Study Of Rhodobacter Sphaeroides Sedimentation And Brewery Wastewater Treatment

PSB (photosynthetic bacteria) wastewater treatment has been widely applied in thefield of sewage treatment and resource recovery, because of its low powerconsumption, pollutants removal and biomass resource recovery at the same time.However, the problem of difficult sedimentation leads to bacteria loss and difficultyin solid-liquid separation, which influences the effluent quality and biomassresource recovery. Till now the PSB sedimentation has received little coverage.This study used a strain of Rhodobacter Sphaeroides as the experimental material tostudy the effects of different factors on the biomass growth and natural settlingefficiency, the relationship between EPS and sedimentation, and the preliminaryapplication in brewery wastewater treatment.Considering environmental factors (initial pH, inoculation, Na+concentration, lightintensity, temperature and culture condition), the best growth and sedimentationconditions for Rh. Sphaeroides were as follows: initial pH of8.5, inoculation of20%, initial Na+concentration, light intensity of5000lux, temperature of30℃and anaerobic-light-static condition. Under such conditions, Rh. Sphaeroidesexhibited the best growth and sedimentation state with the biomass of1734mg/Land settling efficiency of85%, which were430mg/L and70%higher than thecontrol group respectively. And among all the factors, initial pH, Na+concentration,light intensity and culture condition were very important.Different extraction methods were studied. The result showed that EDTA extractionmethod was the best, which could achieve higher extraction efficiency with minimalcell lysis. And the influences of different factors on EPS and sedimentation werealso investigated. It turned out to be that time had much effect on EPS compositionand content and little on sedimentation; while initial pH and light intensity had littleeffect on EPS composition and content and much on sedimentation. It was alsodemonstrated in the study that EPS had a negative effect on sedimentation.When applying Rh. Sphaeroides to treating brewery wastewater, the recommendedconditions were as follows: F/M ratio of5.0, no additional nitrogen and phosphorussource, anaerobic-light-static condition and mixed with Rh. capsulatus. Under suchconditions, Rh. Sphaeroides exhibited the best treatment, growth and sedimentationstate with the COD removal of92.5%, biomass of1413mg/L and settling efficiencyof65%respectively. Moreover, different flocculants (aluminum sulfate, PAC, PFC and PAM) were investigated to improve the sedimentation of Rh. Sphaeroides. Theresult showed that PAC could promote bacteria flocculation to obtain more flocsand faster settling velocity with the optimal dosage of75mg/L. Simultaneously,after the addtion of PAC, Rh. Sphaeroides could treat brewery wastewater wellunder weak light-micro oxygen condition, with the COD removal of94%, biomassof1538mg/L and settling efficiency of72%respectively, whose biomass and CODremoval remained and settling efficiency was largely improved compared with theformer conditon.