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Wastewater containing ammonia nitrogen compounds is considered as a harmful material to environment due to eutrophication and toxicity effects; hence, finding practical methods for treating this type of wastewater seems necessary. In this study, performance of two sequencing batch reactors have been assessed for simultaneous nitrification and denitrification in treating synthesized wastewater containing ammonium nitrogen, using leachate obtained from cow dung as the biomass. The leachate obtained from cow dung as the source of bio‐sludge added to the reactors. Experiments were designed according to central composition design and response surface methodology with four operating variables including pH (6, 7.5, 9), cycle time (CT) (4, 12, 20 h), normalCnormalOnormalD/normalNnormalH4+−normalN ratio (5, 10, 15) and carbon source (Sodium acetate: normalSnormalBnormalRnormalS, Glucose: normalSnormalBnormalRnormalG). According to statistical analysis, experimental responses were in acceptable agreement with model predictions. CT was the most important operating variable in chemical oxygen demand (COD) and normalNnormalH4+−normalN removal. The maximum percentage of ammonium nitrogen removal was attained at pH 7.5 and CT 21.5 h. The optimum conditions were composed of pH 7.67, CT 19.15 h, normalCnormalOnormalD/normalNnormalH4+−normalN 10.95 and sodium acetate as carbon source, while COD, normalNnormalH4+−normalN and total nitrogen removals were 94.96%, 94.93% and 93.60%, respectively. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1638–1646, 2018

This work focused on fabricating a novel chitosan/polyvinyl alcohol/ hydroxyapatite (CPH) nanocomposite membrane and its application in removing the Congo red (CR) from aqueous solutions. After proper characterization of the chitosan/polyvinyl alcohol/hydroxyapatite adsorptive membrane, adsorption tests were carried out on the optimum nanocomposite membrane containing 1 wt% hydroxyapatite. The impact of temperature, contact time, initial dye concentration, adsorbent dosage, and pH was investigated. Results of isotherm and kinetic investigation revealed that Langmuir isotherm and pseudo‐second order kinetics best fitted experimental results with R2 values of 0.995. A relatively high adsorption capacity of 491 mg/g, higher than that of activated carbon, was achieved.

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In the present study, the decomposition of phenol in aqueous solutions was investigated in both impinging system and batch reactor. In impinging reactor, catalyst particles with an average diameter of 1.5 × 10 3 μm were confined in a wired cage located in the middle of the reaction vessel. The catalyst was synthesized by impregnation of iron on clinoptilolite zeolite as the support. The mean residence time of the solution in this reactor was 3 s. Therefore, the number of impingements required for the complete degradation of phenol was assessed to be 8 times. The advantage of performing the impinging reactor over a conventional reaction system has been demonstrated in this study. In the impinging reactor at 55°C, time needed for degradation of phenol in aqueous media was measured to be as low as 24 s; however, phenol degraded completely in 10 min in batch stirred reactor. The optimum operating conditions for the impinging reactor were found as: catalyst containing 5 wt% iron, pH = 3.25, weight ratio of H 2 O 2 /phenol = 20, temperature = 55°C.