Membrane technology produces less waste & uses less energy than alternative treatments
The dwindling supply of available fresh water, combined with continued growth in water usage, makes it vital that communities and industries improve on water reclamation efforts.
A key to that reclamation is more efficient treatment of water and wastewater, whether for human consumption or industrial process water at lower cost and less damage to the environment. For this, Steven Gamelsky, P.E., president of civil-environmental engineering firm GEA Engineering P.C., recommends membrane technology, in the form of micro filtration, ultra filtration and reverse osmosis filtration.
“Membrane technology does a superior job at water treatment, producing better water quality with less waste,” says Gamelsky. “Membrane filtration does a much more thorough job at considerably less expense than technologies such as sand filtration.”
Gamelsky points out that sand filtration often requires expensive pre-treatment chemicals to flocculate wastewater so that sand filters can catch the main contaminants. However, those chemicals create a large volume of sludge that adds significantly to disposal costs.
Also, water that has been reclaimed through sand filtration often requires expensive secondary processing because it is relatively ineffective at removing hazardous microbes and VOCs.
Many local wastewater treatment plants, even some that use membranes (in membrane bioreactors) use a wastewater process based on the “activated sludge process,” which requires extensive aeration.
“We’re not a proponent of aeration-based systems because they are very energy-intensive,” Gamelsky says. “We prefer to use a variation on the trickling filter process called an “attached growth process.”
Rather than utilizing aeration, this process requires recirculating wastewater to trickling filters, biodiscs or biofilters, then taking the discharge and sending that to a membrane filter. This process is as effective as the activated sludge process, but saves on energy. The EPA has characterized the trickling process as requiring 25 to 35% of the energy of the activated sludge process.
Gamelsky’s firm has partnered in engineering many in-plant reclamation projects in India, where governments require industries to recycle their wastewater.
“Many industries require a lot of clean water, including the textile, food processing, pharmaceutical, utilities and automotive,” Gamelsky explains. “As a result, often overseas governments require these industries to recycle wastewater for reuse as process water. Using membrane technology including microfiltration, ultra filtration and reverse osmosis, we helped them achieve a standard recovery of approximately 75 to 85%. We’re also doing zero liquid discharge systems where they recover 100%.”
Membranes are an excellent filtration medium for potable water as well, says Gamelsky. Replacing traditional coagulation and sand filtration and disinfection systems with membranes is a cost-effective method of removing sediments, salts, and excess minerals (high total dissolved solids), microorganisms and other contaminants to produce potable water of excellent taste and purity.