A sequential aerated electrocoagulation and peroxicoagulation process for the treatment of municipal stabilized landfill leachate by iron and graphite electrodes.

Electrochemical treatment has emerged as a viable technology for the treatment of leachate due to its efficient removal of ammonaical nitrogen and other recalcitrant organics. The main technical issues that prevent its practical deployment are restricted performance of a single electrochemical process and the lengthy tertiary treatment time required to achieve the disposal quality standards. This study demonstrates the performance of electrochemical treatments such as peroxicoagulation (PC) and aerated electrocoagulation (A-EC) separately and also sequentially for the treatment of stabilized leachate. In aerated electro coagulation iron is used as both anode and cathode, whereas in peroxicoagulation, iron is used as anode and graphite as cathode. The area of electrode used for treatments was fixed as 12.5 cm2. The initial concentration of NH4-N, TN, COD, and TOC of the leachate was found to be 480 mg/L, 997 mg/L, 40,200 mg/L, and 9850 mg/L respectively. Removal efficiency of aerated electrocoagulation for NH4-N, TN, COD and TOC were 25.6%, 23.67%, 25.6% and 28.7% respectively, current density of 30 mAcm-2, electrolysis time of 60 min and pH 7.3. Meanwhile for peroxicoagulation, the removal efficiency was found to be 37.2%, 43%, 37.3%, and 45.6% for NH4-N, TN, COD, and TOC respectively, at an current density of 30 mAcm-2, electrolysis time of 120 min and a pH of 3. The sequential aerated electrocoagulation - peroxicoagulation process achieves a maximum removal efficiency of 63%, 68%, 78%, and 75% for NH4-N, total nitrogen, COD, and TOC respectively for a reaction time of 180 min. Removal of NH4-N, total nitrogen, COD and TOC from stabilized landfill leachate with a BOD/COD ratio less than 0.1 was very much effective with the sequential aerated electrocoagulation - peroxicoagulaton treatment. The results also indicate that for the treatment of leachate, a significant synergistic index of 1.22 exists between aerated electrocoagulation and peroxicoagulation.

Chelate-modified Electro-Fenton process for mixed industrial wastewater treatment.

HIGHLIGHTS: The Chelate-modified EF process for the removal of COD at near neutral pHTreatment of the mixed industrial wastewater with very low BOD/COD ratioInfluence of Fenton catalyst and chelating agent dosage on COD removal.Comparable COD removal of 67% with Chelate-modified EF at near neutral pH and 66% with EF at acidic pH.Mineralization current efficiency and instantaneous current efficiency for COD removal.

Electro-Fenton assisted sonication for removal of ammoniacal nitrogen and organic matter from dye intermediate industrial wastewater.

The intricacy in the treatment of effluents from the textile sector attracts the researchers since 20th century. Dye intermediate manufacturing industries are responsible for producing the toxic pollutants such as nitro-aromatics, benzene, toluene, phenol, heavy metals etc. with intense colour. The present study focuses on the performance of combined Electro-Fenton (EF) and sonication for the removal of ammoniacal nitrogen and COD from dye intermediate manufacturing wastewater. Batch experiments of EF were performed using graphite electrodes and sonication was applied to the EF treated wastewater to enhance the treatment performance. A number of experiments were executed to discover the influence of pH, applied voltage, Fenton catalyst dosage and time of electrolysis on the removal efficiency of EF batch process was scrutinized. The pH was varied between 2 and 4, applied voltage from 1 to 4V, Fenton catalyst dosage between 50 and 200 mg L-1 and time between 15 and 180 min. At optimum condition i.e. pH 3, applied voltage 3V, Fenton catalyst dosage of 100 mg L-1and 120 min electrolysis time, the percentage removal obtained for ammoniacal nitrogen and COD were 59.4% and 79.2% respectively. The removal efficiency was increased to 65.5% for ammoniacal nitrogen and 85.4% for COD after applying sonication to the EF treated wastewater. The removal of ammoniacal nitrogen and COD can be achieved in a scientific and feasible way by combining EF process with sonication.

Mixed industrial wastewater treatment by combined electrochemical advanced oxidation and biological processes.

Nowadays, because the quality and quantity of mixed industrial wastewater keep fluctuating in recent times, the treatment of mixed industrial wastewater has gained more attention. The main target of this study is to degrade the wastewater through a combination of electrochemical advanced oxidation processes (EAOPs) and biological treatment. To enhance the biodegradability of the wastewater, Electro-Fenton process, along with external persulphate addition, was applied before the biological treatment. The effect of voltage, catalyst concentration and persulphate dosage was studied. The optimized conditions selected for the experiments were pH-3, effective area-25 cm2, electrode spacing-1 cm while voltage-10 V, persulphate dosage-200 mg L-1, and catalyst dosage-10 mg L-1 were optimized during the experiments leading towards 60% of COD removal efficiency in course of 1 h of electrolysis. Addition of tert-butyl alcohol and ethanol revealed the existence of sulphate and hydroxyl radicals as the major oxidants that help in pollutant degradation by combining EAOPs and biological treatment. Overall 94% COD removal efficiency was achieved. Therefore, for the organic pollutant degradation, combined process serves to be an efficient and effective treatment option.

Review of zero-valent aluminium based water and wastewater treatment methods.

Zero-valent metals (ZVM) are widely used to remove heavy metals, contaminants, toxicity, etc. from water and wastewater. Zero-valent aluminium (ZVAl) has large surface area and high surface reactivity. It has enormous flexibility for the in-situ application. ZVAl can be applied as either a single or a bimetallic system as well as advanced oxidation processes (AOPs). It is observed that ZVAl is capable of generating hydroxyl and sulfate radicals in water medium, which remove non-biodegradable pollutants from aqueous solution. ZVAl-based processes can remove non-biodegradable organic contaminants from water medium within a short duration. ZVAl is also used as a reducing agent. It is efficient to reduce toxic hexavalent chromium to less toxic trivalent chromium. ZVAl, in various combinations in bimetallic system (Fe/Al, Pd/Al, Cu/Al), is able to remove various contaminants from aqueous medium. Overall, it can be concluded that ZVAl-based methods for water and wastewater treatment are promising environmental technologies.