Combining Coagulation and Electrocoagulation with UVA-LED Photo-Fenton to Improve the Efficiency and Reduce the Cost of Mature Landfill Leachate Treatment

This study focused on the reduction of the treatment cost of mature landfill leachate (LL) by enhancing the coagulation pre-treatment before a UVA-LED photo-Fenton process. A more efficient advanced coagulation pretreatment was designed by combining conventional coagulation (CC) and electro-coagulation (EC). Regardless of the order in which the two coagulations were applied, the combination achieved more than 73% color removal, 80% COD removal, and 27% SUVA removal. However, the coagulation order had a great influence on both final pH and total dissolved iron, which were key parameters for the UVA-LED photo-Fenton post-treatment. CC (pH = 5; 2 g L−1 of FeCl36H2O) followed by EC (pH = 5; 10 mA cm−2) resulted in a pH of 6.4 and 100 mg L−1 of dissolved iron, whereas EC (pH = 4; 10 mA cm−2) followed by CC (pH = 6; 1 g L−1 FeCl36H2O) led to a final pH of 3.4 and 210 mg L−1 dissolved iron. This last combination was therefore considered better for the posterior photo-Fenton treatment. Results at the best cost-efficient [H2O2]:COD ratio of 1.063 showed a high treatment efficiency, namely the removal of 99% of the color, 89% of the COD, and 60% of the SUVA. Conductivity was reduced by 17%, and biodegradability increased to BOD5:COD = 0.40. With this proposed treatment, a final COD of only 453 mg O2 L−1 was obtained at a treatment cost of EUR 3.42 kg COD−1.

Wastewater Treatment of Wet Coffee Processing in an Anaerobic Sequencing Batch Reactor Pretreated with Electro Coagulation

The interest for improving the quality of coffee production has led to the increased use of wet processing so as to highlight the quality and aroma of the beverage. The coffee pulping process has been causing environmental problems at the local level not only due to the consumption of water, but more due to the discharge of effluents with large volumes of organic waste. The wet processing generates enormous quantity of wastewater which causes irrepairable damage to the receiving water bodies. Indispensable. However, physico chemical treatment method coupled with biological treatment as proved effective treatment mode for safe and proper disposal of the wastewater generated. In this sense, the objective of the present study is to evaluate the efficacy of electrocoagulation batch reactor as pretreatment for anaerobic sequencing batch reactor to treat coffee processing wastewater.

Effect of Current Density and Contact Time of Electro-Coagulation on the Characteristics of Activated Sludge and Membrane Filtration

Objectives : The effect of current density and contact time of electro-coagulation on membrane fouling was investigated. In order to elucidate the reason why the membrane fouling was reduced by electro-coagulation, the changes in the characteristics of activated sludge were examined before and after electro-coagulation.Methods : A series of electro-coagulation of activated sludge suspensions was carried out with current density of 2.5, 6, 12, 24 A/m2 for 0, 2, 6, 12 hours. After membrane filtrations of the activated sludge suspensions, the membrane fouling was compared before and after the electro-coagulation. Characteristic changes in the activated sludge were also analyzed quantitatively.Results and Discussion : Total fouling resistances (Rt) of the electro-coagulated activated sludge decreased as current density and contact time increased. For example, Rt decreased 15%, 63% and 86% under the condition of current density of 24 A/m2 and 2, 6, 12 hours of contact time. Particularly, three activated sludge suspensions having very different initial MLSS concentrations showed a similar reduction of Rt, indicating that the membrane fouling was reduced not dominantly by particulates but by soluble foulants. The MLSS increased as current density increased, but MLVSS had not changed accordingly, which means that inorganic solids such as Al(OH)3 and AlPO4 produced during electro-coagulation were the main reasons for the increased MLSS concentration. These solids could play a key role in the reduction of membrane fouling by means of a dynamic membrane. As current density increased, the EPS (extracellular polymeric substances) and soluble COD concentration were reduced, which led to the reduction of membrane fouling. Soluble TN and TP were not significantly changed after electro-coagulation.Conclusions : The fouling materials, particularly, EPS and soluble COD decreased as current density and contact time increased, which played a key role in the reduction of membrane fouling. In addition, the insoluble solids produced during the electro-coagulation would act as a dynamic membrane, which led to fouling reduction.

Using Photovoltaic to Remove Heavy Metals from Industrial Water

Heavy metals pollution has become a more serious environmental problem in the last several decades as a result of releasing toxic materials into the environment. The aim of this study is to develop an ecological method for the removal of Ni2+ ions from industrial wastewater by an electro coagulation method using aluminum plates and solar cell as a source of D.C current. In this study, different conditions of pH of 4, 6, 7, and 8, current densities of 0.5, 1.0, and 1.5 mA/cm2, and nickel ion concentrations of 200, 300, and 500 ppm were investigated during a period of time of 120 minutes to remove nickel ions prepared waste water by electro coagulation. The total removal of nickel ions was (97.5- 99.5%), (97- 99%), and (96.67-98.8%) for pH (4-8), current density (0.5-1.5 mA/cm2) and nickel ions concentration (200-500 ppm), respectively. The results show that the optimum condition of electro coagulation process can be obtained at pH = 8 and current density 1.5 mA/cm2 when 120 minutes were elapsed.