The Future of Water Reuse

With the nation in a drought, the reusing of water is now more important than ever. Here are ways water treatment plants can help.
By: Dr. Phil Rolchigo

Around the country, more and more cities are faced with a diminishing water supply due in part to uncontrollable circumstances such as extended drought and changing weather patterns. Conservation alone is not enough to reverse the trend. With more than 32 billion gallons of municipal wastewater produced every day in the United States, water reuse, the use of treated wastewater for beneficial purposes including irrigation, industrial uses, and drinking water augmentation, has the potential to increase the nation’s total water supply, while also providing an additional revenue stream for municipalities.

As a result, we are seeing three emerging trends in the area of resource recovery from wastewater: Municipal Water Reuse Solutions

Many municipalities are exploring opportunities to expand capability and increase revenue through both direct and indirect water reuse. And, while the technology exists to return wastewater to potable drinking water standards, a more profitable—and perhaps less controversial— avenue is to direct this effluent water to industrial, agricultural and energy customers, since they consume more than 85 percent of our freshwater nationally.
Progress is being made in the acceptance of utilizing reclaimed water to augment our nation’s water supply. California has enacted legislation that reclassifies recycled water as a water resource, as opposed to a waste product. Similarly, the governor of Oklahoma recently signed a law to encourage water reuse, and Florida’s most recent water reuse report indicated that 719 million gallons of water was beneficially reused each day in 2013—the largest in the country.

Nutrient Recovery Solutions
One challenge encountered at many wastewater treatment plants is the concentration of large quantities of nitrogen and phosphorus in their sludge dewatering systems. The dissolved nutrients promote the formation of obstructive scale in pipes, pumps and valves resulting in severe impact to plant reliability, efficiency and operating and maintenance costs. Now, with the help of nutrient recovery technology from companies such as Ostara, municipalities can overcome these challenges by recovering up to 85 percent of the phosphorus and 25 percent of the nitrogen from the wastewater stream before they accumulate in the equipment. With the Ostara process, recovered nutrients are then transformed into a slow-release, eco-friendly fertilizer —providing a revenue stream to the utility. In addition, the process helps plants to meet increasingly stringent discharge limits while improving operating reliability.

Industrial Wastewater Solutions
Water and energy are intrinsically linked—we need energy to treat and move water, and we need water to create energy. Anaerobic bioreactor technology allows us to derive energy from wastewater. Traditional anaerobic bioreactors convert the organic matter in wastewater to a level suitable for discharge to a municipal water treatment system while converting the organic matter into biogas. However, these systems have a large physical footprint and the resulting effluent is often challenging for municipal plants to treat and is not suitable for discharge to local surface waters due to the remaining organic matter.
To address this challenge, Pentair developed a ground-breaking solution in collaboration with Veolia Biothane: the MemthaneTM Anaerobic Membrane Bio-Reactor system. This new design utilizes state of the art ultrafiltration membranes to significantly improve the efficiency of the anaerobic bioreactor. Water discharged from this system is of a higher quality than previously possible and thus suitable for recycling. At the same time, greater levels of high quality biogas are produced and can be utilized for local energy generation.

This technology is broadly applicable to the food and beverage industries with high organic content wastewater streams, such as distilleries, dairies, and bio-ethanol production. It is particularly useful in water stressed regions, and is currently deployed in plants across Europe and the United States.

Phillip M. Rolchigo, Ph.D., is Vice President of Technology at Pentair leading its Global Research, Development and Engineering functions. He may be contacted at phil.rolchigo@pentair.com.

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