Due to economic and ecological reasons metal and alloy processing company, Bodycote decided to replace a conventional treatment in Sweden with a modern vacuum distillation system. By achieving a zero liquid discharge heat treatment process, the company is now looking to roll out the process to other sites globally.
By Jochen Freund
For already quite some time Bodycote, a provider of services for the improvement of metal and alloy properties, was looking at alternatives for its existing wastewater treatment process technology.
Previously, generated wastewater was neutralised and then treated in an ion exchanger to remove heavy metal pollution. Purified water was then disposed to the municipal wastewater network.
However, operation of the system involved a high work load and the quality of the purified water not good enough for recycling back into the process.
The objective was to find a process producing less cost, consuming less fresh water and offering a high reliability. In addition Bodycote wanted to standardise equipment for locations in multiple locations around the world.
Upon further examination, it was considered that a zero liquid discharge (ZLD) process should be developed. This was so that water can recycled back into production and used as process water.
Contact with a wastewater evaporator supplier, H2O GmbH, saw the start of a process being developed. The first phase saw the client's process wastewater studied before phase two, which saw the economic viability checked. In the last phase the new process had to be verified in production scale. H2O then installed a demonstration system at one of Bodycote's production sites. Over several weeks the wastewater generated in the surface technology processes was treated in a Vacudest wastewater evaporator.
After it was shown that the quality or the purified water was very constant, even after several weeks, successful trials for the recycling into the production process were carried out.
The recycling of the purified water has two additional advantages for Bodycote. First of all the distillate leaving the Vacudest wastewater evaporator is warm, thus the purified water must not be pre-heated prior to using it as rinsing water in the production process.
Previously, all this fresh water had to be demineralised prior to using it as rinsing water. The distillate from the Vacudest wastewater evaporator is already free of salts, this process step is not needed. As a result, the site has reduced fresh water consumption by more than 95%.
In the meantime a second Bodycoat site has exchanged its wastewater treatment system for a wastewater evaporator. Other sites are expected to follow in the nearer future.
Jochen Freund is head of product & business development at H2O. Email: [email protected]
