By Thacher Worthen, Schreiber LLC
Wastewater facilities have transitioned from “sewage treatment” to “wastewater treatment”, then to “water reclamation”, and now have progressed toward “water resource recovery facilities” (WRRFs). This metamorphosis has been accompanied by an evolution in the level of treatment, improvements in efficiency, and recognition across the field that the industry is not wasting but managing valuable commodities. Energy, water, and nutrients are the most valuable resources that can be recovered from wastewater for beneficial uses. In this article we will discuss the needs for recovery of valuable resources and how technology providers can collaborate with utility managers, operators, and engineers in providing cost-effective treatment technologies.
Toward Net-Zero Energy
There are a growing number of municipalities that are aiming to produce on-site, all the energy needed to meet the energy required to operate their WRRFs. This fits with the emerging paradigm of wastewater treatment facilities being seen as resource recovery facilities where there is more energy embedded in the wastewater than is required to simply treat it. Energy, in the form of heat and electricity, can be recovered from organic solids to offset power demands of WRRFs. There are many innovative technologies that can be used reliably and economically for energy recovery. Carbon Diversion with primary effluent filtration (PEF) is an emerging technology that increases gas energy production in anaerobic digesters and reduces aeration energy cost in secondary treatment. To demonstrate the feasibility of PEF technology, a two-year demonstration project funded by a grant from the California Energy Commission was conducted by Kennedy/Jenks Consultants in 2013 at the Linda County WRRF in California. Five innovative filtration technologies, including the compressible media filtration technology (Fuzzy Filter), were evaluated at different operational conditions. The successful results of the study demonstrated the viability of PEF technology for carbon diversion.
The term “one water” has been used to note that all water, whether drinking water, or treated effluent, is the same water; just having varying levels of constituents. Our industry is intimately familiar with water scarcity issues and the need for water recycling. Effluent water may be treated to a level that is “fit for purpose” to meet standards for drinking or for specific use (e.g., high-pressure boilers in oil refineries). In water-scarce areas like southern California, water reuse is very critical where WRRF effluent can be treated for direct potable reuse. For Title 22 reuse applications, there are many cost-effective, innovative technologies that provide high-quality effluent (such as the Fuzzy Filter).
Recovering Valuable Nutrients
The need for nutrient recovery from wastewater, especially phosphorus, has arisen because of the global implication of production of fertilizers. The level of phosphorus and nitrogen capture from wastewater is highly dependent on the treatment technologies implemented by WRRFs. Since nutrients are found in low concentrations in wastewater, high levels of phosphorus and nitrogen accumulation in solid form is required for cost-effective recovery. For example, the biological accumulation of phosphorus during wastewater treatment can be enhanced through specific microorganisms like phosphate-accumulating organisms. There are several innovative biological nutrient removal (BNR) technologies that support biological phosphorus removal and accumulation in sludge. One of the most cost-effective BNR technologies is the continuously sequencing reactor process.
To transition into WRRFs, it is incumbent on utility managers, operators, utility staff, engineers, and technology providers to look beyond traditional improvements in wastewater treatment and operations and plan for expanded future goals that include better recovery and use of energy, water, and nutrients.
Thacher Worthen is President of Schreiber LLC, located in Trussville, AL. He is a Water and Wastewater Equipment Manufacturers Association (WWEMA) Board Member and serves on the Executive Committee as Vice-Chairman. For more information on WWEMA, go to www.wwema.org