The COvered High- Rate Anaerobic Lagoon, or COHRAL™ is a modified anaerobic lagoon-type process, but is equipped with several design features to enhance treatment performance beyond that of a traditional anaerobic lagoon. Features like expanded reaction zones, external solids/liquid separation ensure superior treatment performance and high-quality effluent from a simple treatment process.
Typically constructed as an earthen basin with a concrete ringwall at the top perimeter, COHRAL™ systems are also entirely covered by a gas collection membrane cover, designed to facilitate the gas collection, prevent odors, retain heat, and maintain optimal anaerobic conditions. Within the reactor itself, the reaction zone takes up to 75% of the lagoon while the rest of the available space serves as post-treatment digester and (pre-) settling zone.
A partial clarification of the effluent takes place in that final zone, and the settled sludge is pumped back to the inlet area of the lagoon to ensure good biomass-to-waste contact for treatment. Recycling of anaerobic effluent is necessary to allow for sufficient flow and movement into the sludge layer in the lagoon, for dilution, and for prevention of overloading. In applications where an unusually low solids effluent is needed, for example in cases where further aerobic treatment is required, the lagoon is followed by a compact, cross-flow lamella separator (GWE’s SUPERSEP™ – CF), which is installed adjacent to the lagoon reactor.
Industries and applications: as an anaerobic treatment of the various industry wastewater streams, including cassava processing, breweries, distilleries, starch production, meat processing, and many more.