Control of Electrocoagulation Batch Reactor for Oil removal from Automobile Garage Wastewater

Treatment of salt from hides curing stage by electrocoagulation for use in the pickling stage of the tanning industry

The raw materials for the tanning industry, namely hides and skins, are preserved (curing stage) and carried with common salt, i.e., sodium chloride (NaCl). Proceeding to conversion into leather, pickling is a key stage of the tannery process, which entails high demand of water and salt. In this work, the salt-derived brine (SdB) generated from the curing of hides was treated by iron-driven electrocoagulation (EC), aiming at its later application in the pickling stage of the tanning industry, promoting a transition to zero waste emission policy. Focusing on reducing the brine's total organic carbon (TOC), central composite rotational design and response surface methodology were adopted to study the effect of electrolysis time (6.2-14.2 min) and current density (74-431 A·m-2) on the treatment of the SdB (≅ 7.5 % wt. NaCl). The quality of the treated brines was then assessed in pickling trials and compared with virgin brine. 68-83 % removal of TOC from the SdB were achieved under electrolysis time ranging 6.2-14.2 min and current density ranging 126-252 A·m-2. Under these operating ranges the quality of the wet-blue leathers was guaranteed. Lowest power consumption (0.44 kWh·m-3) was achieved under electrolysis time of 6 min and current density of 126 A·m-2, yielding 68 % removal of TOC. Moreover, the shrinkage temperature of the hides was improved with treated brine (103.5 °C-110.5 °C) compared to virgin brine (103.0 °C). The present study provides strong evidence that contaminated salt from the curing stage can be valorised within the tanning industry through electrocoagulation treatment and then used in another production stage, instead of being landfilled.

Application of Box-Behnken design for circulating flow sono-electrocoagulation for oily wastewater treatment

The increasing production of oily wastewater as a by-product of industry has become a major environmental problem. Therefore, this article investigates the removal of mineral oil from oily wastewater by a circulating flow sono-electrocoagulation. The Box-Behnken design was used to study the effects of characteristic electrocoagulation and ultrasonic parameters on mineral oil removal efficiency. A total of 34 different experimental setups were performed at a laboratory scale. A reduced cubic regression model with derived coefficients was developed to describe the mineral oil removal rate. The experimental results show that circulating flow sono-electrocoagulation with iron electrodes can effectively reduce mineral oil by 93.3% under the optimum conditions of 10.948 cycles, a current density of 107.12 A m^-2 and a flow rate of 0.468 L s^-1. The experimental observations agreed well with the modeled values, and the model was verified experimentally. Under the optimal conditions, the average operating cost was 0.77 EUR/m³.

Ayurvedic hospital wastewater degradation using electrochemical treatment

The goal of this research was to remove COD, oil and grease (O&G) and color from raw ayurvedic hospital wastewater (AHWW) using a novel electrochemical coagulation (ECC) process. Cell voltage was initially optimized using iron electrodes in bipolar mode for both raw AHWW and ayurvedic hospital therapy room wastewater (AH-TRWW) for a pre-optimized electrolysis time (ET) of 60 min. O&G, COD and color removals for AHWW at 8 V optimized cell voltage were 96, 61 and 96% respectively. Different electrode materials, copper, aluminum, graphite, were used to evaluate relative performances at 8 V. Iron electrodes showed maximum pollutant removal from raw AHWW. The sludge obtained after the ECC process showed good settling and filterability properties compared to graphite and aluminum electrodes. The low SVI value of 146 mL/g was obtained exercising absolute control on sludge volume. Solids flux values showed assurances of compact settling tank design with least spatial footprint. EDX analysis for ECC sludge of AHWW using iron showed gross elements 40.19% C, 48.63% O and 7.92% Fe redefining the fate of sludge. The XRD pattern of the ECC sludge showed an amorphous nature. Post-ECC filtration effluent showed clear water reclamation of 80-82%, proving the effectiveness of the novel ECC treatment process.

Quartz Sand Filter Media with Special Wettability for Continuous and Efficient Oil/Water Separation and Dye Adsorption

For continuous and efficient oil/water separation and adsorption of dyes, coconut shell powder was grafted onto the surface of quartz sand by dip-coating method to make coconut shell powder-covered quartz sand filter media (CSQS) with superhydrophilic and underwater superoleophobic properties and superoleophilic and underoil highly hydrophobic properties. The contact angles of the underwater oil and underoil water with CSQS were more than 151.2° and 134.2°, respectively. A continuous oil/water separation device was designed. The separation device filled with CSQS can separate oil/water mixture (whether heavy or light oil) into water and oil at the same time with a separation efficiency of above 99.92%. The filter layer can be recovered through reverse extrusion even after lyophobic liquid penetrated the filter layer; hence, the separation efficiency of the filter layer was still above 99.99% for diesel and water mixture. Simultaneously, CSQS can effectively adsorb methylene blue with the highest removal rate as 98.94%. CSQS can maintain stable wettability under harsh environment conditions. This paper provides a new idea on continuous and efficient oil/water separation and simultaneous dye adsorption.