Sj. You et al., Phosphorus removal characteristics of a combined as-biofilm process cultured by different COD/TP ratios, ENV TECHNOL, 22(1), 2001, pp. 1-6
The COD/TP ratio of influent is an important parameter for the phosphorus r
emoval in a biological nutrient removal (BNR) process. In this study, we in
vestigated the phosphorus removal and denitrification characteristics of a
combined activated sludge-biofilm process, as cultured by different influen
t COD/TP ratios ranged from 12 to 120. Experimental results indicated that,
when COD/TP ratios exceeded 30, the removal efficiencies of COD, TN and TP
were 98%, 76% and 100%, respectively. However, when the COD/TP ratios were
less than 30, the COD removal efficiency still surpassed 98%. but the TP r
emoval efficiency decreased to 41%, and 31.8% when COD/TP ratios were 20 an
d 12. Moreover, the weight percentage of phosphorus in the sludge attained
a stable value when the COD/TP ratios were below 30. The maximum weight per
centage of phosphorus in the sludge was found to be about 6% and, under thi
s condition, the critical COD/TP ratio of influent was 30 of the process un
der a sludge retention time of 12 days. Although the amount of accumulated
PHAs per mg phosphate released (gamma (PHA/PO4)) remained stable between a
COD/TP ratio of 30 to 120, it increased with a decreased of the COD/TP rati
o when the COD/TP ratio was less than 30.