| In recent years,with the rapid development of social economy and the acceleration of urbanization construction,frequent human activities and changeable natural climate make the problem of water eutrophication in China more and more serious.With the development of ecological water conservancy environment,ecological ditch technology is an ecological restoration project which follows the principle of near nature.It has been proved that it can be used as an effective eutrophication water restoration technology in practice.However,in the cold and arid areas of northern China,due to the reasons of high cold,less rainfall and strong evaporation,the alkalization of soil and water is serious,which is not conducive to the normal play of plants and matrix in the ditch system,thus limiting the application of ecological ditch technology.According to the climate conditions,the characteristics of surface eutrophication water body and the treatment demand in the cold and dry areas,this paper carried out the research and demonstration of multi-media composite ecological ditch technology.Based on the combination of indoor simulation test and field demonstration project,this paper analyzes the removal effect of nitrogen and phosphorus by different packing combinations and plant collocation methods from the perspective of optimal allocation of plants and substrates,and optimizes the packing combinations and plant collocation methods suitable for the ecological ditch system in cold and arid areas.Based on this,the ecological ditch demonstration project is established with the water intake ditch of Saihantala Wetland Park as the research object.Through the analysis and evaluation of the operation effect,environmental benefit and economic benefit of the project,the feasibility of its practical application is explored,in order to design the ecological ditch suitable for controlling the non-point source pollution in the cold and arid areas.The main research results are as follows:(1)Based on the isothermal adsorption test,comprehensive test results and material economy,natural zeolite,waste brick and slag were selected as the ecological ditch filling matrix.The results show that the removal efficiency of ammonia nitrogen and phosphorus is the best when the waste brick,natural zeolite and slag are combined according to the mass ratio of 1:1:3,and the removal rate is more than 90%.Based on the experiment of temperature,pH and salinity,it is found that the composite matrix can give full play to its advantages according to the water quality characteristics of surface eutrophication water in cold and arid areas.(2)In the experiment of plant optimization,taking the slow seedling time,survival rate and plant growth status as the index of plant adaptability,it was found that typha,iris,chelidae and shallot could better adapt to the cold and arid environment.In addition,the growth of five plants changed greatly before and after the experiment,especially typha.Because of the unique climate conditions in the cold and arid areas,the wind is strong all the year round,which is not conducive to the growth of shallots.Finally,cattail,lythrum and iris are selected as ecological ditches for planting plants.Through the plant configuration optimization experiment,it is found that the removal rate of ammonia nitrogen in the treatment system composed of three plants is 34.5%,the removal rate of phosphorus is 21.2%It is superior to the system composed of two plants and a single plant system.Finally,the ecological ditch plant is planted in the way of cattail,lythrum and iris.(3)The total nitrogen,ammonia nitrogen,total phosphorus and COD in and out of the field ecological ditch demonstration project were detected.The results showed that the removal efficiency of total nitrogen,ammonia nitrogen,total phosphorus and COD in the ecological ditch system were good,and the removal rates were 42.2%,36.7%,39.5%and38.4%.According to the environmental quality standard for surface water(GB3838-2002),the effluent concentration of ammonia nitrogen meets the requirements of class-IV,the effluent concentration of total phosphorus meets the requirements of class III water,and the effluent concentration of COD meets the requirements of class-V.(4)Through the analysis of the effects of temperature,rainfall and HRT on the removal of pollutants in the water during the experiment,it is found that from July 3 to the beginning of September,the removal growth rates of total nitrogen,ammonia nitrogen,total phosphorus and COD are respectively 134.35%,147.59%,42.32%and 128.86%.After September 10,due to the unique climate conditions in the cold and arid areas,the temperature difference between day and night is too large,and the removal growth rate of total nitrogen,ammonia nitrogen,total phosphorus and COD in the ecological ditch system decreases,respectively 98.79%,106.6%,20.83%and 97.94%.In July,the average removal rates of total nitrogen,ammonia nitrogen,total phosphorus and cod were 26.13%,26.91%,21%and 24.38%,respectively.In August,the growth and microbial activity of plants were in the active period,and the removal capacity of pollutants was strong.The average removal rate of pollutants in the three rainfall processes was more than 30%.When the hydraulic retention time is 23.89 h The removal rates of total nitrogen,ammonia nitrogen,total phosphorus and COD are respectively 54.15%,47.89%,45.98%and40.04%The removal effect is relatively better.(5)The total nitrogen,ammonia nitrogen,total phosphorus and COD of the ecological ditch demonstration project were reduced to 2.277kg,0.823kg,0.108kg and19.639kg respectively during the experiment.The total construction cost is 5,367.75 yuan.According to the test time,the treatment cost is about 4.5 Yuan/m~3,and it can realize the secondary utilization of waste bricks and slag.It has many advantages such as adjusting measures to local conditions,economy and effectiveness,simple management,energy conservation and emission reduction,etc.It fully embodies the concept of sustainable development. |
PDF Full Text Request