On Building-up A Synthetic Microbe Agent And Its Treating Of Domestic Sewage

Containing large amount of organic contaminants, suspended solids, nutrient matters and pathogens, the domestic sewage always poses eutrophication in water body and threatens human health. With socio-economic development and rapid increasing in population size, the domestic sewage discharge amount rises sharply and the ratio of it to waste water discharge amount has been increasing each year. Domestic sewage treatment has been the focus of wastewater pollution control. Activated sludge process is one of the most important technics for domestic sewage treatment. The activated sludge must have supper degradation ability and settling ability to meet the requirement of domestic sewage treatment efficiently. This study aims to construct a synthetic microbe agent based on the principle of bioaugmentation to improve the removal rate of contaminents and settling ability.At present, synthetic microbe agent are mainly composed of degradable strains rather than flocculant-producing strains. As the flocculation of flocculating-producing strains has been neglected, the chief target of this paper is to screen flocculant-producing strains. Moreover, filamentous microorganism is one kind of important strains to screen, because it can form skeleton frame of sludge and further strengthen the settling ability of activated sludge. In addition, the strains with high degradation ability to the pollutants in domestic sewage are also been screened. These strains are combined together to build a synthetic microbe agent. The high degradation ability of the strains and the flocculation of the bioflocculants can improve the removal rate of contaminents. The cementing power of the flocculant-producing strains and the skeleton frame effect of filamentous strains can enhance the settling ability of activated sludge.A flocculant-producing strain named C3 is isolated and its culture medium and culture condition are researched. Then, C3 and another flocculant-producing strain named A9 are domesticated with synthetic domestic sewage and domestic sewage. The results show that the two strains can live in domestic sewage and produce flocculants. Six strains, named El, E10, S10, S16, B6 and B20, with high degrading ability to some pollutants of synthetic domestic sewage are isolated. Eland E10 are all filamentous fungi and can degrade starch and oil. S10 and S16 can degrade starch and cellulose. B6 and B20 can degrade starch, oil, cellulose. Among the strains, B6 and B20 have the most effective degradation ability to pollutants of synthetic domestic sewage with the removal rate of chemical oxygen demand reaching to 81.6% and 80.3%, respectively. E1, E10, S10 and S16 can enhance the settling ability of activated sludge. A synthetic microbe agent is built up with the strains C3, A9, E1, E10, S10, S16, B6 and B20. The optimum culture medium and culture condition are: synthetic domestic sewage culture medium, initial pH 6, culturing temperature 35℃, rotating speed 80rpm.The synthetic microbe agent is introduced to activated sludge to dispose of sewage. The results show that the synthetic microbe agent can accelerate the startup of the activated sludge system and can resist shock load well. The condition for the bioaugmentation of the synthetic microbe agent to domestic sewage treatment is:the dosage of synthetic microbe agent 1/80～1/40, dissolved oxygen 3mg/L-4mg/L, aeration time 6 hours. Under such condition, in the control group which contains only activated sludge, the removal rate of chemical oxygen demand, sludge index and flocculating ability are 54～73%,77～94 mL/g and 42～45%, while in the treatment group containing synthetic microbe agent, the removal rate of chemical oxygen demand, sludge index and flocculating ability reach to 70～78%, 66～84 mL/g and 49～57%, respectively. In the sequencing batch reactor, the bioaugmentation of the synthetic microbe agent for activated sludge to dispose of domestic sewage can last for 30 days. Therefore, the synthetic microbe agent can be introduced into the activated sludge system repeatedly with a period of 30 days without losing its effect.The mechanism of the bioaugmentation is studied. The results show that the cementing power and the flocculation of the flocculant-producing strains, as well as the skeleton frame effect of filamentous strains, enhance the flocculating ability and settling ability. The supper flocculating ability and settling ability of activated sludge and the flocculation reduce the suspended solids and colloid in the discharge. Moreover, the synthetic microbe agent causes a transformation of the existing microbes in activated sludge. A Large number of strains with high degradation ability dominate the activated sludge and they are favorable to the disposal of the domestic sewage.