1. Training on
Anaerobic Process for CDM Project
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2008

2. WASTEWATER TREATMENT PLANT IN GENERAL
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2008

3. Wastewater Constituents and Unit
Operation and Processes for their Removal
Constituent Unit Operation or Process
Suspended Solids Screening; Grit removal; Sedimentation;
Clarification; Flotation; Chemical
Precipitation; Surface Filtration.
Biodegradable Organics Aerobic and anaerobic suspended growth
variations; Aerobic and anaerobic attached
growth variations; Lagoon variations;
Advanced oxidation; Membrane filtration;
Chemical oxidation.
Nutrients Chemical oxidation; Suspended-growth
nitrification and denitrification; Fixed-film
Nitrogen nitrification and denitrification; Air stripping.
Phosphorous Chemical treatment; Biological phosphorous
Nitrogen and Phosphorous removal; Biological nutrient removal
Pathogens Chlorine compounds; Chlorine dioxide;
Ozone; Ultraviolet (UV) radiation.
Colloidal and dissolved solids Membranes; Chemical treatment; Carbon
adsorption; Ion exchange
Volatile organic compounds Air stripping; Carbon adsorption; Advanced
Oxidation;
Odors Chemical scrubbers; Carbon adsorption;
Biofilters;
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2008

4. Typical Contaminants of Untreated Domestic
Wastewater
Total Solids [TS]
Dissolved [TDS] + Suspended [SS] + Settleable
Biochemical Oxygen Demand [BOD5]
Total Organic Carbon [TOC]
Chemical Oxygen Demand [COD] - Quantity of oxygen needed to
oxidize the components of the sludge – primarily oxidized to CO2 and
H2O
Nitrogen (total as N)
Organic + Ammonia + Nitrites + Nitrates
Total Kjeldahl Nitrogen [TKN] = Organic + Ammonia
Phosphorous (total as P)
Organic + Inorganic
Chlorides
Sulfate
Alkalinity
Grease
Volatile Organic Compounds [VOCs]
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2008

5. Biological Process Systems
Anaerobic Process
Aerobic Process
Suspended Growth Systems
SBRs
Activated Sludge
Low Speed Aearators
High Speed Aerators
Disc Aeration
Orbal
VLR
VertiCel
Brush Aeration (Mammoth Rotor)
Diffusers
Coarse Bubble
Fine Bubble
JetAeration
MBR
Fixed Film (Attached Growth) Systems
Trickling Filter
RBC
Suspended Media
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2008

6. Physical Unit Operations
Used for Wastewater Treatment
Operations Applications Device
Screening, coarse Removal of coarse solids such as sticks, rags, and other Bar rack
debris in untreated wastewater by interception (surface
straining)
Screening, fine Removal of small particles Fine screen
Screening, micro Removal of fine solids, floatable matter, and algae Microscreen
Comminution In-stream grinding of coarse solids to reduce size Comminutor
Grinding/ Grinding of solids removed by bar racks Screenings grinder
maceration Side-stream grinding of coarse solids Macerator
Flow equalization Temporary storage of flow to equalize flow rates and mass Equalization tank
loadings of BOD and suspended solids
Mixing Blending chemicals with wastewater and for homogenizing Rapid mixer
and maintaining solids in suspension
Flocculation Promoting the aggregation of small particles into large Flocculator
particles to enhance their removal by gravity sedimentation
Accelerated Removal of grit Grit chamber
sedimentation Removal of grit and coarse solids Vortex separator
Sedimentation Removal of settleable solids Primary clarifier
Thickening of solids and biosolids High-rate clarifier
Gravity thickener
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2008

7. Physical Unit Operations
Used for Wastewater Treatment
Operations Applications Device
Flotation Removal of finely divided suspended solids and Dissolved-air floatation (DAF)
particles with densities close to that of water; also
thickens biosolids Introduced air flotation
Removal of oil and grease
Aeration Addition of oxygen to biological process Diffused-air aeration
Mechanical aerator
Postaeration of treated effluent Cascade aerator
VOC control Removal of volatile and semivolatile organic Gas stripper
compounds from wastewaters Diffused-air and mechanical
aeration
Depth filtration Removal of residual suspended solids Depth filters
Surface filtration Removal of residual suspended solids Discfilter®
Cloth-Media Disk Filter ®
Membrane Removal of suspended and colloidal solids and Microfilteration, ultrafiltration,
filtration dissolved organic and inorganic matter nonofiltration, and reverse osmosis
Air stripping Removal of ammonia, hydrogen sulfide, and other Packed tower
gases from wastewater and digester supernatant
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2008

