Analysis of performance and potentials of energy saving and reduction for anaerobic digester in Wastewater Treatment Plant

Operation performance of a typical anaerobic digester of sewage sludge within Shen Yang North Wastewater Treatment Plant in recent 3 years was evaluated. Results showed that a stable treatment efficiency was attained with regard to sludge reduction and stabilization. Historical data on air temperature and sludge temperature were used to perform a sludge heating requirements analysis on a monthly basis. Finally, suggestions on energy saving and reduction were dealt with. Two possible ways were put forward, namely heat recovery from digested sludge and CHP unit (combined heat and power) for biogas utilization. Heat regeneration with a conventional counter flow heat exchanger between sludge (digested) outflow (35°C) and sludge (raw) inflow (14 °C) preheated the inflow raw sludge to a temperature of 27.8°C at HRT of 10 min. Biogas utilization for energy production was feasible concerning the advantages of both covering heating requirements for operation of mesophilic digestion and additional electricity production.