The Microbial Diversity In Aerobic/Anaerobic Subsurface Flow Constructed Wetland And Its Relationship With Water Purification Capacity

With the rapid development of economy and society in Chinese villages, thevolume and concentration of domestic sewage became more and more, and thepollution problems have become extremely severe day by day. Rural sewage withhigh dispersion, big changes in the water volume and quality, far away from themunicipal pipe and large-scale wastewater treatment generally was not processed ordischarged into the rivers and lakes, which caused serious environmental pollutions.Constructed wetlands purification systems have the advantages of low cost, lowenergy consumption, easily spreading the construction and management and so on. Soit was suit to Chinese situation of sewage treatment in towns, and were one of themost appropriate rural sewage treatments.Due to the structural limitations, conventional subsurface flow constructedwetlands （SFCWs） cannot provide strict aerobic and anaerobic environment at thesame time, and the removal efficiency of pollutant was not very high, generallybetween40%and55%. In the early study, we aimed to improve the removalefficiency of pollutant in the traditional wetland by optimizing its structure andenhancing its function. The results showed that artificial aeration could enhance theremoval efficiency of COD and NH₄⁺-N, the dissolved oxygen and carbon sourceswere important factors affecting denitrification. Two measures of adding influent andextending the length of anaerobic stage could remarkably increase removal rate ofTN.In order to investigate the mechanism of better efficiency of the type of wetland,FDA, DAPI and BIOLOG methods were used to measure the activity, quantity andfunction diversity of the microorganisms, and to analyze their relevance with capacityof water purification. The results indicated that, along with the water flow, themicroorganisms in different kinds of SFCWs showed different trend of change of theactivity and quantity. And the relationship between the value of96h AWCD and theirrespective outflow total nitrogen removal rate was extremely significant （p<0.01）. Thequantity of microorganisms was related to COD removal amount, total nitrogenremoval rate and total nitrogen significantly （p<0.01）.We used AWCD values got from the BIOLOG for the classification of carbonsource analysis, principal component analysis and cluster analysis. The results showedthat the microbial utilization degree of carbohydrate, amino acids were significantlyhigher than that of fatty acid and lipid, metabolic intermediate. The microbialutilization degrees of four kinds of carbon sources in sampling site3.3（the anaerobiczone） in OBAAO （aerobic-buffer-anaerobic-anoxic-aerobic） A were the lowest,and it had significant difference with that of the other sampling sites （p<0.05）. Theresults of principal component analysis and cluster analysis indicated that themicrobial community of the sampling site3.3in OBAAO A had high difference with that of the other3anaerobic zones. The microbial utilization degrees in sampling site4.3（the anaerobic zone） in OBAAO A MSI had certain advantage. The OBAAO A,extending the length of anaerobic stage, provided the anaerobic environment formicroorganisms. However, because of lack of carbon source as energy, the microbialactivity was inhibited. The OBAAO A MSI, adding influent and extending the lengthof anaerobic stage, effectively promoted the strength of denitrification, increasing theremoval efficiency of nitrogen. The results provided basic data for revealing therelationship between microbial diversity and pollutant removal rate, and providedevidence for optimizing the running of the subsurface constructed wetland.Rural sewage may carry pathogens, especially E.coli that could affect humanhealth, but the traditional disinfection processes, for example disinfectant method andultraviolet method were difficult to bring into the constructed wetland system. In ourresearch, coliphage T4, f2and their host were served as model organisms, and ourpurpose was to analyze the bactericidal effect of fungi on E.coli and to chooseallelopethy which had strong ability to affect E.coli by means of biologicalallelopethy. The results showed that fungi had obvious promotion effect on the bothkinds of coliphage, and rate reached the top at5th day for T4coliphage,4th day for f2coliphage. Using liquid-liquid extraction method extracted and separatedallelochemicals from fungi and the allelochemicals could enhance the growth ofcoliphage. Five solvents （petroleum ether, dichloromethane, ethyl acetate, n-butanoland distilled water） extractive parts showed that promotion rate of saturated n-butanolphase （fraction D） on coliphage T4and f2were the strongest, and next was thepetroleum ether （fraction A）.