Feasibility Study About Tianjin Huanxin Sewage Wastewater Treatment Plant’s Reconstructionand Expansion Project

Municipal wastewater treatment plants are not only the significant componentsof municipal infrastructure but also the key step to control the urban water pollution.However, their construction and operation costs are large and they are restricted byvarious factors. To optimize the treatment craft is the key factor to ensure itsoperation performance and to reduce its cost. Thus, it is necessary to choose treatmentcraft with advanced technology, feasibility and reasonable costs according to thedefined quality target and the design concept about integrative optimization. What’smore, the design scale, water quality characteristics and local physical condition andrequirements should also be taken into account. After a general technical andeconomical consideration, the best treatment craft can be selected.The municipal wastewater in Tianjin is belong to common municipal wastewaterand the requirements to the outlet water should attain the second class of ‘Dischargestandard of pollutants for municipal wastewater treatment plant’(GB18918-2002); itis not very difficult to deal with, and there is also a treatment plant in Jinnan newdistrict (Huanxin sewage wastewater treatment plant), but as the development of thecity’s economics, the outlet water quality of the plant can’t meet the requirements ofdevelopment of Jinnan new district. To promote sustainability of the city andameliorate the water environment quality in the district, and to build a goodatmosphere for the economic development, it is urgent to reconstruct the wastewatertreatment plant. The craft in this plant has the function to remove nitrogen andphosphorus. Based on the characteristics of the project, the two crafts of circulationoxidation ditch with vertical impeller aeration and inverted AAO with inletting waterin different points. After comparing these two plans comprehensively, the invertedAAO is one of the most common craft to remove nitrogen and phosphorus and eachreaction group is a reactor, and to divide it into anaerobic zone, anoxic zone andaerobic zone, the reflux quantity should be adjusted by adjusting water inlet pointsand pump system, to control the effect of removing nitrogen and phosphorus. The finebubble aerator can be used to improve the oxygen utilization. In order to save theelectric energy in a large scale, the adjustable aerator should be adopted. In anaerobicand anoxic zone, the agitator under water can be used to ensure the performance. Inthe operation management, it has been used widely and many experiences could be studied. Its work condition also can be regulated according to the inlet water qualityeasily. To the investment, two crafts are just as the same, but AAO plan spends muchless cost to treatment and operation, and its floor space is smaller. Thus, the projectchooses inverted AAO plan.The treatment plant adopts the craft of inverted AAO with inlet wastewater indifferent points, and discharges the water into Dagu River after treated. Aftermechanical thickening and dehydration, the rubbishes and surplus biological sludgein the process will be transported to landfill to dispose. The project will preventmunicipal wastewater to pollute the underground water and protect the groundwaterresources. At the same time, it is the sustainable utilization to wastewater resourcesthat supply ensure to the social economic sustainable development.