The Effect Of Dissolved Organic Matter And Aquatic Plant Humidification On Chemical Oxygen Demand In Yilong Lake

Yilong Lake is one of the nine plateau lakes in Yunnan Province.It has various functions such as water storage and flood control,farmland irrigation,production and living water supply,aquaculture,sightseeing and climate regulation.Since the beginning of the 21st century,the water quality of the whole lake has changed from the original type III water to the type IV or inferior type V water.Yilong Lake is one of the four lakes with long-term inferior V water quality in the nine plateau lakes.From January to December 2017,the main pollutants were chemical oxygen demand?COD?,total nitrogen,and permanganate index(COD_Mn),the mean values were 50.54mg/L,2.02 mg/L,and 11.94 mg/L,respectively.This study analyzes the source of COD in Yilong Lake from the dissolved organic matter and aquatic plants.In May and September 2018,samples was sampled,the organic matter was separated and adsorpted by XAD-8 and XAD-4 resin in series,and investigate the effect of hydrophilic and hydrophobic substances on COD.Select five representative aquatic plants in Yilong Lake,then prepare a certain concentration of solution to simulate the humification degradation process and explore the changes of COD during the process.Study results are as follows:?1?The analysis results of effluent water samples from Chenghe,Lake and sewage treatment plants,the contribution of insoluble suspended solids,hydrophobic organic matter and hydrophilic organic matter to COD was different in May and September 2018.The average value of the lake surface,the proportion of hydrophobic organic matter was 21.50%and 16.83%and the proportion of hydrophilic organic matter was 6.89%and 15.78%,respectively,in May and September.The river into the lake,the proportion of hydrophobic organic matter was 18.17%and16.56%and the proportion of hydrophilic organic matter was 6.48%and 15.19%,respectively,in May and September.The sewage treatment plant effluent,the proportion of hydrophobic organic matter was 22.28%and 37.86%and the proportion of hydrophilic organic matter was9.95%and 22.68%,respectively,in May and September.?2?In aquatic plant humification degradation experiment,among 5 aquatic plants,according to the contribution to the COD value of the receiving water,their order is Phragmites communis>Typha orientalis>Potamogeton wrightii Morong>Potamogeton pectinatus L.>Hydrilla verticillata,at the end of the culture period,the COD value of aquatic plants is closed to the blank water sample.?3?In the process of algae microbial degradation,the COD value of algae tended to be stable after reducing,in culture period,and the experimental group with seawater addition has a faster rate of reduction than the blank control group.