8. Anaerobic versus aerobic processes
Aerobic processes
Advantages :
wellknown, widely used, many types of installations for small up to high
capacities.
applicable for low concentrations of BOD or COD and low temperatures ( 5
- 30 C ).
very shockresistant to loading fluctuations and toxic chemicals.
can produces high quality effluent for direct discharge to surface waters.
Disadvantages :
requires usually large areas for construction due to low load and large
dimensions for aeration bassins and sedimentation tanks.
relatively high energy consumption for air compressor or aeration
equipment ( mixers, dissolver, surface aerators etc )
large production of surplus solids ( primary sediments and secondary
sludge ). Increasing problem to find acceptable solutions for the solids (
dumping, incineration, agricultural applications ). often 50% of total
treatment costs are related to solids disposal.
when shortage, then relatively high dosage of nutrients is required ( N, P, S,
micro hutrients )
often problems related to emissions ( stench, volatile solvents ) and
hygienic risks ( disease germs ).
not well suited for high concentrated effluents.
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2008

9. Anaerobic versus aerobic processes
Anaerobic processes
Advantages :
applicable for concentrated effluents; BOD from 1000 mg/l and higher, and
for medium to large volumes.
produces valuable biogas ( 70 - 90 % CH4 )
requires no energy for oxygenation, only low energy consumption for pumps
( possible for biogas compressor )
compact construction ( high loading rate ), thus small areas required. Usually
completely closed equipment preventing emission problems.
produces only a fraction of excess secondary sludge. Sludge is well
stabilized and often used in new installation ( starter culture ) or ready for
agricultural application. Biomass granules have long term stability, ideally for
use in campaign plants.
when shortage, only low dosage of nutrients required ( N, P, S micronutrients
)
Disadvantages :
temperature of waste water should be 20 C to 35 C, may require preheating.
rather sensible to toxic chemicals, may require special precautions
effluent is usually not suited for discharge to surface waters, requires aerobic
posttretment and sedimentation to reach discharge limits
not suitable, unless special precautions, for waste waters containing
relatively high concnetrations of nitrate and/ or sulfate ions.
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2008

10. ANAEROBIC PROCESS
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2008

11. Theory
The anaerobic conversion of dissolved organic C compounds into CH4 and CO2
is a complex process, in which numerous micro organism play a role
Hydrolytic micro organisms break down large molecules ( polymers ) into smaller
soluble molecules ( monomers ) through the action of enzymes.
Hydrolysis usually proceeds rapidly. The COD concentration of the liquid does not
change
Acidifying microorganism convert the dissolved monomers into volatile fatty acids
( VFA ) and some H2 gas.
Main products are :
Formic acid C1
Acetic acid C2
Propionic acid C3
(iso) Butyric acid C4
(iso) Valeric acid C5
Acetogenic micro organism, this group converts the higher fatty acid C3, C4
and C5 into acetic acid and H2 gas.
Example for propionic acid :
CH3 - CH2-COO- + 3 H2O CH3-COO- + H+ + 3H2 +76 kJ
The H2 gas escape from the liquid phase, thus the COD concentration
decreases; according to the following calculation.
Methanogenic micro organisms, this group converts the endproducts of the
foregoing processes ( hydrogen, formic acid, methanol, methylamine and acetic
acid ) into CH4 and CO2 )
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2008

12. Anaerobic Process
Sakti Siregar
2008 M ul i
t phase nat e ofAnaer c Di
ur obi gest on ( il e & Col an,1988)
i W lki er

13. Sakti Siregar
2008

14. Commonly Used Names for Methane­forming Bacteria
Methanogenic bacteria
Methanogens
Methane-forming bacteria
Methane-producing bacteria
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2008

15. SULFATE-REDUCING BACTERIA
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2008

16. Respiration
Substrates Used by Methane-forming Bacteria
Acetate CH3COOH
Carbon dioxide CO2
Carbon monoxide CO
Formate HCOOH
Hydrogen H2
Methanol CH3OH
Methylamine CH3NH2
CH3COOH CH4 + CO2
CO2 + 4H2 CH4 + 2H2O
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2008

