Anaerobic Process For Cdm Project


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Anaerobic Process For Cdm Project

  1. 1. Training on Anaerobic Process for CDM ProjectSakti Siregar 2008
  3. 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;Sakti Siregar 2008
  4. 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]Sakti Siregar 2008
  5. 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 MediaSakti Siregar 2008
  6. 6. Physical Unit Operations Used for Wastewater TreatmentOperations Applications DeviceScreening, 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 screenScreening, micro Removal of fine solids, floatable matter, and algae MicroscreenComminution In-stream grinding of coarse solids to reduce size ComminutorGrinding/ Grinding of solids removed by bar racks Screenings grindermaceration Side-stream grinding of coarse solids MaceratorFlow equalization Temporary storage of flow to equalize flow rates and mass Equalization tank loadings of BOD and suspended solidsMixing Blending chemicals with wastewater and for homogenizing Rapid mixer and maintaining solids in suspensionFlocculation Promoting the aggregation of small particles into large Flocculator particles to enhance their removal by gravity sedimentationAccelerated Removal of grit Grit chambersedimentation Removal of grit and coarse solids Vortex separatorSedimentation Removal of settleable solids Primary clarifier Thickening of solids and biosolids High-rate clarifier Gravity thickenerSakti Siregar 2008
  7. 7. Physical Unit Operations Used for Wastewater TreatmentOperations Applications DeviceFlotation 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 greaseAeration Addition of oxygen to biological process Diffused-air aeration Mechanical aerator Postaeration of treated effluent Cascade aeratorVOC control Removal of volatile and semivolatile organic Gas stripper compounds from wastewaters Diffused-air and mechanical aerationDepth filtration Removal of residual suspended solids Depth filtersSurface 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 osmosisAir stripping Removal of ammonia, hydrogen sulfide, and other Packed tower gases from wastewater and digester supernatant Sakti Siregar 2008
  8. 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.Sakti Siregar 2008
  9. 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.Sakti Siregar 2008
  10. 10. ANAEROBIC PROCESSSakti Siregar 2008
  11. 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 )Sakti Siregar 2008
  12. 12. Anaerobic ProcessSakti 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. 13. Sakti Siregar 2008
  14. 14. Commonly Used Names for Methane­forming Bacteria Methanogenic bacteria Methanogens Methane-forming bacteria Methane-producing bacteriaSakti Siregar 2008
  15. 15. SULFATE-REDUCING BACTERIASakti Siregar 2008
  16. 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 + 2H2OSakti Siregar 2008
  17. 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 bac­teriaSakti Siregar 2008
  18. 18. Trend in Anaerobic WWTPSakti Siregar 2008
  19. 19. Typical PFD DRAWN on WHITE BOARDSakti Siregar 2008
  20. 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 CompoundsSakti Siregar 2008
  21. 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.Sakti Siregar 2008
  22. 22. ANAEROBIC LAGOONSakti Siregar 2008
  23. 23. ANAEROBIC LAGOON Process Flow Diagram Pretreatment Oil/ Water Separator Cooling Water Pond Anaerobic Lagoon Acidification Pond Methane Generation PondSakti Siregar 2008
  24. 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 pipeSakti Siregar 2008
  25. 25. ANAEROBIC LAGOON FLARESakti Siregar 2008
  26. 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.Sakti Siregar 2008
  27. 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 SulfidesSakti Siregar 2008
  28. 28. Thank You Sakti Siregar Wastewater Treatment Engineer Siregar 2008