[Formation and characterization of aerobic granules in a pilot-scale reactor for real wastewater treatment].

Microbial granules were successfully developed in a pilot-scale sequencing batch reactor (SBR) for the treatment of real municipal wastewater. The aerobic granules developed had good settleability with a settling velocity of > 21 mh-1. The mature granular sludge was capable of simultaneous removal of chemical oxygen demand (COD), nitrogen (N) and phosphorus (P). With the cycle of 3 h, the effluent COD, ammonium nitrogen (NH+4 -N) and total nitrogen (TN) concentrations were <50 mg L-1, <5. 0 mg L-1, and <15 mgL-1, respectively. The removal efficiency for TN and total phosphorus (TP) was about 50%. Examinations by confocallaser scanning microscopy (CLSM) showed that extracellular polymeric substances (EPS) were uniformly distributed throughout the granules, forming the granule structure matrix. X-ray diffraction (XRD) analysis indicated the presence of SiO2 and other metal oxides inside aerobic granules, implying that minerals in real wastewater might function as the seed in the initial stage of aerobic granulation.

[Treatment of municipal wastewater using the combined reversed A2/O-MBR process].

For the treatment of municipal wastewater, the effects of the reversed A2/O-MBR system on COD, NH4+ -N, TN, TP, SS and transmembrane pressure (TMP) were investigated through two-point feeding. The results indicated that the removal efficiencies for COD and NH4+ -N were high in the system, the effluent met the requirements of the Class A in first grade discharge standard of GB 18918-2002. The effluent TN was < 15 mg x L(-1) when the reflux ratio of nitrification was 200%, whereas the average TP removal rate was 90% after the excessive sludge was removed. The effluent SS was < 10 mg x L(-1) before the large-scale breakage of membrane. The TMP increased gradually with the operation of the system, if the way of aeration was not correct, the TMP would increase quickly. Efficient separation by the membrane contributed to the removal of COD, TP and SS. Because there was no sludge washout in the system, SRT could be properly controlled, it was good for the ammonia-oxidizing bacteria and denitrifying bacteria which both have long life-cycle. Even if the inflow was increased to 1.5 fold, the effluent quality was good when the sludge concentration was increased to 6500 mg x L(-1).

[Effects of two typical substrates as the sole carbon source on biological phosphorus removal with a single-stage oxic process].

To investigate the performances of phosphorus removal in a sequencing batch reactor (SBR) with single-stage oxic process using synthetical wastewater, glucose (R1) and acetate (R2) were fed to two SBRs as the sole carbon source, respectively. The operation run mode was determined to be: influent --> aeration (4 h) --> settling (8 h) --> effluent. The results showed that the performance of phosphorus removal in R1 was higher than that in R2 after steady-operation. Total phosphorus (TP) removed per MLVSS in R1 and R2 were 7.2-7.7 and 3.8-4.6 mg x g(-1) during aeration, respectively, but the rate of phosphorus release at the two reactors were 3.6-3.8 and 2.7-3.1 mg x g(-1) during the idle zone, respectively. The energy storage of poly-beta-hydroxyalkanoates (PHA) was constant nearly in R1 during the whole period, but glycogen was accumulated to the maximum value at 30 minutes of aeration, and then was decreased to the initial level. However in R2, PHA and glycogen were both accumulated at about 45 minutes of aeration. This phenomenon suggested that glycogen is the main energy source for metabolism during aerobic period in R1, and the main energy resource come from the decomposition of PHA and the hydrolysis of glycogen in R2. The facts showed that glycogen could replace PHAs to supply energy for phosphate uptake and polyphosphate accumulation in such a single-stage oxic process. Since glycogen accumulated in R1 was more than that in R2, the efficiency of phosphorus removal in R1 was higher than that in R2.