Advanced Materials Research Vol. 777

Abstract: To achieve efficient removal of phenolic pollutants in water, the catalyst of Fe (III)-Cu (II)/γ-Al₂O₃ was prepared. In the presence of Fe (III)-Cu (II)/γ-Al₂O₃, microwave-induced hydrogen peroxide (H₂O₂) catalytic oxidation process was conducted for the treatment of synthetic wastewater containing PNP, a representative of phenolic pollutants. Effectiveness of the process and factors influencing PNP removal were investigated and results showed microwave-induced H₂O₂-Fe (III)-Cu (II)/γ-Al₂O₃ process could achieve 99.41% PNP removal percentage, corresponding to 77.9% TOC removal in a given condition. The process remained effective in the 2-8 pH range with high reusability of Fe (III)-Cu (II)/γ-Al₂O₃ catalyst. The kinetics study showed microwave-induced H₂O₂-Fe (III)-Cu (II)/γ-Al₂O₃ process could be divided into microwave induction stage and catalytic oxidation stage, both of which fitted first-order kinetics, with reaction rate constants of 0.0453 min^-1 and 4.7552 min^-1 respectively.

Abstract: Chitosan modified by microwave irradiation were used for hexavalent chromium removal from aqueous solutions. Sorption parameters including pH, temperature, initial concentration and contact time have been investigated. The maximum sorption of Cr (VI) on modified chitosan occurs at pH 5,whereas the sorption capacities of modified chitosan were significant over pH 2 to 7. The results obtained from equilibrium sorption studies are fitted in various sorption models such as Langmuir and Freundlich and the model parameters have been evaluated. Maximum sorption capacity of was 147mg/g at 15°C. Kinetic models including Lagergren first-order and second-order were used to test kinetic data. The results showed that second-order has good agreement with experimental data. Thermodynamic parameters of the process were also. Thermodynamic parameters including free energy (DG^o), entropy (DS^o) and enthalpy (DH^o) of sorption were also investigated at different temperatures. The negative values of Gibbs free energy and enthalpy changes for Cr (VI) indicated the spontaneous and exothermic nature of the sorption process.

Abstract: The phosphorus removal from low concentration phosphorus wastewater in two BAFs with different artificial crystal seed meida and the influence of HRT, Ca/P and pH on the treatment performance were investigated. The results showed that the artificial crystal media BAFs was more efficient than that of the current commercial filter media for phosphorus removal and recovery, and the suitable pH range of wastewater was also enlarged. When the initial phosphorus concentration was 10 mg/L, the optimum operational condition of steel slag base composite meida filter was HRT=30 min, n (Ca)/n (P)=1 and pH=8, as well as the optimum condition of water slag base composite media filter was HRT=60 min, n (Ca)/n (P)=2.5 and pH=8. XRD analysis showed that the reaction products of phosphorus removal by the two artificial crystal seed media filters were all hydroxy calcium phosphate, but its crystallinity was not high, which might due to the production of calcium carbonate in the reaction of phosphorus removal simultaneously.

Abstract: The performance of three BAFs with zeolite, activated carbon and anthracite media for the treatment of polluted Huaihe raw water were investigated. All three BAFs performed promising permanganate index (COD_Mn) and ammonia nitrogen (NH₄⁺-N) removal efficiency as well as the turbidity removal was over 60%. Moreover, the COD_Mn and NH₄⁺-N removal in the three BAFs were affacted by the characteristics of filter media. Activated carbon and anthracite had better COD_Mn removal than zeolite. Zeolite had the best NH₄⁺-N removal, followed by activated carbon, anthracite was the worst.

Abstract: Used Fenton reagent and fly ash combined process to treat dioctyl phthalate (DOP) simulated wastewater. Influences of pH, concentration of H₂O₂, Fe²⁺ concentration, fly ash dosage and other factors effect of COD were studied. The results showed that, under the synergies of the fly ash, Fenton reagent on the COD removal efficiency was better than Fenton reagent used alone. When the pH was 5, H₂O₂ concentration was 1.2 g/L, Fe²⁺ concentration was 1.0g/L, fly ash dosage was 4 g, and COD removal efficiency reached 83.21%.

