Biologicial Phosphorus Removal In Different Operating Factors Of SBR

Nitrogen (N) and phosphorous (P) are the main pollutants that cause eutrophication of receiving waters. However, compared with N, the function of phosphorous is stronger. The low P concentration in influent could result in eutrophication. To restrict phosphorous concentration is paid more and more attention. At present, the aim of improving the efficiency of P and ensuring the steady operation are main goal all the time in biological phosphorus removal. Based on it, the effect of the sludge type, idle time and metal ions on biological phosphorus removal in SBR were studied in this paper. The conclusions as follows:(1) Two SBRs were concurrently operated to investigate the different phosphorus removal characteristics between granules (R1) and flocculate sludge (R2). Results indicated that R2 had a faster progress for enriching phosphorus-accumulating organisms compared with R1.and the phosphorus removal reached the steady state after 40 days in R1 but only 30 days in R2. Flocculent sludge could release and take up more phosphorus. The special phosphorus release rate (SPRR) and special phosphorus uptake rate (SPUR) were 8.818mg/gVSS-h and 9.921 mg/gVSS-h in R2 which were consistently larger than that (0.999 mg/gVSS-h and 3.017mg/gVSS-h) in R1. Moreover, the phosphorus removal rate was more than 90% in R2 which was higher than that (81.72%).However, the granules had a higher removal efficiency of NH(+-N. However, The moisture content of granules (85.5%) was smaller than that (98.7%) in R2. The results of DGGE of PCR-amplified 16SrDNA fragments revealed that the diversity and the amount of phosphorus accumulating microbial of bacteria in flocculent sludge were much more than that in the granules. It can be concluded that the flocculent sludge showed a better phosphorus removal.(2) To study the influence of idle period in biological phosphorus removal through setting different idle time of 0.5h (R1),8h (R2) and16h (R3). When the influent P was low (8mg/L), the P removal rate in R2 was higher than that in R1 and R3. Moreover, the P removal rate in R3 was not stable, but rose steadily in R1 and R2. However, when the influent P was higher (16mg/L), the P removal rate began to decline in R2 and R3. Especially, it was suddenly descending of SPUR and SPRR in R2. In steady state, the concentration of phosphorous released in anaerobic stage, SPUR and SPRR were similar in R1 and R2, where the corresponding values were lower in R3, respectively. But the better phosphorus removal capacity the every system presented, the P removal rate reached 90% upwards. DGGE profiles of 16SrDNA fragments for different microbial communities were analyzed. The results showed that Pseudomonas sp. (GQ183242.1) and Unculturedβ-Protebacteria (AY823971) were dominant microbial species in Rland R2. Unculturedγ-Proteobacteria (EU434903.1) was the dominating organisms.β-Protebacteria andγ-Protebacteria were reported to be responsible for enhanced biological phosphorus removal. However, Uncultured Sphingomonas sp. (AM889077) belonged to glycogen accumulating organisms that deteriorates the phosphorus removal was found in R2 and R3 concurrently. These results indicated that phosphorus had best removal and stabilization in R1. The idle time was longer in R2 and R3, which made for forming intracellular polyhydroxyalkanoates. Furthermore, they did not get stable phosphorus removal and were hard to adapt to the change of the water.(3) Finally, the importance of Magnesium of the influent wastewater on the enhanced biological phosphorus removal was investigated. The phosphorus accumulating organisms (PAOs) was cultured and the system was startup successfully in a short term with appropriate and excessive magnesium. By contrast, the system tended to deteriorate with the shortage of magnesium, and the phosphorus removal efficiency dropped below 50%. Statistical analysis of the experimental data also showed a strong correlation between Mg and phosphorus concentrations. Mg/P was between 0.29 and 0.59 in R2 however the ratio of was from 0.25 to 0.54 in R3. It seems that they were in a parallel range. At the same time, Mg/P was between 0.06 and 0.1 in R1.The oxidation-reduction potential (ORP) was monitored online. When ORP decreased to negative values, a larger decrease rate of ORP corresponded to more phosphate release. In anaerobic condition magnesium were released together with phosphates. On contraries, magnesium would uptake under aerobic conditions. The appropriate Mg was important factor for EBPR.