Grantee Research Project Results
Final Report: Phosphorus recovery and high efficiency biological nutrient removal from wastewater with an innovative aerobic granular sludge sequencing batch reactor process
EPA Contract Number: EPD15031Title: Phosphorus recovery and high efficiency biological nutrient removal from wastewater with an innovative aerobic granular sludge sequencing batch reactor process
Investigators: Coleman, Thomas E.
Small Business: dTEC Systems LLC
EPA Contact: Richards, April
Phase: I
Project Period: September 1, 2015 through February 29, 2016
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2015) RFA Text | Recipients Lists
Research Category: SBIR - Water , Small Business Innovation Research (SBIR)
Description:
This Phase I research project was intended to demonstrate an innovative approach for growing phosphate accumulating microorganisms (PAOs) within an aerobic granular sludge through modifications to existing sequencing batch reactor (SBR) wastewater treatment plants. These aerobic granular sludge particles consist of self-assembling microbial communities which will form naturally in an activated sludge reactor when the right selective pressures are applied to the system. The use of PAOs to remove phosphorus from wastewater is termed enhance biological phosphorus removal (EBPR) and is the most sustainable and cost effective method for protecting natural waters from degradation due to eutrophication cause by treatment plant discharges. The use of EBPR also makes possible the recovery of phosphorus as a high value fertilizer product. The recovery of phosphorus helps to reduce our dependence on phosphate rock mining to meet our agricultural needs. Our phosphorus economy has become one that is based on using mined phosphate once and “throwing it away” thus turning a critical resource into a pollutant.
The research conducted under this Phase I project utilized a pilot-scale reactor installed at the Cashmere, WA wastewater treatment plant. The pilot reactor incorporated an innovative influent distribution and mixing concept as needed to create an anaerobic feed zone with a high soluble organic substrate to biomass diffusion gradient in an SBR reactor, together with the aeration, settling, and decant piping systems all as necessary for selecting, growing, and maintaining aerobic granular sludge in the reactor. After setting up the 300-gallon pilot reactor and associated feed tank, the process was monitored on a daily basis for influent and effluent parameters (including soluble chemical oxygen demand, nitrogen species, soluble reactive phosphorus and total phosphorus). Additionally, the bacterial biomass was monitored daily using both conventional and microscopic methods.
Summary of Findings:
The results of the Phase I research demonstrated that the feed and mixing concept designed to introduce influent wastewater into the settled sludge bed under anaerobic conditions as implemented in the pilot reactor design was able to create the conditions necessary to produce aerobic granular sludge as confirmed by photomicrographs and stereo photomicrographs. Good phosphorus and nitrogen removal was also achieved in the pilot scale reactor without a separate anoxic phase or additional carbon addition indicating that both phosphorus and nitrogen removal were occurring in the aerated React cycle as is characteristic of aerobic granular sludge systems. The selection for the faster settling granular aerobic sludge bacterial clusters over floc forming and filamentous bacteria was achieved by controlling settling times and decant rates. Selection was further improved by implementing surface wasting period during a post react cycle in which the reactor was aerated at very low flux rate while mixed liquor was drawn from the surface through the decanter.
The Phase I results and findings provide valuable insight into the design elements and operational strategies which will be needed to implement our innovative concept for SBR wastewater treatment plant modifications at full scale. It will be critical to carefully manage the organic substrate loading during the start up phase to be in proportion to the mass of granular biomass in the system. The granules are slow growing relative to floc forming and filamentous bacteria and therefore the feed rate will have to be increased gradually during the start-up period. Throughout the start-up period the aggressive selective wasting of floc formers and filaments must also be maintained.
The inherently slow growth rate of aerobic granules did not allow us to develop sufficient granular biomass within the time constraints of the Phase I project to conduct a separate test of phosphorus release from PAO containing granules under anaerobic conditions. However, adequate data for P release rates from PAOs in flocculent activated sludge is available from the literature and from previous work conducted by project team members. It is reasonable to assume the release rates from PAOs will be the same in flocculent sludge as it is from PAOs in granular sludge. The estimates of P concentration which could be achieved in the supernatant from a stripping tank were developed from this related work and these P concentrations would be more than adequate to efficiently produce struvite using an upflow reactor such as those which have been developed by our commercialization partner.
From our discussions with potential end users of our technology and from the Commercialization Assessment Report prepared by Foresight Science & Technology, we can conclude that there is little interest on the part of small WWTP owners and operators at this time to implement a separate phosphorus recovery unit process until there is a greater economic or regulatory incentives to do so. However, if a small plant which employs EBPR also utilizes aerobic digestion as part of their biosolids management infrastructure, they could benefit from installing a struvite recovery unit on the digester supernatant stream to avoid returning high phosphorus loads back through the liquid stream process which could in turn increase plant effluent phosphorus concentrations. Under such a scenario phosphorus recovery together with our SBR upgrade technology would be highly feasible.
Conclusions:
The feed and mixing concept designed to introduce influent wastewater into the settled sludge bed under anaerobic conditions as implemented in the pilot reactor design was demonstrated to create the conditions necessary to produce aerobic granular sludge. Good phosphorus and nitrogen removal was also achieved in the pilot scale reactor. The selection for the faster settling granular aerobic sludge bacterial clusters over floc forming and filamentous bacteria was achieved by controlling settling times and decant rates. Selection for granular sludge was further improved by implementing a surface wasting step during a post react cycle in which the reactor was aerated at very low flux rates.
The pilot plant operation during Phase I has provided valuable insight into the important design considerations for the full-scale implementation. We worked closely with the engineering staff of a potential customer for early adoption of our technology on site-specific design concepts for the implementation of our concept for upgrading their existing SBR plant to meet stringent new phosphorus effluent limits.
Commercialization:
The commercial market opportunity of this research focuses first on the SBR treatment process configuration which has been widely used for small communities. There are currently over 700 SBRs in the U.S. Most of the existing SBRs in the U.S. have been provided as packaged systems comprised of aeration and mixing equipment, decanters and proprietary control systems. The retrofit of existing SBR plants will be our initial commercialization focus. Many of these plants have not been able to achieve their design operational performance and capacity objectives. They have been hampered by very poor settling and inability to provide reliable nutrient removal, especially phoshorus removal.
There are currently over 16,000 WWTPs in the U.S. In the coming years most of these plants will need to be upgraded or replaced to provided nutrient removal while serving growing populations. Phosphorus recovery should be an important part of all WWTPs to prevent the one-time use and disposal of this essential non-renewable resource. The value that we offer to small municipalities experiencing operational difficulties and/or new regulatory requirements is the ability to meet these needs by upgrading existing facilities at a modest cost rather than constructing new facilities costing several million dollars.
As do most wastewater treatment process equipment manufacturers we plan to use manufacturers’ representatives to market and sell our technology. As part of the commercialization activities conducted in Phase I, we negotiated and executed a representation contract with a major manufacturers’ representative who covers the Pacific Northwest and Alaska.
Looking forward, we are positioning ourselves to market our technology in Greater China as well. China recently promulgated a new water pollution act known as the ‘Water Ten Plan’ to Safeguard China’s Waters last November. Effluent from most current plants will need to cut these concentrations by half to meet the requirements, and thousands of new WWTPs will be designed and built by the new standard. In order to open an opportunity to participate in this huge market we have also entered into a representative agreement with a Taiwan based company.
SBIR Phase II:
Phosphorus recovery and high efficiency biological nutrient removal from wastewater with an innovative aerobic granular sludge sequencing batch reactor process | Final ReportThe 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.