Electrocoagulation treatment of dairy processing and slaughterhouse wastewaters

Comparative evaluation between Taguchi method and response surface method for optimization of electrocoagulation process in the context of treatment of dairy industry wastewater

The presence of a large amount of organic and inorganic pollutants in dairy effluent is a substantial environmental issue. This study investigated electrocoagulation (EC) as a potential treatment method for dairy wastewater under different operating conditions, such as applied voltage (5-25 V), electrolysis time (30-90 min), and inter-electrode distance (1-2 cm) by using aluminum electrodes. This study focuses on achieving the maximum removal of BOD, COD, and nitrate in dairy effluents with the aforementioned operating conditions. The process was optimized using the response surface methodology (RSM) and Taguchi method. RSM method optimized the electrocoagulation operating conditions such as the voltage at 23.75 V, time of 90 min, and inter-electrode distance at 1.07 cm. This optimization achieved the maximum removal percentage of BOD, COD, and nitrate at 79.06%, 84.35%, and 79.64%, respectively, in dairy effluent. Taguchi method optimized the electrocoagulation parameters such as the voltage at 25 V, time duration of 90 min, and inter-electrode distance of 1.00 cm, showcasing improved removal percentages of BOD, COD, and nitrate as 90.54%, 89.28%, and 82.74% respectively. The current study attempts to understand the optimization efficiencies between Taguchi method and response surface method for diary wastewater treatment.

Optimizing electrocoagulation for poultry slaughterhouse wastewater treatment: a fuzzy axiomatic design approach

White meat consumption is increasing day by day, and accordingly, there is an increase in the amount of wastewater resulting from the processes. Today, the reuse of wastewater has become a goal within the scope of the Green Deal. For this reason, wastewater treatment with high pollution and volume has gained importance. In this study, the fuzzy axiomatic design (FAD) method, one of the multi-criteria decision-making methods, has been used. With this method, coagulation, electrocoagulation (EC), dissolved air flotation (DAF), and anaerobic treatment alternatives preferred in poultry slaughterhouse wastewater (PSW) treatment were compared with each other and their information contents were calculated. The information content from the smallest to the largest is EC, DAF, coagulation, and anaerobic treatment, respectively. This treatment method was chosen because the smallest information content is in electrocoagulation. EC was applied to bloody PSW containing 1% blood by volume. The effectiveness of Fe and Al electrodes for PSW treatment in the batch EC reactor has been compared. The effective surface areas of 2 anodes and 2 cathodes connected bipolarly in the processes are 288 cm2. The electrolyte, pH, time, and current density effects on energy consumption were also investigated. The optimum conditions for Al and Fe electrodes were found to be 0.5 g·L-1 NaCl concentration, pH 5, 0.639 mA·cm-2 current density, and 5 min time. Under optimum conditions for the Fe electrode, COD, TOC, TN, and oil-grease removal efficiencies were determined as 76.3%, 71.8%, 70%, and 74%, respectively. Moreover, the highest COD, TOC, TN, and oil-grease removal efficiencies were achieved with an Al electrode (82.2%, 82.3%, 82.7%, and 78.9%, respectively). The experimental data were fit to a variety of isotherms and kinetic models to determine the characteristics of the EC. The results indicated that the pseudo-second-order equation provided the best fit for COD removal. Under optimum conditions, the operating cost was calculated as $3.39 and $3.09 for Al and Fe electrodes, respectively. In this study, the fuzzy axiomatic design method was used for the first time to select the most appropriate treatment method for PSW. In addition, blood, a major problem for the poultry slaughterhouse industry, was mixed with PSW at a ratio of 1% (v/v) and treated with EC for the first time with high removal efficiency. By treating PSW, which has a high pollution load, with electrocoagulation, the pollution load of the water to be given to secondary treatment has been greatly reduced.

