Introduction | Protecting what lies beneath our feet

Every rainfall event triggers an invisible but critical environmental chain reaction. Rainwater flows across impermeable surfaces such as parking lots, roads, and logistics areas before infiltrating into the ground. Along the way, it accumulates anthropogenic pollutants that, without adequate treatment, migrate into deeper soil layers, groundwater systems, and ultimately drinking water resources.

This challenge sits at the heart of regulatory obligations established by the EU Water Framework Directive (2000/60/EC) and the Groundwater Directive (2006/118/EC), both of which require member states to achieve good chemical status for water bodies. Yet in France, only 70.7% of the country’s 689 groundwater bodies achieved good chemical status in 2019.

Managing stormwater quality at source has therefore become a strategic priority for municipalities, engineering consultants, and environmental design teams alike.

It is precisely to address this challenge that Solmax developed the OSMORIA® range of depolluting aquatextiles. Unlike passive filtration systems that simply retain pollutants, aquatextiles actively biodegrade hydrocarbons directly within infiltration structures through an autonomous and durable biological process. OSMORIA Geoclean Origin environmental performance has been independently evaluated through ETV verification according to EN ISO 14034 as well as additional testing conducted by public research laboratories.

Part 1 | How water becomes polluted during infiltration

Where do the pollutants come from?

A critical distinction must first be made between rainwater and runoff water. Rainwater itself generally contains relatively low pollutant concentrations before coming into contact with urban surfaces. It is runoff, the movement of water across impermeable surfaces, that creates a wash-off effect carrying pollutants into infiltration systems or directly into the environment.

On roads and parking areas, the primary pollution sources include:

• Hydrocarbons generated by vehicle traffic, including motor oils, fuels, and combustion residues

• Polycyclic aromatic hydrocarbons (PAHs), recognized for their toxicity and, in some cases, carcinogenicity

• Heavy metals

Diffuse hydrocarbon pollution on parking surfaces is estimated at approximately 10 g of hydrocarbons per m² per year.

What are the risks for natural environments?

According to DRIEAT Île-de-France, total hydrocarbon concentrations in roadway runoff can reach up to 10 mg/L and may exceed this threshold on heavily trafficked roads. PAHs are particularly concerning because of their mobility in water and their persistence in soils and living organisms.

Without treatment, these pollutants migrate into groundwater systems, disrupt soil microbial diversity, and weaken underground ecosystems. This is particularly important given that approximately 25% of global biodiversity exists below ground.

The Groundwater Directive (2006/118/EC) explicitly requires member states to prevent groundwater pollution and deterioration.

The limitations of conventional infiltration systems

The standard response to hydrocarbon pollution has historically relied on oil separators. These systems mechanically separate floating oils from water, but their limitations are well documented:

• They require regular and rigorous maintenance that is not always performed

• They are frequently undersized relative to actual runoff volumes

• They do not treat dissolved pollutants

• Most systems include bypass mechanisms

During intense rainfall events, precisely when pollutant loads are highest, bypass systems activate once hydraulic capacity is exceeded. Untreated runoff water is then discharged directly into receiving environments or drainage systems.

This is a major limitation because the largest pollutant loads occur during the very storm events where bypasses are most likely to activate.

In addition, the regulatory discharge threshold for Class 1 oil separators remains fixed at 5 mg/L hydrocarbons, a residual concentration significantly higher than the levels achieved by OSMORIA aquatextiles.

Part 2 | How aquatextiles work in stormwater treatment

The principle: active biodegradation inspired by biomimicry

OSMORIA aquatextiles are inspired by the natural functioning of soils. Designed to be maintenance-free and durable, OSMORIA aquatextiles provide an enhanced and sustained biodegradation process. The textile’s matrix releases essential natural minerals that attract and support native soil microorganisms, such as bacteria and fungi. These microorganisms multiply and accelerate pollutant breakdown, delivering consistent performance independently of soil characteristics.

OSMORIA aquatextiles rely on a dual-layer matrix structure:

Upper layer

The upper layer irreversibly captures up to 99.9% of hydrocarbons carried by infiltrating runoff water while providing natural mineral nutrients that support indigenous microorganisms.

Lower layer

The lower layer maintains moisture conditions favorable to hydrocarbon-degrading microorganisms while providing additional hydrocarbon retention capacity, particularly during small accidental spills.

Together, these mechanisms combine irreversible adsorption with enhanced biodegradation to create an autonomous, maintenance-free, and durable stormwater treatment system.