Abstract: During thermal drying of dewatered sludge, odor will be produced, and also plenty of condensate water. Currently, there is little research about odor gas and condensate water produced during thermal drying of dewatered sludge. To supply engineering design basis for treatment scheme of odor and condensate water produced during thermal drying of dewatered sludge, it analyzes pollutants concentration of odor and condensate water produced in Sludge Drying Project in Shenzhen Nanshan Thermal Power Plant, and it verifies removal performance of chemical odor removal system of the Project. It is concluded that during thermal drying of dewatered sludge, odor will be produced, which components are mainly ammonia gas, H₂S, CS₂, CH₃SH and dimethylsulfide, etc.. It is found that organic components in condensate water is high, BOD/COD is about 0.2, NH₃-N and TN is high, C/N is about 8, and TP is low.

Abstract: The paper is researched the main applications of micro-electrolysis enhanced by united advanced oxidation processes (UAOPs): O₃/UV/Fe (OUF) and micro-wave/Fenton (MWF). Better removal efficiency was found in O₃/UV/Fe³⁺ (OUFIII) METs than O₃/UV/Fe²⁺ (OUFII) METs in the same pH conditions. In acid condition, the best degradation rate 44.7% could be achieved in the whole study. However, a 37.3% decrease in TOC was observed in basic condition. An inflexion point was observed at 2 hour at different dosages of H₂O₂ by MWF METs, which were probably caused by the branched chains cleavage from the s-triazine ring. With H₂O₂ dosage of 10% and a hydraulic retention time (HRT) equals to 5 hours, a best deduction of 26.5% was observed. Nevertheless, it is suggested OUFIII technology was found to be the optimum enhanced METs for the treatment of s-triazine wastewater.

Abstract: In order to improve the methane yield and removal efficiency of organic matters in anaerobic sludge digestion, effects of addition of food waste were investigated at mesophilic condition. Results showed that the optimal TS ratio between sewage sludge and food waste was 4:1, with a methane yield of 592.7 ml/g-VS, methane content of 66.84% and the VS removal efficiency of 31%, which were 47%, 50% and 55% higher than those of sole sludge digestion, respectively.

Abstract: In this study, suspended carrier bed process was applied to treat the effluent from the chemical-biological flocculation plant. The bio-startup characteristics and the mechanisms of biofilm maturation were investigated. Results showed that the NH₃-N removal efficiency was higher than 80% after a 10d run, and the NH₃-N concentration of effluent was lower than 5.0mg/L, which satisfies the needs of The Pollutants Discharge Standard for Municipal Wastewater Treatment Plants (Class I-A). In other words, the suspended carrier used here did a good job. The bed finished its bio-startup process with stable nitrification efficiency. The biofilm formed on the carriers wing plates, which was helpful for its adhesion and ageing biofilm to fall off. It was found through electron microscope observation and PCR-DGGE (Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis) that the biofilm which formed on the surface of the carrier contained plenty of microbes. The stability of the microbial system was efficient in stabilizing nitrification.

Abstract: The nitrosation rate was around 85% after 33 continuous cycles (20d) with the alternative influent of high and low ammonium wastewater in a sequencing batch reactor (SBR) under low oxygen (0.15~0.40mg/L). The growth of nitrobacteria was inhibited successfully which led to steady and high accumulation of nitrite. Factors of accumulation of nitrite were investigated and the effects of DO and pH were analyzed during the startup for nitrosation. The results showed that it could improve the efficiency of nitrosation when DO concentration was increased appropriately. The activity of nitrite oxidizing bacteria (NOB) was recovered gradually when DO was higher than 0.72mg/L. The key factor of nitrosation reaction was the concentration of free ammonia (FA), while the final factor was the concentration of DO. pH was a desired controlling parameter showing the end of nitrification in a SBR cycle, while DO concentration did not indicate the end of SBR nitrification accurately because it increased rapidly before ammonia nitrogen was oxidized absolutely.