Complying with stricter non-ionic surfactant limits at an aluminium processor

In the aluminium processing industry, wastewater must comply with strict standards before it is discharged. For companies to maintain their environmental permits, the effective treatment of this water flow is crucial. By combining sand filtration and a DESOTEC mobile activated carbon filter, the Belgian branch of a major multinational got to grips with the issue.

The Problem

Rinsing is an essential stage in the production of rolled aluminium products. After the rinsing process, the wastewater contains many organic contaminants (COD) such as non-ionic detergents. Legislation has recently been tightened, and now stipulates that the level of non-ionic detergents must be lower than 3 ppm. 

An important aluminium processing company approached DESOTECfor advice on meeting this new limit.

Aluminum metal rolled up in factory
Falling drop of water

The Solution

After consultation with the customer, we were confident that activated carbon would be the right approach, provided that the operating costs were not too high. Initial calculations showed that the annual use of activated carbon could possibly exceed 200 tonnes per year. These calculations were based on the fact that activated carbon is non-selective, adsorbing all organic contaminants.

However, activated carbon also preferentially adsorbs certain substances. The operational cost would be cut considerably if that was the case for these non-ionic surfactants.

To find out, we ran a pilot test. We sent a limited wastewater flow over a small-scale mobile activated carbon filter (capacity 1 m³), so that we could accurately estimate the behaviour of both the adsorption process and the breakthrough curve.

The COD broke through quickly at the outlet of the activated carbon filter, showing that the installation did indeed preferentially adsorb the non-ionic detergents.

This was great news for the company, as it meant that less activated carbon would be required, driving down operating costs. New calculations suggest that just 50 tonnes of activated carbon per year would do the job, cutting consumption costs by 75%. On this basis, the customer promptly gave the green light to a full-scale installation.

The Results

The full-scale installation (capacity 20 m³) was put in 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 wastewater can now simply be discharged.