Study And Estimate On Energy Balance Analysis For Municipal Wastewater Treatment

Energy consumption is so high and energy efficiency is low in operation of wastewater treatment Plant(WWTP), which restricts the Progress heavily in China. But study on energy consumption and energy efficiency for municipal wastewater treatment processes hasn't made great progress.In the dissertation based on Thermodynamic analysis, water quality index and energy index is coupled. Energy-balancing model was used to analyse the main energy dissipation units of three sewage treatment plants which adopt dominant processes in Henan province, and their energy-efficiency is evaluated. In order to provide guidance for energy saving in WWTP's design and operation.Main work and the conclusions are as follows:(1) Based on investigation on energy utilization status in three representative processes in Henan province, energy consuming features of wastewater was summarized, and energy requirement level of main units in treatment plant were analyzed.(2) Based on thermodynamic analysis, energy-balancing black-box model and exergy-balancing gray-box model was improved in main units of energy requirement, and the using ranges of two kinds of model was distinguished in bioreactor tanks.(3) In the paper, the energy-balancing black box model and exergy -balancing gray box model was applied to analysis the energy and exergy consumption of the three WWTPS. The exergy efficiency of upgrading pumping station is 30%-70%, there are possibility of saving energy; the energy accumulated of substrate in Biological treatment unit is mainly used for microbial cells's maintenance and splashing(15%～35%), cell proliferation (15%～30%) and surplus sludge (15%～30%), so the exergy of microbial cells's maintenance and splashing should be increased to increase internal exergy loss;The most exergy loss of aeration system is the external loss, so it should devote in reducing needless, excessive driving force, and optimizing operation mode.(4) Combined with model analysis results, energy indexes(single energy consumption index, heat efficiency, purpose of exergy efficiency) was applied to analyse and contraste the energy utilization status of different processes:The oxidation ditch process has less excess sludge and higher energy efficiency than the A2/O process.