| The development of the different administrative regions of the Taihu Lake Basin,and the degree of pollution, lead to a different approach to the various regions. Takinginto account the division of the Taihu Lake Basin by the environmental protectiondepartment and the department of water resources, as well as a combination ofadministrative divisions, the rivers, which are directly connected with the Taihu Lake,flowing through the region is divided into four pollution control districts. It is for thebetter development in Taihu Lake Basin water quality survey research and subsequentpollution control plan formulation. In this paper, the water quality spatial andtemporal distribution characteristics of20rivers in the four pollution control area ofthe Taihu Lake Basin were investigated. And it takes the representation of the targetrivers-the Hengtang River as the research object to study river water qualityinter-annual variation,so as to provide data to support lake protection. In order toachieve the purpose of the elimination of the threat of eutrophication and purify thewater source, this is the first to carry out biological wetland bed technology to dealwith eutrophication of water test according to the basis of the variation of river waterquality. In this paper, Biological wetland bed plants screened, Optimization ofProcess Parameters, Comparison of long-term operating results with the traditionalwetland system, Analysis of the dynamic model of pollutants and Microbial diversityof plant rootsr, espectively, were carried out.1) Based on four defined polluted regions of Taihu Lake basin, different waterquality indexes of20rivers around Taihu Lake were measured between June2009toMay2010, and the characteristics of the spatial-temporal variation were analyzed. Theresults showed that the rivers in the northern heavily polluted control region werepolluted more serious than those in other polluted regions. The overall pollutionintensity order was: northern heavily polluted control region> western heavilypolluted control region> polluted control region of western Zhejiang Province>eastern polluted control region. And northern heavily polluted control region wassignificantly higher (p<0.05) the pollution level than the polluted control region of western Zhejiang Province and eastern polluted control region, and no significantlydifference with western heavily polluted control region. The nutrient concentration ofriver water had significantly difference between winter and summer except CODMn.2) From June2010to May2011, the water samples of Hengtanghe River werecollected in Zhoutie town near the village of Yangxi, Yixing. The variation of riverwater quality was analyzed throughout the whole year. The results showed that:(1)the annual total nitrogen (TN) concentration was inferior to Class V water qualityexcept in August, while other indexes were superior to Class V water quality.(2)Dissolved total nitrogen (DTN) accounted for the main form in TN in the river, andNH3-N concentration had similar tendency with TN concentration, while TP wasmainly in the form of particulate phosphorus (PP). Permanganate index (CODMn) hada higher concentration during June and August compared to other months, and themaximum chlorophyll a (Chla) concentration was monitored in August. There weresignificantly higher CODMnand Chla concentrations in the hot season than that in thecold season, while the TN concentration exhibited the opposite tendency with CODMnand Chla.(3) There was a significant correlation among the water quality indexesexcept TP.3) A comparative study of the efficiency of contaminant removal between fourplant species in the bio-rack wetlands and between bio-rack system and controlsystem to evaluate the decontamination effects of four different wetland plants. Therewas generally a significant difference in the removal of total nitrogen (TN), ammonianitrogen (NH3-N) and total phosphorus (TP), but no significant difference in theremoval of permanganate index (CODMn) between bio-rack wetland and controlsystem. Bio-rack wetlands planted with Thalia dealbata had higher nutrient removalrates than wetlands planted with other species, and removal of TP was significanthigher (p<0.01) than others. Plant fine root (root diameter≤3mm) biomass rather thantotal plant biomass was related to nutrient removal efficiency. The study suggestedthat the nutrient removal rates are influenced by plant species, and high fine rootbiomass is an important factor in selecting highly effective wetland plants for thebio-rack system. According to the mass balance, the TN and TP removal were in therange of61.03--73.27g/m2and4.14--5.20g/m2in four bio-rack wetlands during the whole operational period. The N and P removal by plants uptake constituted34.9%--43.81%of the mass N removal and62.05%--74.81%the mass P removal,respectively. The study showed that nitrification/denitrification process and plantuptake process are major removal pathways for TN, while plant uptake is an effectiveremoval pathway for TP.4) The different roots were selected randomly from the bio-rack wetland planted withThalia dealbata in October2011, and the microbial diversity was analyzed. Theresults showed that there were obvious different in bacterial species, number andpopulation diversity among the different roots. Part of the microbial community ofdominant bacteria was analyzed through cloning, sequencing and phylogeneticanalysis, Pseudoalteromonas sp., Flavobacteria sp., Tolumonas sp., Streptomyces sp.,Clavibacter sp., Clostridium sp., Mesoflavibacter, Brevundimonas sp., andChromobacterium sp. were included in different roots and these dominantmicroorganisms planted key roles in the removal of pollutants in bio-rack wetlands.5) Bio-rack wetland was used to pretreat eutrophicated source water for the firsttime. Five bio-rack wetlands were conducted in the natural conditions. The optimalHLR is0.54m3/(m2·d) and the optimal water surface level is40cm, as well as thedensity of plants was100plant/m2when bio-rack wetland used as source waterpretreatment process, in which the contaminants were removed effectively.6) A comparative study of the efficiency of contaminant removal was conductedbetween the bio-rack wetland and the conventional constructed wetland from March2011to February2012. The results showed that the plants could be adaptable to givencircumstance with the low pollution loads and higher plant density. The monthly averageremoval rates in the bio-rack wetland and the constructed wetland were:27.09%-59.10%and37.64%-48.45%for total nitrogen (TN),37.37%-59.70%and29.53%-46.43%for ammonia nitrogen (NH3-N),61.01%-75.87%and57.31%-82.15%for total phosphorus (TP), and9.39%-25.48%and22.39%-46.80%for permanganate index (CODMn), respectively. The nutrient removal rates andeffluent DO concentration were significantly higher (p<0.05) in bio-rack wetland thanin constructed wetland during the operational period except in July and August,whileCODMnremoval rates were significantly lower(p<0.01) in bio-rack wetland than in constructed wetland.7) According to the actual instance,pollutants removal rate of bio-rack wetlandsystem was not steady。Based on reactor kinetics theory, the relation between CODMn,TN, NH3-N, TP removal rate of bio-rack wetland system and effluent concentrationwas studied, the results showed that degradation reaction of CODMn, TN, NH3-N, Twas complicated.
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