17. Bacteria
ACETATE-FORMING BACTERIA
Acetate-forming (acetogenic) bacteria grow in a symbiotic
relationship with methane-forming bacteria. Acetate
serves as a substrate for methane-forming bac­teria
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2008

18. Trend in Anaerobic WWTP
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2008

19. Typical PFD
DRAWN on WHITE BOARD
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2008

20. Factor in Anaerobic Treatment
Physical factors
Temperature, 35 deg C
Hydraulic Retention Time
Solid Retention Time
Organic Loading
Mixing , 10 – 20 W/m3
Solid Concentration
Sludge type
Chemical factors
pH, 6.8 – 7.2
Alkalinity , bicarbonate alkalinity 2500 – 5000 mg/l CaCO3
Volatile Acids, 50 – 300 mg/l
Nutrients COD : N : P = 350 : 5 :1
Trace Element
Toxic Compounds
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2008

21. Anaerobic lagoon
Description Application
the anaerobic lagoon is the most simple type Anaerobic lagoons are really primitive anaerob
of anaerobic treatment. Wastewater is fed to a digester. They were first used in the meat
pond in which conversion to biogas takes processing industry because the waste is
place spontaneously. Modern lagoons are peculiarly well adapted to this form of
covered and the biogas is collected for further treatment. Meat processing wastes contain
use. high concentrations of fats that form a scum
Lagoon depths vary from 2.5 to 6.0 m. on the pond surface. This scum often reaches
Figure 2.1 Anaerobic Lagoon a thickness of 2 cm or more and provides
Operation performance insulation and prevents the escape of large
HRT : 7 - 80 days amount of reduced sulfide compounds.
Load : 0.15 - 0.3 kg COD/ m3.d Insulation is important because methane
COD reduction usually < 80% fermentation, the critical step in anaerobic
Advantages digestion or treatment, is extremely
Simple systems temperature sensitive.
Cheap Two types of anaerobic ponds or lagoons are
Also degradation of SS. in use, those for sludge and those for soluble
Disadvantages waste. Sludge lagoons have been used for
Large area requirement over 70 years in municipal waste treatment
Smell for not covered lagoons systems and have been introduced as a
manure disposal process for dairies, feedlots
and chicken ranches. Most sludge lagoons are
shallow ditches or ponds that are intermittently
filled with sewage sludge or manure. No
temperature control is provided. Nuisance
odors are a common problem, and location of
sludge lagoons can be expected to be well
known to naone living nearby.
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2008

22. ANAEROBIC LAGOON
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2008

23. ANAEROBIC LAGOON
Process Flow Diagram
Pretreatment
Oil/ Water Separator
Cooling Water Pond
Anaerobic Lagoon
Acidification Pond
Methane Generation Pond
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2008

24. ANAEROBIC LAGOON
Process Equipment
Incoming Flow Meter
Oil/ Water Separator
Oil Skimmer
Oil Launder/ Baffle
Cooling Water Pond
Oil Skimmer
Oil Launder/ Baffle
Anaerobic Lagoon
Feed pump
Mixer ( Submersible mixer, ejector, pump + perforated pipe )
Dewatering pump
Membrane
Desludging Pipe
Sampling port
Pressure indicator
Degasser pipe
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2008

25. ANAEROBIC LAGOON
FLARE
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2008

26. Process : Alkalinity
When volatile acids accumulate, the following chemical
reaction occurs :
HCO3- + HVA VA- H2O + CO2
Bicarbonate alkalinity is consumed, carbon dioxide
production increase, and eventually the pH falls.
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2008

27. Process : Failure
Indicators Solutions
Volatile acids concentration increases Adjust alkalinity using a supplement
Bicarbonate alkalinity drops Adjust feed schedulle
pH falls Pretreatment
Gas production rate drops Clean Lagoon
Percentage of CO2 in gas increase
Typical causes of process
failure
Hydraulic overload
Dilute feed
Excessive sludge production
Frit and scum accumulation
Alkalinity washout
Organic overload
Increase in ww production
Increase in ww concentration
Change in ww characteristic
Too rapid startup
Infrequent feeding
Toxic overload
Heavy metals
Detergent
Chlorinated organics
Oxygen
Cation
Sulfides
Sakti Siregar
2008

28. Thank You
Sakti Siregar
Wastewater Treatment Engineer
sakti-siregar@bdg.centrin.net.id
Sakti Siregar
2008