A Biofilm Reactor Used In Wastewater Denitrification And Phosphorus Removal

Activated sludge samples were collected from Sibao wastewater treatment plant in Hangzhou. Based on colony characteristics, bacterial strains were separated, purified, and functional strains were screened by screening media. Partial 16S rDNA of these strains were sequenced, compared and a phylogenetic tree was constructed based on 16S rDNA.9 Denitrifying bacterial strains (DNBs),8 Phosphorus-removing bacterial strains (PRBs) and 4 Flocculating bacterial strains (FBs) were selected. DNB8, PRB22, FB4 which were efficient were chosen to determine their abilities. DNB8, PRB22, FB4 were co-immobilized in a biofilm reactor proportionally using alginate gel to determine the effect of wastewater denitrification and phosphorus removal.Among the 9 DNBs, DNB2, DNB4, DNB8 and DNB12 were Alphaproteobacteria, DNB2, DNB8 were identified as members of genus Paracoccus, DNB4 was identified as a member of genus Sphingomonas, DNB12 was identified as a member of genus Aquamicrobium. DNB7 and DNB11 were identified as Diaphorobacter sp. and Alcaligenes sp. respectively, and they were Betaproteobacteria. DNB1, DNB5 and DNB6 were identified as Pseudomonas sp., Aeromonas sp. and Acinetobacter sp. respectively, and they were Gammaproteobacteria. Among the 8 PRBs, PRB10 which was Alphaproteobacteria was identified as Xanthobacter sp.; PRB2, PRB5, PRB17 and PRB22 were Gammaproteobacteria, PRB2 and PRB5 were identified as members of genus Pseudomonas, PRB17 was identified as a member of genus Stenotrophomonas, PRB22 was identified as a member of genus Serratia; PRB3, PRB14 and PRB18 which were Actinobacteridae were identified as members of genus Microbacterium, Arthrobacter and Brevibacterium, respectively. Among the 4 FBs, FB2 which was Bacillales was identified as Paenibacillus sp., FB3 and FB4 which were Alphaproteobacteria were identified as Rhizobium sp. and Sphingobium sp., respectively, FB1 which was Gammaproteobacteria was identified as Erwinia sp.Ability determination results showed that the average denitrification rate of DNB8 was 1.59μg·mL-1·h-1 at a shake condition and 1.12μg·mL-1·h-1 at a static condition; the total phosphorus removal rate in supernatant liquid for PRB22 was 85.36%at 48h at a shake condition and 7.57%at 192h at a static condition; the maximum flocculating rate for FB4 was 65.77%at 72h at a shake condition and 20.90%at 192h at a static condition, respectively.Synthetic wastewater was treated using the biofilm reactor. Total nitrogen (TN) removal rate was 73.56%in supernatant in the first batch at 32h, TN balance showed that the actual denitrification rate was 41.61%; Total phosphorus (TP) removal rate was 53.67%in the first batch at 24h. Batch tests showed that TN removal rate at 32h in supernatant was above 72%in the first three batches, and then gradually decreased to 62.72%in the sixth batch; TP removal rate at 24h gradually increased from 53.67% in the first batch to 55.71%in the third batch, and then gradually decreased to 47.35% in the sixth batch.