The Quantitative Evaluation And Emission Reduction Research Of Greenhouse Gas Emission In Sewage Treatment System

In recent years, as the greenhouse effect problems become more prominent,and the inclement weather occurs more frequently, the global warming issue has attracted the world attention. Sewage treatment system is one of the important sources of greenhouse gas emissions, however the research about this problem is still less at present. The number of the sewage treatment plant increased rapidly in our country since" Eleven five", and greenhouse gas emissions increased too, thus the greenhouse gas emissions quantification evaluation of the sewage treatment system and putting forward measures of reducing emission are of great significance.This study describes the background of the issues raised,the research status of domestic and abroad, and analysis the current situation and existing problems of sewage treatment plant in our country. Through accessing to relevant information, the greenhouse gases emissions of the sewage treatment system can be divided into three categories,direct emissions, indirect emissions and other indirect emissions. To quantify the greenhouse gases emissions, firstly the size of the sewage treatment plant, the boundaries and the processing technology are must be cleared, and then divide the operating activities relating to greenhouse gas emissions into three categories, identifying the calculation method of each part, and select the appropriate carbon emission coefficient.After quantifying the greenhouse gas emissions, in the prerequisite of achieving sewage treatment standards as the constrained conditions,analysis the potential emission reduction of the operating activities, and propose practical emission reduction measures.The subject which took the Jinan western district sewage treatment plant as typical project, analysised and studied the related information and operating data in recent three years, according to proposed evaluation and quantization scheme,obtained the quality of total carbon emissions of the sewage treatment system in nearly three years, they are3392.67tons,3944.31tons,4581.08tons.Simultaneously according to the quantitative analysis of greenhouse gas emissions in2012, research derived the proportion characteristics of the three types greenhouse gas emissions and carbon emissions of processing units,besides study the carbon emissions characteristics of different devices.Through one year on-site test and investigation in Jinan western district sewage treatment plant in2012, the major carbon emissions equipments of each processing unit are analysised, and emission reduction measures are proposed. In primary treatment unit, most of the time the grilles are in the low efficiency state, but the energy-saving measures are not took. The influent lift pump uses frequency conversion technology, but there is energy wasting still. Before being transformed, the working efficiency of the cyclone grit chamber is not high (now the transformation has been completed). In secondary treatment unit, the model of reflux pump and propeller too large. In anaerobic tank, the stirring effect of stirrer is ineffective, so there is energy-saving space. In aerobic pond, the aeration effect of aerators is poor, so the utilization of DO is not high, and there is aeration excessive phenomenon. In tertiary treatment unit, the frequency conversion of secondary lift pump is controlled by manual, and the frequency is high, so it is not the optimal energy saving.Because the backwashing intensity of V-filter is too large, there is energy wasting. In sludge processing unit,it can save20kg PAM weekly after the mpaddle being transformed (now the transformation has been completed). The sludge dewatering uses the belt concentrated press filter, which is not the most energy-efficient equipment. For the saving space of the four processing unit, we can take corresponding measures of energy saving and emission reduction. For instance, the cyclone grit chamber was changed to be controlled by the PLC according to the time, reducing carbon emissions.For the aerobic pond, we can take three power-saving measures, which are replacing the aerators,changing the arrangement of aerators and installing inverter in the aeration rotary disk etc.After taking related emission reduction measures, in the sewage treatment system,we can predict the annual carbon emission reduction of the primary treatment; the secondary enhanced treatment unit; advanced treatment unit and sludge treatment unit are56.5tons,518tons,0.9tons,315tons, and the annual carbon emission reduction is about890tons. Finally the other greenhouse gas emission reduction measures are proposed.