[Effects of composite substrates on the phosphorus removal in granule-based EBPR system and its optimization...

Based on the mature granular sludge, effects of composite substrates [m(C)/m(N)/m (P)] on the process of phosphorus removal in granule-based EBPR system was conducted by the optimal mixed-carbon sources ratio. Results showed that it was observed with the expanded filamentous bulking to granular sludge in the system of R2 [m(C)/m(N)/m (P) = 400:10:5], R3 [m(C)/m(N)/m (P) = 600: 10:10] and R5 [m(C)/m(N)/m (P) = 400:20:15]. The presence of large amount of granular fragments led to the poor performance of R6 [m(C)/m(N)/m (P) =600:20:5], and it returned back after the particulate debris was removed off the system. The particle size of R3, R8 [m(C)/m(N)/m (P) = 400:30:10] and R9 [m(C)/m(N)/m (P) = 600:30:15)] gradually decreased from 0.8 mm to 0.3 mm, and other systems were similar to the initial size. More than 95 percent of the COD was consumed in the anaerobic stage in R1 [m(C)/m(N)/m (P) = 200:10:15], R4 [m(C)/m(N)/m (P) = 200:20:10] and R7 [m(C)/m(N)/m (P) = 200:30:5], and the phosphorus release/uptake rates fluctuated within the range of 60-100 mg x (g x h)(-1), 60-80 mg x (g x h)(-1) and 40-60 mg x (g x h)(-1), respectively. However, the COD consumption was mainly occurred in aerobic stage in other systems, and the phosphorus release/uptake rates gradually declined, even decreased to 0 mg x (g x h)(-1). Phosphate removal rate of each system was (from R1 system to R9 system) 83.5%, 52.8%, 7.1%, 96.7%, 19.7%, 72.2%, 79.7%, 28.1% and 48.7%, respectively. Finally, we also found that the optimal composite substrate condition for the granule-based EBPR system was the ratio of the m(C)/ m(N)/m (P) = 200:20: 15.