Why Gas and Odour Emissions in WWTPs Are an Environmental Issue

Wastewater treatment plants (WWTPs) play a critical role in safeguarding public health and the environment. However, the treatment process itself can become a source of environmental concern if not properly managed — particularly when it comes to gas and odor emissions.

During various stages of wastewater processing, such as sludge thickening, primary sedimentation, and biological treatment, volatile compounds are released into the atmosphere. Among the most prevalent are hydrogen sulphide (H₂S), ammonia (NH₃), and organic mercaptans. These gases are not only unpleasant to smell, but they also pose health risks for workers and nearby communities. Prolonged exposure to hydrogen sulphide, for instance, can cause respiratory problems and, at higher concentrations, be life-threatening.

From an environmental standpoint, these emissions contribute to air pollution, accelerate corrosion in equipment and infrastructure, and undermine the sustainability goals of water management authorities.

In response, regulatory bodies across Europe and beyond are tightening controls on air quality around WWTPs. Odor management is no longer a secondary issue — it’s a key component of plant design and compliance. This is where modular FRP covers (fibre-reinforced plastic) come into play, forming an essential first line of defense by sealing off open tanks and channels, allowing for controlled gas capture and treatment.

How Modular FRP Covers Help Minimise Environmental Impact

Modular covers made from fibre-reinforced plastic (FRP) are an increasingly common solution for controlling emissions in wastewater treatment plants. Their core function is simple yet crucial: isolating odour and gas-emitting components of the treatment process — such as sludge tanks, screw conveyors, or grit chambers — from open-air exposure.

Key Environmental Benefits

Containment of Hazardous Gases

By enclosing tanks and channels, FRP covers prevent harmful gases like hydrogen sulphide and volatile organic compounds (VOCs) from escaping into the environment. This containment allows facilities to implement downstream gas capture and treatment systems, such as chemical scrubbers or biofiltration units, reducing the environmental footprint of the plant.

Corrosion Resistance and Durability

WWTPs are harsh environments, especially due to the presence of aggressive gases. FRP covers are designed to withstand long-term exposure to corrosive agents such as H₂S and mercaptans without degrading — unlike metal or concrete structures, which require frequent maintenance or replacement. This results in lower environmental impact over the lifespan of the installation.

Modular and Adaptable Design

The modular nature of these covers allows them to be custom-built and installed over existing infrastructure, extending their application to both new and retrofitted facilities. They can be designed in flat, dome-shaped, circular, or rectangular formats depending on the needs of the site, making them an environmentally responsible upgrade without the need for major structural changes.

Reduced Need for Chemical Products

By ensuring effective gas containment, these systems reduce the dispersion of contaminants, which can limit the volume of chemicals needed in downstream gas treatment systems. This indirectly helps reduce the use and storage of hazardous substances on-site.

Tecnium’s FRP Covers: Engineering for Sustainability

At Tecnium, environmental protection is not an add-on — it’s an integral part of every engineering decision. Our modular FRP (fibre-reinforced plastic) covers are designed with the specific challenges of wastewater treatment plants in mind, offering both operational performance and environmental safeguards.

Modular Covers

Designed for Harsh Conditions

Tecnium covers are engineered using high-quality polyester reinforced with glass fibre, ensuring long-term resistance to corrosive environments. These include gases such as hydrogen sulphide (H₂S) and mercaptans, commonly found in sludge treatment areas, screw conveyors, and settling tanks. Thanks to a precise design process based on laminated structures and ribbed reinforcement, the covers maintain mechanical integrity even under extreme stress or high load scenarios.

Customised for Any WWTP Configuration

Whether for circular sludge tanks, rectangular biofilter beds, or screw conveyors, Tecnium offers tailored solutions that adapt to the layout of each facility. Options include:

  • Domed (self-supporting) covers for tanks and thickeners.

  • Flat or rectangular modular covers for open channels and biofilters.

  • High-resistance fabric flat covers for grit removal areas, pumping pits, or fume-prone locations.

  • Covers integrated with gas collection systems, easily connectable to odour control units.

These configurations provide full flexibility while maintaining a uniform aesthetic, with integrated colouring during the lamination phase and optional paint finishes that help blend into the site’s surroundings.

Modular Cover

Maintenance-Free and Easy to Install

One of Tecnium’s greatest advantages lies in the reduced operational cost of its covers. The corrosion-free nature of FRP means no painting, rust treatment, or structural repairs — all of which are commonly required with metal solutions. In addition, the modular design allows for fast, safe assembly and disassembly during inspections or maintenance without specialised tools or teams.

Why WWTP Operators Choose FRP Covers for Compliance and Cost Efficiency

Enabling Compliance with Environmental Regulations

Modern wastewater treatment plants (WWTPs) must meet increasingly strict environmental regulations regarding odor control, gas containment, and air quality. FRP modular covers from Tecnium play a central role in helping operators stay compliant:

  • Odor Containment: Closed structures prevent the release of gases such as H₂S, ammonia and volatile organic compounds (VOCs), which are tightly regulated due to their environmental and health impacts.

