Study On Characteristics And Factors Of Phosphorous Removal Using Dissimilatory Fe(Ⅲ) Reduction In Activated Sludge System

The main way of causing eutrophication is the phosphorus in water from municipalwastewater treatment plants, in order to decrease the negative impact of phosphorusdischarged into environment, the concentration of TP should be limited strictly in wastewaterfrom treatment plants. Alienation Fe (III) reduction process exists in some anaerobic biotopeand its reaction subject is Iron-reducing bacteria (IRB). Therefore, the action of alienation ofFe (III) reduction and its role in pollution government cause people’s attention gradually. IRBoccupies3%of microorganism in activated sludge system, while Fe (II) produced by ironreduction progress can react with HPO2-4、H-2PO4and PO3-4forming precipitation whichincreases the removing of phosphorus in anaerobic environment. Therefore, dissimilatoryFe(III) reduction was used in removing phosphorus by adding Fe (III) source under anaerobicconditions,this progress is combined with chemical technology and biological technologywhich has a outstanding significance for phosphorus remove of wastewater.In this paper, activated sludge was inoculated in the anaerobic (facultativeanaerobic/strictly anaerobic) thermostat. On the base of studying the effect of alienation Fe(III) reduction process in activated sludge system by different activated sludge, carbon, initialpH and temperature, the orthogonal and single factor experiments of factors were conductedafter activated sludge was chose to proceed iron-reducing bacteria enrichment, the alienationFe (III) reduction accompanied phosphorus removal process and its factors in the system wasmainly studied and the phosphorus removal mechanism of alienation Fe (III) reductionprocess was also analyzed and discussed by determining different phosphorus forms in thesystem. The microorganism in the system was also identified. The main conclusions are asfollows:(1) Reduction capabilities of Fe(Ⅲ) by different activated sludge were comparativelydifferent.The reduction performance of Fe(Ⅲ) by bio-ferric sludge was significantly greaterthan that by conventional activated sludge. The reduction capacities by bio-ferric sludgeunder anoxic and anaerobic conditions were1.87and1.76times of that by conventionalactivated sludge, respectively. It was also found that carbon sources had little effect on Fe(III)reduction by bio-ferric sludge, while it had a negative effect on Fe (III) reduction byconventional activated sludge. Moreover, the two sludge showed a better reducing Fe(III)performance under anaerobic condition compared with anoxic condition.(2) In facultative anaerobic/strict anaerobic conditions, neutral to slightly alkalineconditions in activated sludge system was better for microbial alienation Fe (III) reductionprocess, and pH in every system tended to stabilize with the increasing of reaction time.Increasing temperature was better for activated sludge microbial alienation iron reductionprocess in range of15~35℃. (3) Using enrichment cultured activated sludge as inoculated sludge, study on effect ofFe (III) dosage, initial phosphorus concentration and initial pH to the Fe (III) reductionperformance and phosphorus removal. System expressed better Fe (III) reduction performanceand phosphorus removal with increasing dosage of Fe (III). The increasing of initialphosphorus concentration in the system significantly inhibited alienation microbial Fe (III)reduction. Condition of neutral to slightly alkaline was better for phosphorus removal processby activated sludge alienation Fe (III) reduction.(4) Orthogonal experimental results showed that the importance of factors in activatedsludge alienation Fe (III) reduction and phosphorus removal process is that: carbon source>Initial phosphorus concentration> amount of bacteria> initial pH. The results of varianceanalysis showed that the initial concentration of phosphorus and the dosage of carbon sourcehad a significant impact on phosphorus removal in the system, and phosphorus removal ratedecreased with the increasing of initial concentration of phosphorus and the dosage of carbonsource.(5) In this process, iron-reducing bacteria played an important role in phosphorusremoval and the adsorption phosphorus removal in Fe (III) surface also existed.(6) The mixed bacteria in sludge before and after enrichment culture were identified, andit mainly included Firmicutes (25%), Bacteroides (25%), Proteobacteria (35%), Chloroflexi(10%), Mutual bacteria (5%). Bacteroides sp. W7, Macellibacteroides fermentans,Desulfomicrobium hypogeium, Fusibacter sp. SA1and pira sp. IHB B2277was determinedion-reducing bacteria in activated sludge system. The pure strains with strong reductioncapability was separated, and they were determined Klebsiella.The iron oxide which is cheap and easy to get was chose as Fe (III) source in reactionsystem, and it could provide electron acceptor to achieve better phosphorus removal. Aneconomic and efficient technology of anaerobic biological phosphorus removal would bedeveloped, and it has very broad development prospects in water treatment process.