Studies On Microbiology Character And Intensified Nitrogen Removal Technics In Subsurface Infiltration System

Microbial population and diversity, enzyme were studied in subsurface infiltration system (SIS) in this paper. Preliminary study on judgment of the start-up period of the SIS and the methods of such judgment for similar processes have been investigated and the spatial characteristics of microbe and enzymatic activities have been acquired. The research offers the theoretical basis for using substrate enzymatic activity as evaluation index of purification efficiency. The DGGE has been successfully employed in the study on the microbial ecology of the SIS; From above results, the inflow distributary is designed,which can significantly improve the effect of SIS on removal of total nitrogen. The main conclusion are shown as follows:A multi-use experimental device is designed, which fits for SIS, slow infiltration system and rapid infiltration system because of the design of main body and distributive water system. Inflow can distribute even with ten font style distributive pipe. Study on substrate and internal environment is easy with side sampling point.The results of substrate experiments show that boiler slag or water-granulated slag of blast-furnace can enhance penetrability, phosphorus adsorption capacity, the ammonia adsorption capacity, the nitrifying capacity, the denitrifying capacity of meadow palm soil.The removal effects and start-up period performance have been studied. The experimental results show that the start-up period for achieving a removal of TP, COD and NH4+-N are27d,40d and22d, respectively. As a whole treatment system, its start-up period would be the longest one of the main research index. So its start-up period is40d. After its start-up period completed, the removal of COD、NH4+-N、TP is more than respectively82%,85%and90%.The number of substrate microorganisms in different depth in SIS has been monitored by plate counting and dilution methods, and the correlation between number of substrate microorganisms and purification effects has been studied. The results show that the number of microorganisms is different in different spaces and there were no obvious changes in different seasons. There is a fairly significant relationship between the number of microorganism in substrate and removal rates of BOD, COD, TN, NH4+-N, showing that microorganism probably is the main way of their removal. The number of microorganisms is not interrelated markedly to removal of TP, showing that the action of microorganisms probably has no relationships with removal of TP.The correlation of substrate enzymatic activities and their wastewater purification effects has been studied in SIS. Substrate enzymatic activities in different depths are different, even in different months the substrate activities of proteinase are different. There is significant correlation between activities of phosphatase in the substrate and removal rates of TP. It probably proves that activities of phosphatase in the substrate are important factor in the removal of TP. There is significant positive correlation between activities of urease in the substrate and removal rates of TN. It probably indicates that activities of urease in the substrate are responsible for removal of TN. Activities of proteinase are not interrelated markedly to reduction of BOD、COD、TP、TN、NH4+-N. These conclusions give reference to future researches on utilizing substrate enzymatic activities as evaluating purification effects in SIS. DGGE, the molecular biological method based on the polymerase chain reaction, has been used to study microbial community diversity especial the bacteria diversity of different sites in SIS. The results of the two subsurface infiltration systems are similar. The similarity of the microbial communities in same bed and in different bed is respectively74.4%-80%,73.2%-85%of two subsurface infiltration systems; The microbial communities are the most abundant in depth of30cm and the lowest in depth of70cm; The microbial community Shannon index of infall is higher than other beds. The microbial community Shannon index decreased with depth increasing below infall.Study on microbiology mechanisms indicate that the reason of low removal efficiency of total nitrogen is deficiency of carbon in vertical infiltration, From which infolw distributary is broughted forward. The test show that the infolw distributary can significantly improve the effect of SIS on removal of total nitrogen, with TN removal rate increase from60.09%(without taking distributary measures) to67.82%, and it has no great influence on the removal of COD and total phosphorus, when distributary ratio is one to one and infall is in depth of70cm. Denitrifying bacteria amount increases one magnitude and activities of urease increase in depth of70cm.