)
2.0m
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