| Anaerobic digestion has been an integral part of wastewater treatment for over one hundred years. In recent years, anaerobic digestion has been rediscovered as a very effective method of treating high strength industrial wastewaters. However, the industrial use of anaerobic digestion has brought the problems of controlling the digestion process back to the attention of consultants and researchers and has shown a continuing need for fundamental operating knowledge.; This study was conducted to investigate the fundamental characteristics of anaerobic microbial populations during metabolism of specific organic substrates with known nutrient addition, including seven trace metals, at varying retention times. The substrates utilized during this study were representative of the major components of wastewater and included: sodium butyrate, glutamic acid, glucose and sodium benzoate. The seven trace metals added were: cobalt, copper, iron, manganese, molybdenum, nickel and zinc. The retention times of the laboratory anaerobic digesters varied from 10 days up to 43 days. The digesters were operated as batch-fed units for a length of time to allow the digesters to approach equilibrium culminating with the performance of a rate study.; The results of this study indicate that hydraulic and solids retention times are very important parameters affecting batch anaerobic digestion systems. Optimum metabolism occurs with sufficient accumulation of active microbial mass and limited accumulation of inert suspended solids. Daily feeding with long retention times results in the accumulation of inert solids, both soluble and suspended, which have an adverse effect on metabolism.; Sufficient alkalinity must be provided to neutralize the intermediate organic acids formed during metabolism of the organic substrates if optimum rates of stabilization are to be achieved.; The results also indicated the amount of COD energy incorporated into the synthesized microbial mass in the 37{dollar}spcirc{dollar}C digesters for the different substrates was: 1.6 percent of sodium butyrate COD, 1.8 percent of glutamic acid COD, 3.2 percent of sodium benzoate COD and 13.7 percent of glucose COD.; The metabolism of the acetogenic bacteria was the primary rate limiting step for all substrates tested in the laboratory batch anaerobic digesters. The shift from one substrate to another produced significant changes in the microbial populations, requiring varying periods of acclimation and reseeding. The presence of the seven trace metals contributed to long term operational stability. |
