Catalytic Ozonation of Phenolic Wastewater: Identification and Toxicity of Intermediates

A new strategy in catalytic ozonation removal method for degradation and detoxification of phenol from industrial wastewater was investigated. Magnetic carbon nanocomposite, as a novel catalyst, was synthesized and then used in the catalytic ozonation process (COP) and the effects of operational conditions such as initial pH, reaction time, and initial concentration of phenol on the degradation efficiency and the toxicity assay have been investigated. The results showed that the highest catalytic potential was achieved at optimal neutral pH and the removal efficiency of phenol and COD is 98.5% and 69.8%, respectively. First-order modeling demonstrated that the reactions were dependent on the initial concentration of phenol, with kinetic constants varying from 0.038 min−1 ([phenol]o = 1500mg/L) to 1.273 min−1 ([phenol]o = 50mg/L). Bioassay analysis showed that phenol was highly toxic to Daphnia magna (LC50 96 h = 5.6mg/L). Comparison of toxicity units (TU) of row wastewater (36.01) and the treated effluent showed that TU value, after slightly increasing in the first steps of ozonation for construction of more toxic intermediates, severely reduced at the end of reaction (2.23).Thus, COP was able to effectively remove the toxicity of intermediates which were formed during the chemical oxidation of phenolic wastewaters

Degradation and toxicity reduction of phenol by ultrasound waves

The effects of parameters such as pH, kinetic constants and initial phenol concentration on the sonochemical degradation of phenol and toxicity assay were studied. The experimental results showed that lower pH and lower concentration of phenol favor the phenol degradation. But the rates of phenol degradation under sonication have always been quite low. It is found that the rate of ultrasonic degradation of phenol for initial concentration of 1 mg/L is 0.018 min-1 but later it reduces with increasing of phenol initial concentration substantially and the experimental data fitted well with pseudo first-order reaction rate equation. Bioassay tests showed that phenol was toxic to Daphnia magna and so resulted in quite low LC50 values. Comparison of toxicity units (TU) between phenol and effluent toxicity showed that the TU value for effluent was 1.21 times lower than that obtained for phenol solely. Thus, the toxicity of metabolites formed during the degradation of phenol is lower than the toxicity of phenol itself. KEY WORDS: Phenol, Ultrasound, Sonochemistry, Toxicity assay  Bull. Chem. Soc. Ethiop. 2007, 21(1), 33-38

Application of novel Modified Biological Aerated Filter (MBAF) as a promising post-treatment for water reuse: Modification in configuration and backwashing process

Biological Aerated Filter (BAF) reactors due to their plentiful biomass, high shockability, high efficiency, good filtration, availability and lack of need for large land areas, are enjoying from great importance in advanced wastewater treatment. Therefore, in this study, Polystyrene Coated by Sand (PCS) was produced as a novel media and its application in a modified down-flow BAF structure for advanced wastewater treatment was assessed in two steps. In step one, the backwash effluent did not return to the system, while in step two backwash effluent returned to increase the water reuse efficiency. The backwash process was also studied through three methods of Top Backwashing (TB), Bottom Backwashing (BB), as well as Top and Bottom Backwashing Simultaneously (TBBS). The results showed that return of backwash effluent had no significant effect on the BAF effluent quality. In the second step similar to the first one with slight differences, the residual average concentrations of TSS, BOD5, and COD at the effluent were about 2.5, 8.2, and 25.5 mg/L, respectively. Additionally, in step two, the mean volume of disposal sludge/volume of treated water (v(ds)/v(tw)) decreased a large extent to about 0.088. In other words, the water reuse has increased to more than 99.91. The backwash time in methods of TB and BB were 65 and 35 min, respectively; however, it decreased in TBBS methods to 25 min. The concentrations of most effluent parameters in this system are in concordance with the 2012 EPA Agriculture Standards, even for irrigation of Non-processed agricultural crops and livestock water consumption. (C) 2017 Elsevier Ltd. All rights reserved

Influence of bioaugmentation on biodegradation of phenanthrene-contaminated soil by earthworm in lab scale

Background: Use of earthworm to eliminate the phenanthrene from the soil (bioaccumulation) is developed as an economical method. Bioaugmentation of microorganism was used for promotion of bioaccumulation by earthworm. The aim of this study was to determine the bioaccumulation or biodegradation of phenanthrene by Eisenia fetida and bacterial consortium in polluted soil. Methods: The amount of 0.4 kg of the polluted soil in the ratio of 10 and 30 mg phenanthrene per kg of dry soil was transferred into each pot. Afterwards, bacteria and earthworms were added to each pot in separate and combination. The samples were kept under field conditions, and the retention concentrations of phenanthrene were analyzed after 8 weeks. Results: Results showed that the Eisenia fetida was able to significantly remove phenanthrene from the polluted soil samples. Bioaccumulation and bioaugmentation alone have the removal efficiency of 60.24 and 50.3, respectively. In the combined mode, phenanthrene removal efficiency was 63.81. Conclusions: The current study indicated that the use of earthworms, could improve both phenanthrene bioavailability and microbial activity, which led to enhancing removal of carbon-based pollutants. ©2014 Asgharnia et al

