The Effect Of Carbon Source On Biological Dephosphatation And Denitrifying Phosphorus Removal

Traditionally, acetate was considered as a good corbon source for enhanced biological phosphorus removal (EBPR). However, it was reported that the EBPR could be broken down by the addition of acetate-sodium or glucose as carbon source. In this paper, PAOs (phosphorus accumulating organisms) and DNPAOs (denitrifying phosphorus accumulating organisms) were cultivated under two different operations with acetate-sodium and glucose as carbon source, the effect of carbon source: acetate-sodium, butyric acid, glucose and methanol as 4 kinds of carbon source was studied, and carbon concentration on the biological dephosphatation and denitrifying phosphorus removal were also focused on at the same time. The experimental results showed that:(1) The system run stably with high efficiency of phosphorus removal in both DNPA process and EBPR process. Under the same condition, by calculating the phosphorus uptake rate of anoxic or aerobic, the percents of DNPAOs before cultivated were 22.25%, 18.08%, after cultivation, the ratio could respectively reached to 78.61%, 51.25%; There contains preparation relationship between the nitrite dosage and phosphate contents, the result was 1.2166mgN/1.0mgP and 1.0892 mgN/1.0mgP with acetate sodium and glucose as substrates;(2) SBR was operated in the pattern of A/O and A/A with Acetate sodium and glucose as carbon source. The degressive order by the maximum quantity and the rate of phosphorus release was: acetate-sodium, butyric acid, glucose and methanol. Acetate sodium was the most favourite substrate with maximum quantity of phosphorus release in anaerobic condition. The degressive order by the phosphorus uptake rate was: butyric acid, acetate-sodium, glucose and methanol. The same carbon metabolism has been observed under anoxic conditions and aerobic conditions. It also demonstrated that butyric acid as a substrate can achieve good EBPR performance;(3) The higher the C/P, the more the quantity of P release, but the rate was decreased when C/P was beyond 40. When used acetate sodium as carbon source, the curve of Prelease was near to be linear at first, the length of the line was deterimined by the carbon concentration;(4) When the ratio of C/P was 30 under the dosage of acetate sodium was as carbon source, the release rate was 2~4.6 times than others, the ratio of the quantity of phosphorus uptake to the release was 1.58, higher than others. When the ratio of C/P was lower than 40, the denitrifying rates approximately had the same value, but the lower the rate of C/P, the faster the rates of DNPA, it was demonstrated that the residual of COD to anoxic period was harm to EBPR; When the ratio of C/P was exceed 40, the coexist of substrates and nitrite would lead to the reactions of P uptake , P release and denitrifying happened simultaneously, In contrast, when the ratio of C/P was 30, it acted perfect EBPR;(5) When used acetate sodium as carbon source, the effect of the release of P was not so good when the ratios were not in the range of 20-40. When the C/P ratio was 40, the ratio of the quantity of phosphorus uptake to the release was the best. When C/P was 50, the residual COD in anoxic stage would affect the rate of denitrifying phosphorus. In contrast, the C/P range of 30~40 was fertilization.