ABSTRACT
The wastewater released from various agricultural activities and food processing industries is one of the major contributors in increasing the pollution load of the environment. Due to the presence of a high load of dissolved organics, suspended and dissolved solids, organic matter, nutrients in the form of fertilizers, high biochemical and chemical oxygen demand, inorganic salts, fats, oils, detergents, the wastewater from these activities must be effectively treated before releasing it safely into the water and soil. Anaerobic digestion proved to be an economic and simple method for efficient treatment of both agricultural and food processing waste. High concentration of organic content makes them suitable for maximum biogas production. Biogas contains 63% methane, 30% carbon dioxide, 4% nitrogen, 1% hydrogen sulphide with fractions of hydrogen, oxygen, and carbon monoxide. Biogas can be used as a biofuel in rural areas for cooking and lightening. Anaerobic decomposition takes place in a sealed vessel known as a reactor, which is designed and constructed in various shapes and sizes specific to the site, environmental conditions, and feedstock material. Various anaerobic reactors have been designed for complete breakdown of waste into biogas (biofuel) and sludge (biofertilizer) under optimized conditions like pH, organic loading rate (OLR), hydraulic retention time (HRT), temperature, nutrient addition, strict anaerobic conditions, carbon and nitrogen ratio, dimensions of reactor, strict anaerobic conditions, particle size for maximum growth of anaerobes. The efficiency of anaerobic digestion depends on design, development and operating conditions of high-rate anaerobic reactors. Optimally operated bioreactors can decrease the total time of treatment and increase the overall treatment efficiency by lowering the cost of treatment.
