Research On Characterof Molecular Weight And Degration For SMP During TheAerobic Process

Most of the effluent organic matter in sewage plant are soluble microbial products(SMPs).These metabolites will not only affect the quality standard of water,some of them are also the precursor of harmful substances.In this paper,we studied the degradation of organic matter in aerobic process,the characteristic of SMP molecular weight distribution in ammonia-nitrogen nitrification,SMPs’composition and degradation characteristics,In this way,we treid to obtain further theoretical knowledge of the organic matter removal in the effulent of the wastewater plant.The main conclusion as follows:(1)In microbial organic matter degradation process,the organic degradated fastest in the first0-2h.With the subtences consuming,the rate of organic matter degradation is leveling off.However,the rate of SMPs producing is fastest in0-4h,about0.513mgTOC/(h·L),accounting for60.12%of the total SMPs. With the organic matter consumption,the SMPs rate drops,the rate of SMPs producing is only0.215mgTOC/(h·L). When the reaction come to6-8h,microorganismdelay and crack,a large number of SMPs released to the water.(2) In the process of nitrification,the SMPs released in the water is extremely low. In the first4h,the SMPs in water cannot be dected,this is mainly because that the organics which microorganism produced by using carbon dioxidestored in their bodies.Since5h,we can detect the SMPs concention in the water,and most of SMPs are large molecules.This is mainly because that the nitrification cannot satisfy the need of microorganism,then the microorganism delay and crack,the macromolecular organic matter enter into water.(3) When nutrients are sufficent, mainly under the control of the substrate dehydrogenase, a lot of low molecules of SMP Da (0-1000) produced, when large numbers of nutrient consumption, the generation of SMP is influenced by endogenous respiration dehydrogenase, mainly aremacromolecular SMP (1w-450wDa), eventually the SMP present "U" type distribution.(4). In the process of organic matter degradation reaction within0to6h, MLSS changes were positively related with the SMP;In nitrification process, MLSS is negatively related with SMP.This is largely because, in the process of reaction, the microbial utilization substrates for appreciationand metabolism, producing SMPs, so the MLSS and SMPs changes consistent, but in the end of the reaction, nutrients in system consumpted, microbial decompositionand decline, the MLSS concentration decreased, organic matter released to the water.(5)The main components of SMP are polysaccharide and protein, the variation trend of polysaccharide and protein concentration is in keeping with the variation trend of total SMP. Polysaccharide concentration is relatively stable in the whole reaction process, basic maintained at0.49～0.67mg/gMLSS, mainly produce in the early reaction; The content of protein is sustained growth.(6)In the process of aerobic reaction, the sludge after a period time of domestication, SMP can still be used by microorganisms. Most of SMP (0-1000Da) can be used by the microorganisms, and the rate of uptake is relatively fast; Apart of SMP ranged from1000-1w Da can be used by the microorganisms, but rate speed is relatively slow; Macromolecular SMP are difficult to be used by microbial and will soon be added in reaction, this is mainly because of the process of the use of SMP trend is that low molecule SMP come to macromolecular SMP.(7)Temperature and aeration rate impact SMP mainlyon molecular weight distribution, temperature and aeration rate increases, the microbial metabolic more activity, the SMPs’ producing rate is increasing in initial stage, at the same time the utilization rate on the substences is accelerated, the organisms come into decay, cracking period earlier, more macromolecular organic matter released into the water, the "U" type trend of SMPs is more obvious.Initial organic load mainly affect the SMP production.Organic load impact mainly on quatities of SMPs, the higher the organic load is,the more the SMPsproduce, Organic load donot influence on molecular weight distribution of SMPs.