Yanping Zhu

Removal of antimonate from wastewater by dissimilatory bacterial reduction: Role of the coexisting sulfate

The priority pollutant antimony (Sb) exists primarily as Sb(V) and Sb(III) in natural waters, and Sb(III) is generally with greater mobility and toxicity than Sb(V). The bio-reduction of Sb(V) would not become a meaningful Sb-removal process unless the accumulation of produced dissolved Sb(III) could be controlled. Here, we examined the dissimilatory antimonate bio-reduction with or without the coexistence of sulfate using Sb-acclimated biomass. Results demonstrated that 0.8mM Sb(V) was almost completely bio-reduced within 20h along with 48.6% Sb(III) recovery. Kinetic parameters qmax and Ks calculated were 0.54mg-Sb mg-DW-1h-1 and 41.96mgL-1, respectively. When the concentrations of coexisting sulfate were 0.8mM, 1.6mM, and 4mM, the reduction of 0.8mM Sb(V) was accomplished within 17, 9, and 5h, respectively, along with no final Sb(III) recovery. Also, the bio-reduction of sulfate occurred synchronously. The precipitated Sb2O3 and Sb2S3 were characterized by scanning electron microscopy coupled with energy dispersive spectrometer, X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with bacterial compositions of the seed sludge obtained from anaerobic digestion tank in a wastewater treatment plant, new genera of Pseudomonas and Geobacter emerged with large proportions in both Sb-fed and Sb-sulfate-fed sludge, and a small portion of sulfate reduction bacteria emerged only in Sb-sulfate-fed culture.

Control of disinfection by-product derived from humic acid using MIEX process: optimization through response surface methodology

This work investigated the removal of humic acid (HA) as the precursor of disinfection by-product (DBP) using a magnetic ion exchange (MIEX) resin. The Box–Behnken design of response surface methodology (RSM) was used to evaluate the effect of process variables (initial pH, MIEX dose and reaction time) and their interaction for HA removal. Specific ultraviolet absorbance (SUVA) removal was selected as the response value. The analysis of variance (ANOVA) of the quadratic model demonstrated that the model was significant, and the optimum conditions were obtained as pH 2.3, MIEX resin dosage 0.95 mL L−1, and reaction time 59.18 min. At these applied optimum conditions, 39.74% SUVA removal from an initial SUVA value of 10.06 L mg−1 m−1 was achieved. Also the reduction in DBP (chloroform, dichloroacetic acid and trichloroacetic acid) formation potentials was about 76%, 73% and 80%, respectively. The MIEX process was effectively optimized by RSM with a desirability value of 1.0. After the process optimization, the MIEX treatment was proven to be a good option for controlling the DBP derived from HA.

Removal of perchlorate from water using a biofilm magnetic ion exchange resin: feasibility and effects of dissolved oxygen, pH and competing ions

A biofilm magnetic ion exchange (BMIEX) resin was obtained by mixing a magnetic ion exchange (MIEX) resin with perchlorate-acclimated cultures. Four-cycle batch tests using the BMIEX resin, virgin MIEX resin and cultures of perchlorate-reducing bacteria (PRB) were performed to investigate the feasibility and performance of the BMIEX resin in removing perchlorate (ClO4−). This novel approach can achieve efficient simultaneous perchlorate adsorption and reduction through biofilm formation on the MIEX resin. Moreover, the effects of dissolved oxygen (DO), pH and common coexisting ions (NO3− and Cl−) on the BMIEX process were investigated to optimize perchlorate removal using BMIEX resin. Excellent perchlorate removal only occurred under anaerobic conditions, and a DO concentration of 2.07 mg L−1 was sufficient to inhibit perchlorate removal by the BMIEX resin. A neutral pH range was optimal, and maximum perchlorate removal was obtained at pH 6.8. The presence of NO3− or Cl− could adversely affect perchlorate reduction, and the inhibition of nitrate was substantially stronger than that of chloride. Increasing nitrate concentrations significantly inhibited the perchlorate removal efficiency of the BMIEX process. Community analysis of the biofilm revealed α-, β-, γ- and δ-Proteobacteria as the main PRB, accounting for approximately 21.04%, 12.44%, 24.33% and 0.71%, respectively.

Impact of preoxidation of UV/persulfate on disinfection byproducts by chlorination of 2,4-Di-tert-butylphenol

UV/persulfate (UV/PS) has been as an efficient method to remove many organic contaminants in water. However, little is known about the impact of UV/PS pretrement on the formation of disinfection byproducts (DBPs) during chlorination of 2,4-Di-tert-butylphenol (2,4-D). This research evaluated that UV/PS preoxidation of 2,4-D greatly decreased the DBPs generation during following chlorination. In the 2,4-D solution without any treatment system (O system), trichloromethane (TCM) as the only detected DBP increased with the increase of chlorine dosage. While the formation of TCM declined with the increase of PS dosage in the PS and UV/PS preoxidation systems and decreased the estimated toxicity accordingly. And it was found the residual PS in system could combine free chlorine to further oxidize 2,4-D. And intermediate products were analysed by high-performance liquid chromatography combined with triple quadrupole mass spectroscopy analysis. In the presence of bromine, the bromodichloromethane augmented first and then slowly decreased while dibromochloromethane and tribromethane increased both in O and UV/PS systems with the increase of [Br-]. Bromine substitution was decreased by preoxidation of UV/PS. UV/PS could decrease the total-DBPs formation when used in the real water matrix contained 100u202fμg/L 2,4-D.

Adsorption of bentazon on two kinds of granular activated carbons: equilibrium, kinetic and thermodynamic studies

AbstractThe adsorption of bentazon on two types of granular activated carbons (GACs), VRU F36X16 (VRU) and WS-480 (WS) from aqueous solution was evaluated by kinetics, isotherms, and thermodynamic models in this study. The impacts of initial bentazon concentration, temperature, and initial solution pH were also investigated. The equilibrium adsorption capacity (qe) of each GAC was appreciable under the experimental condition, especially VRU. For either GAC, the adsorption process fitted pseudo-second-order equation best and statistics matched two-step intra-particle diffusion model well. Dubinin–Radushkevich model was the most suitable one for bentazon adsorption on VRU, while Redlich and Peterson model best described bentazon adsorption on WS. Both for VRU and WS, the adsorption process was exothermic and belonged to physisorption. The qe of VRU and WS increased as initial bentazon concentration increased, though the removal rate of bentazon decreased. 25°C was the optimal condition for bentazon adsorpti...