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FRP Anaerobic Digesters

Products / FRP Process Equipment / Equipment for Sewage Treatment Plants (STP)

FRP Anaerobic Digesters are specialized FRP vessels designed to handle the anaerobic digestion of sewage sludge and organic waste. These digesters are completely sealed (gas-tight) FRP reactors that promote bacterial breakdown of sludge in the absence of oxygen, producing biogas (methane and CO₂) and stabilized solids. The FRP construction resists the harsh environment inside digesters—hydrogen sulfide, organic acids, and high moisture—which can quickly corrode concrete or steel. Typically cylindrical or egg-shaped, FRP digesters can include integrated mixing systems and hatches. Their smooth, impermeable surfaces prevent leakage of effluent or odorous gas. FRP digesters often feature a domed cover, either fixed or floating, to capture biogas and withstand internal pressure. The composite material’s inherent strength allows thin walls, reducing dead volume, and the light weight simplifies installation of large tanks. In modern STPs, FRP digesters are valued for reliability and minimal maintenance.

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Key Features

  • Gas-Tight FRP Construction: Entire tank and cover made of corrosion-resistant FRP laminate (polyester or vinylester resin) that contains biogas safely.
  • Corrosion Resistance: Resins are selected to withstand hydrogen sulfide, organic acids, and microbial byproducts typical in anaerobic digestion.
  • Structural Stability: High glass-fiber content (often pultruded panels or filament-wound shells) provides the required structural integrity for full tanks and gas pressure.
  • Custom Shapes and Sizes: Available as round or egg-shaped (ovoid) for gravity mixing; sizes range from a few cubic meters to multi-million-liter industrial units.
  • Integrated Accessories: Options include agitator mounts, manways, gas collection headers, safety vents, and observation ports.

Benefits

  • Odor and Gas Containment: Leak-free FRP prevents escape of odorous gases, improving plant hygiene and worker safety.
  • Longevity: Superior resistance to sulfate attacks and biogenic corrosion, meaning decades-long service life vs. 10–15 years for unlined concrete.
  • Low Overall Cost: Reduced maintenance (no concrete repair, no recoating) and lighter foundations offset initial cost.
  • Thermal Efficiency: FRP’s low thermal conductivity can help retain digestion heat in cold climates (or allow easy insulation).
  • Fast Installation: Prefabricated sections or one-piece tanks minimize on-site construction time.

Applications

  • Municipal Wastewater Plants: Primary digesters for sewage sludge, stabilizing solids and producing methane for energy recovery.
  • Industrial Waste Treatment: Digesting high-strength industrial organic waste (food, beverage, pulp & paper effluent).
  • Co-digestion Facilities: Handling multiple waste streams (e.g., food waste, manure) in a single reactor for biogas production.
  • Lagoons and Sludge Holds: Retrofit covers for existing tanks (floating covers) or upgrade of traditional tanks with FRP liners.

Technical Specifications

  • Material: FRP made with corrosion-resistant resin (often vinylester) and high-strength glass (E-glass or AR-glass for acid).
  • Pressure Rating: Designed for slight positive pressures (typically up to 0.1–0.2 bar above atmosphere) to store biogas safely.
  • Temperature Range: Suitable for mesophilic (30–40 °C) or thermophilic (up to 55 °C) digestion processes; FRP tolerates up to ~80 °C in water.
  • Thickness: Wall thicknesses typically range from 5–20 mm, depending on diameter and load requirements.
  • Codes: Often built to meet pressure vessel codes (ASME, EN) if pressurized, or at least ARV requirements for safety.
  • Anchorage: Designed for buoyant forces if unanchored floating cover; certified mounting for heavy sludge loads and hydrostatic pressure.

Unique Selling Points (USPs)

  • Turnkey Biogas Solutions: We deliver not just the tank, but integrated systems (gas piping, flame traps, control panels) for biogas utilization.
  • First-Generation FRP Digesters: Pioneering projects in biogas-enabled STPs show our leadership and proven designs.
  • Odor Control Expertise: Combined use of FRP digesters with carbon filters or bio-scrubbers in our solutions ensures minimal odor from plants.
  • Flexible Design: Fixed-dome, floating-drum, or mobile cover options to suit site space and process needs.
  • Robust Construction: Vacuum-infused/filament-wound panels for extra strength under load, exceeding industry norms.

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