Before initiating a project and setting discharge limits, it is crucial to have a clear understanding of the type of water being managed. This is important for several reasons:

• To identify specific contaminants and potential risks
• To select the appropriate treatment technologies
• To comply with applicable laws and regulations
• To assess environmental impact
• To ensure both effective and cost-efficient solutions

For example, stormwater may contain oil and heavy metals, while dewatering water from construction sites often has high levels of particles and particle-bound contaminants, such as metals. Therefore, different treatment technologies are required depending on the water's characteristics.

So, what types of water do we manage in our projects, and what defines them? Here are the main water types we treat:

Dewatering water, also known as construction site drainage water, is a term commonly used in the construction industry. While the term is not specifically defined in legislation, it generally refers to water that has been diverted as a result of human activity. In practice, this includes rainwater, infiltrating groundwater, and process water generated by activities such as excavation, blasting, or drilling—commonly occurring in earthworks, quarries, and mining operations.

Irregular flow rates

The amount of dewatering water varies depending on weather conditions such as precipitation and snowmelt, with flows increasing after heavy rainfall and decreasing during dry periods. In addition, flows are affected by excavation work, as water accumulates in the trenches and natural drainage paths are altered. In deep excavations, groundwater can also seep in, further increasing the amount of dewatering water.

Typical contaminants and varying concentrations

Dewatering water often contains high levels of suspended solids, such as gravel, clay, and sand, which may be mixed with metals and other contaminants present in the soil. The composition and concentration of pollutants vary depending on the specific activities at the site, making it difficult to predict contamination levels in advance.

During concrete casting, elevated pH levels in the water can be an issue that requires treatment. In some cases, hexavalent chromium may also be present, necessitating specific treatment with RexOx3. Therefore, we always recommend conducting water sampling and soil investigations before starting a project, as these can often provide valuable insights into water quality.

Read about the tunneling project Johannelund, where we treated dewatering water with high levels of hexavalent chromium.

Stormwater is rainwater or melted snow that runs off from roofs, roads, and other impervious surfaces. When heavy rain or rapid snowmelt occurs, stormwater can collect pollutants from these surfaces, such as oil, heavy metals, chemicals, and debris, before flowing downstream and eventually reaching rivers, lakes, or even groundwater. Since stormwater has specific characteristics that influence both treatment and management, it is important to understand these in order to plan and implement the correct treatment processes.

Irregular flow rates

Stormwater flow varies depending on weather conditions such as rainfall and snowmelt. Large amounts of precipitation can result in high flow rates, while prolonged dry periods may lead to low or even negligible flows. These variations impact both the treatment process and the capacity of the treatment system.

Diffuse pollution and varying concentrations

Stormwater collects pollutants from many different sources, such as oil, heavy metals, chemicals, and debris on roads, roofs, and other impervious surfaces. Since the water runs off from large areas and is mixed from multiple sources, pollutant concentrations vary depending on where the water is collected and how much time has passed since the last rainfall. During heavy rain, large amounts of dirt and particles may be washed away, while breaks in precipitation can lead to more concentrated pollutants.

Read about the Stena Recycling project, where we installed a stormwater system to manage large volumes of water from their stormwater pond.

Industrial stormwater primarily refers to rainwater that has come into contact with industrial activities and surfaces. Recycling facilities are an example of an industry where pollutants, such as dissolved metals, may be present in stormwater. Industrial stormwater differs from regular stormwater, particularly in terms of the types of pollutants it contains, as these are influenced by the specific activities taking place within the area.

Irregular flow rates

Just like regular stormwater, the flow of industrial stormwater can vary depending on precipitation and weather conditions. Since industrial areas are often large and water collects on many different surfaces, the flow may be concentrated in certain areas while being more dispersed in others.

Varying pollution impact and concentrations

Pollutants in industrial stormwater can originate from many different sources within the industrial area and often include chemicals, oils, and solvents from production processes. Since the water runs off large surfaces, these pollutants mix, making it difficult to precisely define all the sources. Additionally, the concentration of pollutants varies depending on the ongoing industrial activity. During certain periods, levels of dissolved metals or organic chemicals may be higher, while they may be lower at other times. This means that industrial stormwater often requires more intensive treatment before it can be discharged.

Read about the Bo Altenstam project, where we handled challenging industrial stormwater with good results.

