Floating ballast balls or plates are a new entry into the floating cover market. Balls and floating geometric plates are made from plastic and offer many traditional benefits of floating covers. Individual balls or hexagonal plates are not connected but drift naturally into orderly, close-fitting configurations with minimal space between them. Thermal insulation and light-blocking ratings for balls are in the 90% range, while those for hex plates are even higher. Modular floating objects like balls and plates are the simplest to install - essentially, this involves dumping sacks of balls or plates into the basin until the surface is covered. The balls and plates automatically rise and fall as water levels change, stacking and reforming to maintain complete surface coverage.
A valid sales point for floating ball and hex covers is their ease of access and minimal maintenance requirements. Since the balls move effortlessly, creating gaps to allow debris and water to flow through, there's no need for annual cleaning and inspection. Access for water sampling or equipment maintenance is simply a matter of pushing balls aside while you work. Once finished, the balls float back into place.
Interestingly, the same qualities that make these disconnected floating covers exceptionally easy to install and access mean they can't provide the same benefits as flexible, impermeable geomembrane covers. No matter how closely they float together, discrete objects like floating balls can't stop rainwater from carrying in contaminants or flooding the storage pond. In a similar vein, while they offer visual deterrence to animal and human visitors, if an animal or person were to walk up to the edge, there's nothing to keep them from drinking or climbing into the water once they push the balls aside.
Even relatively small ponds and tanks can experience intense wind that can cause waves to damage the surrounding banks. A flexible, solid, floating cover stops waves, prevents erosion, and is securely anchored to avoid lifting even during severe storms. Floating balls are free to move with the wind, so they are rarely damaged, but they're also prone to blowing away entirely in a strong enough wind.
Since floating balls move freely and accommodate objects passing through the cover, they offer no physical barrier to curious animals, debris from storms, or litter that seems to appear out of thin air. Scum and other floating rubbish drift around until they are manually removed. Passive but effective solutions like scum submergence don't work with a floating cover made of independently moving objects.
Choosing a floating ball system primarily for ease of installation or reduced maintenance demands will cost you some of the most significant benefits of a cover. In addition to lacking control over water entering the pond or reservoir, floating balls do nothing to stop the escape of gases generated by the water they're covering. Only an impermeable layer of geomembrane will capture gases so they can be safely released or stored and put to good use. Selling or using the methane generated by manure and sewage lagoons is a great way to offset the costs of building these management structures and covering them. Since wastewater ponds pose a high risk of environmental damage if water runs in and floods out their contents, geomembrane covers with sump pumps are the best option for keeping them at a steady level.
Combined Systems
Some floating covers designs reach for the best of both worlds by combining the two systems. A layer of geomembrane is installed first, with floats, to control evaporation and contain gases. Ballast balls are then added on top of the geomembrane to replace the usual weights and add extra UV protection to extend the life of the solid cover. Unfortunately, you're unlikely to see a long-term benefit here because you're buying two systems that don't always complement each other.
Instead of being essentially maintenance-free, operators must remove floating balls annually to clean the geomembrane. Debris that passes right by the floating balls remains there, atop the geomembrane. Access still needs to be planned since the geomembrane can't be so easily pushed aside, and as any engineer knows, an increasingly complex system with additional moving parts often adds more failure points.
