Characteristics and performance of anaerobic wastewater treatment (a review)

Summary: Pakistan's current population of 180 million is expected to grow to about 221 million by the year 2025. In developing countries such as Pakistan water pollution is a major threat to the livelihood of people. Pakistan is also currently experiencing profound demographic, economic changes and energy crisis that have major implications for water management. The contamination of aquatic and terrestrial ecosystems with heavy metals is a major environmental problem. Each pollution problem calls for specific optimal and cost effective solution so if one technology proves less or ineffective other takes its place. Every day the vast amounts of the municipal, industrial and agricultural wastes are released in to the environment and create serious problems. Anaerobic digestion is very attractive and cost-effective option and technology for the highly loaded waste water treatment and energy conversion. The anaerobic process is in many ways ideal for waste treatment. It has several significant advantages over other available methods. In this process organic matter is utilized as source of electron donor to reduce carbon dioxide to produce methane gas. It involves three bacterial groups namely: hydrolytic, acetogenic and methanogenic bacteria that work optimally at pH and temperature ranges of 6.8 to 7.5 and 30-35 degree C, respectively. The residence time in a digester varies with the amount and type of feed material, the configuration of the digestion system, and whether it be one-stage or two-stage. It is ideal for all kinds of wastewaters. Currently anaerobic technology is being operated at full scale in many industrialized nations. (author)