Treatment of poultry slaughterhouse wastewaters by electrocoagulation

Treatment of poultry slaughterhouse wastewater (PSW) by electrocoagulation (EC) has been investigated batchwise in this paper. Effects of the process variables such as medium pH, electrode material, current density, and operating time are investigated on chemical oxygen demand (COD) and oil-grease removal efficiencies, electrical energy consumption, and sacrificial electrode consumption. The highest COD removal efficiency is reached with aluminum as 93%, and maximum oil-grease removal is obtained with iron electrodes as 98%. Combined use of both electrode materials in the EC unit may yield high process performances with respect to both COD and oil-grease removals. Further work needs to be carried out at pilot scale to assess the technical end economic feasibility of the process.     

Contact time optimization of two-stage batch adsorber design using second-order kinetic model for the adsorption of phosphate onto alunite

The adsorption of phosphate onto alunite in a batch adsorber has been studied. Four kinetic models including pseudo first- and second-order equation, intraparticle diffusion equation and the Elovich equation were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of phosphate onto alunite could be described by the pseudo second-order equation. Adsorption of phosphate onto alunite followed the Langmuir isotherm. A model has been used for the design of a two-stage batch adsorber based on pseudo second-order adsorption kinetics. The model has been optimized with respect to operating time in order to minimize total operating time to achieve a specified amount of phosphate removal using a fixed mass of adsorbent. The results of two-stage batch adsorber design studies showed that the required times for specified amounts of phosphate removal significantly decreased. It is particularly suitable for low-cost adsorbents/adsorption systems when minimising operating time is a major operational and design criterion, such as, for highly congested industrial sites in which significant volume of effluent need to be treated in the minimum amount of time.     

Treatment of dairy wastewaters by electrocoagulation using mild steel electrodes

The removal of COD and oil-grease from dairy wastewater was experimentally investigated using direct current (DC) electrocoagulation (EC). In the EC of dairy wastewater, the effects of initial pH, electrolysis time, initial concentration of COD, conductivity and current density were examined. The COD and oil-grease in the aqueous phase were effectively removed when iron was used as sacrificial anode. The optimum operating range for each operating variable was experimentally determined. The batch experimental results revealed that COD and oil-grease in aqueous phase was effectively removed. The overall COD and oil-grease removal efficiencies reached 98 and 99%, respectively. The optimum current density, pH and electrolysis time for 18,300 mg COD/L and 4570 mg oil-grease/L were 0.6 mA/cm2, 7 and 1 min, respectively. Mean energy consumption was 0.003 kWh/kg of COD.     

A review on microalgal growth stress parameters for sustainable biofuel production

Clean Technologies and Environmental Policy - Rapid growth and high carbon-fixation properties make microalgal biomass a preferred source of energy-production technologies, particularly biodiesel...     

Natural weathering of spruce wood chemically modified by re-used ε-caprolactone solution

Increasing environmental pressures over the last few years have led to attention for non-biocide treatments in the wood protection field. The ε-caprolactone modification of wood by substitution or blocking of hydroxyl groups with hydrophobic poly(ε-caprolactone) (PCL) is one of the novel modification methods developed in recent years. In this study, ring-opening polymerisation of ε-caprolactone in wood cell walls was evaluated by the third and sixth re-use of recovered monomer and by oven-curing method. Spruce samples were modified by re-used ε-caprolactone and exposed to the natural weathering agents for 12 months. After weathering, the colour change, surface roughness measurements, and macroscopic and ultra-microscopic observations revealed that the modified wood had better surface properties than reference wood. Fourier-transform infrared (FTIR) analysis proved that PCL could be found on the weathered surface up to the sixth month, but very little amount was detected on the surfaces with a longer weathering period. The results clearly showed that the efficiency of PCL modification with re-use of the monomer solution was sufficient during the initial weathering periods, but efficiency was reduced after a prolonged exposure period.