Optimization of Integrated Electro-Bio Process for Bleaching Effluent Treatment

Effect of polarity shift on the performance of electrocoagulation process for the treatment of produced water

A novel electrocoagulation (EC) system for the treatment of produced water (PW), with a provision to shift polarity is designed with the aim of reducing the problems resulting from electrode passivation. The enhancement of performance in terms of the rate and completion of the pollutant removal, energy and electrode consumption, sludge formation and ultimately the operating cost has been investigated by performing statistically designed experiments using RSM. The switching mode operation of EC had brought about significant improvement in the oil removal than the conventional mode. The polarity changeover in short span of batch recirculation time (BRT) was found to be more effective. Greater current density (CD) and supporting electrolyte concentration (SC) were found to enable a still lower switchover time (SOT) so that changeover frequency can further be increased. It was possible to remove a maximum of 99% COD and 98% Oil & Grease from a PW sample having initial concentration of 360 mgL^-1of oil (1280 mgL^{- 1}COD) at BRT of 15 min, CD of 1.6 Adm^-2, SC of 3 gL^-1 and SOT of 1 min. The combination of operating variables (BRT- 3 min, CD- 2.14 Adm^-2SC- 3 gL^-1and SOT- 1.9 min) giving minimum operating cost (0.65 US$/kg COD removed) achieving oil removal (88%) meeting discharge standards was found out by optimizing the RSM models for cost and oil removal. The method can be considered as an effective alternative for treating PW especially in offshore oil basins where time and space are the major constraints.

Sugar beet industry process wastewater treatment using electrochemical methods and optimization of parameters using response surface methodology

Sugar production is a water intensive process that produces a large amount of wastewaters with high concentration of chemical oxygen demand (COD), mostly consists of organic carbon compounds. Conventional treatment methods are limited to provide the necessary treatment of effluent COD to meet the regulatory limits prior to discharge. The treatment performance of electrooxidation (EO) and electrochemical peroxidation (ECP) for organic removal were investigated in a laboratory scale study. The experimental conditions were optimized for both EO and ECP using Box-Behnken Design (BBD) and the models provided highly significant quadratic models for both treatment methods. The effects of pH, H₂O₂ dosage, current density, and operation time were investigated using BBD. The results showed that EO could remove 75% of organics at optimum conditions of pH 5.3; current density of 48.5 mA cm^-2; and operation time of 393 min. The predicted values were in reasonable agreement with measured values. ECP could remove total and soluble COD and total and dissolved organic carbon by 65, 64, 66, and 63%, respectively at optimum conditions of H₂O₂ dosage of 21 mL L^-1; current density of 48 mA cm^-2; and operation time of 361 min. The methods were compared based on removal efficiency and energy consumption during operation.

Treatment of canola-oil refinery effluent using electrochemical methods: A comparison between combined electrocoagulation + electrooxidation and electrochemical peroxidation methods

A comparative study of combined electrocoagulation (EC) + electrooxidation (EO) and electrochemical peroxidation (ECP) treatment processes were carried out to treat canola oil refinery (COR) wastewaters. The effect of applied current density and operation time in the removal of organic pollutants were investigated and discussed. Total chemical oxygen demand (TCOD), soluble chemical oxygen demand (sCOD), total organic carbon (TOC), dissolved organic carbon (DOC) and total suspended solids (TSS) were measured. Using only EC process was found to be significantly successful in removing suspended and colloidal pollutants and could remove more than 90% TCOD and 80% of TOC at current densities between 0.91 and 13.66 mA cm^-2. From the statistical model, the optimized conditions for TCOD at a current density of 7.61 mA cm^-2 and TOC at 7.99 mA cm^-2 under 40 min operation, validated to remove 93.45% and 94.5% respectively. However, the maximum removal of dissolved organic pollutants was relatively low in EC process and reported to be 75% for sCOD and 74% for DOC. Therefore, EC + EO process were run to increase the removal of sCOD and DOC to 99 and 95%, respectively. On the other hand, treatment using ECP process achieved a removal of sCOD and DOC between 77 and 86%. TSS were removed completely in both EC + EO and ECP processes. A statistical model was applied to compare the performance of two methods and found that the combined EC + EO process provided lightly better treatment compared to ECP method.

Coupling biofiltration process and electrocoagulation using magnesium-based anode for the treatment of landfill leachate

In this research paper, a combination of biofiltration (BF) and electrocoagulation (EC) processes was used for the treatment of sanitary landfill leachate. Landfill leachate is often characterized by the presence of refractory organic compounds (BOD/COD < 0.13). BF process was used as secondary treatment to remove effectively ammonia nitrogen (N-NH4 removal of 94%), BOD (94% removed), turbidity (95% removed) and phosphorus (more than 98% removed). Subsequently, EC process using magnesium-based anode was used as tertiary treatment. The best performances of COD and color removal from landfill leachate were obtained by applying a current density of 10 mA/cm(2) through 30 min of treatment. The COD removal reached 53%, whereas 85% of color removal was recorded. It has been proved that the alkalinity had a negative effect on COD removal during EC treatment. COD removal efficiencies of 52%, 41% and 27% were recorded in the presence of 1.0, 2.0 and 3.0 g/L of sodium bicarbonate (NaHCO3), respectively. Hydroxide ions produced at the cathode electrode reacted with the bicarbonate ions to form carbonates. The presence of bicarbonates in solution hampered the increase in pH, so that the precipitation of magnesium hydroxides could not take place to effectively remove organic pollutants.

Improvement in treatment of soak liquor by combining electro-oxidation and biodegradation

A combined process involving electro-oxidation and biodegradation by halophilic bacteria was applied to treat wastewater effectively for discharge.

The application of advanced oxidation technologies to the treatment of effluents from the pulp and paper industry: a review

The paper industry is adopting zero liquid effluent technologies to reduce freshwater use and meet environmental regulations, which implies closure of water circuits and the progressive accumulation of pollutants that must be removed before water reuse and final wastewater discharge. The traditional water treatment technologies that are used in paper mills (such as dissolved air flotation or biological treatment) are not able to remove recalcitrant contaminants. Therefore, advanced water treatment technologies, such as advanced oxidation processes (AOPs), are being included in industrial wastewater treatment chains aiming to either improve water biodegradability or its final quality. A comprehensive review of the current state of the art regarding the use of AOPs for the treatment of the organic load of effluents from the paper industry is herein addressed considering mature and emerging treatments for a sustainable water use in this sector. Wastewater composition, which is highly dependent on the raw materials being used in the mills, the selected AOP itself, and its combination with other technologies, will determine the viability of the treatment. In general, all AOPs have been reported to achieve good organic removal efficiencies (COD removal >40%, and about an extra 20% if AOPs are combined with biological stages). Particularly, ozonation has been the most extensively reported and successfully implemented AOP at an industrial scale for effluent treatment or reuse within pulp and paper mills, although Fenton processes (photo-Fenton particularly) have actually addressed better oxidative results (COD removal ≈ 65-75%) at a lab scale, but still need further development at a large scale.