Anaerobic wastewater treatment, Advantages, Limitation and its application in industries

Anaerobic wastewater treatment, Advantages, Limitation and its application in industries

1. Anaerobic wastewater treatment

2. Introduction Anaerobic wastewater treatment is a biological process where microorganisms degrade organic contaminants in the absence of oxygen. Anaerobic Treatment is a collection of biological processes by which microorganisms break down biodegradable material present in the wastewater, in the absence of Oxygen. (Anaerobic Microorganisms) Organic Pollution ------------------------------------  CH 4 + CO 2 +Sludge (In the absence of Air) Organic Pollution -----------------------------------------  Biogas + Sludge

3. Advantage of anaerobic processes Low Production of Loids, about 3-5 times lower than that in aerobic Processes Low Energy Consumption as no aeration leading to very low operational costs Production of Methane, a high calorific fuel gas. Tolerance to high Organic Loads Energy generation in the form of methane gas Less biomass (sludge) generation Application of higher organic loading rate Low land requirement and low construction cost. Ability to transform several hazardous solvents Low nutrient consumption Application in small and large scale

4. Limitations of anaerobic processes Anaerobic micro-Organisms are susceptible to inhibition by a large number of compounds Process start-up time is slow in the absence of adapted seed sludge. Some form of post treatment is usually necessary The bio chemistry and micro biology of anaerobic digestion are complex and still require further studies More susceptible to changes in environmental conditions and Long recovery time Further Treatment of sulfate-rich wastewater required Further Effluent quality of treated wastewater required Possible generation of bad odors Unsatisfactory removal of nitrogen & Phosphorus and pathogens

5. Limitations of anaerobic processes Anaerobic micro-Organisms are susceptible to inhibition by a large number of compounds Process start-up time is slow in the absence of adapted seed sludge. Some form of post treatment is usually necessary The bio chemistry and micro biology of anaerobic digestion are complex and still require further studies More susceptible to changes in environmental conditions and Long recovery time Further Treatment of sulfate-rich wastewater required Further Effluent quality of treated wastewater required Possible generation of bad odors Unsatisfactory removal of nitrogen & Phosphorus and pathogens

6. Anaerobic degradation of Organic Matter Process Anaerobes biodegrade complex organic wastes into CO 2 , CH 4 , and H 2 O via a series of four biochemical reactions: 1) Hydrolysis - Transformation of higher molecular mass compounds suitable for use as an energy and carbon source 2) Acidogenesis - Bacterial conversion of the hydrolyzed compounds into identifiable lower molecular mass intermediate compounds 3) Acetogenesis - Lower chain volatile fatty acids produced during acidogenesis are utilized by acetogens to produce hydrogen and acetate 4 ) Methanogenesis - Bacterial conversion of the hydrogen and acetate into final end products, methane and carbon dioxide.

7. Types of Reactors used in Anaerobic Process Attached Biomass Fixed Bed: Fixed film, filter, submerged filter, /stationary fixed bed Moving Bed - Rotting discs, Rotating biological contactor Expanded bed - Anaerobic attached film expanded bed Fluidized bed - Anaerobic Fluidized bed reactor, Carrier-assisted contact process Non-attached Biomass Recycled flocks, Sludge blanket, Digester- Contact process, Upflow anaerobic sludge blanket reactor (UASB), Upflow sludge blanket (USB), Clarigester type

8. Best industrial wastewaters for anaerobic treatment Alcohol production Brewery & Winery Sugar process Starch Industries Food Processing Bakery Plant Pulp and paper Dairy Slaughter House Petrochemical Waste Municipal Sewage Sludge