[Assessment of the efficiency of electro-Fenton process in degradation of formaldehyde from a highly concentrated aqueous solution by aluminum and iron electrodes]

Due to its high reactivity, colorlessness, stability, purity in different commercial forms and low price, formaldehyde is increasingly used in industries. According to the CERCLA list, formaldehyde is toxic and dangerous to the humans and environment. The aim of this study was to investigate the efficiency of electro-Fenton process for pretreatment of industrial wastewater containing high concentrations of formaldehyde. This was an experimental laboratory study. First of all a reactor was designed and built. Then optimal reaction time was determined and kept constant to determine optimal pH. Finding optimal pH and reaction time, the influence of initial hydrogen peroxide concentration and arrangement of iron and aluminum electrodes as anode and cathode material in constant density, with 1 L/min aeration was investigated for treatment of synthetic wastewater containing initial concentration of 7500 mg/L of formaldehyde. MS Excel 2010 and relative standard deviation were used for data analysis and interpretation. Our findings demonstrated that the increase of pH and initial hydrogen peroxide concentration resulted in an increase of formaldehyde removal by Electro-Fenton Process. Increasing the reaction time up to 10 min resulted in an increase in formaldehyde removal, but increase of the reaction time more than 10 min led to a decrease in formaldehyde removal by the above mentioned process. Use of iron as anode and cathode electrodes led to more removal of formaldehyde in comparison to other possible arrangements between iron and aluminum. The results indicated that the maximum formaldehyde removal was 71.54 percent which was achieved at operational conditions of pH=10, current intensity of 8.5 mA/cm2, primary H2O2 concentration of 50 mM/L after 10 minutes by using iron for anode and cathode electrodes

[Removal of high concentration of phenol from synthetic solutions by fusarium culmorum granules]

Effluent generated in several industries contains phenolic compounds, which have been classified as priority pollutants. Due to its toxicity, the conventional systems are inefficient for treatment of phenol-Laden wastewater. Biological processes using pure microbial culture, including fungi and yeast, are environmentally friendly techniques capable of complete destruction of contaminants. This work was aimed at investigating the efficiency of a fungi specie in the decomposition of high concentrations of phenol ranging from 500 to 20000 mg/L. Several batch reactors were operated at different phenol concentration. The concentration of residual phenol was monitored over time using colorimetric method 4-aminoantipyrine. The removal efficiency was calculated considering the initial phenol concentration. Experimental data indicated that the phenol could efficiently degrade using the selected culture. The developed granules could completely degrade phenol at concentrations up to 20000 mg/L. It can be concluded from the experimental data that the biodegradation using the Fungi granules is a very efficient and thus promising technique for treatment of wastewaters containing phenolic compounds

[Removal of xylene fromwaste air stream using catalytic ozonation process]

Volatile organic compounds [VOCs] are one of the common groups of contaminants encountered in the industrial activities, emitted through air stream into the atmosphere. To prevent the human and environmental health from the adverse effects of VOCs, air streams containing VOCs need to be treated before discharging to environment. This study was aimed at investigating the catalytic ozonation process for removing xylene from a contaminated air stream. In the present work, a bench scale experimental setup was constructed and used for catalytic ozonation of xylene. The performance of catalytic ozonation process was compared with that of single adsorption and ozonation in removal of several concentration of xylene under the similar experimental conditions. The results indicated that the efficiency of catalytic ozonation was higher than that of single adsorption and ozonation in removal of xylene. The emerging time and elimination capacity of xylene for inlet concentration of 300 ppm was 1.4 and 5.8 times of those in adsorption system. The activated carbon acted as catalyst in the presence of ozone and thus attaining the synergistic effect for xylene degradation. Catalytic ozonation process is an efficient technique the treatment of air streams containing high concentrations of xylene. The adsorption systems can also be simply retrofitted to catalytic ozonation process and thereby improving their performance for treating VOCs

[Adsorption of reactive red 198 azo dye from aqueous solution onto the waste coagulation sludge of the water treatment plants]

Much attention has been recently paid on using waste materials as adsorbents for removal of contaminants from water and wastewater. A new low cost waste was examined for its capacity to adsorb RR198, an azo reactive model dye, from an aqueous solution. The waste was dried, powdered and characterized before being used as an adsorbent. The effects of pH [3-10], adsorbent dose [0.2-3 g], dye concentration and contact time on the adsorption efficiency were investigated. Equilibrium study data were modeled using Langmuir and Freundlich models. The characterization analysis indicated that it was composed mainly of ferric hydroxide. The powder had a BET and average pore size of 107 m2/g and 4.5 nm, respectively. The results showed that dye removal was highest at a solution pH of 7 to 8 and a powder dose of 2 g/L. The RR198 removal percentage decreased from 100 and to 43% and at 140 min contact time when the concentration of dye was increased from 25 mg/L to 100 mg/L, at optimum pH and dosage. The Langmuir equation provided the best fit for the experimental data. The maximum adsorption capacity was calculated to be 34.4 mg/g. According to the obtained results, the water coagulation waste sludge appears to be a suitable low cost and effcient adsorbent for removing reactive azo dyes from waste streams

[Biological removal of propylene glycol from wastewater and its degradation in soil by the activated sludge consortia]

Propylene glycol is the main compound of anti-freezing chemicals. A significant amount of propylene glycol is released to the environment after application and contaminates the soil. The main objective of this study was to determine the biological removal of propylene glycol from wastewater and its degradation in soil by the isolated bacteria from activated sludge process. In the present study, the sludge taken from the return flow in a local activated sludge treatment system was used as the initial seed. The performance of the bioreactor in treating the wastewater was evaluated at four different retention times of 18, 12, 6 and 4 h, all with the inlet COD concentration of 1000 mg/L. This phase lasted around 4 months. Then, a part of the adapted microorganisms were transported from the bioreactor to the soil which was synthetically contaminated to the propylene glycol. The average of propylene glycol removal efficiency from the wastewater in detention times of 18, 12, 8 and 4 h in steady state conditions was 98.6%, 97.1%, 86.4% and 62.2% respectively. Also, the maximum degradation in soil was found to be 97.8%. According to the results obtained from this study, it appears that propylene glycol is inherently well biodegradable and can be biodegraded in liquid phase and soil after a short period of adaptation