[Modified Fenton oxidation of pyrene in contaminated soils using iron nano oxides]

Problems related to conventional Fenton oxidation, including neccesity of having a low pH and production of considerable amounts of sludge, have prompted researchers to consider chelating agents to improve the pH operating range and iron nano-oxide particles to reduce excess sludge. The main objective of this study was to remove pyrene from contaminated soils by a modified Fenton oxidation method at neutral pH. Experiments were conducted using various concentrations of H2O2 [0-500 mM], iron nano-oxides [0-60 mM], reaction times [0.5-24 hours] and several chelating agents, namely, sodium pyrophosphate, ethylene diamine tetra-acetic acid, sodium citrate, fulvic and humic acids, to eliminate pyrene from soil [concentrations of 100-500 mg/kg]. The efficiency of removal of pyrene at an initial concentration of 100 mg/kg was 99% at the following reaction conditions: H2O2 and iron nano-oxide concentrations of 300 mM and 30 mM, respectively; pH=3; and a reaction time of 6 hours. The initial pyrene concentration of 100 mg/kg decreased to 7 mg/kg at optimum conditions using sodium pyrophosphate as the chelating agent at pH 7. The modified Fenton oxidation method, using iron nano-oxide at optimum conditions as defined in this research, is an efficient alternative for chemical remediation or pre-treatment of soils contaminated with pyrene at neutral pH

Fluoride removal from water by adsorption using Bagasse, Modified Bagasse and Chitosan

Fluoride is widely used in industries such as manufacture of semiconductors, power plants, glass production etc and release to the environment via their effluents. The purpose of this sturdy was to compare the efficiency of low price adsorbents in fluoride removal from water. The optimum values of pH, contact time and adsorbent dosage were determined and different concentrations of fluoride were experimented in lab scale conditions for bagasse, modified bagasse and chitosan. Then Langmuir and Freundlich coefficient were determined based on optimum conditions. The pH value of 7. contact time of 60 min and adsorbent dosage of 2 g/L were determined as optimum conditions for all three adsorbents. The most fluoride removal efficiency of 91% was obtained for modified bagasse in optimum conditions. Based on data obtained in this study, it can be concluded that adsorption by modified bagasse is an efficient and reliable method for fluoride removal from liquid solutions

[Evaluation of electrochemical treatment in degradation of wastewater contaminated by propylene glycol]

Propylene glycol is applied in many industries as raw material and can be released to the environment through wastewater of such industries. The biological treatment of solutions containing high concentration of propylene glycol is difficult and some problems can be observed during this process. The main objective of this study was the investigation of electrochemical degradation of propylene glycol and the parameters influencing on improving removal efficiency. In this study the degradation of propylene glycol was made by passing an electrical current though the synthetic wastewater containing propylene glycol. In order to investigate this process several types of electrode with applied voltage ranging between 5 to 50 V was used. Due to the effect of NaCl concentration on removal efficiency which was mentioned in the literature, the experiment was performed for different NaCl concentrations. In optimum condition, the maximum removal efficiency of propylene glycol [based on COD] was obtained equal to 90%. The results showed that rising applied voltage, NaCl concentration and retention time increase the removal efficiency. The optimum retention time was obtained equal to 50 min. The maximum removal was obtained when aluminum electrode was used. It can be attributed to the production of coagulant material such as Al[+3] during this process. The results revealed that this process can be useful for treating the industrial wastewater containing propylene glycol

[Optimization of propylene removal in a complete mixed activated sludge bioreactor by Taguchi method]

Exposure to propylene glycol can lead to many health risks on blood, skin and kidney. Biodegradation of synthetic wastewater containing propylene glycol was studied in a continuous conventional activated sludge bench scale reactor. Optimum conditions of microorganisms growth for biodegradation of propylene glycol were determined by Taguchi method. Primary microorganisms for start up of the bioreactor were obtained from sludge return line of a municipal wastewater treatment plant and adapted to different concentrations of propylene glycol in a conventional activated sludge reactor. Optimum growth conditions of microorganisms and also operational conditions of the system including pH, influent COD, source of nitrogen and salinity were determined in three levels by Taguchi method. COD removal efficiency in conventional activated sludge reactor for influent concentrations of 400, 700, 900, 1100 and 1300 mg/L were 98%, 95%, 95%, 90% and 85% respectively. Optimization of the process by Taguchi method showed that source of nitrogen urea, pH = 8, salinity of 8% and influent COD of 1300 mg/L with importance priority of 41%, 25%, 17.11% and 16.142% were as optimum growth conditions of microorganisms and also, operational conditions of the system for propylene glycol biodegradation respectively. According to the results obtained from this work, it can be concluded that optimum conditions of biological processes and improvement the efficiency of bioreactors can simply be done by the use of such experimental designs

[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