Seasonal Purification Effect And Ecological Health Assessment Of Water Source Ecological Purification System

The water source ecological purification system with artificial wetland as the core has gradually become one of the hot spots of micro-polluted water source pretreatment.Due to its unique semi-natural and semi-manual conditions,its purification effect and influencing factors are different from the general pretreatment process.Due to the long-term impact of the upstream river water pollution load,the seasonal purification effect of different treatment units in the water source ecological purification system is explored,the ecological health assessment of the current water quality and sediment of the system can provide theoretical guidance for the operation and management of the water source ecological purification system,and also provide a guarantee for the water quality safety.The main results are as follows:(1)Seasonal changes and characteristics of upstream water quality in water source ecological purification systemThe water temperature of the upper reaches of the water source ecological purification system is distinct;the lowest concentration of DO is in summer(2.2 mg/L),and the self-purification ability of the water body is so bad that the quality are the worst;the storm runoff leads to the summer turbidity and the fluctuation is large(30~120NTU);the total nitrogen(TN)in the upper reaches of the river exceeds the standard,and the DO,total phosphorus(TP)and permanganate index of the water in the summer water also exceed the Class III;the FI index in the upstream is 1.55~1.72,BIX index is 0.82~0.97,and HIX index is 1.2~5.1;in spring,autumn and winter,endogenous organisms dominated,and humification was the highest in summer;PARAFAC model divides dissolved organic matter(DOM)spectra into three components: fulvic acid,tryptophan and humic acid,among which fulvic acid accounts for the largest proportion;the upper three rivers have little difference in time and space.(2)Seasonal purification effect of water quality in different treatment units of water source ecological purification systemThe DO concentration in different seasons has been significantly improved by the YLH ecological purification system;DO in spring and summer was the lowest,as low as 2mg/L,which was improved after submerged vegetation area;the turbidity of YLH water decreased significantly in spring and summer,mainly due to the precipitation and adsorption of pretreatment units;the main causes of ecological problems such as algae outbreak in the system are that the concentration of TN is not up to the standard all the year round,basically between the fourth and fifth water quality,and the high concentration of TP in the system(0.06~0.32 mg/L)and the condition of the existing static water body;nitrogen has certain removal effects in the YLH system in different seasons,and the ammonia nitrogen removal is obviously different,and mainly because of the effects of pretreatment area and emergent plant area;the permanganate index exceeded the standard in summer,and the removal efficiency of each system was unstable;FI index is 1.56~1.72,BIX index is 0.84~0.95 and HIX index is 1.20~4.20,which indicates that DOM mainly comes from the contribution of microorganisms in water body,and its autogenetic characteristics are obvious;DOM can be divided into four components: terrestrial humus,fulvic acid,tryptophan and humic acid,among of them,humic acid is produced by artificial disturbances in winter sediments.(3)Ecological health assessment of water source ecological purification systemAccording to the comprehensive state index evaluation,the water quality of YLH influent in different seasons is between mild pollution and moderate pollution,the water quality gradually improves with the purification of each unit,and the water quality of effluent is basically at the level of mild pollution;the contents of total nitrogen,total phosphorus and organic matter in YLH surface sediments are 156.43~1130.00 mg/kg,615.23~1580.66 mg/kg,5.00%~49.04%,respectively;nutrient pollution of S1 in pretreatment area and S2 in emergent plant area is the most serious,while S6 in deep purification area is the lowest;the total concentration of heavy metals in sediments is in the order of Fe > Mn > Zn > Cu > Ni > Cd from large to small,and the order of heavy metals concentration in different areas is S1 > S2 > S3 > S5 > S4 > S6 from large to small;it is suggested that silt removal be carried out in units S1 and S2.