  • Integration with Air Treatment Systems: Tecnium covers are designed to support active gas capture and redirection to scrubbers, biofilters, or chemical odor control systems, ensuring full-cycle containment and purification.

  • Compliance with Occupational Safety Standards: By minimizing the presence of toxic gases near operating personnel, Tecnium’s covers help WWTPs meet workplace safety directives like EU Directive 98/24/EC or OSHA air quality standards.

Reducing Operating and Maintenance Costs

Unlike steel or aluminium alternatives, FRP covers offer a low total cost of ownership:

  • No Corrosion, No Repainting: Resistant to corrosion from chemical and biological agents, FRP covers do not require regular repainting or anti-corrosion treatment.

  • Fast and Safe Access: Modular panels can be individually removed for inspection or intervention without dismantling entire structures, saving time and reducing disruption.

  • Long-Term Structural Stability: The material’s resistance to UV radiation and environmental stress means fewer repairs and replacements over decades of service life.

Contributing to ESG and Circular Economy Goals

FRP covers not only support regulatory compliance and cost control but also align with broader environmental, social, and governance (ESG) goals:

  • Reduced Chemical Use: By sealing off open tanks and channels, the need for chemical neutralisers in open-air odour dispersion is reduced.

  • Durability and Recyclability: The long service life and reusability of FRP components contribute to circular economy principles.

Case Studies: FRP Covers in Action

Sludge Thickeners: Odour Control and Structural Integrity

In municipal wastewater treatment plants, sludge thickeners are known sources of foul odours, primarily due to the decomposition of organic matter and release of hydrogen sulphide (H₂S). Tecnium’s FRP modular covers, installed over several large-diameter thickeners, have demonstrated:

  • Effective odor containment by isolating emissions and directing gases to chemical scrubbers.

  • Ease of access for maintenance via removable modular panels without structural compromise.

  • Structural performance under extreme weather conditions and gas-induced corrosion.

One notable installation featured a 36-metre circular FRP dome with integrated gas extraction ports, offering both compliance and operational durability.

Biofilter Covers: Lightweight and Maintenance-Free

Biofiltration systems rely on maintaining consistent humidity and temperature within the filter media. Tecnium’s rectangular FRP covers for biofilters:

  • Ensure protection from external weather fluctuations.

  • Prevent moisture loss, improving filter longevity and efficiency.

  • Require zero maintenance, even under continuous operation in aggressive environments.

Plants operating in coastal and industrial regions, where corrosion risks are high, have especially benefited from the resilience of Tecnium’s polymer-based solutions.

Screw Conveyors and Grit Chambers: Safety and Environmental Protection

Open screw conveyors and grit chambers are frequent sources of accidental emissions and odour complaints in urban WWTPs. Tecnium’s flat modular FRP covers have been applied to these components with tangible improvements:

  • Improved workplace safety by minimizing exposure to aerosols and gas build-up.

  • Environmental containment that complies with urban air quality standards.

  • Visual integration with plant surroundings thanks to custom pigment options.

The use of Tecnium’s covers in such applications has proven critical in public-facing installations where community concerns are a growing operational factor.

Designing for the Future: Tecnium’s Commitment to WWTP Innovation

As environmental regulations tighten and urban populations grow, the need for efficient, durable, and sustainable solutions in wastewater treatment becomes more urgent. Tecnium’s modular FRP cover systems are not only a response to current challenges — they are an investment in future-ready infrastructure.

Long-Term Environmental Impact

By containing emissions and reducing chemical exposure, these covers contribute directly to:

  • Improved air quality in surrounding urban and industrial zones.

  • Reduced chemical usage thanks to compatibility with closed-loop odour control systems.

  • Minimized water contamination risks via splash and aerosol containment.

This aligns with broader sustainability goals and enhances public trust in water treatment operations.

Tailored Engineering for Modern Facilities

Tecnium’s engineering team collaborates closely with WWTP designers and plant managers to:

  • Adapt covers to existing structures without major civil works.

  • Integrate gas extraction systems and access hatches as needed.

  • Ensure aesthetic and structural cohesion within complex plant layouts.

Whether upgrading legacy infrastructure or designing new installations, Tecnium delivers robust solutions that scale with operational needs.

Future-Oriented Materials and Design

Tecnium continually invests in material science and fabrication techniques to stay ahead of industry demands:

  • Use of UV-resistant gelcoats and long-lasting pigments for outdoor installations.

  • Modular systems designed for quick assembly and minimal downtime.

  • Integration with smart environmental monitoring systems (upon request) to anticipate maintenance and optimise performance.

Protect the Environment While Future-Proofing Your Facility

At Tecnium, we understand that every wastewater treatment plant faces unique environmental and operational challenges. Our modular FRP cover systems offer a smart, compliant and sustainable solution for odour control, emissions reduction and long-term structural protection.

Get in touch with our engineering team today and discover how our tailored designs can support your facility’s environmental goals — efficiently, durably, and with zero compromise.