Totally found 3517 items.

  • [期刊] Changes in filtration properties of digested sludge under the influence of magnetic field
    A key element in the management of sewage sludge is the process of sludge dewatering. The reduction of sludge hydration is the basis for its efficient and economical drying and also transport, natural utilization, or combustion. An important aspect is also the quality of supernatant from sludge dewatering. Supernatant is recirculated to the wastewater treatment process and increases the load of pollution in the influent wastewater. In order to efficiently dewater sewage sludge, conditioning agents, especially polyelectrolytes, are used. There are many known and tested conditioning methods such as chemical, physical, biological, as well as their combinations. In this study, the possibility of sludge conditioning prior to the dewatering process was investigated. Ferric coagulant, polyelectrolyte, and magnetic field generated by a solenoid were used as conditioning agents. It was suggested that dual conditioning of sludge with ferric coagulant and polyelectrolyte could be effectively supported by the use of a magnetic field. It was assumed that the magnetic field would enhance the forming of rigid and condensed dry matter structures in the sludge. Such changes in the structure and properties of sludge could allow for an easier extraction of the water contained in the flocs. Substantial importance was attributed to the presence of the paramagnetic material in the conditioning mixture. It was concluded that the superior method of conditioning was the dual method using the PIX-113 and polyelectrolyte. The use of the magnetic field caused heterogeneous changes in the characteristics of the conditioned sludge. The doses of the PIX coagulant and the direction of sludge flow by the solenoid were the main variables in this study.
  • [期刊] Integration of fuzzy theory and multi-hierarchy comprehensive index system for health assessment of water environmental ecosystem
    Ecosystem health assessment is an effective way to cope with water pollution, environmental degradation and operation deterioration caused by human activities. Due to the complexity of water environmental ecosystem and the uncertainty of indicators, fuzzy theory improved approach for Multi-Hierarchy Fuzzy Comprehensive Evaluation (MHFCE) method is proposed in reservoir assessment. In the traditional MHFCE, the importance scale and membership degree of indicators are easily impacted by personal experience and subjective consideration, 0-1 scale is present in the process of weights calculation which avoids linguistic uncertainty when making comparison. Moreover, trapezoidal membership function and triangular membership function are presented in the process of fuzzy mapping in this method. A model application has been made in Lianhe Reservoir in Dongjiang Basin, South China, and it is concluded that reservoir assessment value belongs to the second lever of reservoir health. Overall, the improved MHFCE method provides better reservoir assessment to support reservoir management decisions with the decrease of uncertainty and increase of robustness.
  • [期刊] Efficient utilization of bio-energy process residue for removal of Drimarine Yellow HF-3GL dye from aqueous solution
    Bio-energy is an emerging field to address the energy crisis. The biomaterials used in bio-energy production processes undergo various chemical/physical/biological treatments which lead to the activation of biomass. The exploitation of residual biomass of bio-energy processes for wastewater treatment is an attractive option. In this work, the de-oiled/residual biomass of an insect species; Trogoderma granarium (khapra beetle) which was neither previously exploited for biofuel production nor for wastewater treatment was tested for the adsorptive removal of Drimarine Yellow HF-3GL dye from aqueous solution. The study was designed in batch mode, and important influencing parameters have been optimized including pH, contact time, biomass dosage, temperature and initial dye concentration. The residual insect biomass depicted maximum adsorption capacity (481.9 mg/g) by keeping solution pH 2 and temperature at 30 degrees C. Adsorption of Drimarine Yellow HF-3GL dye onto insect residual biomass was found to be a quick process and equilibrium was attained within 15 min. The adsorption mechanism was investigated by applying different equilibrium models. Thermodynamic study was also conducted to check out the feasibility of process. Different kinetic models have been applied on experimental results and pseudo-second-order kinetic model was found to be best fitted on the experimental results. The biomass was characterized by Fourier transform infrared spectrometer analysis, scanning electron microscope analysis and point of zero charge determination (pH(pzc)). The study results indicated that Trogoderma granarium de-oiled biomass has good adsorption potential and bio-energy process residues can be an attractive option for reducing the water pollution.
