Study On Treatment Effect Of Low-polluted Water In Compound Ecosystem Of River Channel

With the improvement of environmental awareness and the construction of sewage treatment facilities,more and more low-polluted water enters the landscape water body,which will have a certain impact on the water quality and water ecology of landscape water bodies.The existing low-polluted water treatment technology have advantages and disadvantages.How to deal with large amounts of low-polluted water economically and efficiently is an important part of improving water quality in rivers.In this context,this paper intends to use the river ecosystem as a carrier to conduct ecological coupling between the substrate and the aquatic plants,and develop an in situ remediation technology-the river channel complex ecosystem.It can meet the treatment requirements of low-polluted water,save land and costs.This article takes this system as the research object,analyzes its dynamic operation condition through bench-scale and optimizes,mainly draws the following conclusions:?1?Construction of river complex ecosystem?1?The selection of substrate.The isothermal adsorption and adsorption kinetics experiments are used to screen the nitrogen and phosphorus adsorption capacities of the three substrates A,B and C.The isothermal adsorption processes of the substrates TN,NH₃-N and TP correspond with the Langmuir model.The maximum saturated adsorption capacity of TN and NH₃-N in matrix A are 1.27mg/g and 3.04mg/g.But TP adsorption capacity of substrates A is weaker than TN and NH₃-N.The removal rates of TN,NH₃-N and TN of matrix A are 22.7%,84.9%,and 6.2%in adsorption kinetics experiments,which are much higher than those of the other two matrices.Considering that the main concern factor for the treatment of low-polluted water is TN,matrix A is chosen as the test body for the inter-conglomerate contact oxidation method.?2?Aquatic plant screening.The indoor static hydroponics experiments are used to screen the nitrogen and phosphorus removal capacity of six aquatic plants:papyrus,lythrum,calendula,iris,cress,and umbrella grass.The experimental results show that under the premise of not adding low polluted water and landscape water,TN removal ability of lythrum,calendula,papyrus is stronger than other plants,and the removal rate of the above three plants is more than 60%.Lysbeckiae and papyrus have the strongest NH₃-N removal ability followed by iris and umbrella,the removal rate of all four plants is above 85%;Plants with strong phosphorus removal ability are calamus and lythrum.The TP removal rate of above plants is above 74%,and the TP removal rate of other plants is around 70%.In order to achieve the best treatment effect,three kinds of plants with strong nitrogen and phosphorus removal capacity are selected:lythrum,calamusand appendix,and they are combined with substrates A to construct river compound ecological system.?2?Dynamic Operation and Optimization of River Complex EcosystemThe river complex ecosystems with matrix A+calamus?AC?,matrix A+Lythrum?AQ?,and matrix A+iris?AY?are in good operation during the test period.During the early test period?temperature is 14³1??,the AC system has the highest organic removal rate of 60%.In the later stage?temperature is-2²2??,the removal rate of organic matter in each system decreased significantly,and the AQ system is relatively stable.The TN and NH₃-N removal of each system in the early stage of the experiment is not significantly different.The NH₃-N removal rate of the AQ system decreases to the minimum at the later stage of the test,and the removal rate of NH₃-N is 80.4%,higher than the other two systems?AC:57.5%,AY:9.6%?.The average removal rate of TP in the pre-test period of system is 30.3%.In the later stage,TP removal rate in the late AQ system test is reduced to 15.7%?AC:22.9%,AY:26.9%?.Although the removal effect of AQ on TP is lower than that of AC and AY systems,the AQ system has better removal of organic matter,TN and NH₃-N,and the treatment effect is stable,and it has strong adaptability to low temperature environment.Considering the characteristics of low-polluted water and system removal efficiency,the AQ system is recommended to be used as the construction scheme of the river channel composite ecosystem.The removal rate of all pollutants in the AQ system optimized by microbial agglomeration technology is higher than that of the unmodified AQ system:COD_Mnn removal rate is 65.2%?Unoptimized AQ system is 50.9%?;TN removal rate is 32.5%?Unoptimized AQ system is 15.2%?;TP removal rate is 54.5%?Unoptimized AQ system is 28.0%?.The decrease in temperature?-2²2??at the later stage of the test has impact on the purification capacity of the optimized system,but the system's pollution purification capacity is still stronger than that of the unmodified system.At the end of the test,TN removal rate is 10.8%?Unoptimized AQ system is-12.1%?,and TP is 28.0%?Unoptimized AQ system is 15.7%?.Tests show that under the same conditions,the ability of the river complex ecosystem to optimize the purification of water is further enhanced,and the adaptability to low temperature environments becomes stronger.The construction of the river channel compound ecosystem has improved the richness and diversity of microbial colonies in the river channel.The Chao1 index of system water and plant roots is 56.6%and 54.5%higher than that of ordinary simulated river waters.Nitrospira sp.,Nitrosomonas sp.,etc.with nitrification and denitrification,which are not detected in common simulated river channels,are detected in the river channel complex ecosystem.This proves the superiority of the river channel compound ecosystem in handling low-pollution water.In short,the use of a riverside compound ecosystem in an ordinary simulated river channel can effectively reduce the pollution caused by the entry of low-polluted water into landscape water bodies.The AQ-based river channel composite ecosystem is more suitable for the treatment of low-polluted water.The purification capacity of the process after the optimization of microbial agglomeration technology is further improved,and the adaptability to the low temperature environment is stronger.In practical applications,the degradation of TP by the process can be improved by other means such as optimizing the parameters.