Life Cycle Assessment And Study On Energy Conservation For Municipal Wastewater Process

The article mainly focuses on the energy consumption study. Using Life Cycle Assessment (LCA) to analysis energy consumption for wastewater treatment pocess, which contributes to choosing saving-energy operation and puting forward saving-energy ways.With the aid of investigation on energy utilization status in quote of domestic representative processes, energy consumption features were induced for usually adopted wastewater or sludge treatment processes and energy requirement level were acquired for common used facilities and units in treatment plant. Found the reason of energy consumption loss and influence factor in every procedure according to analysis on composition and flow-direction of energy consumption.Using Life Cycle Assessment (LCA) to identify and quantify energyconsumption for WWTP, starting from raw metiral extraction, through manufacture to plant construction, treatment operation and plant demolition, and then improvement of energy consumption is presented. The results show that most of the energy is consumed in aeration system of secondary biological treatmentprocess and 80% of energy provided is depleted in this procedure.Based on energy analysis approach mentioned above, two experiments wereconducted inthe article. Firstly, study was on influence of DO concentration on organic matter and NH3-N degradation rate and mainly provided theoretic basis for traditional supplying-oxygen model. The experimental results show that the DO concentration has a positive correlativity with organic matter and NH3-N degradation rate when it is below 2.0mg/l. The former has little influence on the latter when DO concentration is above 2.0mg/l. Organic matter specific degradation rate is near maximum and NH3-N degradation rate has little increasing trend but not. Presently, increasing DO concentration can not improve organic matter specific degradation rate also. So, for energy conservation, we can adjust feasible DO concentation through influent quantity and quality and sludge load. Secondly, Continuous flow intermittent aeration process was studied in the model. According to activated sludge oxygen uptake rate (SOUR) and maximal penetrated time of pollutant, aeration-pausing time has been confirmed. 8 operation cycles of aeration & intermittent aeration with one hour as basic alternation unit were arranged to be tested in the model. The results of Life Cycle Assessment (LCA) show that aerating for 2 hours and aeration-pausing for 2 hours & aerating for 3 hours and aeration-pausing for 3 hours can save energy 71.1% and 57.4% compared to continuous aeration process and have better removal effect. Moreover ,under the given condition of two operations, the concentration of CODcr,SS,NH3-N and TP in effluent had achieved the first grade discharge standard of GB8978-1996。Intermittent aeration operation can save energy 48.4 percent compared to continuous aeration process.