WERF Recognizes San Antonio Water System for Achieving a Clean Water Trifecta

Polymerized drying bed pour.

This year’s winner of the WERF Award for Excellence in Innovation is the San Antonio Water System (SAWS). A long-time WERF subscriber and active participant in many WERF research projects; San Antonio began its quest to implement their “clean water trifecta” more than 15 years ago. SAWS’ goal to recycle and use all treatment process residuals grew from their conviction that treatment process residuals are valuable resources to be beneficially used, not waste products for disposal. That goal resonates well with recent WERF objectives to help the water quality industry embrace a different view of wastewater – not as a waste, but as a valuable resource. To that end, this year’s Excellence in Innovation award winner has set a strong example for many WERF subscribers to strive to achieve.

In the 1990s, SAWS recognized that water scarcity was plaguing watersheds locally and regionally. Recycled water could be the solution to many environmental challenges. Consequently, SAWS embarked on one of the largest environmental protection and enhancement projects ever conceived and constructed in Texas. SAWS sought to build 130 miles of major trunk lines to deliver 35,000 acre-feet of recycled water. WERF research on water reuse and 21st century water issues influenced the planning, design, and ultimately the outcome of this $140,000,000 project.

Completed in 2011, SAWS reduced aquifer demand by providing highquality tertiary treated recycled water to commercial and industrial customers. SAWS also augmented depleted streamflow through strategic discharge placements for aquatic ecosystem enhancement. Ultimately, 130 miles of pipeline was installed beginning in 1997. The result was that the San Antonio River Authority documented return of logperch and improved turbidity, fecal coliform, and algal growth measurements (documented in a case study in WERF 91-AER-1) on the San Antonio River.

The streamflow enhancement resulting from the strategic discharges were also an important factor in the removal of Salado Creek’s dissolved oxygen impairment on EPAs 303(d) list of Impaired and Threatened Waterbodies. Not only an example of using innovation to affect a regulatory outcome, ultimately, the project created an “aquatic greenbelt” that is a recognized community asset.

Around the same time, SAWS sought to tackle its biosolids challenges relying in part on WERF research. First envisioned in 1996, SAWS designed and built the capability for all solids go to one facility – the best performing and newest. By installing two biosolids transfer lines and a raw water interconnect, SAWS’ innovation eliminated the need for rehabilitation and replacement of equipment at three treatment plants. It also reduced staffing needs. The final result has been a higher quality product produced at a lower cost which influences long-term rate stability.

Recycled water outfall in Brackenridge Park.

Other innovations implemented by the Dos Rios Water Recycling Center processing included drying bed optimization and a public-private partnership. Innovative drying bed management practices save over $70,000 a year. They include a drying bed polymerization program and use of natural vectors to eliminate pesticide application. A biosolids compost public-private partnership for operations and marketing was put in place. By 2009, it significantly eliminated landfilling because it captures 98% of the biosolids generated (140,000 tons). Moreover, composting reduces watering demand. These SAWS biosolids innovations have been widely accepted by the public.

The third element of San Antonio’s trifecta was securing beneficial use of digester gas. This last challenge was met using, then, state-of-the-science information from WERF and entering into a public-private partnership. SAWS partner built a gas conditioning/compressing facility next to SAWS digesters. The partners perform all operations and maintenance. The gas simply goes into a large distribution pipeline and is sold wherever gas is used. So far the contract has been returning about $20,000 per month to SAWS. A quickly evolving field, beneficial use of biogas remains an ongoing goal for many WERF subscribers. Through their partnership, SAWS has enabled 900,000 cubic feet to be beneficially used daily, ultimately, this use results in an overall reduction in carbon emissions of nearly 20,000 tons annually.

It has taken SAWS 15 years to complete implementation of their innovative vision. Working with WERF as volunteers on several project steering committees and issue area teams has helped SAWS establish itself as a leader in the water quality industry. A subscriber since 1995, San Antonio has been able to illustrate the value of building on past research to achieve evolving goals.