10.22376/ijpbs.2019.10.1.p1-12 Volume 9 Issue 1 2018 (January-March) Wastewater- used water from farms, communities, villages, homes, urban areas or industry that could hold harmful dissolved or suspended matter. Nevertheless, waste water also has necessary nutrients for plants (e.g. nitrogen and phosphorus) and is potentially a very favorable fertilizer. The organic carbon in the waste water, formerly stabilized, is a potential soil conditioner because it improves soil structure for plant roots or can be altered into energy through bio-digestion or incineration. The aim of this review is to assess scientific techniques used to boost the performance of anaerobic digestion lessThan b greaterThan ( lessThan /b greaterThan AD) in order to improve the quality as well as the quantity of its products. Anaerobic digestion depends on several different parameters for an optimum performance. Completely different teams of microorganisms are involved in the methane production and suitable conditions have to be established to keep all the microorganisms in balance. Some of these parameters are: pH, temperature, substrate composition, C/N ratio and hydraulic retention time (HRT). There are chiefly two temperature ranges that provide optimum digestion conditions for the production of methane- the mesophilic and thermophilic ranges. A pH range of 4.0-8.5 is acceptable for the continuation of activity for hydrolysis, acidogenesis and acetogenesis, while methanogens operate within a much narrower pH range, typically between pH 6.5–7.5. Digestion is leisurely process and it takes at a minimum of three weeks for the microorganisms to adapt to a new condition when there is a change in substrate or temperature. BERHANU KIBEMO, PUNITHA THAMBIDURAI AND MOORTHY KANNAIYAN* Anaerobic digestion, Bioenergy, Bio-fertilizers, Environment, Optimization factors, Waste water 275-280