Preliminary Study On The Exergy Analysis Method And Energy-saving Ways Of WWTP

Wastewater treatment plant (WWTP) is the most significant and effective solution for water pollution control. But due to the high cost of daily wastewater treatment, the progress is restricted heavily. In the cost of wastewater treatment, energy consumption accounts for 60%~70%. The high energy consumption not only causes to the increase in the cost of wastewater treatment and more importantly affects the sustainable use of energy,resources and so on, but also possibly causes the new environmental pollution question in the energy production process. Therefore, the research on the energy consumption analysis of the WWTP and the energy-saving measures have the particularly important practical significance. Detailed work and major conclusion are as follows:(1) The wastewater treatment processes comply with thermodynamic laws. Based on essential principles of thermo dynamical analysis, exergy balancing model for wastewater treatment process is established and the formula of exergy efficiency for every treatment units is stated in this dissertation. The energy of NH3-N is contained in the bioreactor exergy balancing model and the exergy balancing model of anaerobic digestion tank is proposed for the first time.(2) In the paper the exergy balancing models are applied to analysis the energy consumption of the Beishiqiao sewage purification center and the nitration system of wulumuqi east of river treatment plant. The exergy efficiency of upgrading pumping station is only 59%. There exists high energy-saving potential. The exergy efficiency of aeration system is 85.54% and the most exergy loss is the external loss which is caused by the no matching of oxygen supply and demand, so it should devote in reducing nonessential,oversized propelling force or the change operating way to reduce the exergy loss of the process and equipment; The exergy efficiency of nitration system is only 33.19% and it is very low. It should aim to upgrade the overall level of sludge digestion,increase the gas yield and energy recovery and minimize the volume of sludge.(3) Based on the exergy balancing analytic method and the energy consuming analysis of the wastewater treatment plant, it is putting forward energy-saving ways. Because the analysis is based on the non-driving ideal process, it has only pointed out the improvement potential or the possibility of the process characteristic and can not state whether these possible improvements are feasible. Therefore, it is divided into the avoidable exergy loss and the inevitable exergy loss for the exergy loss and it obtains the practical efficiency from this. Compared with the above conventional exergy efficiency, the practical efficiency has the practical value to the wastewater treatment plant in the actual operation. The definitions of the avoidable exergy loss and the inevitable exergy loss have clearly point out the feasibility of the energy conservation improvement.