  • [期刊] Characterization and sorption behavior of some toxic metal ions on Fusarium oxysporum as biomass adsorbent
    In this study the possibility of the pretreated biomass of Fusarium oxysporum in biosorption of heavy metal ions such as Pb2+ and Co2+ from single metal solutions is investigated. The structural morphology and composition of the studied biosorbent were evaluated by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The dead F. oxysporum biomass was pretreated and tested in batch system. The effects of the operating parameters, such as pH, contact time, initial metal concentrations, biomass dosage, and temperature on the removal efficiency of metal ions have been studied. The optimum pH for biosorption was 6.0. F. oxysporum exhibited selectivity for Pb2+ and Co2+ in the order of Co2+ > Pb2+. The interaction between metal ions and biomass function groups was characterized by FTIR spectroscopy. The equilibrium biosorption data were analyzed using different isotherm models. The biosorption data were best described by Langmuir and Flory-Huggins isotherms. The breakthrough capacity obtained from column study was found to be equal to 10.10 and 12.15 mg/g for Pb2+ and Co2+, respectively. Thermodynamic parameters (Delta H degrees, Delta G degrees, and Delta S degrees) were calculated and indicated that an endothermic spontaneous process. The main novelty of this work was the preparation of F. oxysporum biomass in rigid beads suitable for column operation with reasonably good breakthrough capacity.
  • [期刊] High recovery MSF desalination process
    Calcium sulfate scale deposition in the widely used multistage flash (MSF) seawater desalination process is prevented by restricting the top heating temperature of the recycling brine to less than 120 degrees C and the fractional water recovery to less than 50% so as not to exceed a concentration factor above 1.8-2.0. Removal of calcium ions from seawater extends the solubility limits of the CaSO4 polymorphs. This should enable MSF operation at higher fractional water recoveries and higher brine temperatures thereby providing significant economic benefits, notably a marked reduction in heating steam requirement. The objective of this study was to evaluate the maximum CF and top brine temperature (TBT) levels at which an MSF process can be operated with seawater depleted from 80% of the calcium ions by a hybrid electrolytic Ca removal-MSF process. A single stage MSF evaporator was constructed enabling long duration desalination experiments. The most significant result of this study was in demonstrating operation of the experimental unit for several days without any scale deposition at a CF of 4 and a heating temperature of 140 degrees C. Comparison of a typical MSF unit of conventional design with the hybrid MSF unit operating at CF of 4 and TBT of 140 degrees C indicates a potential for substantial cost reduction by the proposed concept.
  • [期刊] Enhancement of Reactive Red 198 dye photo catalytic degradation using physical mixtures of ZnO-graphene nanocomposite and TiO_2 nanoparticles: an optimized study by response surface methodology
    The photo catalytic activity of ZnO-graphene (ZnO-G) nanocomposite and TiO2 nanoparticles physical mixtures for the enhanced degradation of reactive red dye 198 (RR198) under UVC light was evaluated and established. The photo catalytic results revealed that the RR198 was degraded at around 34.4% and 37.7% after 180 min of irradiation, respectively, in the presence of ZnO-G nanocomposite and TiO2 nanoparticles, solely. Interestingly, physical mixtures of both catalysts induced an enhanced catalytic activity comparing to the bare ones. The ideal mixing ratio was found to be 66:34 wt% (ZnO-G:TiO2) with 71.8% degradation performance after 180 min of irradiation. Moreover, the response surface methodology using the best mixture was employed to optimize and determine the interaction effects between three independent operational parameters which are photo catalyst dosage (0.4 - 0.025 mg), initial pH (3-11), and initial dye concentration (5 - 15 mg/L). Based on the results obtained, it was found that a maximum predicted degradation efficiency of RR 198 reached 99% was in agreement with the average of three experimental values (96%) under the following optimal conditions: 0.4 g mixture dose, initial pH of 3.8, and 5 mg/L initial dye concentration. This convergence between the predicted and experimental results indicates the validity of the model for predicting the maximum percentage degradation of RR198 under the above-mentioned optimum conditions. The ANOVA result indicated that the model is significant with the P value of 8.683 x 10(-10) is less than 0.0001, which implies that the model terms are highly significant. Regression analysis with an R-2 value of 0.986 indicated a satisfactory correlation between the experimental data and predicted values. Additionally, non-toxic metabolites with respect to Daphnia Magna and high total organic carbon reduction after treatment with the mixture evidenced that this process can significantly decrease toxicity and mineralize the dye. Finally, the universal degradation ability of the photo catalysts mixture was evaluated and proven towards many model substrates.
