Applied Mechanics and Materials Vols. 522-524

Abstract: Invasive aquatic species has been considered one of the greatest threats to the worlds oceans and marine ecological system. A novel of ships ballast water treatment based on ion exchange membrane electrolysis system to deal with algae has been proved. In this paper, an optimized treatment for inactivating algae is proposed based on the developed ballast water treatment system. In this optimized method, different experimental conditions are studied, which contain the injection times and small injection dose of anodic electrolytic products. The contrast experiments were conducted, the results show that the lethal time and available chlorine dose can respectively save up to 66.67% and 50% under the optimized method. The results show that the proposed have the more efficient kill ability for the algae life.

Abstract: The aim of this study was to investigate the use of a model to determine everyday harvest area of Eichhornia crassipes in environmental phytoremediation. A logistic model was constructed to eatimate the area of Eichhornia crassipes and tested in Eichhornia crassipes samples. The area of Eichhornia crassipes was measured nine times in experiment period using GPS data and satellite remote sensing images. The measurements were shown to lead to a determination of the parameters of accurate logistic model with an overall Goodness of Fit Index of 0.9753. This indicates that there is a possibility of obtaining everyday harvest area of Eichhornia crassipes from the logistic model and suggests that it is possible to implement environmental phytoremediation with the everyday harvest at the equal sustainable area of Eichhornia crassipes.

Abstract: This study investigated operational performance and microbial communities in the integrated acidification-denitrification bioreactor and the followed methanogenesis process. Industrial wastewater, cassava stillage (CS) was used as the carbon source amended with or without nitrate. The results showed that acidification and denitrification could occur simultaneously in a single acidification-denitrification reactor, and denitrificatoin did not suppress the acidogenic activity. Both denitrification and DNRA could contribute to nitrate reduction and proportions of them were about 60% and 40% respectively at the tested condition of COD/NO₃-Nof 50. The introduction of nitrate into acidogenic phase did not have any effect on the followed methanogenic process. Microbial communities sampled from two systems were analyzed by culture-independent techniques based on PCR-DGGE. The relative abundance of acid-producing bacteria (primarily Parabacteroides distasonis and Chloroflexi) in the nitrate-amended reactor further confirmed that the addition of nitrate did not suppress the activity of acid-producing bacteria. Bacteria involved in denitrification and DNRA were also detected. The archaeal communities in methanogenic reactors of two systems showed no significant differences. And Methanoculleus and Methanolobus were the dominant bacteria in the culture.

Abstract: The problem of nutrient pollution from piggy wastewater has been considered as a serious problem. Enhancing struvite crystallization process is an efficient technology for ammonium recovery. In our study, the optimal reaction conditions of pH, Mg²⁺: NH₄⁺: PO₄^3- molar ratio, mixing reaction time, and different kinds of chemicals combinations for ammonium recovery were examined. The conclusions were drawn as following. The optimal pH for ammonium recovery was 9.0. The optimal Mg²⁺: NH₄⁺: PO₄^3- molar ratio for ammonium recovery was 1.3:1:1. The optimal mixing reaction time for ammonium recovery was 10 min. The chemicals combination of MgCl₂ + Na₂HPO₄ was the most efficient for ammonium recovery. Scanning electron microscopy analysis indicated the unshaped struvite crystal was coarse and its size was irregular.

Abstract: Azo compounds constitute the largest and the most diverse group of synthetic dyes and are widely used. The release of coloured wastewaters represents a serious environmental problem and a public health concern. The aim of this study was to investigate the impact of sulfate and redox mediator on the reduction of an azo dye (Acid orange 7, AO7) by anaerobic sludge. The kinetics showed the AO7 reduction rate can be greatly improved by the addition of sulfate and RF, thus it is possible to speed up the start-up of AO7 reduction system under appropriate condition.

Abstract: Denitrification is strongly dependent on carbon quantity and quality in most constructed wetlands (CWs), and pH may be a key factor in determining the supply of available carbon source (ACS) in the pre-treatment of external plant biomass. In this study, three bath CWs were designed, and were fed with nitrate-dominated water to investigate nitrate removal affected by external cattail litter with different pH pre-treatment (pH = 7.0, 10.0, 12.0). During the experiment, higher nitrate removal was observed in the wetland using pH12.0 pre-treatment litter leachate as the carbon source. Strong alkaline fermentation at ambient temperature can be considered as a sustainable technology for wetland plant litter pre-treatment.

Abstract: A novel denitrification process with wheat straw as both carbon source and biofilm carrier was developed to simultaneously remove nitrate and pentachlorophenol (PCP) from contaminated drinking water. The experimental results indicated that the reactor packed with wheat straw could be started up readily, and the removal efficiencies of nitrate and PCP reached approximately 98% and 40%, respectively, with 8 h of HRT at 25 °C. A significant increase in PCP removal was observed with prolonged HRT. Approximately 85% of PCP removal efficiency was reached, and 1.61mg/L of chloride ion was released from the contaminated water containing 5 mg/L of PCP with 16 h of HRT. Reductive dechlorination reaction was a major degradation mechanism of PCP under the denitrifying conditions with wheat straw as carbon source.

Abstract: Fulvic acid (FA) is a common refractory organic compound in landfill leachate. The degradation of FA in supercritical water oxidation (SCWO) was conducted in a SS 316 batch reactor. The effects of temperature, pressure, residence time, oxidation ratio and initial FA concentration on the degradation of FA were investigated. Results showed that FA could be easily destructed in SCWO process, and a total organic carbon (TOC) removal efficiency of 98.0% was available at 600 °C, 420 s, 25 MPa and 1% FA. Oxidation coefficient had a significant positive effect on the degradation of FA. Total carbon (TC) and TOC removal efficiencies increased from 78.9 % to 97.2 % and from 86.4 % to 97.2, respectively, when oxidation coefficient increased from 0 to 4. Benzene, phenol and naphthalene could be regarded as the intermediate products in SCWO.

Abstract: Chemical companies, food industries usually produce wastewaters with high salinity. In consideration of economy, biological methods are preferred to physicochemical methods to remove organic matters. When sequence batching reactors are applied, aeration rate is of great importance to the COD removal efficiency. In this bench scale experiment, the aeration rate of 0.40 m³/m³.min led to sludge disintegration, poor COD removal efficiency and superfluous foam. After sludge conditioner addition, the aeration rate of 0.19 m³/m³.min led to good sludge flocs, satisfactory COD removal efficiency and few foam. It is the oxidizing environment caused by the high dissolved oxygen that harmed the sludge and made it work with low efficiency.

Abstract: The removal of ammonia nitrogen from the polluted water was investigated in three different types of horizontal subsurface flow constructed wetlands, reed (Phragmites australis)/gravel bed (W1), hybrid vegetation {reed, cattail (Typha latifolia), bulrush (Scirpus validus)}/gravel bed (W2) and reed/hybrid substrates (gravel, zeolite, slag) bed (W3). At HRT of 28 d, NH₃-N removal efficiencies of W1, W2 and W3 were-130%98%, -120%98% and 21%98% respectively throughout the whole year. The results showed that zeolite and slag contributed to higher NH₃-N removal than gravel, especially in winter, and that cattail and bulrush did not show significant influences on NH₃-N removal. The ranges of NH₃-N removal rates were-2.332.14, -2.272.33 and 0.082.52 g·m^-3·d^-1 respectively under HRT of 2 d. NH₃-N removal rates of W1 and W2 were much more affected by temperature than that of W3, which was due to the adsorption/desorption of zeolite.