Removal of phenol by activated alumina bed in pulsed high-voltage electric field.

A new process for removing the pollutants in aqueous solution-activated alumina bed in pulsed high-voltage electric field was investigated for the removal of phenol under different conditions. The experimental results indicated the increase in removal rate with increasing applied voltage, increasing pH value of the solution, aeration, and adding Fe2+. The removal rate of phenol could reach 72.1% when air aeration flow rate was 1200 ml/min, and 88.2% when 0.05 mmol/L Fe2+ was added into the solution under the conditions of applied voltage 25 kV, initial phenol concentration of 5 mg/L, and initial pH value 5.5. The addition of sodium carbonate reduced the phenol removal rate. In the pulsed high-voltage electric field, local discharge occurred at the surface of activated alumina, which promoted phenol degradation in the thin water film. At the same time, the space-time distribution of gas-liquid phases was more uniform and the contact areas of the activated species generated from the discharge and the pollutant molecules were much wider due to the effect of the activated alumina bed. The synthetical effects of the pulsed high-voltage electric field and the activated alumina particles accelerated phenol degradation.

[Impacts of alkaline thermal treatment on characteristics of sludge from sewage treatment plant].

Alkaline thermal treatment is an important pretreatment method for sewage sludge. In this paper, in order to optimize the alkaline thermal treatment conditions for sludge pretreatment, four pretreatment parameters ( sludge concentration, pH, temperature and treatment time) were investigated through orthogonal experiments to determine their effects on the sludge disintegration, sludge concentration and sludge morphology of sewage sludge. The experimental results showed that the significance of the four factors on sludge characteristics was in the order of pH > temperature > treatment time > sludge concentration. Additionally, the optimal conditions of the four factors for the release of soluble chemical oxygen demand (SCOD) of unit sludge and decrease of sludge concentration were as follows: 36.55 g x L(-1), pH 12.45, 175 degrees C and 60 min. While the optimal conditions for the decrease of particle size and fractal dimension were 36.55 g x L(-1), pH 12.5, 175 degrees C and 45 min.

[Mechanism of the organic pollutant degradation in water by hybrid gas-liquid electrical discharge].

The method of hybrid gas-liquid electrical discharge was investigated for the removal of phenol. The results indicate that this new method can remove phenol in water effectively. The removal rate increases with increasing voltage and air aeration. The production quantity of H2O2 and O3 is measured respectively in the discharge region and the production quantity increases with increasing of voltage and air aeration. The energy consumption analysis indicates that with increasing the voltage, the increase extent of the phenol removal rate is smaller than the energy's, so the increase of energy efficiency is very small. Air aeration increases the energy consumption. At the same time, a considerable part of energy in the overall input energy makes the temperature of the solution increase, and more energy is transformed into heat, which leads to the waste of energy.