This work investigates the feasibility of the coupled electrochemical (electrocoagulation/flotation) and physical processes such as sedimentation, sand filtration, and activated carbon for treatment of automotive service wastewater (ASWW). The impacts of critical parameters viz. pH solution (5-9), reaction time (30-90) and current intensity (1-2) on linear alkylbenzene sulphonate (LAS) and phenol removal efficiencies as well as energy consumption and operating cost are studied. Central composite design (CCD) as a response surface methodology (RSM) is employed. The results reveal by increasing current intensity at low levels of pH, the phenol removal efficiency was increased significantly up to 95%. On the other hand, at pH 9.5 with current intensity of 1.5A, the highest removal efficiency of LAS was achieved with 98.5%. Moreover, at the optimum conditions, LAS and phenol removal efficiencies, energy consumption and operating cost are obtained 96.7%, 87.65%, 15.99 Wh, 0.001 US$, respectively. This process reveals a feasible technology for phenol and LAS removal from ASWW.

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Background: Application of potassium ferrate is a chemical oxidation approach used for water and wastewater treatment. The aim of this study is to apply central composite design (CCD) and response surface methodology (RSM) to optimize potassium ferrate consumption in the treatment of wastewater from carpet industries. Methods: Samples in this experimental study were collected from wastewater, originating from a carpet factory. Wastewater sampling was carried out monthly for a period of two seasons. Ferrate oxidation experiments were conducted by means of a conventional jar-test apparatus. The time and speed for mixing were set with an automatic controller. Parameters of study were measured based on given methodologies in Standard method for examining water and wastewater. CCD and RSM were applied to optimize the operating variables including potassium ferrate dosage and pH. Results: Results showed that potassium ferrate concentration (A), pH (B), their interactions (AB) and quadratic effects (A 2 and B 2) were significant in the removal of COD, turbidity, color and TSS from carpet industries effluents. At an optimum point (COD: 160 mg/L of potassium ferrate and pH 4, turbidity: 165 mg/L of potassium ferrate and pH 4, color and TSS: pH 4.5 and 150 mg/L of potassium ferrate) removal efficiencies for COD, turbidity, color and TSS were 86, 86, 87 and 89%, respectively. Conclusion: Potassium ferrate has a significant impact on pollutants decomposition and the removal of color from wastewater produced in carpet industries. This process can be employed for the pretreatment or post treatment of wastewaters containing refractory organic pollutants. CCD and RSM are suitable tools for experimental design.

Solid waste production has increased in recent years. Many studies have shown that generated leachate from solid waste contains a high concentration of heavy metals. Their removal efficiency from leachate was investigated in aerobic suspended and attached growth systems in lab-scale within 72 hours of aeration. All of the materials used were analytical grade (Merck). Maximum efficiency of the attached growth system in removal of BOD 5 and COD was, respectively, 80% and 78.28%. Maximum removal efficiency for both attached and suspended growth was related to lead, and minimum removal efficiency was related to vanadium for the attached growth, and cadmium for suspended growth. Heavy metals removal efficiencies in attached growth from max to min were lead, iron, manganese, cobalt, zinc, mercury, magnesium, copper, chromium, nickel, cadmium, and vanadium, respectively; and the removal efficiencies for suspended growth from max to min were lead, manganese, iron, zinc, copper, magnesium, cobalt, mercury, chromium, nickel, vanadium, and cadmium, respectively. Generally it can be concluded that both systems are suitable for young leachate treatment, but to satisfy environmental discharge standards post treatment will be necessary.

Due to the lack of affordable and feasible wastewater treatment technologies, various industries in developing countries are discharging chromium (Cr) without meeting the environmental standards. Here, the aim was to employ forward osmosis (FO) using aquaporins (AQP)-based biomimetic membranes and optimize the Cr rejection through response surface methodology (RSM). The initial concentration of draw solution, feed solution, and time was selected as independent variables in order to optimize Cr rejection and water flux. A high Cr rejection efficiency and water flux were achieved under the optimal conditions. These results revealed that the FO process applying an AQP membrane beside the RSM could be considered to treat wastewaters containing heavy metals.