The Characterization Of S_S, X_S And S_A Of COD Component In Wasterwater And Its Application

Understanding of wastewater biodegradable characteristics is not only a necessary precondition for designing of wastewater treatment engineering and operation optimization of treatment facilities, but also the basic work for further theoretical researches and application of activated sludge models (ASMs).This dissertation, based on COD compartmentalization of ASMs, focuses on scientificalness, accuracy and practicability of characterizing method of several important components (VFA, RBCOD and SBCOD, etc.). A set of benchmark method for characterizing wastewater COD component was established based on the former researches on COD components testing and characterization methods. Through applying it to several real wastewater treatment plants (WWTPs) it can be concluded that:(1) A 9-points pH titration measurement method was developed to test volatile fatty acids (VFA) of wastewater. The experiments proved that this method was easy to operate, with a high accuracy and precision, showing a good reproducibility and practicality.(2) When acetic acid concentration was 10~50mg/L, absolute error of measure results was below 1mg/L, relatively error was -6.6%~1.1% and variance coefficient was less than 6%. Besides, relatively error and variance coefficient decreased with the increasing of acetic acid concentration. When acetic acid coexisted with carbonate, phosphate and ammonia buffer systems, the test relatively error was less than 8% and variance coefficient was less than 5%.(3) The 9-points pH titration method was used to measure VFA content of wastewater, and the results were validated through ion chromatogram method. It was showed that the testing results obtained by 9-points pH titration method was the total content of VFA, while the results measured by ion chromatogram was just the sum of acetic acid and propionic acid which occupied about 90% of the total VFA of wastewater, according with former literature reports.(4)Oxygen utilization rate (OUR) is an external response of heterotrophic organisms using substrate for metabolism, and the OUR curve contains plenty of information on biological reactions and physical-chemical reactions. The dissertation, based on kinetics of heterotrophic aerobic metabolism, proposes using a respirometry technique to simultaneously characterize RBCOD and SBCOD of wastewater, avoiding subjectivity problems when discriminating steps of OUR curve.(5)The results obtained by respirometry OUR curve ASM-based analysis method and traditional OUR curve step discrimination method showed great difference that was the former method led to a smaller result of RBCOD content but a large result of SBCOD than the latter one. This is because the traditional method supposes that the hydrolysis rate of SBCOD is a constant before all RBCOD has been decomposed, underestimating the decreasing of OUR by SBCOD hydrolysis, which is also contradictory with aerobic hydrolysis theoretics of ASM.(6)A set of benchmark method for characterizing COD components of wastewater was proposed, based on 9-points pH titration measurement, respirometry OUR curve ASM-based analysis method and conventional analysis methods. This set of method could be used to characterize wastewater components, including readily biodegradable component (SF), fermentation products (SA), slowly biodegradable component (XS), soluble unbiodegradable component (SI), and particulate unbiodegradable component (XI).(7) This benchmark method was applied to characterize influent COD components of Jingkou WWTP, Qiezixi WWTP and Changshou WWTP located in Three Gorges reservoir area. The results showed that the influent COD components obtained by the benchmark method could well reflect influent characteristics of WWTPs, offering reference for WWTPs to optimize the treatment process.(8)After caliberating ASM1 by the results of influent COD components characterization and actual operation conditions, the paper simulated wastewater treatment process of Qiezixi WWTP using the GPS-X5.0 solftware developed by Hydromantis Inc., Canada, with a result that the errors between simulated values and measured ones of WWTP effluent COD, NH4-N and TN were less than 10%. Thus, it is proved that accurate characterization of COD components could not only improve the simulating precision but also reveal real problems of the WWTP operation.