The Fast Start-up And Influence Factors Of Baffled Autotrophic Denitrification Bioreactor

With the industry and agriculture continuous development and improvement of people’s livingstandards, nitrogen is discharged into the wastewater continues to increase. How to reduce emissions ofnitrogen and harm to the environment on the water has become a serious problem which is great concernedby researchers.Nitrogen recycle exists in nature and denitrification is widespread in the biosphere. Conventionalbiological denitrification process requires lots of aeration, adding more organic carbon and alkalinity,highly investment and operating costs, highly energy consumption and low efficiency which has becomeincreasingly unable to meet the needs of social development. In recent years, with short nitrification anddenitrification, Anammox, Nitrification-Anammox new biological nitrogen removal process emerged.Anammox process is one of the typical process, the mechanism is under anaerobic conditions,chemoautotrophic microbial （anammox bacteria） use CO2or HCO-3as a carbon source, the NH+4as anelectron donor, the NO3-or NO2-as electron acceptor, the bio-oxidation process which transforms them intoN2. Compared with the traditional biological nitrogen removal process， the anaerobic ammonia oxidationprocess needs less oxygen, no external carbon source, low operation cost.Anammox bacteria grow more slowly, yield coefficient is also very low, anaerobic ammonia oxidationreactor start-up problems have also restricted the process used in urban sewage treatment, which is abottleneck. The anaerobic ammonia oxidation reaction needs nitrite as an electron acceptor, the need of thefront half of nitrite matching process, a suitable reactor types and combinations of the process is also topromote research.This topic use a Baffled biofilm reactor, which is high biomass and solid-liquid separation device, thesuccessful start-up the anaerobic ammonia oxidation reactor and study the law and the influence factors ofthe nitrogen remove in the reactor after the reactor stable run. By control the concentration of DO wesuccessful start-up of autotrophic denitrification integration.Our topic is divided into two phases. The first stage is the fast start-up the anammox baffled biofilmreactor and the influence reactors. The main research results were as follows: （1） Start-up and degradation characteristics. In this study the influent apply artificial conditions, theconcentration of the NH4+-N and NO2--N is30⁴5mg/L, temperature for（30±2）℃, DO<0.2mg/L andpH value for7.6⁸.0. After85days of continuous culture, we successfully start the baffled biological filteranammox reactor. In the stabilization phase, the removal rate of NH+4-N and NO-2-N has reached morethan95%, the removal of the ammonia volume load120mg/（L·d） and nitrite160mg/（L·d）. Theproportion of NH+4-N and NO-2-N remove and the generation of the NO-₃N is1：（1.20¹.37）：（0.10⁰.19）, which is close to the theoretical value. The effluent reaches the A national level standard（NH4+≤5mg/L,TN≤15mg/L）.（2） Influencing factors. After the Baffled biofilter Anammox reactor successfully start-up, we nextstudy the influence factors about temperature, pH and COD. The main research results were as follows:①The optimum temperature for30⁴0℃, in this temperature region NH4+-N and NO2--N removal rate canreach95%or even more, when the temperature is low at18℃, the total nitrogen removal rate is very low,the removal rate is NH4+-N57%and NO2--N65%, when the temperature is higher than42℃, the activityof anaerobic ammonia oxidation was severely inhibited, the removal rate is NH4+-N50%and NO2--N55%.②Anammox bacteria optimum pH range of7.1⁸.5, when pH <6.5or pH>8.5removal effect decreasedsignificantly, especially in pH <6.0or>9.5is less than70%nitrogen removal.③COD concentration oforganic matter no less than160mg/L impact of anammox bacteria, but COD concentration higher than200mg/L anaerobic ammonia oxidation reaction will produce significant inhibition.Phase II: Based on the successful launch and stable operation of the baffle anammox biofilm reactor,control DO optimization, the first two chambers DO is45mg/L, DO in the third chambers is0.8¹.0mg/L, after third chambers DO is0.3mg/L, after90days acclimation successfully achieved autotrophicintegration. The main findings are as follows:Control HRT of6hours at a temperature of （30±2）℃, pH7.6⁸.2, NH+4-N influent concentrationbeginning14mg/L, and steadily to35mg/L, after90days acclimation successfully achieved theintegration of autotrophic denitrification reaction. After a successful start-up NH+4-N, TN average removalrate were95%and85%, nitrogen removal is obvious, the reactor nitrogen load up to140mg/（L·d）.