Status of Methane Emission in Sewage Treatment Process and Emissions Estimate in Henan Province
Abstract
Methane produced during sewage treatment is a source of greenhouse gases which cannot be ignored. The estimate of methane emissions during wastewater treatment has an important significance for proposing methane reduction measures on the technical and economic feasibility. In this paper, the status of CH4 emissions during sewage treatment of Henan Province is described. By obtaining the sewage treatment-related data and emission factor in Henan Province in 2010, CH4 emissions in the year is estimated. The results show that CH4 net emissions during domestic wastewater treatment is 21,764.10 tons in 2010 and that can evaluate the greenhouse effect and provide a basis for environmental management.
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Introduction
Methane (CH4) emissions caused by human activities include those energy activities, industrial manufacturing, agriculture activities, forest planting, animal husbandry and the process of living sewage and industrial wastewater treatment. Sewage biological treatment technology was oxidation and decomposition of the organic pollutants and plant nutrients in water and putting them into stable inorganic substance through Microbial metabolism of biological function itself. Sewage biological treatment technology is mainly composed of aerobic and anaerobic method. During the processing of the sewage aerobic method, mainly is use artificial aeration or natural aeration to provide oxygen for aerobic microorganisms, so that the organic matter is absorbed and decomposed, such as activated sludge, biological filter, rotating biological contactors and oxidation ponds. In the process of anaerobic wastewater treatment, organic matter in anaerobic conditions is a common action of anaerobic microorganisms, eventually be converted to CH4, H2S, and CO2, such as sludge anaerobic digestion, anaerobic bioreactor and anaerobic pond. Organics in the condition of anaerobic or anoxic to produce CH4, the most important emissions place is the aeration tank and anaerobic tank.
There are three methods to estimate methane emissions such as measured method, material balance algorithm and emission factor method. They have different features and complement each other. Emissions coefficient method is also known as emission factor method. The activity level data of coefficient method is the amount of emissions of unit product emission quantity under normal production conditions. It can generally be obtained by measurement, investigation and material balance method.
In 2010, It has built 146 municipal sewage treatment plants and 27 town sewage treatment plants in Henan province and the provincial industrial and urban sewage emission is 3.587 billion tons. The industrial wastewater emission is 1.504 billion tons accounting for 42% of the wastewater emission and the urban sewage emission is 2.083 billion tons accounting for 58%. Chemical oxygen demand (COD) of the main pollutants is 619700 tons. In this paper, we adopt IPCC emission factor method and calculate the emissions of methane in the sewage treatment process in Henan and the results are analyzed and discussed.
Conclusion
This paper chose activity level data in the sewage treatment process in recent years and the relevant emission factor which think the actual status of CH4 emissions. According to the method recommended by IPCC guidelines for national greenhouse gas inventories 2006, a calculation model was established to assess methane emissions of wastewater treatment in Henan. Methane emission from sewage and industrial wastewater treatment process was estimated. In 2010, net CH4 emissions from sewage treatment process are 21764.1 tons. Through the analysis of CH4 emission from sewage treatment, we can see that the net emissions of CH4 in 2010 was 7087.69 tons more than that of 2005. Clean development mechanism (CDM) of anaerobic denitrifying of sludge in sewage treatment system will be the next focus.
