Theoretical Preliminary Investigation On Biological Wastewater Treatment Processes And Development Of Toolbox

With the increasing serious environmental pollution, more attention has beenfocused on the operation of wastewater treatment plants (WWTPs). A lot of WWTPsfor municipal wastewater were built everywhere in China, but these WWTPs are smalland medium sized plants with the scale from1000-2000m3/d. Their influent flow rate andwater quality changed frequently, however well-skilled works are lacked in these plants,and thus failure of operation and management are frequently happened in these plants.In order to resolve the unstability of above mentioned conditions, the operatingparameters in these WWTPs should be adjust frequently. However, the conventionalmeans of monitoring parameter including water quality parameters, such as COD, NH4+-N, could not difectly indicate the biological processes status, with long time lags of theadjustment effect. Kinetic parameters can characterize the biological processes well,however, to obtain these parameters needs complex experiment set-up and the proceduresare time-consuming, and the application of kinetic parameters in WWTPs’ managementis also difficult. Therefore, a toolbox which could indicate the biological process inWWTPs has been investigated. The findings in this study, provide new theoretical basisand decision support tools for the operation and management of WWTPs. The mainresults of the current research are as follows:1. Endogenous respiration process has been defined. The whole endogenousrespiration process can be divided into three stages according to the variation of oxygenconsumption rate: the rapid decline phase, the slow decline phase and the stabilizationphase. Furthermore, pH can be used to indicate the process of endogenous respiration,i.e., the time of pH reaching the highest point is the time of activated sludge into the endogenous respiration. Meanwhile, the calculation of multiple parameterssimultaneously fitting under continuous flow conditions also has been discussed in thisstudy.2. Extracellular polymeric substances(EPS) of microbial metabolic processeswere studied. Loose-bouned EPS, such as protein, soluble microbial products categoryand humic content are closely related to the processes types. The relative position of thesethree types of substances, the location of peaks of fluorescence, water quality (chemicaloxygen demand and ammoniacal nitrogen), and the ratio of endogenous respiration arewell correlated.3. Based on the above findings, the operational management toolbox based onrespirogram has been developed. The toolbox can control the important parameters thataffect the kinetic measurements, such as pH, temperature and other parameters through aprogrammable logic controller to achieve the automation of the test process. Apreliminary solution is obtained to resolve the above mentioned problems of kineticparameter measurement, such as complex, time-consuming, and this toolbox couldprovide basic data for the metabolic state of biological sewage treatment plant operationand management, and it is of practical value.