Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).
Per- and Poly- Fluoroalkyl Substances (PFAS) are a large family of organic compounds, including more than 5,000 artificial fluorinated organic chemicals used since the 1940s. They have been used extensively in surface coatings and protectant formulations for consumer products including paper and cardboard packaging products, carpets, leather products and clothing, construction materials, and non-stick coatings.
Recent studies have shown PFAS in WWTP influents to be in the tens to hundreds of nanograms per liter (ng/L). Conventional sewage treatment methods do not efficiently remove PFAS. Application of biosolids from WWTPs as a soil amendment can result in a transfer of PFAS to soil, which can then leach to groundwater or be available for uptake by plants and soil organisms and biomagnify to grazing livestock. PFAS have been detected in soils, groundwater, crops, and livestock near agricultural fields that receive PFAS-contaminated biosolids, fueling public concern.
As PFAS are recalcitrant and are not removed through conventional wastewater treatment, management of PFAS in biosolids is gaining increased concern and scrutiny.
This presentation will address the following questions related to PFAS in wastewater and biosolids:
What are PFAS?
Why are PFAS in wastewater?
What is the fate of PFAS in biological treatment systems?
What is the current status of regulations related to PFAS in biosolids
What technologies can be used to treat PFAS in biosolids?
Data will be presented on PFAS measured in biosolids before and after various biosolids treatment technologies including digestion, composting, drying, and pyrolysis. This presentation will help utility planners, operators, engineers and administrators understand the nature of the PFAS issue, how these compounds are introduced into wastewater and biosolids, the rapidly changing regulatory landscape, and what technologies are being used to eliminate these compounds from biosolids products.
3:45pm - 4:30pm
Water Quality Modeling and Monitoring to Support an Update of the Tualatin River Phosphorus TMDL
Raj Kapur, Scott Mansell, Leila Barker, Ken Williamson, Clint Cheney, Bob Baumgartner
Clean Water Services, United States of America;
Since 1988, the Tualatin River has had a total phosphorus TMDL which established stringent effluent limits. Clean Water Services has used a combination of biological processes and alum addition at the tertiary stage of the treatment process to meet phosphorus limits. Since 1988, the river has changed dramatically in terms of operations, flows, and water quality. Additionally, EPA has recently finalized a new aluminum standard in Oregon that will make it impractical to continue to use alum in the tertiary process for phosphorus removal. Clean Water Services conducted modeling that suggested that the Tualatin River was no longer sensitive to phosphorus inputs as it once was. Clean Water Services conducted a study in 2019 and 2020 where only biological processes were used for phosphorus removal with no tertiary alum addition and the effects on the Tualatin River were assessed. Results indicate that the treatment facilities can effectively reduce total phosphorus using biological processes without negatively impacting water quality in the river. Data gathered during the study will be used to update the water quality model and prepare a technical report to support an update of the Tualatin River phosphorus TMDL.
4:30pm - 5:15pm
Seeing the Whole Picture – Addressing Puget Sound Nitrogen Regulation Uncertainty as part of Biosolids Planning at Bellingham, WA
Anne Conklin1, Tadd Giesbrecht1, Susanna Leung1, Trung Le2, Rick Kelly2, Steve Krugel2, Rob Johnson3
1Carollo Engineers; 2Brown and Caldwell; 3City of Bellingham; ,
The City of Bellingham (City) provides wastewater service for over 100,000 people at the Post Point facility. The City has been in planning efforts to replace their aging incinerators and implement a Class A biosolids and biogas strategy that aligns with their values and recovers the resources. The Washington State Department of Ecology (Ecology) has taken implementation steps to control nitrogen discharges from wastewater treatment plants to Puget Sound. Ecology recently issued a draft General Permit for public comment that identifies facility action level thresholds as a first step of potential future lower limits.
The City recognizes that nitrogen reduction will ultimately require significant costs and substantial treatment plant space, necessitating the need to plan for nitrogen removal Nestled at the edge of Bellingham Bay and surrounded by environmental critical areas, community amenities, and residential areas, Post Point is land constrained, requiring that “build out” conditions be evaluated to determine the ultimate capacity of the site.
The BC/Carollo project team evaluated the feasibility of two effluent scenarios and treatment strategies that would bookend the likely future range of nitrogen regulations:
Worst Case: 3 mg/L total inorganic nitrogen (TIN) year-round,
Moderate Case: 8 mg/L TIN summer only.
At least one treatment strategy was found for each scenario that could fit within the site constraints.