In 2019, we implemented a new measuring method on a project basis – mass balance – which measures exactly how much of the toxic substance PFOS that is removed from the water treated at our plants. As a result we have gained a greater insight into our purification efficiency, and the method has now been made permanent for all substances and measuring points.

Some substances cannot be decomposed in nature. An example of such a substance is PFOS is accumulated in the food chain. It is carcinogenic, can effect reproduction and is acutely toxic. Even though PFOS is forbidden today, it is still present in small quantities in the wastewater which we receive from different sources.

Fortunately it is a substance which can be removed and destroyed. At our plant at Stigsnæs, we remove – and document that we remove – 99.4 percent of all PFOS in the water we receive. That is better than any other purification plant in Denmark.

The importance of addressing PFOS has been obvious at fire schools and fire stations. Until 2008, PFOS-containing firefighting foam was used. Sometimes, the water from fire schools and fire stations was discharged without being purified first, resulting in issues such as food contamination.

Why monitoring is crucial

Today the risk of PFOS is realised. The substance is banned and steps are taken to avoid contamination. However, there are still residues of PFOS in many types of wastewater. Therefore, it is crucial not just to purify the water from PFOS - but also to monitor the quantities and purification effect.

At our plant at Stigsnæs we measure the exact quantities of PFOS (and many other substances) in the water we receive. In each step of the purification process – biological purification, mechanical filtration, and active carbon filters – and again before the discharge, the exact weight of hazardous substances is measured. Thus, the removed quantities can be documented precisely.

Introducing new technologies 

Besides being able to document our exact purification effect through mass balance for many substances, we are also able to improve our plants thanks to technology. As we measure the effect of the purification at several points during the process, we are able to monitor and
optimize each step very precisely and achieve better results.

With this documentation we are able to disprove the opinion held by some that water purification is about diluting contaminated water with clean water until an acceptable result is obtained.

Ecotoxicological tests

Every year RGS Nordic purifies up to 450 million liters of contaminated water, primarily from companies in Denmark, Norway, and Sweden. We protect the marine environment from thousands of tonnes of hazardous substances. Besides measuring the purification, we also carry out ecotoxicological tests on algae and crustacean, documenting that our discharge does not have a negative impact

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