Need for secure containment


Containment of water and wastewater in ponds may be neededfor reasons as wideranging as seepage avoidance to prevention of groundwatercontamination.


Whatever the reason for lining a pond, the use ofgeosynthetics in these types of applications is growing. Geomembranes create anessentially impermeable barrier that prevents any liquid that is in the pondfrom migrating to the subsurface. Geonets, geocomposites, geotextiles andgeogrids may be used to vent gases, cushion against uneven subgrade or providereinforcement as needed.


Potable-wastewater treatment


The water containment applications with the longest historyare those of potable water and wastewater treatment facilities. These types ofapplications primarily are found in industrial and municipal treatmentfacilities. Examples of lined structures include treatment lagoons,sedimentation basins and digestion ponds. The simplest example incorporates ageomembrane as a low permeability barrier between the water or wastewater beingcontained and the subgrade. More complex systems may incorporate geosyntheticsas a protective layer for concrete structures, or in grit chambers and verticalflow control baffles. Geosynthetics also have proved to be an inexpensivealternative to refurbishing older concrete, clay or steel-lined structures thathave begun to crack and leak over time.


Golf and decorative ponds


Up until the mid-1980s, the most common liner for golf andother decorative type ponds was a compacted clay liner. Because these linersare subject to cracking and subsequent leakage over time, geosynthetics now arebeing used to line these types of ponds. Geosynthetics can be installed morequickly and more economically than most compacted clay liners. In addition, thepermeability of a geomembrane can be up to six orders of magnitude less thanthat of a typical compacted clay liner, which results in much more economicaland effective performance.


Deicing ponds


Ethylene and propylene glycols are used extensively indeicing operations. If allowed to migrate into bodies of water, these chemicalsdeplete the available oxygen. Because of this, ponds that store used deicingsolution often are lined with geosynthetics. In most of these applications, thegeosynthetics are used as a barrier material underneath concrete. Suchapplications for deicing operations include detention ponds, deicing pads, snowdumps and settling ponds.

Agricultural applications


As an increasing amount of livestock production is beingconcentrated into large agricultural farms, the need to contain animal wasteproducts is growing. These livestock usually are raised in large barns withconcrete floors. Jets of water spray the wastes from the gently sloped floorsinto waste lagoons. Once in the lagoon, degradation of the waste may beaccelerated by anaerobic microbes. Geosynthetics are used to line holdinglagoons, treatment ponds, floating covers and evaporation ponds.


Aquaculture ponds


Geosynthetics also are used to line holding ponds for shrimpand fish in large aquaculture farms. The lined ponds have many advantages overstandard soil or clay-lined ponds including decreased permeability and ease ofcleaning and harvesting. The low permeability membranes ensure that more waterstays in the ponds. It also assures that disease, should it occur, is notallowed to migrate through the subsurface soils and contaminate other ponds.

Floating covers

Whether the application is for storage of potable water or wastewater applications, floating covers can provide additional protection. Floating covers for potable water applications can limit infusion of contaminants into potable water. For wastewater applications, it can limit rain water intrusion into the pond and prevent nuisance odors from being released. For anaerobic applications such as animal waste containment, it can contain emissions gases and prevent oxygen from entering the pond, thus increasing the efficiency of the anaerobic digestion system.


Summary


There is a wide range of applications in which geosynthetics are being used successfully to improve the process of storing and treating water and wastewater. The applications include decorative ponds, potable water storage and wastewater treatment lagoons. Geosynthetics have lower permeability and generally are less expensive and easier to install than alternative liners.


The Geosynthetic Materials Association (GMA) is directed by the needs of the North American geosynthetics industry. It serves as the central resource for information regarding geosynthetics and provides a forum for consistent and accurate information to increase the acceptance and to promote the correct use of geosynthetics.


Source: New Cloth Market, August-2010


Image Courtesy: geosysindia.com