Independently verified performance

The performance of OSMORIA Geoclean aquatextiles has been evaluated through multiple independent studies and testing campaigns.

A 2021-2022 study conducted by CEREMA and LEESU assessed both pollutant retention rates and biodegradation performance for OSMORIA Geoclean Crystal. The results demonstrated:

• ≥ 99.9% retention of C10-C40 hydrocarbons

• Residual hydrocarbon concentrations between 0.03 and 2 mg/L after treatment

• Retention rates between 62% and 78% for the six most toxic PAHs commonly identified in runoff water

• ≥ 77% retention of benzo[a]pyrene, a confirmed carcinogenic PAH

In parallel, a voluntary Environmental Technology Verification (ETV) process according to EN ISO 14034 independently assessed two key performance parameters for OSMORIA Geoclean Origin:

• Water permeability according to EN ISO 11058: 8 × 10⁻² m/s

• Biodegradation capacity for C10-C40 hydrocarbons: 18.15 g of hydrocarbons biodegraded per m² for an initial load of 157.23 g HC/m²

These independently verified results position OSMORIA as a reliable solution for source infiltration systems and nature-based stormwater management strategies.

The interaction between textile, water, and soil

One of the defining advantages of OSMORIA aquatextiles is their compatibility with existing infiltration systems, including:

• Swales

• Reservoir pavements

• Drainage trenches

• Open infiltration basins

• Underground basins

• Permeable pavement systems

Their maintained permeability, between 40 and 100 mm/s, ensures continuous infiltration performance even during intense rainfall events and even once maximum adsorption capacity has been reached.

Part 3 | The benefits of aquatextiles for infiltrated water quality

Measurable and verified improvements in water quality

After treatment through an infiltration system equipped with OSMORIA Geoclean aquatextiles, hydrocarbon concentrations remain at or below 0.7 mg/L.

For comparison, the legal discharge threshold for Class 1 oil separators is set at 5 mg/L, a limit seven times less demanding.

For PAHs, which are particularly concerning because of their carcinogenic properties, retention rates of up to 78% for certain probable carcinogens provide a level of infiltrated water quality that conventional pretreatment systems struggle to achieve.

Long-term protection for soils and groundwater

Durability is one of the key advantages of OSMORIA aquatextiles for project owners and municipalities. Their service life exceeds 100 years according to NF EN ISO 13438, making them a long-term solution requiring neither replacement nor planned preventive maintenance.

Studies conducted by CEREMA and LEESU also highlight an important secondary benefit: aquatextiles preserve nearly all functional microbial diversity within hydrocarbon-exposed soils.

This is especially valuable in environmentally sensitive areas such as drinking water catchments, wetlands, and protected natural zones where regulatory requirements are most stringent.

Operational and environmental advantages

From both engineering and project management perspectives, OSMORIA aquatextiles provide several practical advantages:

Integrated directly into infiltration systems

Aquatextiles integrate directly into nature-based infiltration structures without requiring additional pipe networks, electromechanical systems, or complex infrastructure.

No maintenance requirements

Once installed, the system operates autonomously. The textile continuously regenerates through microbial renewal supported by naturally available mineral nutrients.

Adaptability

The OSMORIA Geoclean range is available in three variants, Origin, Crystal, and Pure, allowing engineering consultants to select the appropriate treatment level depending on traffic intensity, contributing surface area, and environmental sensitivity. OSMORIA Indigreen is specifically designed for permeable parking systems.

Environmental traceability

OSMORIA solutions are manufactured in France, and Solmax is certified according to ISO 9001, ISO 14001, and ISO 45001. Environmental Product Declarations are available upon request.

Today, more than 2,500 projects across Europe have implemented OSMORIA solutions in a wide range of applications, including urban parking lots, vegetated swales, infiltration systems beneath cycle paths, construction equipment storage areas, and logistics platforms.

Conclusion | Integrating water quality at source

At Solmax, we believe stormwater management can no longer be approached as a purely hydraulic equation. Regulatory requirements, increasing pressure on groundwater resources, and Water Framework Directive objectives now require water quality to be integrated directly into the design of infiltration systems.

OSMORIA aquatextiles provide a documented technical and environmental response to this challenge. They measurably improve infiltrated water quality, protect soils and groundwater over the long term, and integrate seamlessly into alternative stormwater management systems.

CEREMA and LEESU verified performance data, French manufacturing, and more than eight years of operational field experience provide specifiers and project owners with reliable, independently supported performance evidence for long-life infrastructure projects.