Search

Bisphenol A (BPA) is one of the endocrine disrupting compounds that has significant estrogenic effects and if it is not treated, it will enter into water resources and will cause irreparable environmental problems. Thus, this study aims at determining the efficiency of heterogeneous Fenton-like process using modified magnetic nanoparticles with sodium alginate in removing BPA from aquatic environments. In this experimental research, the effects of environmental factors including pH (3–9), contact time (10–180 min), initial concentration of catalyst (0.5–20 g/L), initial concentration of hydrogen peroxide (50–300 mg/L) and the initial concentration of BPA (10–60 mg/L) were studied in removing efficiency of BPA using processes of heterogeneous Fenton-like, alginate sodium and hydrogen peroxide. Results of present study showed that during heterogeneous Fenton-like process, the highest removal efficiency (BPA) is achieved (95) at pH 5, catalyst concentration 5 g/L, initial concentration of hydrogen peroxide 100 ppm and BPA concentration 20 ppm in 120 min in a way that the processes of sodium alginate and hydrogen peroxide had smaller removal efficiency. Also, studies of kinetic reaction revealed that removal of BPA in heterogeneous Fenton-like process followed a second-order kinetic model (R2 = 0.98). Results demonstrated that heterogeneous Fenton-like process is able to remove BPA effectively from aquatic environments using modified magnetic nanoparticles with sodium alginate as a catalyst under optimal conditions and this process could be used to remove other similar compounds. © 2018 Desalination Publications. All rights reserved.

Abnormal use of antibiotics and discharging them into the sewage systems bring about serious and dangerous harms to the environment. The present study aims at the feasibility evaluation of amoxicillin removal from the aqueous solutions by means of enzymatic oxidation by taking advantage of response surface method based on Box–Behnken model. The present study is a library research. Therefore, the experiments are carried out in a laboratory for discontinuously evaluating the effects of independent variables such as temperature, pH, contact time, enzyme activity, hydroxybenzotriazole mediator concentration and the antibiotic concentration. The remaining amoxicillin’s concentration has been determined by HPLC device. To implement the experiments, Box–Behnken model was used for measuring the variables’ mutual effects. One-way analysis of variance was used for data analysis. The results showed that enzymatic oxidation output increases with the increase in contact time and enzymatic activity as well as with a decrease in the antibiotic’s concentration. The highest and the lowest removal percentages were 91.5 and 5.36, respectively. According to the high amounts of R2 (0.974) and R2adj (0.955), it can be said that the selected model is appropriate for data analyses. Finally, a quadratic polynomial model was applied as the best model of choice for figuring out the relationships between the main variables and amoxicillin elimination output. Response surface method can be effective in amoxicillin oxidation optimization and laccase can be used for amoxicillin elimination. © 2018 Desalination Publications. All rights reserved.

Since most industrial wastewaters contain phenol compounds, achieving eco-friendly and economic processes for filtration of such wastewaters is one of the concerns of environmental researchers. Thus, present study aims to determine the efficiency of bio-filter and activated sludge (BF/AS) combined process in phenol removal from aqueous solution. In this experimental study, BF/AS reactor in a pilot scale with continuous flow and useful volume of 24 L, made of Plexiglas was utilized. Effect of dissolved oxygen concentration, hydraulic residence time, mixed liquor suspended solids (MLSS) and glucose concentration on phenol removing efficiency were evaluated. In order to determine the phenol removal model and optimum removal conditions using central composite design in response surface methodology environment, the reactor was studied in separate runs according to software design. Accuracy of results was evaluated in MLSS concentrations of 2,250 mg/L, glucose of 250 mg/L and dissolved oxygen of 3 mg/L and quadratic model (R2 = 0.99) well fitted to the results. With regard to high yield of BF/AS biological system in decreasing phenol content from wastewater, the system under study could be used widely in refining the toxic wastewaters of industries given the appropriate operation conditions. © 2017 Desalination Publications. All rights reserved.

Due to the efficiency and flexibility of integrated biological systems, they have been widely developed for the treatment of various waste-waters in recent decades. Present study aims at revealing the efficiency of bio-filter and activated sludge (BF/AS) integrated biological system in phenol removal from wastewater. The cylindrical bioreactors (continuous flow, 12 L) are made from Plexiglas. Interlaced plastic discs were fixed inside the reactor to hold the biofilm. The effects of pH (6.5–8), phenol concentration (100–500 mg/L), nitrogen (30–80 mg/L), phosphorous (6–16 mg/L), glucose concentration (50–500 mg/L), MLSS concentration (1450–3500 mg/L) and hydraulic retention time (2–4.4 h) were evaluated. Results of the study showed that this system could remove 500 mg/L of phenol concentration and 4–4.5 kg COD/m3d organic load in 4 h under favorable conditions. Pearson correlation coefficient between removal efficiency and phenol concentration was –0.446 (P < 0.001). By increasing phenol concentration, removal efficiency decreased. Appropriate COD/N/P for maximum efficiency was equal to 100/10/2. Dominant identified bacteria in the system include: Pseudomonas aeruginosa, Pseudomonas alcaligenes, acetinobacter, morexella and Brevundiomonas vesicalaris. Phenol decomposition was done according to the second-order kinetic reaction. Concentration difference (ΔA) to retention time difference (ΔT) ratio were 53.9, 69.5 and 100 for retention times of 2.2, 6 and 7 h, respectively. The BF/AS integrated biological system is highly efficient in removing phenol from aqueous and as an environment-friendly procedure could treat waste-waters containing average phenol concentrations in a relatively short period. © 2017 Desalination Publications. All rights reserved.