Rapid cultivation of nitrifying microgranular sludge and its response to sulfides

The dewatered sludge of municipal wastewater treatment plant was inoculated in a continuous flow gas lift internal circulation reactor, and the rapid culture of nitrified granular sludge and its response to sulfides were investigated. The results showed that under the condition of high inoculation sludge concentration (19.3g/L), sludge granulation was basically achieved within 30 days by gradually shortening HRT (7h to 2h) and increasing influent ammonia nitrogen load (0.5kg/(m3·d) to 3.1kg/(m3·d)). The SVI3=SVI30 was (16.8±0.3)mL/g, and the average particle size of granular sludge was 266 µm. The high concentration nitrification granular sludge [(11.9±0.2)g/L] ensured the high load operation of the system (ammonia nitrogen removal load (2.4±0.3)kg/(m3·d)). Sulfides in the influent significantly inhibited ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in granular sludge, but the recovery of AOB activity was faster than that of NOB, so nitrifying micro-granular sludge achieved the function of nitrification. When the sulfide concentration increased to 10mg/L, the nitrification rate reached about 80%. However, when the sulfide concentration was further increased to 20mg/L, the nitrification rate did not increase significantly. The batch experiments on the 82nd day showed that AOB activity decreased with the increase of initial sulfide concentration, while NOB activity increased, which was closely related to the stratified distribution of AOB (outer layer) and NOB (inner layer) in granular sludge. In addition, the effect of sulfides on nitrifying granular sludge with small particle size ( © 2023 Chinese Society for Environmental Sciences. All rights reserved.