Treating rinsing water from the pickling process

A vacuum evaporator for Vendée Concept in La Roche-sur-Yon (France) for treating industrial wastewater on site

The Vendée Concept plant in La Roche-sur-Yon (85) manufactures systems for the food industry using specific technological processes. The product lines and mechanical systems offer solutions in the areas of robotics, calibration, weighing procedures, monitoring, transportation and maintenance. Vendée Concept specialises in the poultry, fish and shellfish sectors as well as the meat industry. When manufacturing their machines from welded stainless steel, water is generated as a by-product: namely rinsing water from the pickling and passivation processes.

Previously this wastewater has been treated on site using a physicochemical facility. Vendée Concept has now decided to use a sustainable vacuum evaporator from H2O.

Vendée Concept - H2O collaboration

Background

Stainless steel is particularly suitable for applications in the food industry. Manufacturing and processing this material at the Vendée Concept plant requires specific tools for cutting, welding, removing grease, pickling and passivating.

After the parts are welded they are degreased before undergoing surface treatment. The pickling and passivation process helps make the material more resistant to corrosion. To achieve this, small parts are completely immersed in an acid bath, while larger components are sprayed. After pickling or passivation the parts are rinsed off using a high-pressure cleaner supplied with mains water. The resulting rinse water is directed into the physicochemical treatment system to be processed.

Vendée Concept’s stainless steel system

For a long time, Vendée Concept has treated its rinse water using a traditional physicochemical treatment facility, with the wastewater subsequently being passed on to the public sewage plant. In accordance with their agreement with the district authorities, the wastewater was checked regularly and subjected to analysis. Nevertheless, the old system had to be constantly and meticulously monitored in order to ensure it complied with the standards. An additional challenge was the quantity of wastewater produced.

Even when this water treatment process adhered to all prescribed threshold values, it was impossible to avoid harmful pollutants being discharged into the environment. The resulting, persistent pollution was damaging future generations.

Project initiation

Consequently, an alternative solution was essential to replace the ageing legacy system. Eric Legendre, head of the La Roche-sur-Yon location, was already interested in environmental protection and wanted to find out more about wastewater-free production using vapour recompression. H2O experts paid him a visit and outlined the benefits.

The vaporisation solution enables the following:

recirculation of the treated process water (distillate) in the production process
no more restrictions due to checks by the wastewater authorities
absolutely no emissions or environmental pollution

The decision to adopt this solution was made by Vendée Concept to bring their activities more into line with their own strict environmental policies. Other factors were the simple, automated operation of the new system and its low maintenance requirements.

Processing and treating the rinse water from pickling processes

Separate examination steps

The wastewater flow and corresponding volumes are closely monitored.
The products used (degreaser, treatment baths and rinsing baths for pickling or passivation) are brought up to date. This part is fundamental, as it enables conclusions to be reached and any potentially critical products or flows can be considered in isolation.
The acid baths for pickling and passivation are no longer used as they are too concentrated.
Storage capacity in the overall system is determined. The existing subterranean storage tank is used again. A neutralisation tank is required to balance the pH value of the acid wastewater before this goes through the evaporation process. The distillate is stored in a tank until it is reused by a high-pressure cleaner.
The necessary post-treatments for the distillate are defined to comply with the quality requirements, namely none. The treated water is ideal for rinsing the parts.
The average flow rate through the evaporator or the compression factor obtained are determined.

The solution for this application scenario is a VACUDEST 90 evaporator. It treats up to 1.5 m³ per day, with a compression factor of 14. Vendée Concept is particularly delighted to have enabled production without wastewater. Since the company now discharges no water into the municipal treatment plant, it is no longer bound by the restrictions of wastewater checks.

Storage of the distillate with compressor for reusing the treated water

Functionality and initial findings

Following three months of operation, the findings have been highly satisfactory. Site manager, M. Legendre, explains: “Commissioning was really fast and comprehensive training was offered. The new system enables direct recycling of the distillate within the production cycle. The water quality is much higher than with the old physicochemical system, in fact this would have been inconceivable with the traditional approach.” He is also delighted that the system reuses 90 percent of the water used. H2O’s customer service also receives high praise from Vendée Concept: “Not only are they highly capable, they offer excellent availability and rapid response times. Service is provided within an hour or no more than 24 hours.”

Conclusion

Vendée Concept confirms that the VACUDEST system from H2O was the right choice. Since installation, H2O’s technical team have worked to ensure the availability of the system, responding to any questions, undertaking important maintenance work and engineering improvements.

The system was financed in conjunction with the Loire-Bretagne water authorities, with the subsidy contributing 50 percent of the overall project costs.

Author:

Dipl.-Ing. Laurent Dumas
Sales Manager for Western France / H2O GmbH