Grantee Research Project Results
Final Report: Zero-Waste (ZeWa) water and energy recovery system
EPA Contract Number: 68HERC21C0035Title: Zero-Waste (ZeWa) water and energy recovery system
Investigators: Rogers, Tate W
Small Business: Triangle Environmental Health Initiative
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2021 through August 31, 2021
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2021) RFA Text | Recipients Lists
Research Category: SBIR - Clean and Safe Water , SBIR - Water , Small Business Innovation Research (SBIR)
Description:
Triangle Environmental (TE) proposes the Zero-Waste (ZeWa) water and energy recovery system; a net-energy positive onsite wastewater treatment system to eliminate brine and produce three output streams for reuse.
The Zero-Waste (ZeWa) water and energy recovery system is an onsite black- and greywater treatment technology that exploits the chemical energy potential contained in wastewater to produce zero-waste and three valuable products: (1) clean water for non-potable reuse, (2) concentrated fertilizer for local nutrient supply, and (3) Class A biosolids for local soil amendment. The ZeWa system consists of three main subsystems: 1) sludge treatment and energy recovery (STERS), 2) water recovery (WRS), and 3) nutrient recovery (NRS). The team already possesses functional prototypes of the WRS and NRS for testing.=A0 The key innovation and primary goal of Phase I was the development and testing of the STERS to validate the onsite treatment of a blackwater sludge/brine stream with only energy produced directly from the waste. This validation is anticipated facilitate two key breakthroughs in onsite domestic wastewater treatment: (1) elimination of concentrate/brine streams through recycle and treatment of the concentrate and (2) elimination of required emptying and transport of sludge in OWTS via vacuum truck. The technical risk for this proposal was low as the ZeWa system, and specifically the STERS, leverages and integrates components developed by the team over the past decade of onsite wastewater treatment research.
Over the course of the Phase I project period, a fully integrated, three-phase solids treatment system was designed, built, and tested. Owing to previous testing and development of the WRS and NRS, the focus of our Phase I technical efforts centered on the novel STERS subsystem. STERS was comprised of four interconnected components to collect, harvest energy, transport and treat the sludge (or concentrate stream). Each STERS subcomponent was built and tested independently before assembling into the connected STERS unit, which was further examined and optimized. Performance verification for treatment efficiency was assessed by measuring the number of fecal coliforms in solids before and after treatment as well as tracking key performance metrics, including chemical oxygen demand (COD), total suspended solids (TSS), and nutrient concentrations, in the influent and effluent that moved through each ZeWa subsystem.
Summary/Accomplishments (Outputs/Outcomes):
The fully-integrated ZeWa system was satisfactorily designed, built, and tested, demonstrating the expected system performance metrics consistent with TE Team members=92 previous experience using different subcomponents for blackwater treatment. The ZeWa system was able to achieve complete treatment of the solids stream to Class A Biosolids standards. In addition, the ZeWa demonstrated successful processing of the liquid effluent, creating two valuable streams for reuse: clean, high-quality effluent water for non-potable reuse and a nutrient-rich concentrate that could be applied for agricultural use (see Figure 2 for results). Furthermore, the system displayed consistently excellent nutrient and COD-reducing performance for three different influent treatment conditions: (1) greywater only, (2) STERS effluent only, and (3) greywater combined with STERS effluent (a 3:1 mixture). This finding suggests that greywater and blackwater streams could be combined for easy and efficient household treatment. Overall, the complete ZeWa system was able to reduce blackwater COD by 99.3%, TSS by 100%, Total N by 91.7%, and Total P by 90.6% (Figure 2).
Figure 2: ZeWa Phase I system performance for each subsystem.
Conclusions:
Each ZeWa subsystem demonstrated it was capable of reaching its treatment performance targets. The STERS system effectively removed and concentrated suspended solids from the blackwater feed while simultaneously converting the organics into usable energy. That harvested energy was then demonstrated to treat the suspended solids (concentrate stream) to Class A biosolids standards. The liquid effluent was also treated to a high quality through the WRS and NRS systems with high percent removals demonstrated for parameters of interest. Phase II (if awarded) will incorporate learnings from Phase I testing into the design, build, and testing of a pilot scale system(s) for treatment of domestic waste streams and concentrated brines from existing onsite water reuse systems.
Aging sewer infrastructure coupled with a growing population and sewer demand in the US have fostered a shift to higher usage of onsite wastewater treatment systems (OWTS). In the US, decentralized wastewater systems are used in 25% of existing residential homes and 33% of new development. The revenue for the OWTS market is growing as well, which was projected to nearly double from 2010 ($2.35 billion) to 2020 ($4.57 billion). Although becoming more prevalent, OWTSs are either very basic (i.e. septic tanks) or utilize technologies that create concentrated brine and/or sludge streams which require occasional emptying & transport via vacuum truck, and further treatment at wastewater treatment plants (WWTPs). The proposed ZeWa system seeks to not only eliminate these brine streams, but capture the high energy content they contain and convert them to high-value onsite reuse products. By optimizing all reuse potential of wastewater, ZeWa can shift black- and greywater treatment nationally to net energy positive while offsetting energy costs across the municipal water & wastewater, septage, and agriculture sectors. Phase I has demonstrated that ZeWa can meet all proposed performance metrics for complete reuse of black- and greywater streams. Phase II (if awarded) will focus on working with commercial partners in onsite wastewater treatment and water reuse sectors to pilot systems at scale and move into productization.
SBIR Phase II:
Zero-Waste (ZeWa) Water and Energy Recovery SystemThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.