Posts Tagged ‘floating tank covers’

Part 1 of Biogas and Anaerobic Digestion

October 21, 2010

Biogas is formed solely through the activity of bacteria, unlike composting in which fungi and lower creatures are also involved in the degradation process.  Microbial growth and biogas production are very slow at ambient temperatures.  They tend to occur naturally wherever high concentrations of wet organic matter accumulate in the absence of dissolved oxygen, most commonly in the bottom sediments of lakes and ponds, in swamps, peat bogs, intestines of animals, and in the anaerobic interiors of landfill sites.

The overall process of anaerobic digestion (AD) occurs through the symbiotic action of a complex bacteria consortium as show in diagram.  Hydrolytic microorganisms, including common food spoilage bacteria, break down complex organic wastes.  These subunits are then fermented into short-chain fatty acids, carbon dioxide, and hydrogen gases.

Syntrophic microorganisms then convert the complex mixture of short-chain fatty acids to acetic acid with the release of more carbon dioxide, and hydrogen gases.  Finally, methanogenesis produces biogas from the acetic acid, hydrogen and carbon dioxide.  Biogas is a mixture of methane, carbon dioxide, and numerous trace elements.  According to some, the two key biological issues are determining the most favorable conditions for each process stage and how non-optimal circumstances affect each stage as a whole, and the governing role of hydrogen generation and consumption.

Wastewater Lagoons

June 22, 2010

Lagoons

Wastewater lagoons have been used as a process for wastewater treatment for centuries.  In the 1920’s artificial ponds were designed and constructed to receive and stabilize wastewater.  By 1950, the use of ponds had become recognized as an economical wastewater treatment method for small municipalities and industries.  As of 1980, approximately 7,000 waste stabilization lagoons were in use in the U.S. Today, one third of all secondary wastewater treatment facilities include a pond system of one type or another.  Of these, just over 90% are for flows 1 MGD or less.  But ponds can be used for larger cities for wastewater treatment as well.  Some of the largest pond systems in this country are in Northern California, serving such cities as Sunnyvale (pop. 105,000), Modesto (pop. 150,000), Napa (pop. 175,000), and Stockton (pop. 275,000).

Floating tank covers can be custom designed for lagoon or tank applications.   Floating covers are a cost-effective alternative to many aluminum or fiberglass dome applications and do not require venting (non-gas-collection applications), recirculation or explosion proof equipment.  Tank covers can adapt to varying water levers and in-basin equipment.  They also install easily and quickly.

What Do Floating Covers Do?

April 15, 2010

A floating membrane cover installed over the surface of a lagoon or tank rises and falls with the changing level of the liquid.  When used on water reservoirs, floating covers protect the contents from contamination and evaporation.  Used to cover chemical, industrial waste and wastewater lagoons they protect the surrounding area from the material contained.  Floating covers can also collect methane, which is released when anaerobic digestion takes place in concentrated animal feeding operations (CAFO) and food processing plants.  The methane (biogas) is often used to help power the facility, or it may be sold to utility companies for resale.

The cover shown includes a series of floats arranged in strings of parallel pairs with weights centered between them, forming troughs.  The floats that are laid out around the cover create sufficient tension to allow workers to walk on it.  That tension also channels rainwater to the troughs, then to dewatering pumps for removal.

While material selection for floating covers is site-specific, in all cases it must be resistant to UV degradation, tears, and punctures; it must have excellent seam strength—enough to hold up to foot traffic; and it must be very flexible.  The type of liquid contained, its chemical composition, its temperature range, the ambient temperature range, environmental conditions, and the intended function of the cover are some of the variables that must be considered.  For example, reinforced polypropylene was used for the water reservoir shown.

Floating covers are an economical way to protect water resources in ponds and reservoirs. Compared to building a tank, a pond with a floating cover is a much less expensive option. Floating covers have many uses from the storage of potable water to the collection of biogas from waste water.

Custom Floating Tank Covers

April 13, 2010

Floating Tank Covers

Floating tank covers can be custom designed for lagoon or tank applications.   Floating covers are a cost-effective alternative to many aluminum or fiberglass dome applications and do not require venting (non-gas-collection applications), recirculation or explosion proof equipment.  Tank covers can adapt to varying water levers and in-basin equipment.  They also install easily and quickly.


Tank Co
ver Advantages:

  • maintenance free
  • fabricated to your exact tank shape
  • the contents of the tank can be mixed without removing the cover
  • hatches provide access to in-basin equipment
  • can be designed to operate around piping/mechanicals inside the tank

Floating tank covers are used on open topped tanks where a structural cover would be too expensive. Floating tank covers are made with flexible geomembrane materials made to stand up to sunlight and the many chemicals found in tanks.