Development And Optimazation Of The Nitrogen Removal Of High Ammonium Sludge Dewatering Water

Wastewater originated from the anarobic digestion process is called reject water,which mainly includes the digerster supertanant and sludge dewatering liquros.Reject water is difficult to treat due to its high strength ammonium and unfavorableC/N ratio. Therefore, development the novel porcess and technology for reject watertreatment presents signifcantly application value, which is benefical to improve theeffluent quality of the wastewater treatment plant (WWTP) and derecease theoperational cost. Besides, this study is useful to for the treatment of other kinds ofhigh strengten ammonoium wastewater.In this thesis, sludge dewatering liquors from a WWTP were used toconduncted the experiment. Initially, the nitrite pathway of the high ammoniumwastewater was studied. The affacting factors and the mechnisms for start-up andmaintanence of the nitrite pathway were investigated. Two novel processes forsludge dewatering liquors treatment were afterwards developed, which were sludgefermentation and denitrification process and intergrated biofilm anammox process.The reaction mechnisim, affacting factor as well as the porcess control of the twonovel reactors were investigated. Based on above resluts, the feasiblity of theapplication of the novel process on sewage treatment was estimated. The strategy forchosing optimum porcesses for reject water treatment was also discussed.A continuous bioreactor was used to investigate the nitrite pathway of the highammonium wastewater, including start-up, maintanence and affecting factors.Experimental results indicated that influent ammonium loading rate (ALR) was oneof the key factors that determined the nitrite pathway. Nitrite pathway was difficultto control when ALR was lower than0.5kg N/(m~3·d). The maintanence of thepartial nitrification was mainly attributed to the selective inhition of free ammonia(FA) and free nitrous acid (FNA) on nitrite-oxidizing bacteria. The inhibitive effectof FA was reduce when ALR was deceased, but partial nitrification could be stillmaintained when FNA inhibition exsited. The feasibility of bio-augmentationprocesses in promoting start-up of partial nitrification of sewage was investigated.Appropriate bio-augmentation strategies could significantly improve the build uppartial nitrification of sewage. Sewage was treated in the adsorption/biodegradationreactor. The nitrite pathway was obviously promoted by addition of the previousactivated sludge from high ammonia wastewater treatment. Nitrite accumulationefficiency of sewage was quickly increased from26%to86%and maintained at ahigh level for two months.A novel nitrogen removal approach using primary sludge as additional carbon source was studied. In the novel process, the nitritation effluent was injected into thesludge fermentation reactor for enhancing denitrificaiton. At optimum conditions,85%removal of ammonium and75%of total nitrogen were obtained in a continuoussystem, resulting in a suitable effluent for recycling into the inlet of the wastewatertreatment plant. Primary sludge could be well degraded in the novel reactor. Over50%volatile suspended solid (VSS) of primary sludge was utilized, and the ratio ofVSS/SS declined from0.76to0.39. Compared to conventional sludge fermentation,the integration of denitrification and fermentation was better at carbon production.The release of phosphate and ammonium during sludge degradation process wasalso obviously reduced.Anammox process is a promsing technology for high ammonoum wastewatertreatment, which presents significant ecnomical and eviromental value. In this thesis,two-stage and single-stage anammox processes were respectively investigated. Apliot-sacle upflow anarobic sludge reactor was used to start the two-stage process.Anammox process was started with the activated sludge as the seed sludge.Maximum nitrogen removal rate of1.2kgN/(m~3·d) was achieved, with a nitrogenremoval efficiency of85%. The granulation of the anammox process was alsoinvestigated. The experimental results showed increase of upflow velocity andinjection of anaerobic granular were useful to the formation of the anammoxgranular. Nitrogen removal rate and resistance of the reactor was promoted by thegranulation.A pilot-scale integrated fixed-film activated sludge (IFAS) reactor wasinoculated with normal nitrifying activated sludge, and this reactor started nitritationanammox process after six months operation. Moreover, the segregation of AOB andanammox bacteria was achieved by providing different niches in the reactor. AOBpopulations were more abundant in suspended activated sludge phase whileanammox bacteria were primarily located in the biofilm phase. Biomass segregationallows for applying different conditions for different microbial groups, leading toconvenient operation and efficient nitrogen removal performance by achieving amaximum nitrogen removal rate of1.2kg N m-3d-1and an average nitrogen removalefficiency of90%. Clone libraries established with16S rRNA genes amplified fromgenomic DNA of the microbial consortia in the IFAS reactor demonstrated thatNitrosomonas was the predominant AOB in both suspended activated sludge and thebiofilm. However, the predominant anammox bacteria in the activated sludge andbiofilm were Candidatus Kuenenia and Candidate Brocadia, respectively.