Study On The Running Strategy Of Combined Shortcut Biological Nitrogen Removal Processes And Its Nitrifier Biofilm Characteristics

The classical biotechnology has been widely applied in biological nitrogen removal process of wastewater. But the new requirement has challenged the classical biotechnology of removal nitrogen with the progressive eutrophication. The organic substances in wastewater have been removed effectively from domestic and industrial wastewater by classical biotechnology, but nitrogen removal efficiency always couldn't reach the wastewater discharge standard. Therefore it is important that researching and developing new nitrogen removal biotechnology which is free from the use of organic carbon and save the consumption of energy. In recent years, the new biotechnologies have been the focus of research all around the world. Whereas the most new nitrogen removal processes running in different reactors, few researchers was effort to implemented combined nitrogen removal processes in sole reactor. It has been many problems in those processes when it was applied in single reactor. The problems include lower stability and the difficulty of controlling. Our research based on domestic and foreign new biological nitrogen removal achievements and implemented the shortcut nitrification and autotrophic denitrification process, examined the feasibility and the stable control strategy of nitrogen removal in the single reactor. This report adopted the new biotechnology of nitrogen removal provide certain theoretical basis for the nitrogen removal technology to treatment the actual wastewater. The conclusions are as follows:1. This study examined the feasibility and the stable control strategy of shortcut nitrification and denitrification in the novel united fixed bed biofilm reactor. At the end of start-up period, the NLR was 0.89 kg N-NH4+m-3 d-1 and ammonium was almost entirely converted to nitrite. The nitrite ratio (NO2--N/(NO2--N+NO3--N)) was above 85% and total nitrogen removal percentage above 90% during the steady period. The results showed that the ammonia oxidation bacteria (AOB) community of the bioreactor consists almost entirely of Nitrosomonas spp. and Nitrosospira spp.. AOB were 64.1±5.0% of the total volume on the biofilm which reproduced in 0-80μm of the biofilm surface. Nitrite-oxidizing bacteria (NOB) were 5% of the total volume of the biofilm samples which reproduced under the 80μm of the biolfilm surface.2. Simultaneous elimination of sulfide and ammonia from synthetic wastewaters was investigated using the fixed bed biofilm reactor to evaluate the feasibility, the stable control strategy and effect of sulfide and nitrite ratios and substrate concentrations on the process performance. The effluent fluctuation at S/N ratio of 3:2 was less than at the other two ratios and nitrogen removal percentage reached 90%. High ammonia, nitrite, sulfide and nitrate concentrations in the bioreactor contributed towards the inhibition of the combined process. The observation of biofilm results proved that the autotrophic and heterotrophic biofilm structure and microbial populations were different, preponderant bacteria in nitrifier and denitrification biofilm were Nitrosomonas spp. and sulfur oxidation bacteria, respectively.3. This study investigated the feasibility and the stable control strategy of successfully achieved stable partial nitrification and Anammox processes of synthetic ammonium rich wastewater in the fixed bed biofilm reactor. The results conformed HRT plays an important role in the 50% nitrite accumulation, while half alkalinity plays a critical role in achieving the desired 50% partial nitrification in the effluent. The effluent from the bioreactor could be quite easily and very stably used as a feed to the Anammox reactor for the course of the experiment. The combination of this system with the subsequent ANAMMOX process has great potential and nitrogen removal percentage reached 52% after four months running, ammonium and nitrite removal rates were between 1:1.2 and 1:2.3. The results showed that the sulfur oxidation bacteria community of the bioreactor consists most of bacteria and Anammox bacteria reproduced in bottom of the biofilm.4. In this study, we examined the composition and distribution of extracellular polymeric substances (EPS) that were extracted from autotrophic nitrifying biofilm and activated sludge. The results for EPS content, including carbohydrates, proteins, humic and DNA, with different layers changed great. Autotrophic biofilm PN/PS ratios were 4-7 and the cell hydrophobicity were increased which make the extraction of EPS became harder. The TB-EPS and pellets are mainly composed of carbohydrates and proteins. There are about 94% proteins and 89% carbohydrates associated with TB-EPS and pellets layers. In contrast, there were almost no proteins in slime and LB-EPS.