Tolerance to organic loading rate by aerobic granular sludge in a cyclic aerobic granular reactor.

Sodium acetate as carbon source, tolerance to organic loading rate (OLR) by aerobic granular sludge in a cyclic aerobic granular reactor (CAGR) was investigated by gradually increasing the influent COD. AGS could maintain stability in the continuous flow reactor under OLR⩽15kg/m(3)d in the former 65 days, and SVI, granulation rate, average particle size and water content was 21 ml/g, 98%, 1.8mm and 97.2% on the 65th day. However, AGS gradually disintegrated after the 66 th day when OLR increased to 18 kg/m(3)d, and granules' properties deteriorated rapidly in a short time. High removal rates to pollutants were achieved by CAGR in the former 65 days, but the removal rates of pollutants dropped sharply from the 66 th day. With the increase of OLR and particle size, anaerobic cores inside the granules were formed by massive dead cells, while instability of anaerobic core eventually led to the collapse of the system.

[Research on cultivation of aerobic granular sludge and its characteristics in sequencing fed batch reactor].

Aerobic granular sludge was cultivated in the sequencing fed batch reactor, and granules' characteristic and reactor's performance to the pollutants were studied. The SFBR was operated under the conditions as: inoculated with activated sludge former self-cultivated, fed with simulated wastewater, and continuous feed/intermittent discharge and alternately anaerobic/aerobic operation mode. The results showed that through gradually decreasing the settling time, aerobic granular sludge was successfully cultivated in 28 days, which was yellow, irregular shape, and small particle size (the average particle size was 0.56 mm). Under normal circumstances, the SVI stayed under 70 mLg-1. EPS (as MLVSS) reached the maximum 373.24 mg.g-1 on the 59 d, which increased about 2.5 times over the inoculums. However, EPS decreased sharply during the later period due to the disintegration of aerobic granular sludge. MLSS was always below 3 000 mg L -1 during the middle and later periods in the reactor. During the 63 days' operation, the removal rate of COD by the reactor maintained at about 90% except the abnormal circumstances, and the effluent COD was less than 100 mg.L-1. TIN and ammonia nitrogen's removal efficiency by the reactor fluctuated greatly, and the removal rates were 44.45% -94. 72% and 43. 87% -93. 13% respectively. The removal rate of TP was between 44. 50% -97. 40% , which could remain above 60% under normal circumstances. Limited to the automatic control level, AGS was disadvantage in the competition with filamentous bacteria that overgrew easily during the long time aerobic starvation period at night, which eventually led to the collapse of AGS.

The stability of aerobic granular sludge treating municipal sludge deep dewatering filtrate in a bench scale sequencing batch reactor.

Inoculated with mature aerobic granular sludge in a sequencing batch reactor, gradually increasing the proportion of municipal sludge deep dewatering filtrate in influent, aerobic granular sludge was domesticated after 84 days and maintained its structure during the operation. The domesticated AGS was yellowish-brown, dense and irregular spherical shape, average size was 1.49 mm, water content and specific density were 98.13% and 1.0114, the SVI and settling velocity were 40 ml/g and 46.5m/h. After 38 days, NO3(-)-N accumulated obviously in the reactor as lack of carbon sources. When adding 1-3g solid CH3COONa at 4.5 and 5.5h of each cycle from the 57th day, the removal rate of TN rose to above 90% after 20 days, where effective COD removal and denitrification were realized in a single bioreactor. Finally, the removal rates of COD, TP, TN and NH4(+)-N were higher than 95%, 88%, 96% and 99%.

Rapid cultivation of aerobic granular sludge in a pilot scale sequencing batch reactor.

Aerobic granular sludge which had good performance to pollutants removal was successfully cultivated within 18 days in a pilot scale sequencing batch reactor, about 25% mature aerobic granular sludge was inoculated when the setting time of activated sludge was reduced to 10 min. Anaerobic biological selector was implemented to inhibit filamentous bacteria overgrowth, where the maximum COD could reach to 1703.74 mg/L. The cultivated aerobic granular sludge was irregular and pale yellow, average particle size, SVI, SV30/SV5, PN/PS, EPS and water content were 1.58 mm, 67.64 mL/g, 0.91, 2.17, 268.90 mg EPS/g MLVSS and 98.16% on the 18th day. Mechanism of rapid granulation mainly included crystal nucleus hypothesis and selection pressure hypothesis. The inoculated aerobic granules could maintain stable under short setting time environment, making it directly as the crystal nucleus and the carriers for new particles without obvious disintegration, which eventually shortened the granulation time greatly.