Effect Of Typical Organic Phenol On The Metabolism Of Activated Sludge And The Mechanism

In the activated sludge process, the polluted organicsin the wastewatercan beconverted into simple inorganics with the help of the microorganisms to improve thewater quality. While the microorganism removest he organicsin the wastewater, it willproduce soluble microbial products (SMP) at the same time. SMP is an importantcomponent of the residual COD in the biological effluent. In this paper, the sequencingbatch reactor (SBR) was used to investigate the effect of toxic organic phenol on themicroorganism metabolic process and the production of SMP when switching thecarbon source from acetic acid to phenol. In addition, activated sludge mathematicalmodelwas used as a tool to elaborate the mechanisms focused on the point of the carbonelectronic flow variation. The main conclusions are as follows:The COD of influent was about330mg/L, and aeration time is4h when usingacetic acid as the carbon source in the SBR system. In the initial2h, themicroorganisms in the reactor consume COD quickly, the COD reduced to46.8mg/Lrapidly. In the following2h, the microorganism in the system being in the endogenousrespiration, the COD decreased was only15mg/L. In the initial2h, intracellular storagepolymer (XSTO), extracellular polymeric substances (EPS) and SMP were graduallyaccumulated in the system. At2h, the concentrations of XSTO, EPS and SMP were131,347.5and35.5mg/L, respectively. In the endogenous respiration stage, XSTOand EPSwere utilized by microorganisms as the carbon source, and their concentrationsseparately decreased to124.5and340mg/L in the end of the aeration. The majoringredient of EPS and SMP are proteins and polysaccharides.At the time of2h, the ratioof proteins to polysaccharides in EPS was4.8, while the ratio in SMP was2.55. SMPmakes contribution to the residual COD in the effluent. The theoretic calculation showsthat the SMP equate to the COD in the effluentis account for78%in the total effluentCOD.The influent carbon source acetic acid was replaced by phenol, while the COD wasabout350mg/L and the aeration time was still4h. The results show that themicroorganism cannot use phenol as carbon source for growth in the first day and theywould consume XSTOas the carbon source for growth. In the first operating cycle, theinitial XSTOwas about142mg/L, while the concentration decreased to54.6mg/L at the end of aeration, reducing the amount of87.4mg/L. With the extension of theacclimatization period, the internal microbial carbon utilization decreased gradually.The microorganisms can partially degraded substrates at day10, and the CODdecreased from333.2mg/L to196.6mg/L during the operation. However, the internalcarbon source consumption was still high. The EPS concentration decreased from365.9mg/L to245.6mg/L, reducing the amount of124.3mg/L, and the effluent SMPconcentration was83.5mg/L, which is2.3times as acetic acid as substrate. Protein wasthe main component of SMP, accounting for49.7%. the sludge was fully domesticated18d later and the system entered the stable phase. The substrate can be fully degradedduring this period. The metabolic characteristic was similar to the period that usingacetic acid as the carbon source.The storage and growth process of this stage of wererelatively weakened. The effluent SMP concentration at the end of aeration was about2.4times than that using acetic acid as substrate.Based on ASM3model, the paper illuminates the forming mechanism about theEPS, SMP and XSTOin the aerobic metabolism of the activated sludge.An ASM3-SMPmodel was built by coupling the electron transfer of EPS, SMP and XSTO.The sensitivityof the different components parameter in the model are arranged as follows: μH, kUAP,YH, KOin UAP,khydin BAP, μH, kEPSYH, KO, μEPS, YEPS, KEPSinEPS,μH,kSTOYHinXSTO.The simulative results showed that the distributed percentagesof the electrons inthe substrate are as follows: UAP9%, EPS37%, XSTO19%, DO9%, the synthesis ofnew cells26%when using acetic acid as the carbon source. While using phenol as thecarbon sourcein the stable operation phase, the distributed percentages of electrons inthe substrate areas follows: UAP16%, EPS40%, XSTO13%, DO16%, the synthesis ofnew cells15%. The simulative results have a high matching degree with the actualmeasurement, and it described the effect of toxic organic matter on SMP productionandtheir mechanisms preferably.