Posts Tagged ‘potable water’

Floating Covers For Evaporation and Odor Control

November 11, 2010

Floating Cover Applications

Properly designed reservoir floating cover systems prevent fluid loss due to evaporation, reduce chemical demand and improve water quality by preventing contamination from bird droppings, airborne particulates, dead animals pollen and other pollutants.  Floating covers block off sunlight preventing algae bloom.  They also reduce the production of trialomethane (THM) type compounds such as chloroform from forming that result from the combining of organic substances with chlorine due to reductions in chlorine demand.  In anaerobic digester systems, floating covers are increasingly being used to capture organic gases and to reduce biological oxygen demand (BOD).

Floating cover systems were introduced over 30 years ago.  Many have provided a service life beyond 20 years.  When first introduced, materials and designs were not developed and in some cases had limited success. Today, with advancements in design and materials, floating covers offer the low cost quality solution of choice where water quality standards require potable water reservoirs be covered.

Floating cover applications range from anaerobic digestion covers for wastewater systems, to potable water reservoir covers for municipal drinking water applications.  In farming applications they have been successfully used with enzymes to capture methane gas that is used to fuel electricity producing generators that can satisfy 150% of a typical swine farm’s electrical power requirements.  This alternative generates renewable “green energy” from an otherwise polluting system that provides zero return on investment.  In agricultural and other water management applications, floating covers are increasing  being used for evaporation control and odor control.


Why Use Floating Covers?

October 12, 2010

Floating Cover Systems

Floating Cover Systems are successfully used in several commercial and municipal applications.  Some examples include:

  • evaporation and algae growth prevention
  • potable water protection from pollution and contamination
  • odor and emission control
  • biogas recovery for power generation or flaring
  • protection of birds and waterfowl from contact with hazardous liquids
  • remediation contamination

Why Use Floating Covers?

The best engineered floating cover systems cost 75% to 85% less than most every acceptable rigid roof structure.  A single floating cover can exceed over a million square feet / 93,000 square meters of surface area and be viable.  Saving of natural resources is another large factor that should be considered.

Floating cover systems prevent water loss due to evaporation; greatly reduce algae growth and treatment chemical demand resulting in improved water quality.  They also provide barriers against contamination by dead animals, airborne particles such as pollen and bird droppings.

In potable water contamination applications, another advantage is treatment chemical cost reduction and positive health impact as considerably less chlorine is required in covered reservoirs.  Using less chlorine in potable water enhances safety by reduced production of trihalomethane (TTHM) (a methane-derived compound that contains three halogen atoms, e.g. chloroform, formed especially during the chlorination of drinking water) type compounds like chloroform that result from the combining of organic substances with chlorine.

Floating Cover Systems have been used for about 35 years.  Service life’s of 20 years or more have been recorded in potable water applications.  Gas collecting floating cover systems can be expected to perform for about ten years.

Floating Covers For Potable Water

September 21, 2010

Floating Cover Systems For Potable Water

Floating covers prevent losses through evaporation.  Odor and taste free, they help protect potable water supplies by minimizing reservoir contamination from dust and dirt, leaves, insects, animals, etc.  Literally tons of such debris can collect at the bottom of uncovered reservoirs.  This can actually trap chlorine, and make it difficult, if not impossible, to maintain a sufficient amount in the water itself.

Floating covers also exclude sunlight.  This reduces problems with algae growth and chlorine depletion.  Floating cover systems are customized for each client’s lagoon or tank size and shape.

The American Water Works Association and many states recommend covering all reservoirs containing potable water that will be delivered directly to customers.  Some states even require it.

Floating cover applications:

  • any type of gas collection from water basin
  • keep rain & snowmelt water separate from wastewater under the cover

Geosynthetics In Agricultural Applications

August 3, 2010

Agricultural Use Of Geosynthetics

Agricultural use of geosynthetics is one of the fastest growing market segments worldwide.  The earliest geosynthetics applications were for on farm use and some of the earliest specifications were directed at agricultural use of pond linings.  These early uses included the lining of ditches to help save valuable water as well as the lining of farm ponds and water harvesting catchments in the arid regions of the world.