Treatment of tomato paste wastewater by electrochemical and membrane processes: process optimization and cost calculation

This study investigated the treatment of wastewater from tomato paste (TP) production using electrocoagulation (EC) and electrooxidation (EO). The effectiveness of water recovery from the pretreated water was then investigated using the membrane process. For this purpose, the effects of independent control variables, including electrode type (aluminum, iron, graphite, and stainless steel), current density (25-75 A/m2), and electrolysis time (15-120 min) on chemical oxygen demand (COD) and color removal were investigated. The results showed that 81.0% of COD and 100% of the color removal were achieved by EC at a current density of 75 A/m2, a pH of 6.84 and a reaction time of 120 min aluminum electrodes. In comparison, EO with graphite electrodes achieved 55.6% of COD and 100% of the color removal under similar conditions. The operating cost was calculated to be in the range of $0.56-30.62/m3. Overall, the results indicate that EO with graphite electrodes is a promising pretreatment process for the removal of various organics. In the membrane process, NP030, NP010, and NF90 membranes were used at a volume of 250 mL and 5 bar. A significant COD removal rate of 94% was achieved with the membrane. The combination of EC and the membrane process demonstrated the feasibility of water recovery from TP wastewater.

Hybrid electrocoagulation reactor for dairy wastewater treatment and methodology for sludge reusability for the development of vermicompost

The dairy industry is a high-water-consuming sector, making water conservation crucial, especially in countries like India that are top milk producers and have large populations. This research evaluates the performance and effluent characterization of dairy effluent treatment systems in Kerala using modern, cost-effective technology to address this issue. A hybrid electrocoagulation reactor (HECR) is designed to operate simultaneously in coagulation, and the electrocoagulation process is proposed in this study. The wastewater treatment parameters of the HECR with those of six existing dairy effluent treatment plants using geological mapping and geographic information system (GIS) were studied. According to inverse distance weighted (IDW) interpolation findings, HECR's effluent treatment profile is comparable to existing technologies, with a minimum required retention time of 9.58 h. The results show the HECR treatment efficiency, removing up to 75.15% of turbidity and 94.5% of COD. Moreover, the sludge generated from HECR is transformed into nutrient-rich vermicompost by adding suitable fillers in the ratio of 5:1:3:1 (industrial dairy sludge/HECR sludge: cow dung, dry leaf, and seed vermicompost). The optimal conversion times for vermicompost developed from dairy industrial sludge are 40 days, with nitrogen, phosphorus, and potassium (NPK) values per gram vermicompost of 8.86%, 3.18%, and 3.6%, respectively. For HECR sludge, on the 60th day, the observed NPK value for the developed vermicompost is at 4.76%, 1.46%, and 5.1%. Overall, this research offers a promising solution to treat dairy wastewater and transform generated waste sludge into a valuable resource, highlighting the importance of technology adaptation in the dairy industry.

Efficient removal of tannins from anaerobically-treated palm oil mill effluent using protein-tannin complexation in conjunction with electrocoagulation

Despite the significant removal of chemical oxygen demand (COD) by anaerobic digestion, anaerobically-treated palm oil mill effluent (POME) still contains tannins and other phenolic compounds, resulting in residual COD and a brownish color. In this study, we investigated the removal of tannins from anaerobically treated POME using protein-tannin complexation in conjunction with electrocoagulation. The amino acid composition of the protein, aqueous pH, and protein: tannin ratios were found to be important parameters affecting the tannin removal efficiency. Pig blood protein was superior to casein protein in removing tannins, possibly because it had aspartic acid as the major amino acid component. At an optimal condition with a pig blood protein: tannin ratio of 0.33 (w/w), a current density of 30 mA/cm², pH 5, and an electrolysis time of 10 min, the removals of tannins, COD, and color were 93%, 96%, and 97%, respectively.

Continuous flow sequencing bed biofilm reactor bio-digested landfill leachate treatment using electrocoagulation-persulfate

