Grantee Research Project Results

Final Report: Zero-Waste (ZeWa) Water and Energy Recovery System

EPA Contract Number: 68HERC22C0036
Title: Zero-Waste (ZeWa) Water and Energy Recovery System
Investigators: Rogers, Tate W
Small Business: Triangle Environmental Health Initiative
EPA Contact: Richards, April
Phase: II
Project Period: January 1, 2022 through December 31, 2023 (Extended to December 31, 2024)
RFA: Small Business Innovation Research (SBIR) Phase II (2022) Recipients Lists
Research Category: Fellowship - Agricultural Ecology

Description:

Through this EPA SBIR program, Triangle Environmental (TE) developed ZeWa, a Zero-Waste, net-energy positive onsite wastewater treatment system to eliminate brine and produce three output streams for reuse. The 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).  Phase I demonstrated each ZeWa subsystem to meet national and international standards for reuse with real wastewater in a laboratory environment, collectively reducing raw blackwater COD by 99.3%, TSS by ~100%, Total N by 91.7%, and Total P by 90.6%.

The primary goal of Phase II was to build on Phase I results to design, build, and test a fully automated, mobile ZeWa Pilot unit to demonstrate system functionality at scale. As TE has multiple WRS and NRS standalone systems currently in commercialization, this Phase II testing focused on 1) demonstrating the first-of-its-kind STERS (patent pending) subsystem, 2) integrating subsystems, and 3) obtaining operational data to inform commercialization of all three subsystems. The ZeWa Pilot design serves as an R&D skid with maximum functionality to monitor and adjust subprocesses to maximize throughput while maintaining high effluent quality and minimizing energy consumption. The pilot unit is also intended to serve as a use case for multiple potential wastewater applications. As such, the ZeWa Pilot unit was designed to facilitate testing multiple wastewaters with one or more ZeWa subsystems in multiple locations. To facilitate these capabilities, the ZeWa pilot is trailer-mounted (mobile) and designed so that each subsystem can run independently or as a fully integrated system. For Phase II, the pilot system was tested at a local wastewater treatment plant with raw sewage (after coarse screening and grit removal) to simulate residential domestic wastewater.

 

Summary/Accomplishments (Outputs/Outcomes):

The fully-integrated and automated ZeWa Pilot system (Figure 1) was satisfactorily designed, built, and tested with domestic wastewater. First, the STERS advanced solids handling mechanisms were built and tested by TE including independently including solids screening and transport. A custom, but simple biogas burner was then fabricated and incorporated by a partner organization based on our specific biogas composition, air flow, and required heat power. The fully assembled solids handling system was then integrated with the custom solids retention digestor tank and biogas collection tank to complete the STERS subsystem assembly on the ZeWa Pilot. The WRS and NRS subsystem were designed and built on based TE’s most up to date data and components from our stand-alone field units. Several commercialization insights were realized through the skid design and build process including component selection, system packaging (layout), and controls strategy.

The ZeWa Pilot successfully demonstrated the capability to run all subsystems independently and as one integrated system. Moreover, the highest risk component, the STERs advanced solids handling system, demonstrated effective separation, transport and treatment of solids at pilot scale. Testing the ZeWa Pilot with domestic wastewater provided several operational insights to finetune controls strategy and operating setpoints. Most importantly, two key commercial off-the-shelf components (COTS) in the WRS system were found to have unforeseen side effects, leading to downstream operational issues with the NRS system. This pilot effort allowed us to identify and rectify these problems with updated COTS components prior to our market release of the WRS standalone system.  

Conclusions:

• This Phase II award enabled TE to successfully design and build a Zero-Waste pilot unit to demonstrate a completely closed loop, onsite domestic wastewater treatment system.
• ZeWa’s three subsystems (STERS, WRS, and NRS) have been demonstrated to run as standalone systems or completely integrated, making ZeWa “tunable” to a client’s incoming wastewater stream and desired output streams.
• The highest risk subsystem, the advanced solids handling system, demonstrated effective solids separation, transport, and treatment.
• Market research and early customer discovery indicates that the STERS system may be best targeted at commercial scale applications to reduce solids/brine handling costs, however it may be some time before user adoption allows significant growth at the residential scale.
• The ZeWa Pilot unit’s mobility positions TE to showcase its capabilities to existing and potential commercial partners with many other wastewater streams of interest.

Commercial Applications of the Research

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). ZeWa 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 II has demonstrated the ZeWa system at scale for domestic wastewater with findings translating directly to the ongoing commercialization of ZeWa subsystems with TE commercial partners

SBIR Phase I:

Zero-Waste (ZeWa) water and energy recovery system  | Final Report