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Phosphate Removal Performance And Operational Characteristics Of Alternative Anaerobic/Aerobic Process Composed Of BAFs With Crystal Seed Media

Posted on:2014-02-16Degree:MasterType:Thesis
Country:ChinaCandidate:K HuangFull Text:PDF
GTID:2252330425481151Subject:Architecture and Civil Engineering
Abstract/Summary:PDF Full Text Request
With the rapid development of society and economy in our country, the problem ofenvironmental pollution is becoming more and more serious in China, the water pollutionproblem which has caused a wide social attention to the safety issue. The fact that waterresource is very limited and precious; however, the urban sewage and industrial sewagedischarged into natural water causes a series of environment problems such as watereutrophication and threatens the drinking water. Excess of nitrogen and phosphorus is theleading cause of water eutrophication, the treatment in situ based on the pollution sources isthe key to effectively control the discharges of nitrogen and phosphors. Opening of sewagetreatment and resource integration technology is an important way for sustainabledevelopment which could ease environment pressure effectively.At present, denitrogenation had achieved remarkable results under the application ofsimulataneous nitrification denitrification, short-cut nitrification and denitrification andanammox. However, the phosphorus removing usually could not meet the discharge standardespecially the biological phosphorus removal. For the low concentration of phosphoruswastewater such as municipal sewage water, chemical phosphorus removal was usually addedto enhance phosphorus removal, so the cost and operation was high and hard. Phosphorusremoval by crystallization was a new approcach which was developed step by step and hadgreat potential of phosphorus removal efficiency and resourceful treatment. Therefore, underthe study of phosphate removing efficiency and operation characteristics based on biologicaland crystallization treatment, the study aimed to propose a promising process route andtechnical countermeasures for synergistic biological-crystal phosphorus removal in dealingwith wastewater with low phosphorus concentration such as municipal wastewater.The keyrole was the appropriate choice of bioreactor in synergistic biological-crystal phosphorusremoval, as a new and developing technique, Biological Aerated Filter (BAF) had developedgradually in China. The process could achieve organics removal, suspended solids (SS)removal, ammonia-nitrogen nitrification capacity and denitrification. Based on the BAF, thestudy introduced crystallization into the biological treatment by the novel crystal seed filter media with charcteristic of continuous releasing of calcium. Under the Anaerobic/Aerobic(A/O) alternative operating process, creating a biological phosphorus removal environmentaimed to enhance the phosphate removing efficiency and reduce the operation costs.Considering the current state of biodegradation and crystallization researches in theremoval of phosphorus and the support of National Natural Science Foundation of China(NSFC50978121), phosphate removing efficiency and start-up characteristics in BAFthrough Anaerobic/Aerobic (A/O) alternative operating process with the novel crystal seedfilter media were studied firstly. Then the characteristics of biofilms and microbial populationwere introduced. At last, the enhancement of crystal phosphorus removal by optimizingconditions such as pH and ionic strength during the crystallization reaction was discussed.The results of phosphate removing efficiency and start-up characteristics indicated thatthe PAOs had been successfully cultured and appropriate selection of dissolved oxygen (DO)and COD volumetric loading rate would improve the phosphate removing efficiency, the sameas the a modest raise of pH. The study preliminarily established operational parametersoptimization of low phosphorus concentration(9~12mg/L):initial ammonia,hydraulicretention time (HRT), alternate time,dissolved oxygen (DO) of Anaerobic and Aerobic andCOD volumetric loading rate were10mg/L,30~40mg/L,4h,36h,0.8mg/L,3~5mg/L and95~110gCOD/(m3filter media·d) respectively. What’s more, SEM-EDS analysispreliminarily indicated that the multi-channel phosphate removal meshods (here, which wascalled “synergistic biological-crystal phosphorus removal in situ”) was achieved in the in theBAF with novel crystal seed media. As differences in crystallization conditions such as time,pH and initial phosphorus concentration, crystal form was developed from little prism tocertain lengths gradually and increased in size and amount.The study of characteristics of biofilms and microbial population showed that thebiological system was still complete and stable as the widespread of bacteria, protozoa andmetazoan under the high alkalinity enviroment. Analysis of PCR-DGGE introduced thesimilarity and diversity of microorganisms. The results showed that the novel biological filterretained features of traditional BAF. After the induction of A/O, there were some differences between backwashing sample and filter media sample. With different crystal seed filtermedias, the specificity also existed to some extent.Crystallization enhancement experiment showed that the crystallization process could beenhanced by adjustment of pH and ionic strength. The data indicated that the max phosphorusrelease had been reduced and put off and effluent phosphorus had been under1.0mg/L withpH8.5~9.0and n(Mg):n (p)=3:1. The COD removal and microscopic observations showedthat the changes of environment had little effect on the process.Lastly, the process and control policy were put forward. Under the continuous operationat about sixty days with the influent quality of initial phosphorus10mg/L, initial ammonia30~40mg/L, pH8.5~9.0, n(Mg):n(p)=3:1, COD volumetric loading rate95~110gCOD/(m3filter media·d) and operation condition of HRT4h, alternate time36h,dissolvedoxygen (DO) of Anaerobic and Aerobic0.8mg/L and3~5mg/L respectively, the COD,ammonia, SS could reach standard A of the first class in GB18918-2002, the phosphoruscould also reach standard B of the first class. The long term operational performance indicatedthat the process had features of high efficiency, low cost and stable operation, etc. The processhad achieved scientific and effective treatment for the waste water with low phosphorusconcentration,the process also provided provide reference for novel phosphorus removal andrecycle technology.
Keywords/Search Tags:Anaerobic/Aerobic (A/O) alternative operating process, synergisticbiological-crystal phosphorus removal, taming revulsion of PAOs, biofilm process, novelcrystal seed filter media
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