Gas Collection Covers

High Rate Anaerobic Lagoon Covers Including Biogas Collection

An effluent anaerobic system requires a covered lagoon with an oxidation and settling pond. An anaerobic system provides many benefits, such as:

  • Land surface area required is approximately half that of an aerobic system.
  • Required retention time is dramatically reduced
  • Because an anaerobic system has the first lagoon encapsulated, most odour problems do not exist.
  • With Fabtech’s design, methane gas is collected and co-generated, providing a tangible pay-back period. You can generate your own power to use and sell, dependent upon your needs.
  • The system ultimately pays for itself and contributes to profitability.

System Description
Anaerobic systems incorporate the use of flexible membrane covers to collect methane gas. This methane gas is collected from around the perimeter via a perforated piping system and then processed in either flaring or co-generation.

Specially designed weights and floats are attached to the cover membrane, which cause the horizontal ‘planes’ or ‘plates’ of the cover to be under tension in two directions. This tension eliminates slack in the cover, providing necessary stability across the surface, as well as clear drainage. Besides providing tension, the weights and floats define the precise location and size of rainwater sumps. At the bottom of the sumps, automatic submersible pumps are placed to discharge rainwater from the cover to wastewater outside the lagoon basin.

Due to its design, Fabtech’s floating cover system has the added benefit of being able to operate and accommodate any fluctuation in the level of the lagoon. The cover is also able to operate as a short term storage facility for any gas produced that can not be immediately processed.

Flotation and gas passages to the piping are manufactured from a closed cell polyethylene foam wrapped in polypropylene and attached to the underside of the cover. The cover is anchored to the top perimeter gas collection pipe.

The gas handling system includes design of the gas and delivery system, pressure control, strainer, fan, control panel, flare stack, flame supervision, instructions, manuals, commissioning and delivery to site, all as a complete package. The flare would be tested completely in the shop, then dismantled and shipped to site. Once installed, Fabtech’s Effluent Anaerobic Lagoon System is simple, environmentally friendly and cost-effective.

Bio-gas flare installed on an anaerobic effluent treatment pond.
An anaerobic digestion pond is covered with a membrane that captures methane produced during the digestion process. This methane and an assortment of other gases are then drawn (via a booster fan) through a gas train system and into an automatically controlled flare.

The flare has an interrupted pilot and flow system that senses the accumulated pressure in the pond and only operates when required. The flare control system also sends signals to the main treatment plant Scada control system to display any malfunctions that may occur.