Aluminium processor complies with more stringent standards with Mobicon filter

Mobile activated carbon filter

In sectors including the aluminium processing industry, waste water must comply with strict standards before it may be discharged. The effective treatment of this water flow is therefore crucial for the environmental permit of such companies. With the combination of sand filtration and a mobile activated carbon filter from Desotec, the Belgian branch of a major multinational got to grips with the issue in an appropriate manner.

The use of rinsing water is a crucial factor in the production of rolled aluminium products. After the rinsing process, the water used contains many organic contaminants (COD) such as non-ionic detergents. The recently tightened standard stipulates that the level of non-ionic detergents must be lower than 3 ppm. An important aluminium processing company approached Desotec for advice to comply with the standards.

Operational costs

After consultation with the customer, a waste water purification by means of an activated carbon filtration proved to be the right approach provided that the operating costs would not be too high. Initial calculations showed that the annual use of activated carbon could possibly exceed 200 tons per year. During these calculations we based ourselves on the non-selective nature of activated carbon, that in principle adsorbs all the organic contaminants.

But activated carbon can also adsorb certain substances preferentially. The operational cost could be cut considerably should that also be the case for the non-ionic detergents. To test that, we installed a pilot plant at this company. We had a limited waste water flow treated in a small-scale mobile activated carbon filter (capacity 1 m³), so that we could accurately estimate both the behaviour of the adsorption process and the breakthrough curve.

Considerable savings

The relatively quick breakthrough of COD at the exit of the activated carbon filter showed that the installation did indeed preferentially adsorb the non-ionic detergents. With this highly positive observation, the company requires considerably less activated carbon, and the operating costs for the customer can be significantly decreased. From new calculations it even appeared that 50 tons of activated carbon per year should suffice, so consumption costs would be no less than 75% lower thanks to preferential adsorption. On this basis the customer soon decided to proceed to a full-scale installation.

The full-scale installation with a capacity of 20 m³ was put into place at the end of 2017. We also installed a sand filter to optimally protect the activated carbon filter. Desotec was also responsible for installing the piping and valves between the sand filter and the activated carbon filter. The installation has been running smoothly since the end of 2017 and ensures that the company fully complies with the more stringent detection limit for non-ionic detergents. As a result, the waste water can now be simply discharged.