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In the present work, electrocoagulation was applied for copper removal from aqueous solution employing iron electrodes in a cylindrical reactor. A four‐factorial central composite design (CCD) based on response surface methodology (RSM) was applied to study the effect of various process parameters on removal efficiency and energy consumption as the responses. On optimization, maximum removal efficiency up to 95% was attained with energy consumption as 0.903 W‐hour per gram removal of Cu (II) at applied current 0.26 A, initial copper concentration of 27.8 ppm, application time of 5.4 min and pH 7. The interaction between the process variables was evaluated by using the obtained 3‐D plots. The models generated were validated by analysis of variance (ANOVA). Studies carried on Cu (II) removal rate showed adsorption suited pseudo‐Ist order kinetics best. Overall, the electrocoagulation process proved efficient, low cost and a promising alternative to conventional treatment procedures in removing Cu (II). Practitioner points Adsorption over hydroxide/polyhydroxide complexes of Fe assisted in enhanced removal of Cu (II) by EC. Higher concentrations treated at lower current but longer duration reduces energy. pH was found to be the deterministic factor for coagulation. CCD‐based optimization reduced energy consumption substantially.

Pulp and paper industry generates effluent containing harmful compounds like chlorophenols which are difficult to biodegrade. It requires an appropriate treatment in order to meet the stringent discharge standards. In this work, a bench scale column type sequential batch reactor (SBR) was employed for treating pulp and paper wastewater. The performance of SBR, seeded with acclimatized sludge was optimized and analysed for maximizing COD and AOX removal. The process parameters viz; pH, initial COD, cycle time and MLSS were optimized and their effects on response variables: COD removal efficiency, AOX removal efficiency and SVI were investigated. The optimum conditions were determined to be: initial COD 1200 mg/l, pH 7.5, MLSS 2100 mg/L and cycle time 15 h, for 73.2% COD removal, 57.6% AOX removal and 122.8 mL/g SVI. The complex compounds were broken down into numerous intermediate compounds thus enhancing COD and AOX removal with low SVI. The bio-kinetics of the optimized system was also analyzed in order to understand the bacterial nature towards substrate utilization. Two kinetic models namely Grau second-order model and Stover-Kincannon model were found to be fitwell with high correlation coefficients (R 2 = 0.99) for COD as well as AOX.

There is an urgent need to look for bio-based technologies to address the pollution related to textile dyes in waterbodies. The aim of this study was to evaluate an engineered laccase variant, LCC1-62 of Cyathus bulleri, expressed in recombinant Pichia pastoris, for the decolorization and detoxification of real textile effluent. The partially purified laccase effectively (~60–100%) decolorized combined effluent from different dyeing units at a laccase concentration of 500 U/L at a 50-mL level. Decolorization and detoxification of the combined effluents, from a local textile mill, were evaluated at 0.3 L volumetric level in a ray-flow membrane reactor in batch and continuous modes of operation. In batch studies, maximum decolorization of 97% and detoxification of 96% occurred at a hydraulic retention time (HRT) of 6 h without any additional laccase requirement. In continuous studies, the reactor was operated at an HRT of 6 h with a lower enzyme dosage (~120 U/L of the effluent). Decolorization was accompanied by a loss in laccase activity which was restored to ~120 U/L by the addition of laccase in two regimes. The addition of laccase, when the residual laccase activity decreased to 40% (~50 U/L), resulted in high decolorization (~5 ppm residual dye concentration) and low variance (σ2) of 2.77, while laccase addition, when the residual dye concentration decreased to ~8% (~10 U/L), resulted in an average dye concentration of 13 ppm with a high variance of 62.08. The first regime was implemented, and the continuous reactor was operated for over 80 h at an HRT of 3 and 6 h, with the latter resulting in ~95% decolorization and 96% reduction in the mutagenicity of the effluent. Less than 10% membrane fouling was observed over long operations of the reactor. The findings strongly suggest the feasibility of using LCC1-62 in an enzyme membrane reactor for large-scale treatment of textile effluents.