Effect Of Carbon Source On Phosphorus Removal And Community Structure In The Denitrifying Phosphorus Removal System

Denitrifying phosphorus removal process exhibited efficient nitrogen andphosphorus removal performance for domestic sewage with low carbon-nitrogen ratio.Carbon source, as the electron donor, had significant effect on process efficienty.However, the effects of different carbon sources on denitrifying phosphorus removaland the microbial community structure are rarely reported. In the current study,denitrifying phosphorus removal sludge with acetate, glycerol and propionate as thesole carbon source were acclimatized in three Sequencing batch reactors (SBRs)operated under strict anaerobic-anoxic condition. The effect of different carbon sourceson denitrifying phosphorus removal performance and sludge characteristics were firstlycompared. The high-throughput sequencing technology was applied to study themicrobial diversity, similarity and community structure of the denitrifying phosphorusremoving sludge with different carbon sources. Moreover the abundances of phosphorusaccumulating organisms (PAO) and Glycogen accumulating organisms (GAO) werealso quantified. The study will eventually provide a theoretical foundation for carbonsource selection or optimization for denitrifying phosphorus removal processes.The acclimation time were53,59,47d respectively for acetate, glycerol andpropionate based phosphorus removal sludge. Stable operation showed that propionatewas the most appropriate carbon source, followed by acetate and glycerol, with averageeffluent phosphorus concentrations of0.79,0.98and0.29mg/L, corresponding to theremoval rates of82.5%,79.2%and93.4%, respectively. Based on the cycle operation,the phosphorus release rate within the initial30min for the above three ractor were23.0,22.8and26.5mgP/(gVSS·h), respectively.The operational parameters on operation performances were studied.The inletCOD/P had the obvious impact on phosphorus removal performance, and phosphorusremoval performance was best under the COD(mg/L)/P(mg/L) of20. Instantaneous andcontinuous dosing of NO3--N had no significant impacts on phosphorus uptake in theanoxic phase. The phosphorus content of sludge with different carbon sources wereabout5.0%~5.5%.Microbial community of sludge with different carbon sources were studied with16S rRNA based high-throughput sequencing. Sludge fed with glycerol had the richestmicrobial diversity, sludge fed with acetate and propionate exhibited similar diversityand bacterial community structure. At phylum level,-proteobacteria was the mostdominant for all the sludge samples. At order level, Rhodocyclales that phosphorusremoval bacteria belonged to was the most dominant for the samples from SBRs.Through sequence local Basic Local Alignment Search Tool (BLAST), it revealed an obvious increase (from4.4%to41.5%for propionate,9.5%for acetate and8.0%forglycerol) of Ca.Accumulibacter-like organisms. As for GAO-like sequences, it was6.9%,1.8%and1.2%for acetate, glycerol and propionate sludge, respectively.Compared with acetate and glycerol, propionate was a more superior substrate forthe enrichment of phosphorus removing bacteria in anaerobic-anoxic EBPR system. itwas favorable for enrichment of PAO and also the surpression of GAO. Based on theresults in the present study, it was suggested to maximize of propionic acid productionduring waste sludge digestion, and then used as carbon sources addition for the processto improve the treatment efficiency.