Nitrogen Nutrient Transformation In Sewer Networks

During the transportation of sewage in the urban sewer system, the physical, chemical and microbial reaction will be occurred, which can change the composition and content of pollutant in the sewage. These changes will affect effluent quality, operation and performance of the wastewater treatment plant(WWTP). For this reason, taking nitrogen nutrient in sewage as research object, the transformation and biological utilization mechanism of nitrogen nutrient were studied. These results were significant in theory of transport and transformation of nitrogen nutrient and the effect of effluent quality of WWTP.By the established 1200 m long pilot sewer system, the transformation of nitrogen nutrient in the sewer under the different nitrogen was studied. The results showed that when ammonia nitrogen or protein as the nitrogen, microbe could utilize them to synthetic living materials. However, under the condition that both of ammonia nitrogen and protein existed, the content of dissolved organic nitrogen(DON) decreased and ammonia nitrogen(NH3-N) increased along the length of the sewer network. The probable reason of this phenomenon was that microbes could utilize the protein in sewage and hydrolyzed it to NH3-N. During the whole process, the content of total nitrogen(TN) remained stable, which mainly due to the relative stable anaerobic environment of the sewer system.Inter-transformation of nitrogen nutrient in sewer system was analyzed by stable nitrogen isotope. The results showed that, in the coexisting system of ammonia nitrogen and protein, microbe utilized protein as nitrogen to synthetic living materials. In adding multiple nitrogen substances conditions, the composition and distribution of DON were studied and along the molecular weight distribution and fluorescence characteristics of the dissolved organic matter(DOM) were investigated ng high-performance liquid chromatography(HPLC) and Fluorescence excitation-emission matrix(EEM). The results showed content of the all of DON were increased except urea. Meanwhile, macromolecular organics were decomposed into micro-molecular organics and biodegradability of sewage was improved.