[Simultaneous nitrogen and phosphorus removal by aerobic granular sludge at normal and low temperatures].

The simultaneous nitrogen and phosphorus removal (SNPR) from real domestic wastewater using aerobic granular sludge (AGS) has been investigated. The effect of temperature changes on the SNPR of AGS was also studied. Two lab-scale sequencing batch reactors (SBRs), named as A and B, were operated for 254 days in alternating anaerobic-aerobic mode. The AGS was cultivated in 20 days using settling time as selection pressure. From the 42nd day onwards, additional carbon (acetate and peptone for A, glucose for B) were added to make the ratio of COD:N:P as 360:60:6. The SNPR by AGS was achieved for 4 months, and the removal ratios of ammonia, total inorganic nitrogen and phosphorus of A were reached to 98.42%, 74.25% and 94.79%, respectively; the removal ratios of ammonia, total inorganic nitrogen and phosphorus of B were reached to 99.45%, 75.96% and 95.60%, respectively. Then, the temperature decreased to 9-13 degrees C, which seriously affected the efficiency of SNPR. The removal efficiencies of SNPR of reactor A and B were recovered after 35 days and 49 days, respectively, and the removal ratios of ammonia, total inorganic nitrogen and phosphorus of A were reached to 96.33%, 79.49% and 99.68%, respectively; the removal ratios of ammonia, total inorganic nitrogen and phosphorus of B were reached to 93.85%, 76.44% and 98.44%, respectively. PAOs and DNPAOs together completed the phosphorus removal and made phosphorus removal faster than nitrogen removal. Nitrification was the rate limiting step for SNPR. The low temperature made the anoxic zone in AGS decrease, together with the absence of PHAs, made denitrification could not complete.