  • [期刊] Preparation and photocatalytic activity of TiO_2/PPy/GO for the degradation of Rose Bengal and Victoria Blue dye in visible light in aqueous solution
    This research work describes a proficient method for synthesis of TiO2 /PPy and TiO2/PPy/GO nanocomposites. These nanocomposites were prepared by one-step in-situ deposition oxidative polymerization of pyrrole hydrochloride using ammonium persulphate as an oxidant in the presence of TiO2 nanoparticles (NPs) cooled in an ice bath. The obtained nanocomposites were characterized by X-ray diffraction, transmission electron microscope, scanning electron microscope, UV-Visible, Brunauer-Emmett-Teller, and photoluminescence spectra techniques. The obtained results showed that TiO2 NPs have been encapsulated by PPy with a strong effect on the morphology of TiO2/PPy and TiO2/PPy/GO nanocomposites. The photocatalytic degradation of Rose Bengal and Victoria Blue dyes were done at different condition viz. concentration of dye, time of illumination, pH, and dose of photocatalyst. The maximum photodegradation of dyes was found at 7 pH, 20 ppm concentration of Victoria Blue and 25 ppm of Rose Bengal dye solution, 800 mg/L for Victoria Blue dye (VB) and 1,600 mg/L for Rose Bengal dye (RB) amount of photocatalyst, and 120 min irradiation of visible light. Kinetics of photodegradation was investigated for VB and RB dye and found first-order kinetics.
  • [期刊] Anaerobic digestion reduces veterinary ionophore lasalocid in dairy manure
    Lasalocid is an antibiotic from the group of carboxylic ionophores, and it is commonly used in cattle and poultry as a coccidiostat and for growth promotion. The widespread use and persistence of lasalocid have led to its detection in the environment. The objective of this study was to determine the fate and effect of veterinary ionophore lasalocid during the anaerobic digestion of dairy manure. Duplicate plug flow field-scale digesters were operated using either non-amended dairy manure or dairy manure amended with 1 or 5 mg/L lasalocid. Results showed that lasalocid was reduced approximately 75% during anaerobic digestion. Methane production from digesters treating manure amended with 1 and 5 mg/L lasalocid were comparable with CH4 production from the duplicate digesters operated without added lasalocid. These results suggest that anaerobic digestion can be used to reduce lasalocid levels in dairy manure, and lasalocid did not affect digester stability at concentrations expected in dairy manure.
  • [期刊] Enhanced adsorption of Cu~(2+), Ni~(2+), Cd~(2+) and Zn~(2+) ions onto physico-chemically modified agricultural waste: kinetic, isotherm and thermodynamic studies
    Removal of Cu2+, Ni2+, Cd2+ and Zn2+ ions from single-and multi-component aqueous solution using porous activated carbon (PAC) has been studied. The PAC was prepared by controlling the carbonation temperature of agricultural waste at 500 degrees C and followed by the acid treatment (10 N H2SO4). The structural morphology and elemental composition of PAC have been determined by SEM and EDX, respectively. Batch adsorption studies have been carried out to optimize the adsorption parameters such as solution pH, adsorption dosage, initial metal ion concentration and contact time. Metal ions concentrations have been determined by atomic absorption spectrophotometer. Adsorption kinetic equations (pseudo-first order, pseudo-second order, Elovich and intraparticle kinetic models) have been examined to identify the adsorption process and mechanism using adsorption data of contact time. The adsorption kinetic studies show that the adsorption of metal ions onto the PAC follows the second-order kinetic model, and the maximum adsorption capacities of the Cu2+, Ni2+, Cd2+ and Zn2+ ions were calculated as 57.2, 68.1, 44.2 and 49.3 mg/g, respectively. The adsorption isotherm results suggest that the Freundlich isotherm has been fitted well with experimental data of mono-and multi-layer adsorption. The effect of temperature on the adsorption of (Cu2+, Ni2+, Cd2+ and Zn2+) on PAC has been studied at 298, 303, 308, 313 and 318 K, and thermodynamic parameters such as Gibbs free energy change (Delta G degrees), enthalpy change (Delta H degrees) and entropy change (Delta S degrees) have been evaluated. This study shows that the adsorption process of metal ions onto PACs is endothermic, feasible and spontaneous in nature.
  • [期刊] New antiscalant for reverse osmosis plants
    A new antiscalant CrestoPro R493C has been developed to effectively control multiple scales such as calcium carbonate, calcium sulphate, iron, silica, etc. This product was tested in a reverse osmosis (RO) plant in Northern China using river water with TDS 710 ppm and pH 7.7, with a recovery of 70%. The major fouling problems in this plant were CaCO3, BaSO4, and iron, even when using conventional antiscalant which was locally manufactured. The major issue at this site was the high cleaning frequency and short life of the RO membranes. This was resolved by using 1 ppm of CrestoPro R493C and the case history will be presented. Furthermore, advances have been made on antiscalant technology, which will be introduced in this paper.