Water Environment & Technology (WE&T) is the premier magazine for the water quality field. WE&T provides information on what professionals demand: cutting-edge technologies, innovative solutions, operations and maintenance, regulatory and legislative impacts, and professional development.
Sustaining San Diego
Because of its limited local water sources, the city of San Diego relies on imported water for approximately 85% of its water needs. To help reduce its reliance on importing water, the city embarked on a three stage water reuse program.
The first stage, which was completed in 2006, was a comprehensive evaluation of methods for maximizing recycled-water use. The second stage, which is ongoing, is a demonstration project to evaluate the feasibility of using advanced treatment technology to produce purified water that can be stored in a reservoir, then treated and distributed as potable water. The third phase, should the demonstration project succeed and contingent upon funding and approval, would involve building a full-scale purification facility and transmission pipeline.
By itself, the town of Highfill, Ark. (pop. 560) would have a hard time finding the technical, financial, and other resources needed to provide wastewater treatment facilities to meet some of the most stringent phosphorus removal requirements in the country.
The same thing is true of nearby Tontitown (pop. 2460) or even much larger Bentonville (pop. 35,300). But as these three and seven other northwestern Arkansas communities learned, they can accomplish much more working together than going it alone.
From 'yuck' to 'yes'
It’s no longer a question of whether treated wastewater will someday become a common contributor to the world’s drinking water supply. It’s a question of when.
That’s the conclusion of four University of California–Davis engineering professors in a new white paper on direct potable reuse published by the National Water Research Institute (NWRI; Fountain Valley, Calif.).
“We’re now treating wastewater to such high-quality standards, it only makes sense to reuse it, especially in places where other sources are already in short supply,” said George Tchobanoglous, one of the report’s authors. “For some municipalities to continue to import water, use it once, treat it, and pump it into the ocean is simply unsustainable.”
Coming in the next issue:
Stormwater ebb and flow
Managing stormwater effectively can bring many new responsibilities for utilities. Choosing, installing, and maintaining stormwater controls requires time, money, and effort. And any source of uncertainty, such as new and changing regulations and requirements, can cause unease.
On the other hand, some stormwater controls, such as those based on green infrastructure principles — tree planting, stream restoration, rain gardens, green streets, and wetland projects, to name a few — do more than just manage flows and protect water quality. These techniques also raise property values, lead to lower energy bills for residents, improve air quality, and create local jobs. Triple-bottom-line assessments can help to quantify these benefits and point out the advantages that stormwater management can provide.
Cleaning the cleaners
When the cleanest effluent is needed, engineers and operators often turn to membranes. Tiny pore sizes help to ensure that most impurities are left behind. But those tiny holes also represent the greatest challenge of membranes: fouling and clogging.
During normal operation, biofilms accumulate on membranes. Traditional solutions for biofouling include chemical treatment, frequent backwashing, and air sparging. But a new approach turns the biology that causes biofouling back on itself. Researchers are experimenting with using bacteriophages — that is, viruses that infect bacteria — to control growth of the microorganisms responsible for biofouling.
When headworks units malfunction, debris and large solids can enter membrane systems, cause damage, and potentially compromise treatment. During such an event, a treatment plant turned to an automated machine to thoroughly clean its membranes quickly, so it could get back to the business of producing excellent effluent.
©2012 Water Environment Federation. All rights reserved.