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Substrate utilization in a glucose-fed anaerobic sequencing batch reactor (ASBR) under different F/M ratios was investigated. Glucose added was quickly taken up by fermentation bacterial in anaerobic digestion, then partly degraded directly to volatile fatty acid (VFA, accounted for 34%-38% of COD-fed) and partly accumulated transiently in the cell as glycogen (accounted for 41%-46% of COD-fed) and degraded to VFA in the following. The bacterial accumulation capacities increased with F/M. The maximum specific storage capacities could reach as high as 116.8, 81.1 and 62.4 mg/g as F/M (COD/VSS) was controlled in 0.27, 0.20 and 0.14 respectively. VFA production rate slowed down due to glucose storage, which resulted in low VFA accumulation and guaranteed a stable operation in ASBR under high loading rate.

The denitrification and excessive P removal can be realized by denitrifying phosphate-accumulating organisms (DNPAOs) under low carbon condition. DNPAOs use poly-3-hydroxy- butyrate (PHB) as electron donor, and use nitrate and nitrite as electron acceptor during the denitrifying phosphate uptake. In this study the biological phosphorus removal granular sludge was induced into the denitrifying and phosphate uptake granular sludge under an anaerobic/anoxic/aerobic alternating operation (referred to as an A/A/O) in a sequencing batch reactor (SBR). When the system is stable, the P and N removal ratio is over 90% and 93% respectively; the release phosphorus is 25-33 mg/L at anaerobic stage; 1g NOx-N approximately takes up P 1.3 g at anoxic stage. In the typical cycle the anaerobic maximum specific release phosphorus rate (max. SRPR) is 18.39 mg/(g x h); the anoxic max. specific uptake phosphorus rate (SUPR) and the max. specific denitrification rate (SDNR) is 23.72 mg/(g x h) and 18.19 mg/(g x h) respectively; the aerobic max. SUPR is 17.15 mg/(g x h). The fraction of DNPAOs rises from 14.9% to 80.7%. Compared with the physical-chemical property of the biological phosphorus removal granular sludge, the settling velocity and the specific gravity of the denitrifying phosphate uptake granular sludge is elevated 0.16-0.7 times and 0.0031 respectively.

Sequencing batch reactor, treating simulated municipal wastewater for N removal and operated at near the minimum SRT (solids retention time) for nitrification (in reactor 2), was seeded daily with nitrifying biomass accumulated with reject water (in reactor 1) came from Xi' an Dengjiacun wastewater treatment plant. Comparison of the nitrification ability, the characteristics of the activated sludge before seeding and after seeding was made. The experiment result shows that, the maximum nitrification rate of the activated sludge in the reactor 1 reached 81.4 mg/(L x h). The effluent concentration of NH4+ -N of the reactor 2 decreased at a rate of 0.992 mg/(L x d) (R2 = 0.903), and the maximum nitrification rate increased 1.36 times. Once seeding was terminated, the effluent concentration of NH4+ -N increased at a rate of 1.956 mg/(L x d) (R2 = 0.999), and nitrification caused by seeding was not completely disappeared after seeding was stopped for 34 d. The amount and varieties of protozoa and the value of SVI in the reactor seeded with nitrifiers increased during the initial time of seeding, but were recovered when the reactor 2 reached stable state.