REVIEW OF LITERATURE
The steady increase in slaughterhouse wastewater quantities is substantial, which requires many facilities to provide a high degree of treatment methods. Among different treatment methods, anaerobic treatment is considered as one of the best treatment option for slaughterhouse wastewater. In this section microbiology and factors affecting anaerobic digestion, different types of anaerobic treatment systems, slaughterhouse process and its pollution potential, slaughterhouse wastewater treatment methods, sludge granulation reported in literatures are discussed.
2.2 CHRONOLOGICAL DEVELOPMENT IN UASB REACTOR
The problem associated with packed bed anaerobic filters and fluidized or expanded bed reactors has led to the development of unpacked reactors that still incorporate an immobilized form of particulate biomass. One of the most successful high-rate unpacked anaerobic digester configurations was developed during the 1970s by Lettinga et al. (1980) in the Netherlands, and was descriptively termed the ‘upflow anaerobic sludge blanket (UASB) reactor’. This reactor was very similar to the first upflow sludge blanket reactor, the ‘biolytic tank’, used by Wilson and Phelps in (1910). Lettinga et al. (1980) have modified this design and applied it to wastewater treatment in a number of studies. However, recent emphasis is on its application for warm and highly concentrated industrial wastewaters and it has been successfully