The Study Of Flocculation Photosynthetic Bacteria In Sewage Treatment

Photosynthetic bacteria(PSB)are a beneficial microorganism that can purify wastewater and recycle resources at the same time.However,it leads to serious loss due to the difficultly natural sedimentation,which influences the practical application of photosynthetic bacteria in sewage treatment.At present,the photosynthetic bacteria flocculation immobilized and combined with the reactor to treat domestic sewage has received little coverage.In this research,the polyaluminium chloride(PAC)used as flocculant,three-phase biological fluidized bed based used as the reaction device.The optimal conditions of flocculation immobilization,wastewater treatment,and the operating conditions of the reactor are explored.The main conclusions are as followings:(1)When 3%PAC solution was added to 60 ml/L,nearly 70%of the photosynthetic bacteria were flocculated and settled.The flocculation PSB particles in the diameter of 50 ?m?100 ?m and had a rapid sedimentation rate,which was conducive to bacteria and water separation.(2)The removal rate of COD and NH4+-N reach to 93.4%and 57.8%respectively when the flocculation PSB was 20%,C/N=11?15,pH=8?9 and the oxygen-dark in good condition.The best condition of flocculating PSB for processing domestic wastewater is 0.3 g/L glucose,12 h of the reaction time,25?35? of the reaction temperature,in which condition,the biggest removal rate of COD,NH4+-N can come to 93.9%and 89.2%individually.(3)The Flocculation photosynthetic bacteria were traped in the reaction zone by three-phase separator effectively,which leads to easy in bacteria-water separation.It takes great effect to the three phase separation and solves the problem of easy loss of photosynthetic bacteria effectively.(4)When the HRT equals to 12 h.the COD,NH4+-N,TP concentration of effluernt are 25.0?77.0 mg/L,1.5?4.0mg/L,0.5?1.0 mg/L respectively,which it meet the first level of standard(GB 18918-2002)of adding 0.3 g/L glucose.Increasing HRT to 24 h,even if extra carbon source is canceled,the synergistic effect of microorganism still maintains the efficiency of the reactor to the sewage treatment.(5)Before and after the addition of glucose,the community abundance of photosynthetic bacteria showed a tendency of slow recovery after rapid decrease.It is shown that the reactor operation process should provide sufficient small molecular carbon source to maintain the growth metabolic activity of photosynthetic bacteria.At the same time,the microbes carried by domestic wastewater are developing constantly,which increase the microbial community diversity rapidly in flocculation granules.The capacity of the reactor to treat sewage is improved under the synergy of photosynthetic bacteria and heterotrophic microorganisms.