[Analysis of microbial community structure at full-scale wastewater treatment plants by oxidation ditch].

The microbial populations of the oxidation ditch process at the full-scale municipal wastewater treatment plants (WWTP) in a city in north China were analyzed by fluorescent in situ hybridization (FISH). Fractions structure varieties and distribution characteristics of Accumulibacter as potential phosphorus accumulating organisms (PAOs), and Competibacter as potential glycogen accumulating organisms (GAOs) were quantified. The results indicated that Accumulibacter comprised around 2.0% +/- 0.6%, 3.4% +/- 0.6% and 3.5% +/- 1.2% of the total biomass in the anaerobic tank, anoxic zone and zone, respectively, while the corresponding values for Competibacter were 25.3% +/- 8.7%, 30.3% +/- 7.1% and 24.4% +/- 6.1%. Lower Accumulibacter fractions were found compared with previous full-scale reports (7%-22%), indicating low phosphorus removal efficiency in the oxidation ditch system. Statistical analysis indicated that the amount of PAOs was significantly higher in the anoxic zone and the aerobic zone compared with that in the anaerobic tank, while GAOs remained at the same level.

Optimization of biodemulsifier production from Alcaligenes sp. S-XJ-1 and its application in breaking crude oil emulsion.

A biodemulsifier-producing strain of Alcaligenes sp. S-XJ-1, isolated from petroleum-contaminated soil of the Karamay Oilfield, exhibited excellent demulsifying ability. The application of this biodemulsifier significantly improved the quality of separated water compared with the chemical demulsifier, polyether, which clearly indicates that it has potential applications in the crude oil extraction industry. To optimize its biosynthesis, the impacts of carbon sources, nitrogen sources and pH were studied in detail. Paraffin, a hydrophobic carbon source, favored the synthesis of this cell wall associated biodemulsifier. The nitrogen source ammonium citrate stimulated the production and demulsifying performance of the biodemulsifier. An alkaline environment (pH 9.5) of the initial culture medium favored the strain's growth and improved its demulsifying ability. The results showed paraffin, ammonium citrate and pH had significant effects on the production of the biodemulsifier. These three variables were further investigated using a response surface methodology based on a central composite design to optimize the biodemulsifier yield. The optimal yield conditions were found at a paraffin concentration of 4.01%, an ammonium citrate concentration of 8.08 g/L and a pH of 9.35. Under optimal conditions, the biodemulsifier yield from Alcaligenes sp. S-XJ-1 was increased to 3.42 g/L.

[Effects of external carbon source on nitrogen and phosphorus removal in subsurface flow and free water surface integrated constructed wetland].

By adding municipal wastewater in effluent of ANOXIC-OXIC (A/O) reactor as external carbon source, effects of external carbon source on nitrogen and phosphorus removal in subsurface flow and free water surface integrated constructed wetland were studied in pilot-scale. Results indicate that, COD/TN and (NO2(-) + NO3(-))/TN in influent of wetland are 1.00 and 0.48, respectively, and load removal rates of COD, TN and TP are 1.82, 1.59 and 0.14 g (m2 x d)(-1), respectively, as directly treating effluent of A/O reactor in wetland (working condition I). COD/TN and (NO2(-) + NO3(-))/TN in influent of wetland are 3.55 and 0.44, respectively, and load removal rates of COD, TN and TP are 19.03, 5.42 and 0.29 g (m2 x d)(-1), respectively, as adding municipal wastewater in effluent of A/O reactor as external carbon source in wetland (working condition II). Compared with working condition I, load removal rates of TN and TP for working condition II increase 3.4 times and 2.1 times, respectively. Impact factors of load removal rate of TN and TP are water temperature, HRT, COD/TN and (NO2(-) + NO3(-))/TN, respectively, when ranges of influent load rates are 3.8 - 38.7 g x (m2 x d)(-1) for COD, 5.07 - 13.08 g x (m2 x d)(-1) for TN and 0.57 - 1.92 g x (m2 x d)(-1) for TP, respectively, and range of HRT is 0.5 - 1.0 d. TN load removal rate decreases by exponent function along with increase of HRT, linearly increases along with increase of water temperature and (NO2(-) + NO3(-))/TN, and increases by power function along with increase of COD/TN. TP load removal rate also increases by power function along with increase of COD/TN.

[Influence of wastewater initial pH on enhanced biological phosphorus removal in sequencing batch reactor (SBR)].

Two laboratory-scale sequencing batch reactors (SBRs) were operated continuously to investigate the influence of wastewater initial pH on enhanced biological phosphorus removal (SBR1: pH = 6.8; SBR2: pH = 7.6). Results show that SBR2 exhibits greater anaerobic phosphorus release than SBR1. During aerobic stage, SBR2 degrades less polyhydroxyalkanoates (PHA) than SBR1, and the ratio of glycogen synthesis to PHA degradation in SBR2 is much less than that of SBR1, but SBR2 takes up more phosphorus. Further studies show that due to less glycogen synthesis in SBR2 than in SBR1, lower PHA degradation in SBR2 doesn't result in lower phosphorus uptake. The higher phosphorus uptake and PHA utilization efficiency in SBR2 is probably caused by its more phosphorus accumulating organisms (PAO). At the end of aerobic phase, SBR2 has significantly higher phosphorus removal efficiency than SBR1 (93.67% against 65.06%). Thus, the efficiency of enhanced biological phosphorus removal can be significantly improved by controlling the initial pH of wastewater. This method is much more convenient than controlling the entire process pH of wastewater biological treatment.

[Studies on nitrogen and phosphorus enhancing removal in combined shale and steel slag subsurface constructed wetlands].

Effluent of municipal wastewater treatment plant operated under A/O process was treated by constructed wetlands for reclamation and reuse. These methods, such as phosphorus removal by adsorption of shale and steel slag, regulating C/N ratio and nitrogen oxidability in influent of wetland, were employed to study efficiency and impact factors of nitrogen and phosphorus removal in pilot-scale in combined shale and steel slag subsurface constructed wetlands. Results indicate that, When COD area load rate, TN area load rate, TP area load rate and hydraulic retention time (HRT) is 6.5-20.7 g x (m2 x d)(-1), 2.57-8.22 g x (m2 x d)(-1), 0.41 -1.32 g x (m2 x d)(-1) and 0.5- 1.6d, respectively. Removal efficiency of ammonium nitrogen, nitrite nitrogen and nitrate nitrogen is 85.8%, 56.3% and 18.6%, respectively. Removal efficiency, area load removal rate and removal kinetic constant of total nitrogen are 58.0%, 3.58 g x (m2 x d)(-1) and 0.31m x d(-1), respectively. TN area load removal rate is linearly increased with the increase of total nitrogen area load rate. Removal efficiency, area load removal rate and removal kinetic constant of total phosphorus are 90.4%, 0.89 g x (m2 x d)(-1) and 0.86 m x d(-1), respectively. TP area load removal rate is linearly increased with the increase of total phosphorus area load rate. Water temperature, HRT, COD/TN ratio and (NO2(-) -N + NO3(-) -N) /TN ratio are primary factors impacting nitrogen and phosphorus area load removal rate. Along with HRT and COD/TN ratio increase, TN area load removal rate increases according to power function. Along with water temperature and (NO2(-) -N + NO3(-) -N)/TN ratio increase, TN area load removal rate increases according to exponential function.