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Ji L.-L.,Hunan University | Yang Z.-H.,Hunan University | Xu Z.-Y.,Hunan University | Li X.-J.,Environmental Protection Research Institute of Zhuzhou | And 2 more authors.
Huanjing Kexue/Environmental Science | Year: 2011

Through controlling the concentration of free ammonia in the sequencing batch reactor(SBR), the single-stage autotrophic biological nitrogen removal process was achieved, including partial nitrification and anaerobic ammonium oxidation. The experiment was completed via two steps, the enrichment of nitrite bacteria and the inoculation of the mixture of anammox biomass. The operating temperature in the SBR was(31±2)°C. During the step of the enrichment of nitrite bacteria, pH was about 7.8. Changes of FA concentration were achieved by controlling the concentration of influent NH4 +-N(56-446 mg·L-1), in order to inhibit and eliminate the nitrate bacteria. The activity tests of the sludge, 55d after enrichment, showed strong activity of aerobic ammonium oxidation [2.91 kg·(kg·d)-1] and low activity of nitrite oxidation [0.03 kg·(kg·d)-1]. During the inoculation of the mixture of anammox biomass, changes of FA concentration were achieved by controlling the concentration of influent NH4 +-N and pH. As the inoculation of anammox biomass, abundant of bacteria and nutrient content were into the reactor and there kept high activity of aerobic ammonium oxidation [2.83 kg·(kg·d)-1] and a certain activity of nitrite oxidation, at the same time, the activity of anammox and heterotrophic denitrification reached 0.65 kg·(kg·d)-1 and 0.11 kg·(kg·d)-1, respectively.

Chen Y.,Hunan University | Yang Z.,Hunan University | Li X.,Environmental Protection Research Institute of Zhuzhou | Tang Z.,Environmental Protection Research Institute of Zhuzhou | And 3 more authors.
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2010

The Box-Behnken design methodology, including five factors: pH, initial Cr(VI) concentration, contact time, stirring speed and adsorbent dosage, was employed to study the removal of chromium(VI) from aqueous solution by waste Agrocybe aegerita (Black poplar mushroom). The thermodynamic characteristics and mechanism of the adsorption process were also studied. The pH, initial Cr(VI) concentration and adsorbent dosage were the three key factors influencing the uptake of Cr(VI). The optimal adsorption conditions were pH 1.19, initial Cr(VI) concentration 148.58 mg·L-1, contact time 89.02 min, stirring speed 180.12 r·min-1 and adsorbent dosage 10.90 g·L-1, and under these conditions, the removal of Cr(VI) was above 96%. Langmuir, Freundlich and Dubinin-Radushkevick isotherms were applied to fit the adsorption equilibrium data and the adsorption process. The Langmuir isotherm adsorption model best reflected the adsorption characteristics. The adsorption capacity of the biosorbent was 46.95 mg·g-1. Apparent thermodynamic parameters, such as ΔG, ΔS and ΔH were calculated and showed that the adsorption process was endothermic and spontaneous, while the entropy of the system increased. Finally, the removal mechanism is discussed by deduction from FTIR spectra. The results of this study show that waste Agrocybe aegerita is a good absorbent for removing chromium (VI) from wastewater, which is a strategy of controlling waste by waste.

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