Today, there is a wide variety of applications ranging from covered and uncovered ditch linings and ponds to protection of the groundwater and surface waters that are being polluted by animal waste.  The use of geosynthetics and in particular geomembranes on the farm has come a long way and has grown significantly in recent years, especially with more stringent governmental legislation as well as public awareness through programs such as those developed by the USDA/NRCS, U.S. EPA and governmental agencies in other countries.

Containment As A Requirement

Potable water sources are becoming more and more scarce and water is becoming more costly.  The requirement to provide a barrier against high rates of water seepage loss is already a reality in many more areas than just the arid and semiarid regions of the world.  And, just as water is important to conserve, it is even more important to environmentally protect surface and groundwater sources from pollution due to animal waste and the air we breathe from noxious gases and odors.  Again, containment with a reliable time proven method is a requirement, not just an option due to  environmental legislation in many parts of the world.

Shown here: Anaerobic digesters with waste lagoon

Geosynthetics will provide a reliable cost effective alternative to traditional compacted soil and clay liners that provide much less in seepage control, are highly variable in quality and may not be acceptable for design and regulatory compliance.  Although geomembranes are the primary type for use as a barrier or odor control cover, other geosynthetics are used in conjunction with geomembranes and include geotextiles, geo-composites, and geonets.

Animal Waste Lagoon Liners

Animal waste lagoons contribute to the pollution of ground and surface waters worldwide.  To control waste seepage, compacted earth linings as well as geosynthetics are utilized.  However, with the increasing concern over pollution and governmental legislation, the use of geosynthetics has been increasing very rapidly.  In particular, exposed geo-membranes, geo-membranes with soil cover and GCL’s with soil cover are currently being used.  In addition, geo-textiles and geo-net composites are utilized for protection / gas transmission.

Animal Waste Odor Control Covers

A growing number of scientists and public health officials have traced a variety of health problems to vast amounts of concentrated animal waste which emit toxic gases such as hydrogen sulfide and ammonia.  Odor control covers can be a low cost geomembrane or coated fabric or they can be a more expensive engineered floating geo-composite cover system dependent on the design and criticality of the containment.

Shown here: Irrigation canal

Water Conveyance
Geosynthetics and most notably geomembranes have been used for decades in preserving and transporting clean water for on farm use.  The conveyance of water in ditches, laterals and main canals for delivery to crops is as common as on farm water storage tanks and ponds.  However, water is becoming more and more scarce and more costly especially with the drought conditions in many parts of the World.  Seepage loss in canals and ditches can approach 30 to 50% but loss of valuable water can be eliminated with the use of geosynthetics as lining systems.  Both soil covered and exposed geomembranes are used extensively in the lining of both new and old canals that require rehabilitation.

In addition, old cracked concrete lined canals have lost their effectiveness over the years and are being replaced or repaired with geomembranes.  Water conveyance systems utilize other geosynthetics in conjunction with geomembranes such as protection geo-textiles, geocomposites and geo-grids.

Water Containment
Water containment in ponds and concrete tanks for on farm use is just as important as water conveyance in that seepage and loss of valuable water should be minimized, especially for remote ponds and tanks.  Soil covered geomembranes and GCL’s are used for the construction of new or the rehabilitation of old ponds.  Exposed geomembranes are used to re-line old stock water concrete tanks or to line

Anaerobic Digesters
Anaerobic digesters are used to rapidly decompose animal waste in a controlled environment thus allowing the recovery and use of methane-rich low Btu biogas.  Biogas is used to fuel combined heat and power (CHP) generators that produce on farm electricity, process heat and domestic hot water.  They are also a viable method of waste management due to the fact that both bottom lining systems as described above and flexible cover systems are used.  With every digester constructed, geosynthetics are used to either line the anaerobic lagoon or cover the lagoon for collection of biogas. The number of operating digesters is rapidly increasing worldwide as government funding is becoming available for farm installations.

Data provided with compliments and R. Frobel.