Water Purifying Solution for a Well-Established Sealing Company

The client uses cutting fluid in three separate processes: metal cutting, rubber cutting, and a robotic cutting operation. In all three cases, process water is generated and divided into three separate streams, each directly connected to the sewage system. The cutting fluid contains elevated levels of zinc, copper, chromium, and nickel.

The management structure in place at the time posed a clear risk of inadequate wastewater handling, with potential impact on the municipal sewage system. Key requirements included consolidating all wastewater streams into a single treatment system and ensuring effective removal of heavy metals, oil, and suspended solids.

The treated water needed to meet strict discharge requirements, specifically Svenskt Vatten’s P95 guidelines (Table 3) for heavy metals such as zinc, chromium, and copper, with effective reduction of suspended solids. The treatment system also had to ensure stable process conditions, including sufficient conductivity for treatment performance, handle variable flow rates, and provide a high level of automation.

Additionally, the existing uncontrolled discharge of untreated wastewater to the municipal sewage network needed to be eliminated to ensure compliant and controlled wastewater management. In addition, high values of oil index and organic contaminants are present, indicating a significant organic load.

The goal was to treat the cutting liquid from rubber cutting, metal cutting, and robot cutting in a reliable and compliant manner. The untreated wastewater would exceed allowable discharge limits before entering the municipal sewage network. The solution was a SRE (Sealed Reactor Electrocoagulation) system with two reactors with an OptiFloc™ flotation unit installed inside a flexible 20-foot standard container.

The system was dimensioned and optimized to ensure that the treated water consistently meets Svenskt Vatten P95 guidelines or locally applicable discharge requirements, even under varying influent conditions. The process water from the different cutting operations is continuously pumped to the SRE treatment system, where it passes through the reactors and flotation unit, separating contaminants.

After treatment, the purified water is discharged to the municipal sewage system in compliance with discharge requirements. Due to its versatile electrocoagulation principle, it was well suited to remove challenging waste products like zinc, chrome, copper, and lead that were present in the cutting liquid.

SRE is based on electrocoagulation. Direct current releases iron or aluminum ions into the water, causing contaminants to coagulate in a manner similar to traditional chemical coagulation with polymer addition. The benefit of electrocoagulation compared to chemical coagulation is that the need for neutralization is reduced and it does not add any chloride ions to the solution. Uniform release of coagulants makes the process fast and efficient.

This results in a more environmentally friendly alternative compared to conventional chemical coagulation. As the wastewater passes through an electric field, surface charges on oil droplets and colloidal particles are neutralized, destabilizing emulsions and improving separation. During the process, hydrogen gas is generated, supporting flotation and separation of oil and other contaminants.