Landfill leachate contains many complex components that have a negative impact on the environment when improperly discharged. This study is the first to treat landfill leachate (after continuous flow sequencing bed biofilm reactor (CF-SBBR) bio-digested) using electrocoagulation (EC) combined with persulfate (PS) on Al and Fe electrodes. The effect of some of the key parameters on the COD, Color, TOC and TN removal efficiencies as part of the EC-PS process were studied using the PS concentration, reaction time, initial pH, current density, and aeration rate. The results show that a PS concentration of 3 g/L improved the COD removal efficiency by 9.0 ± 1.3 % at the Al electrode and 16.0 ± 2.6 % at the Fe electrode. Aeration also improved the COD, TOC and color removal efficiencies by about 10.0 ± 2.3 %, 8.0 ± 1.7 % and 3.0 ± 0.5 % at an optimal aeration rate 3.3 L/min. The optimal operation conditions for the EC-PS process were a PS concentration of 3 g/L, a pH of 2.0 (Al electrode), a pH of 4.0 (Fe electrode), a reaction time of 70 min, a current density of 35 mA/cm² and an aeration rate of 3.3 L/min. The highest COD, color, TOC and TN removal efficiencies were 46.5 ± 1.8 %, 95.8 ± 2.4 %, 83.5 ± 1.7 %, and 40.9 ± 1.6 % at Al electrode and 54.4 ± 2.3 %, 98.5 ± 2.1 %, 78.6 ± 1.5 % and 57.9 ± 1.1 % at the Fe electrode. The EC-PS working mechanisms involve co-precipitation, an advanced oxidation process (AOPs) using oxidation radicals (HO, SO₄^-) and flotation. EC-PS is a promising method to treat bio-digested landfill leachate.

Concept of Flocks Fragmentation and Averaging Method for the Application of Electrocoagulation in Process for Coke Oven Wastewater Treatment

The main objective of the article is to develop the concept of flock fragmentation and the averaging method for the application of electrocoagulation in the process of treating wastewater from coke ovens. The designed solution was part of an innovative system for the coke oven wastewater treatment process. The system is dedicated to removing the hazardous elements and compounds from wastewater from leaching ashes in municipal waste incineration plants. The design of the process and its automatization was based on a quantitative simulation method. The balance equations of mass, energy, and momentum of transport, complemented by the kinetics of the related reaction, are used during the calculation of the process. The main result achieved is a practical solution-the reactor's scheme, classified due to a patent procedure in the Polish Patent Office.

Pollutant removal from dairy wastewater using live Azolla filiculoides in batch and continuous bioreactors

Fast and proper treatment of dairy wastewater is necessary before discharging it to the environment. In this study, healthy Azolla filiculoides was used to remove pollutants, including phosphorus (P), sodium (Na), chemical oxygen demand (COD), biological oxygen demand (BOD), and total dissolved solids (TDS) of dairy effluent in batch, continuous system, as well as continuous with the slow stirring system. These systems were handmade. The maximum removal efficiency was related to the P, which obtained 66.25% after 12 h in the batch bioreactor system. The highest removal of 13.69% after 21 h was obtained for Na using continuous with a slow stirring method. The highest removal related to the COD and BOD was 33.53% and 29.93% after 18 h, respectively, in continuous with the slow stirring system. TDS removal was achieved 31.44% after 24 h using the batch system. The results of these three systems were compared with each other using a one-way analysis of variance (ANOVA). There was no significant difference between them. Azolla filiculoides is an abundant plant in northern nature that a biosystem was used for optimum usage. It can be used as an efficient, inexpensive, and affordable bioadsorbent for dairy wastewater treatment. PRACTITIONER POINTS: Live Azolla filiculoides was used to remove pollutants. P, Na, BOD, COD, and TDS were removed from dairy wastewater. Batch, continuous, and continuous with the slow stirring systems were used. Live Azolla was an efficient, inexpensive, and affordable bio-adsorbent for dairy wastewater treatment.

Treatment of cardboard factory wastewater using ozone-assisted electrocoagulation process: optimization through response surface methodology

Cardboard factory wastewater is usually known by high chemical oxygen demand (COD), color, phenols, lignin, and its derivatives, and usual treatment techniques are not able to treat such wastewaters. This study aimed to investigate the efficiency of ozone-assisted electrocoagulation process (EC/O₃) for the treatment of real cardboard wastewater. The parameters influencing COD removal in the EC/O₃ process were optimized using response surface methodology. Regard to the statistical model, the optimum conditions were obtained at current density 9.6 mA/cm², time 20 min, and pH 12. At optimal condition, EC/O₃ process removed 74.7% and 97.5% of COD and color, which was higher compared to ozonation and EC processes separately. The COD removal followed pseudo-first-order kinetic with the coefficient correlation of 0.97 and the reaction rate constant of 0.073 1/min. To sum up, the combined electrocoagulation process with ozonation could be used satisfactorily for removing pollutants from real cardboard wastewater.