Anaerobic digestion of phosphorus rich sludge

In this study, the main purpose was to investigate the behavior of phosphorus during anaerobic digestion process of İzmir Wastewater Treatment Plant?s (İzmir W.W.T.P.) sludge, which tends to have higher phosphorus concentrations than conventional activated sludge processes because of the mechanism of biological phosphorus removal.The stabilization and gas production potential of İzmir W.W.T.P.?s sludge were investigated. The best anaerobic digestion process parameters and the solids and phosphorus balance during the anaerobic digestion process were determined. According to the determined parameters the anaerobic digesters were designed and the energy productions were determined.The studies were carried out in three stages:In the first stage, the characteristics of primary, excess and mixed sludge were determined.In the second stage the methane production potentials, the COD contents that can be anaerobically converted to methane, of the primary, excess and mixed sludge were determined by using biochemical methane potential (BMP) assay.In the third stage, an anaerobic digester model with five reactors was used. Three of the reactors were used for primary, excess and mixed sludge. The inoculum sludge was taken from Ankara W.W.T.P. anaerobic digester. The dry solids and volatile solids reductions, gas productions and the behavior of phosphorus were monitored.When the volatile solids and COD reductions, the gas production and the methane content of the gas are evaluated, the optimum hydraulic retention time was determined as 15 days for İzmir W.W.T.P primary, excess and mixed sludges. At this HTR the electricity production of the plant would be 112.875 kWh/d which is more than the consumption of the whole treatment plant as 100.000 kWh/d.It can be concluded that, 25 % of the phosphorus was released from the structure of both the excess and mixed sludges during the anaerobic digestion process which adds a 20 % phosphorus load to the influent phosphorus load.