Substances of Very High Concern (SVHC): the silent route of indirect discharges

Introduction

In recent years, Substances of Very High Concern (SVHCs) have received a lot of attention. Their presence in the living environment is worrying because they hardly degrade, accumulate in ecosystems and pose direct risks to health and nature. Within this broad group fall, among others, PFAS and heavy metals; substances that often make the news because of their persistence and harmfulness.

Attention usually goes to companies that discharge directly into surface water. Less visible, but at least as important, are the indirect discharges: substances that enter municipal sewers or industrial systems, end up in wastewater treatment and from there still reach the water system. Precisely this route is often a blind spot in policy and supervision.

Substances of Very High Concern (SVHCs)

In the Netherlands, the term Substances of Very High Concern (SVHCs) is used for substances that are persistent, bioaccumulative and toxic, or that have similarly serious effects such as carcinogenicity or hormone disruption. These substances are high on the policy agenda because they hardly degrade, accumulate in the environment and therefore pose major risks to health and ecology.

Two well-known examples are:

• PFAS (poly- and perfluoroalkyl substances) – a family of thousands of substances widely applied since the 1950s, including in firefighting foam, textiles and food packaging. Because of their extreme stability they are also called “forever chemicals”. Several PFAS are known to be carcinogenic or hormone-disrupting.
• Heavy metals such as lead, cadmium, copper and mercury – naturally present in soil, but often elevated in the environment due to human activity. At higher doses they damage the nervous system, kidneys and ecosystems.

These are only a few examples. The full ZZS list contains many other categories of substances that likewise threaten water quality and ecology. Because of their persistence and toxicity, every discharge – direct or indirect – poses a risk to achieving the WFD (KRW) goals.

Indirect discharges

When people think of discharges, they often picture a factory pipe that ends directly in a river. Yet a significant share of chemical emissions reaches water via another route: indirect discharges.

This process proceeds in three steps:

1. Wastewater from companies – Many companies have no direct discharge permit, but drain their wastewater via the municipal or industrial sewer. Examples include metalworkers with rinse water, or textile companies using PFAS.
2. Wastewater treatment (RWZI) – In a WWTP, nutrients and organic matter are largely removed. For ZZS this hardly works: persistent substances pass almost unhindered, while heavy metals are only partially captured in sludge.
3. Back to surface water – The effluent of the WWTP is discharged into rivers, ditches or canals. As a result, indirectly discharged substances still reach the water system.

Indirect discharges are often fragmented and diffuse, but collectively of great significance.

Risks and consequences

• Persistence and accumulation – Many ZZS hardly degrade and accumulate in soil, sediment and food chains. Even low emissions can cause major problems over time.
• Insufficient removal – WWTPs are designed to reduce nutrients and organic load, not to remove micropollutants or persistent substances. For ZZS they often function mainly as a transit station.
• Hard to trace – Because indirect discharges run via combined streams, it is difficult to determine exactly which companies are responsible. This complicates supervision and source control.
• Threat to policy goals – The European Water Framework Directive requires all water bodies to meet strict standards by 2027. Indirect discharges of ZZS directly threaten achieving those goals; failure has consequences for nature, public health and can lead to legal sanctions and fines.

Conclusion

Substances of Very High Concern (SVHCs) are a persistent challenge to water quality. They reach surface waters not only through direct discharges, but also via the silent route of indirect discharges. Precisely this diffuse and less visible route makes it extra difficult to get a grip on emissions. As long as indirect discharges are insufficiently visible, the task of achieving cleaner water and the KRW goals remains an illusion. The urgency is clear: without attention to the hidden route of indirect discharges, ZZS will continue to burden our water system, with consequences for environment, health, policy and possible sanctions.