Research And Application On Construction Engineering Technology Of Tianjin Eco-city Healthy Water Environment System

Based on the request of a new type ecological and livable city construction,the water environment quality of sino-Singapore Tianjin Eco-city is crucial part.However,the water environment of Eco-city region is extremely poor.In order to meet the requirements of water environment system construction standard,a series of actions should be taken to solve the water environment problems.In sino-Singapore Tianjin Eco-city,high standard of water environment construction,scarcity of water resources,poor background of water environment and high demond of ecological water are all the key problems.In this study,characteristics of water quality and quantity in Eco-city on multi-source water supply and landscape water body were indentified by systematic investigation and diagnosis.The development and utilization of unconventional water sources,recycling and purification of landscape water were investigated,technique project and key parameters were optimized simultaneously through pilot scale experiment.Based on the actual characteristics of Eco-city region,an engineering technology integration system of water environment system construction was proposed.The main results as follows:(1)There are four types of unconventional water sources that can be used to replenish landscape water bodies in Eco-city,namely,reclaimed water,rainwater,transit water and desalinated seawater.According to water quality standards,reclaimed water can be divided into low-quality reclaimed water and high-quality reclaimed water.Low-quality reclaimed water is the main source of water supply,while high-quality reclaimed water is the source of emergency water supply.Rainwater is an important seasonal water source for landscape water.After proper treatment,the transit water may be used as an ecological replenishing water source;The desalinated water mainly comes from the North Jiang desalination plant,which can be used as the source of replenishing water in the near future.(2)The simulation results of the multiple sources replenishing water hydrodynamic-water quality coupling model shows that the concentration of chlorophyll a increases obviously when the effluent of first-class B from the sewage treatment plant and the transit water is used as replenish water.And because of the high concentration of nutrients such as TP and NH3-N in the two water sources,the TP and NH3-N will accumulate near the water rehydration point with the growth of time,the effluent of first-class B and transit water cannot meet the water rehydration quality requirements.(3)Based on the current problem,the present water supply can not meet the requirement of the water replenishment,a trial study was carried out on the treatment of first-class B effluent and transit water by different combination processes.The micro-flocculation and air floatation filtration process has been developed to realize the deep switching treatment of the same facility for the effluent of the sewage plant,rainwater,transit water and other water sources.The technology has been applied effectively in practical projects,which ensures the quality of rehydration and low cost operation.(4)Aiming at the problem of stagnant landscape water in the eco-city,a hydrodynamic cycle-water quality model of landscape water was built to simulate and analyze different seasons and operating conditions of landscape water.The short-term,medium-term and long-term water replenishment and water circulation schemes are put forward.The results show that the scheme of water replenishment and hydrodynamic circulation can improve the conditions of hydraulic circulation,the velocity of water and the water quality.(5)The average values of COD,NH4+-N,TP,TN,chlorophyll a in landscape water were 29 mg/L,0.38 mg/L,0.09 mg/L,1.29 mg/L,45 ?g/L after the implementation of landscape water recycling purification,multi-source water replenishment and ecological restoration projects.Water quality indicators can meet Class IV of Surface Water Environmental Quality Standard(GB3838-2002).At the same time,according to the status quo,the construction and operation tracking observation of the landscape water body of Jing Hu Gu Dao river,especially combined with the actual operation effect of the water body,put forward preliminary suggestions on the seasonal operation mode of landscape water body.(6)According to the overall idea of Eco-city water environment system construction and the project implementation conditions,the basic principles “overall planning,step-by-step implementation,comprehensive design,technology integration,precise construction,coordination,flexible operation,and focus on objectives” were clarified.Technical route of water system construction and water quality maintenance was proposed: analyze demand of ecological water body,ensure water balance,control sources of water pollution sources,ensure clear water source of lake,strengthen self-purification of water system,ensure goal of water quality,optimize approaches of engineering,support restoration of water environment.Finally,engineering technology integration system are meaningful to promote water supply,water source pollution control,water purification and water environment restoration.(7)Based on this engineering doctoral thesis,multi-water source hydration deep treatment and landscape water body circulation purification technology have been successfully demonstrated in Tianjin Eco-city.Technical guide of Tianjin Eco-city water environment system engineering construction was formed on the basis of the demonstration project.Moreover,this Technical guide was adopted by the Tianjin Eco-city Management Committee to provide technical support for the Tianjin Eco-City to meet the surface IV standards in 2020.