Study On The Efficiency And Mechanism Of Sediment/Water Purification By Interfacial Oxygen Content In Muddy Water

Viewed from the current technology of contaminated sediment/water remediation,there are many negative effects,such as high cost,large area,unsustainable,secondary pollution,and little effect due to environmental and seasonal factors.Therefore,from the point of view of eco-environmental protection and economies,it is urgent to develop new methods to reduce pollutants in sediments.In view of the low purification efficiency of contaminated sediments/water bodies,this research will be studied following these aspects.The method of aeration can improve the dissolved oxygen concentration of the slurry-water interface,and keep the dissolved oxygen concentration of the mud-water interface in a certain range.The dissolved oxygen concentration at the slurry-water interface increased significantly with the increase of aeration.When aeration increased from 6 mL/min to 15 mL/min,the dissolved oxygen concentration at the slurry-water interface increased from 4 mg/L to 7 mg/L.While the dissolved oxygen concentration at the sludge-water interface was 7 mg/L,the oxygen content in the system was abundant,the number and activity of aerobic bacteria increased clearly,and the metabolic rate accelerated.At this time,the sediment/water body achieved the best purification effect.Oxygen enrichment in water promoted the improvement of oxygen environment in sediments,and the maximum redox potential in sediments was-332 mV.Under the optimum conditions of sediment oxygen environment,the removal rate of carbon and nitrogen was the fastest,and the system kept the best ammonia nitrogen,total nitrogen,nitrate nitrogen and total organic carbon accumulation rate,reaching 0.07 mgL/d,0.154 mgL/d,0.08 mgL/d and 0.45 mgL/d,respectively.Therefore,aeration is a kind of sediment/water restoration technology with good removal effect.The dissolved oxygen content at the mud-water interface could be effectively increased by the presence of goldfish algae under aeration conditions with a way of the combination of aeration and phytoremediation,which was 0.2-0.4 mg/L higher than that without goldfish algae under the same aeration amount.Oxygen production by photosynthesis and root exudation of goldfish algae supplemented the oxygen content in the system.When the concentration of dissolved oxygen at the mud-water interface was 7 mg/L,the combination with goldfish algae could achieve the bestpurification effect on sediment/water body.The roots of goldfish algae could absorb small molecules of carbon and nitrogen in sediment,and the developed leaf tissues could also absorb carbon and nitrogen in water.Goldfish algae improved the oxygen environment of water body,increase the redox potential of sediment by 34 mV,and further promote the release rate of carbon and nitrogen in sediment.Under this environmental condition,the accumulation rates of ammonia nitrogen,total nitrogen,nitrate nitrogen and total organic carbon increased significantly,reaching 0.097mgL/d,0.2117 mgL/d,0.17 mgL/d,0.46 mgL/d and 0.47 mgL/d,respectively.To sum up,goldfish algae can promote the purification efficiency of sediment/water,and aeration and phytoremediation combined technology has a better purification effect on sediment/water than aeration technology.The improvement of environment promoted the growth of goldfish algae.The higher the dissolved oxygen concentration at the mud-water interface,the more obvious the promotion effect on goldfish algae.When the dissolved oxygen concentration at the mud-water interface was 7 mg/L,the growth of goldfish algae was the best.The plant height,root length,biomass,chlorophyll a content,chlorophyll b content,total chlorophyll content,total nitrogen content and total carbon content increased by 28.8%,70%,133%,41.7%,57.5%,46.9%,28.8% and24.2%,respectively.It indicates that when aeration and phytoremediation are used together,the improvement of sediment environment and plant growth are mutually promoting.Finally the effect of dissolved oxygen on microbial community structure is discussed,by comparing the diversity of microbial communities and microbial on the door,belong to the difference of level,found that increase the dissolved oxygen concentration can promote bacterium door the increase of the relative abundance of aerobic bacteria,such as door deformation bacteria increase in relative abundance makes relative abundance of thick wall fungus door.Under the coupling condition of plant and aeration,the relative abundance of proteobacteria is the largest,57.09%.With the addition of aerobic bacteria with high abundance in the water,the mechanism of sediment/water body with very good repair effect under the combination of aeration and phytoremediation is revealed.