Process water is used in industrial operations such as manufacturing, cooling, or cleaning. After use, it may be contaminated with chemicals, oils, heavy metals, or other substances generated during industrial processes. Unlike stormwater, process water has distinct characteristics that influence its treatment:

Consistent flow rates

Process water typically has a stable and predictable flow, as it is continuously used and generated within industrial operations. This contrasts with stormwater, which fluctuates depending on rainfall.

Well-defined contaminants

Since process water originates from specific industrial applications, its pollutants are often well-documented. Unlike stormwater, which can carry an unpredictable mix of contaminants, process water generally contains known chemicals, metals, or organic substances.

Controlled processes

Water flow and discharge within industrial processes can usually be managed and monitored. This allows for adjustments to treatment efforts and immediate action if changes occur in the water's composition.

High concentration, no dilution

Unlike stormwater, which is diluted by rainwater, process water often contains high concentrations of contaminants. This makes it essential to select the appropriate treatment methods to effectively remove these substances.

Read more about how we treated process water combined with drill cuttings, excavation water, and rainwater in the new Näckenbadet project.

Leachate is water that has come into contact with deposited waste, which is either drained from or retained within a landfill. It primarily forms when rainwater infiltrates the landfill and when water is pressed out of the waste through compression. In older landfills, leachate can also form as groundwater or surface water enters the waste facility. The amount of leachate generated at a landfill depends on factors such as precipitation, waste decomposition, and the surrounding temperature.

Pollutants in leachate vary depending on the type of waste in the landfill, but it typically contains a mixture of suspended particles, organic matter, heavy metals such as zinc, chromium, and cadmium, as well as BOD and/or COD. It may also have high levels of nutrients like nitrogen and sulfur.

Irregular flow rates

The flow of leachate is not constant, as the amount generated depends on precipitation, meaning that flow may be higher during periods of heavy rainfall and lower during dry spells. Additionally, temperature variations can affect the rate of waste decomposition, which also influences the amount of leachate produced.

Diffuse and varying pollution impact

Leachate can contain pollutants from many different sources within the landfill, depending on the composition of the waste. Pollutants can include organic substances such as PFAS, heavy metals, and other chemicals, and they are often difficult to trace to a specific source. Furthermore, pollution levels vary based on factors such as waste decomposition, precipitation, and temperature, making leachate management more complex. Treatment may therefore require both physical and chemical processes to remove the full spectrum of contaminants.

In 2024, we delivered a facility to reduce the amount of PFAS in a utility company's leachate. You can read more about it via the link below

Extinguishing water is a type of contaminated water that needs to be managed, as it often contains high levels of PFAS from fire-fighting foam. As the name suggests, it arises during fire suppression and can contain a range of different pollutants depending on the materials and chemicals exposed during the firefighting process.

Common contaminants

Extinguishing water often contains elevated levels of PFAS, heavy metals, phthalates, oils, chemicals, and various organic substances. These are transported with stormwater to stormwater drains, which means the contaminated water reaches the stormwater network and can spread further into our watercourses.

Quick and simple solution – minimize damage at the source

When extinguishing a local fire, such as a car fire, it can be useful to have products that allow emergency services to quickly minimize the damage to stormwater. Therefore, we have developed a catch basin filter that can be installed in the drain in just a few minutes. The filter prevents hydrocarbons, dirt, sediment, and other pollutants from flowing into the stormwater drainage system. It can also be used on construction sites, industrial facilities, and parking lots.

You can read more about it here: Catch Basin Filter

PFAS in MSB's extinguishing water treated to undetectable levels

Recently, we at Swedish Hydro Solutions participated in a test for the Swedish Civil Contingencies Agency (MSB), where we used BioMedia® to remove environmental toxins from water that had been used to extinguish fires. In this particular case, the water was a mixture from a car fire and a house fire.

The result for BioMedia® was the removal of both PFAS and metals, with an extremely high purification rate. The filter reduced the level of PFAS (slv11) from 1050 ng/l to below the detection limit of 2.5 ng/l. At the same time, the concentration of metals – such as cadmium, chromium, nickel, iron, zinc, and copper – decreased by around or over 99% for each individual metal.

You can read more about the test and BioMedia® here: PFAS - Extinguishing Water

Need more information?

If you would like to learn more about managing a specific water type or have concerns regarding contaminated water in a particular project, please feel free to reach out.