TVOCs and BTEX concentrations in the air of south pars special economic energy zone

cold season were higher than those in warm season. High concentrations of Benzene in cold and warm seasons were used to identify areas of high exposure risk.survey TVOCs and BTEX in the air of South Pars Special Economic Energy Zone in 2014. Materials and methods: In a cross-sectional study sampling and analysis was done by NIOSH 1501 method. The study was carried out in 336 activated carbon tubes and personal sampling pump in 6 sampling stations during one year. The compounds were extracted by solvent carbon disulfide and analyzed using Gas Chromatography- Flame Ionization Detector (GC-FID). Data analysis was performed in SPSS Ver.18 applying Kruskal-Wallis, Fligner test and ANOVA. Results: The mean concentrations of TVOCs and TBTEX were 229.34 and 31.23 µg/m3 in cold season and 212.19 and 29.89 µg/m3 in warm season, respectively. The mean concentrations of Benzene in all stations were 11.72 µg/m3 which were higher than the threshold levels recommended by Iranian Clean Air Act and US Environmental Protection Agency (USEPA). The ANOVA results showed a significant difference between the concentration of pollutants and hour, month and sampling stations (P<0.05), but no significant difference was found between the concentration of pollutants and seasons (P>0.05). Conclusion: The concentrations of measured pollutants in cold season were higher than those in warm season. High concentrations of Benzene in cold and warm seasons were used to identify areas of high exposure risk. © 2016, AMazandaran University of Medical Sciences. All rights reserved

A comparative study of the disinfection efficacy of H<inf>2</inf>O<inf>2</inf>/ferrate and UV/H<inf>2</inf>O<inf>2</inf>/ferrate processes on inactivation of Bacillus subtilis spores by response surface methodology for modeling and optimization

Abstract Although chlorination can inactivate most of the microorganisms in water but protozoan parasites like C. parvum oocysts and Giardia cysts can resist against it. Therefore, many researches have been conducted to find a novel method for water disinfection. Present study evaluated the synergistic effect of H2O2 and ferrate followed by UV radiation to inactivate Bacillus subtilis spores as surrogate microorganisms. Response surface methodology(RSM) was employed for the optimization for UV/H2O2/ferrate and H2O2/ferrate processes. By using central composite design(CCD), the effect of three main parameters including time, hydrogen peroxide, and ferrate concentrations was examined on process performance. The results showed that the combination of UV, H2O2 and ferrate was the most effective disinfection process in compare with when H2O2 and ferrate were used. This study indicated that by UV/H2O2/ferrate, about 5.2 log reductions of B. subtilis spores was inactivated at 9299 mg/l of H2O2 and 0.4 mg/l of ferrate concentrations after 57 min of contact time which was the optimum condition, but H2O2/ferrate can inactivate B. subtilis spores about 4.7 logs compare to the other process. Therefore, the results of this research demonstrated that UV/H2O2 /ferrate process is a promising process for spore inactivation and water disinfection. Keywords Disinfection Bacillus subtilis spores UV radiation/ H2O2 /ferrate Response surface methodology (RSM) Central composite design (CCD

A comparative study of the disinfection efficacy of H2O2/ferrate and UV/H2O2/ferrate processes on inactivation of Bacillus subtilis spores by response surface methodology for modeling and optimization

Although chlorination can inactivate most of the microorganisms in water but protozoan parasites like C. parvum oocysts and Giardia cysts can resist against it. Therefore, many researches have been conducted to find a novel method for water disinfection. Present study evaluated the synergistic effect of H2O2 and ferrate followed by UV radiation to inactivate Bacillus subtilis spores as surrogate microorganisms. Response surface methodology(RSM) was employed for the optimization for UV/H2O2/ferrate and H2O2/ferrate processes. By using central composite design(CCD), the effect of three main parameters including time, hydrogen peroxide, and ferrate concentrations was examined on process performance. The results showed that the combination of UV, H2O2 and ferrate was the most effective disinfection process in compare with when H2O2 and ferrate were used. This study indicated that by UV/H2O2/ferrate, about 5.2 log reductions of B. subtilis spores was inactivated at 9299 mg/l of H2O2 and 0.4 mg/l of ferrate concentrations after 57 min of contact time which was the optimum condition, but H2O2/ferrate can inactivate B. subtilis spores about 4.7 logs compare to the other process. Therefore, the results of this research demonstrated that UV/H2O2 /ferrate process is a promising process for spore inactivation and water disinfection. © 2018 Elsevier Lt

Enhanced chromium (VI) removal using activated carbon modified by zero valent iron and silver bimetallic nanoparticles

Recently, adsorption process has been introduced as a favorable and effective technique for the removal of metal ions from aqueous solutions. In the present study, bimetallic nanoparticles consisting of zero valent iron and silver were loaded on the activated carbon powder for the preparation of a new adsorbent (PAC-Feo /Ag). The above adsorbent was characterized by using XRD, SEM and TEM techniqes. Experimental data were exploited for kinetic, equilibrium and thermodynamic evaluations related to the adsorption processes. The Cr(VI) adsorption process was found to be favorable at pH 3 and it reached equilibrium state within 60 min. The stirring rate did not have a significant effect on the adsorption efficiency. Furthermore, the monolayer adsorption capacity of Cr(VI) based on the Langmuir model was measured to be 100 mg/g. The experimental equilibrium data were fitted to the Freundlich adsorption and pseudo second-order models. According to the thermodynamic study, the adsorption process was spontaneous and endothermic in nature, indicating the adsorption capacity increases with increasing the temperature. The results also revealed that the synthesized composite can be potentially applied as a magnetic adsorbent to remove Cr(VI) contaminants from aqueous solutions