| Nitrate pollution of groundwater constitutes an important and cosmopolitan environmental problem. Concern for possible health consequences has led to the recommendation of an upper limit of 10 mg N/l in water for human consumption as the World Health Organization's standard. Agricultural nitrate pollution were concerned at first. With the development of the city, the nitrate concentration of groundwater at the city areas increased, because of the complicated activities in the cities, It's difficult to ascertain nitrate source. Multiple sources of nitrate contamination generally occur within the same groundwater basin. It's very important to study the nitrate pollution in the cities, to identify the nitrate sources, and to take feasible methods to control nitrate pollution in the city. The most common method has been to measure the two stable isotopes of N (14N and 15N) in nitrate of the sample. The percentage of the two isotopes is nearly constant in the atmosphere at 0.366% 15N.It is usually compared with the ratio in the atmosphere (standard) and is defined bywhere 815N has units of "per mil"(‰). Positive 15N values indicate enrichment inδ15N while negative δ15N values indicate depletion in 15N.To control the groundwater nitrate pollution, people should prevent nitrate from going to the groundwater and remediation the contaminated groundwater. Scientists have already studied the approaches of nitrate removal. The approaches for nitrate removal had a lot of categories: physical methods, chemical methods and biological denitrifiication. Among the techniques available for the removal of nitrate from water, microbial removal (denitrification) stands out for being the most economical and environmentally sound, as well as for being feasible on a large scale. The biological denitrification had some shortcoming, such as, complex technics, high level of operation, the low denitrification rate, bulky reactor and expensive construction. To improve the biological denitrification, solid organic carbon, cellulose-rich waste was used as the sole carbon and energy substrate as well as the only physical support for bacteria in laboratory denitrification reactors in thestudy described here.By the nitrogen isotope method and investigation of the land use in the study area, twenty-one wells were sampled to identify the groundwater quality in urban area, Hangzhou City. This groundwater can be referred to as the Ca-HCO3-type. Cl- and SO42- concentrations were high, and the average concentration were 52.8mg/l and 76.1mg/l, respectively. Nitrate pollution in groundwater was serious. There was a high frequence of groundwater (40.5% of total) with nitrate above WHO's standards of 10mgN/l for NO3-N. Groundwater in Hangzhou belonged to III water standard and could not drink. The different land use areas had the different nitrate concentrations(0.04-34.41mgN/l) and 5 15NNO3 values(7.8~22.0%). At the same time we used nitrogen isotope values of nitrate ( 5 15NNO3) to investigate nitrate sources: in residential area 15NNO3 was 10.4~22.0%, in agricultural area 15N]MO3 was17.5~19.5 %. Domestic wastewater was the major nitrate source of shallow groundwater in urban area, point source (septic tank) still existed in residential settings; at agricultural settings manure was the NO3-N sources. In general temporal variations of NO3 concentration in the groundwater were similar to temporal SO42- and Cl-fluctuations when NO2-N and NH4-N was not existed. The groundwater had the high level of DOC. The temporal variations of NO3-N, Cl-, and SO42- concentrations and the change values of 15NNO3 could indicate the existence of denitrification.Removal of nitrate from groundwater was studied in laboratory columns packed with solid organic carbon sources (cotton, paper, straw, sawdust). It was found that cotton and paper were suitable carbon sources for water denitrification and at the same time, can serve as the sole support for bacterial growth. Startup of the reactor using cotton and paper as carbon source was fast. Cotton and paper dependent d...
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