Field Validation of Electrocoagulation Treatment for Oily Wastewater at Cleveland-Cliffs Steel Mill in Cleveland, Ohio

Project Background

The Industrial Technology Validation (ITV) program aims to identify and demonstrate the performance of new, emerging, and underutilized technologies in the industrial sector to help inform decisions towards accelerating commercialization and deployment.
This initiative aims to identify, validate, and showcase new, emerging, and underutilized technologies in the industrial sector to expedite their commercialization and widespread deployment. By conducting thorough validations and demonstrating the efficacy of these technologies, the ITV program facilitates informed decision-making among industry stakeholders, contributing to the transition towards more sustainable and efficient industrial processes. This ITV demonstration involved the testing of an electrocoagulation (EC) treatment system at a steel plant in Ohio. The system was designed to treat oily wastewater generated from cold rolling operations.

Facility and Technology Description and Scope

Cleveland-Cliffs Inc., located in Cleveland, Ohio, is a leading integrated steelmaking facility near the Cuyahoga River, with two blast furnaces, steel-producing facilities, and various mills capable of producing over three million net tons of raw steel annually. The plant supplies a diverse market with flat-rolled steel products, particularly serving the automotive industry in North America.

The focus of this project is the oily wastewater treatment plant (WWTP) within the Cleveland-Cliffs facility. Currently, the WWTP employs chemical flocculation (CF) to treat oily wastewater with suspended solids, metals, and hydrocarbons before discharging the treated water to the Cuyahoga River after recovering oil and other residues. The CF process involves adding multiple chemicals to the oily wastewater, segregating it into effluent water, oil-water mixture, and solid waste for further processing.

Dynamic Water Technologies (DWT) is a commercial and industrial water treatment company focused on the treatment of process water systems. The process of electrocoagulation (EC) is an electrochemical method used to treat oily wastewater by destabilizing oil-in-water emulsions, neutralizing charges, and bonding oil pollutants to generated flocs. These flocs can then be separated through conventional techniques, like dissolved air flotation, gravity settling, sand filtration, disc filtration, or membrane filtration. The EC process also aids in aggregating fine colloidal particles that are typically not separated with standard coagulants.

According to the technology vendor, EC-treated water contains fewer toxins and is colorless and odorless compared to CF treatment. EC flocs are larger and contain less water, thereby facilitating easier and faster filtration. The EC system would also result in capturing and recovering higher-quality oil, thereby resulting in additional savings and revenue. Since this system relies on electrochemistry for water treatment, the reliance on chemicals would be very minimal once deployed at full scale compared to CF treatment. The absence of moving parts in the EC process results in lower maintenance costs after factoring in the impact on electricity consumption. The measurement scope included the equipment for both the existing CF system and the new EC system that are used for treating the oily wastewater.

Study Design and Objectives

The evaluation focused on testing the EC system at a small scale at the plant’s WWTP, which currently utilizes CF to treat wastewater and recover the oil. The EC system aims to replace chemical treatment, offering potential benefits including reduced chemical usage with higher oil quality. The project involved installing a 100-gallon-per-minute (gpm) EC system alongside the existing 400-gpm CF setup to assess and compare its efficacy in a side-by-side configuration. Anticipated benefits included reduced water usage, increased oil collection efficiency, and decreased chemical consumption. Evaluation objectives include assessing water quality, recovered oil quantity and composition, measuring electricity consumption, and comparing chemical usage between the EC and CF systems

Methodology

The performance assessment was conducted in a side-by-side configuration over a four-week evaluation period, from October 17, 2022 to December 2, 2022, with the EC system handling up to 25% of the oily wastewater from deep well tank and the CF system handling the remaining water. During the evaluation period, the EC system operated for eight hours daily, while the CF system operated continuously throughout the day. Water from the deep well tank is split into two streams, with one going into the EC system and the other going into the existing CF system. Treated water from the EC system and the CF system flowed into their separate primary tanks for further processing. The collected data includes water quality parameters (i.e., turbidity, conductivity, and pH) and oil quality (i.e., BTU and water content) to compare the efficacies of these systems. The evaluation also assessed the electricity consumption and chemical usage of both systems.

Project Results/Findings

The EC system demonstrated effectiveness in treating oily wastewater, enhancing tramp oil collection, and reducing reliance on chemicals, leading to significant cost savings and benefits. Results showed slightly higher turbidity (1.3 nephelometric turbidity unit [NTU] difference) and lower conductivity in EC-treated water, with improved tramp oil collection efficiency (25% increase) and reduced chemical usage (60–100% reduction). The higher turbidity in EC-treated water may be attributed to 1) not accounting for cold mill blow down; 2) insufficient hydraulic residence time (HRT); and 3) filtration was not used or was too loose. However, the EC process consumed more electricity (0.05 kWh per gallon of treated water) and rendered the collected oil with higher-than-expected and out-of-spec iron content (25 grams/kilograms) from the anode plates.