TO: TRANSPORTATION AND
ENVIRONMENT COMMITTEE
FROM: Lori Mitchell
SUBJECT: Nutrient Regulations and
Impacts on the San José-Santa
Clara Regional Wastewater
Facility
DATE: October 11, 2024
Approved Date:
10/24/2024
RECOMMENDATION
Accept a status report on the new nutrient regulatory requirements issued by the San Francisco Bay Regional Water Quality Control Board under NPDES Permit No.
CA0038873, affecting the San José-Santa Clara Regional Wastewater Facility.
BACKGROUND
Wastewater discharges are major contributors of nutrient compounds that accumulate in the San Francisco Bay, specifically nitrogen and phosphorus. Nitrogen levels in the Bay are elevated compared to other large urban water bodies in the United States, such as Chesapeake Bay, Puget Sound, Boston Harbor, and Tampa Bay. For decades, elevated Bay nitrogen has not caused environmental impacts, which would have manifested through effects like harmful algal blooms and low dissolved oxygen levels.
Historically, this was referred to as the Bay’s resistance to the harmful effects of excessive nitrogen.
More than a decade ago, long-term trend monitoring of environmental indicators, conducted since the 1980s, suggested that the historic resistance to harmful effects of high nitrogen was weakening. The waning resistance prompted increased scientific study of the potential impacts of elevated nitrogen in the Bay. The weakened resistance also led to a new nutrient-specific permit for all wastewater treatment plants, including the San José-Santa Clara Regional Wastewater Facility (RWF) that was first issued by the San Francisco Bay Regional Water Quality Control Board (Water Board) in 2014, under NPDES Permit No. CA0038873 (Nutrient Permit). The permit is reissued and updated every five years. The first and second versions of the permit required increased monitoring of nutrients and evaluations of management actions that would reduce nitrogen but did not impose nitrogen discharge limitations. A third version of the Nutrient Permit was reissued on July 10, 2024, and became effective on October 1, 2024. Unlike T&E AGENDA: 11/4/24
ITEM: (d) 2
TRANSPORTATION & ENVIRONMENT COMMITTEE
October 11, 2024
Subject: Nutrient Regulations & Impacts on the San José-Santa Clara Regional Wastewater Facility
the prior two versions of the Nutrient Permit, the 2024 Permit contains nitrogen discharge limitations for all wastewater treatment plants. Nitrogen limitations were anticipated based on information in the second Nutrient Permit from 2019.
The nitrogen discharge limitations in the 2024 Permit were far more stringent than the limitations that were forecast in the 2019 Permit. These more stringent limitations were due to a harmful algae bloom in San Francisco Bay that was dominated by the red tide species Heterosigma akashiwo. The bloom began in the Alameda Inner Harbor and spread throughout the entire Bay in August 2022, extending from Suisun Bay in the north down into the Lower South Bay. The severe effects of the bloom were widespread, and massive fish kills occurred from the Richmond Bridge in the north to the Dumbarton Bridge in the south. While the harmful algae species was detected in the Lower South Bay by City of San José staff and contractors, it was at lower concentrations than other, more impacted regions of the Bay, and there were no documented fish kills within the RWF’s immediate area of influence. A smaller bloom event with the same species of algae occurred again in late August 2023, indicating that the red tide algae species is likely to keep returning.
Before the August 2022 and 2023 events, regulators were poised to cap nitrogen loads discharged by not allowing increases in future nitrogen loads in the 2024 Nutrient Permit. Because of the blooms, regulators are now requiring substantial reductions in nitrogen loads from wastewater treatment plants. A summary of the pending nutrient regulations was provided to the Transportation and Environment Committee in November 2023. However, the extent of the requirements in the 2024 Nutrient Permit, including specific requirements for the RWF, were unknown until Spring 2024. This memo summarizes the draft and final requirements, negotiations to get to the final requirements, and a menu of strategies to comply with the new requirements.
ANALYSIS
The Nutrient Permit was reissued in July 2024 and requires reductions to nitrogen discharges to the Bay over the next ten years. This will be implemented by imposing two limits, which are based on the total inorganic nitrogen discharged to the Bay as average daily loads in kilograms per day during the Permit-defined dry season (May 1 through September 30) of each year. The two limits are:
(1) An interim discharge limit of 6,400 kg/day that must be achieved immediately and cannot be exceeded in the future, and
(2) A lower limit, or final limit of 5,000 kg/day that must be achieved within ten years.
The RWF’s current average daily dry season nitrogen load is approximately 4,000 kg/day. The Water Board set the interim limit, which is not intended to require
TRANSPORTATION & ENVIRONMENT COMMITTEE
October 11, 2024
Subject: Nutrient Regulations & Impacts on the San José-Santa Clara Regional Wastewater Facility
immediate reductions, to reflect current performance and account for inherent variability.
This interim limit is intended to serve as a backstop so that nitrogen discharges do not increase while agencies are implementing projects that will reduce their nitrogen levels.
Projects to reduce nitrogen levels in wastewater take many years to implement and often require significant capital and maintenance expenditures. The RWF’s interim limit will be challenging to meet over the next ten years because upgrades to the sludge dewatering process, which should be in full operation by dry season 2026, will increase nitrogen discharges to the Bay. The new sludge dewatering process is driven by separate regulations that require reductions in climate pollutants. The operational changes to sludge processing comply with climate pollutant reduction requirements but will eliminate a nitrogen removal pathway achieved by the older process. The RWF is evaluating the magnitude of the impact to our nitrogen discharges and what operational adjustments and regulatory remedies (permit modifications or legal challenges to the permit) may be necessary and available if the RWF cannot meet the new interim limit.
The final limit, which will not be effective until 2035, is being imposed proportionately across all wastewater treatment plants based on flow volumes. This effectively requires all facilities to achieve a minimum level of nitrogen reduction and maintain reduced loadings in perpetuity even as service area populations grow. The first draft of the Nutrient Permit did not impose loads proportionately and the RWF received a far more stringent final limit (3,700 kg/day) than nearly every other treatment plant in the region.
The more stringent draft limit assumed that the RWF would have the same ability to achieve significant nitrogen reductions as other facilities and did not fully account for the investments made as an early actor of nitrogen reductions. The City met Water Board staff numerous times between March 2024 through June 2024 to explain the significant capital cost impact the proposed limits would have on the RWF. Additionally, RWF partnered with other wastewater agencies to seek regional support for a proportional load allocation framework in the final permit. The efforts were highly successful, and the adopted permit imposes nitrogen limits fairly throughout the region.
Current nitrogen reduction performance and future projections for the RWF The RWF already removes a significant portion of the nitrogen it receives due to the advanced secondary treatment process in place since 1998. This process, combined with recent process optimizations and loads diverted from the Bay by non-potable reuse water recycling, results in an 85% nitrogen reduction throughout the plant. This high removal efficiency puts the RWF ahead of other wastewater treatment plants in the region in terms of needing to achieve significant reductions beyond our current loads.
However, meeting the interim and final nitrogen loads will be challenging for the RWF as the population increases and changes to solids processing occur, both of which will increase the nitrogen levels the RWF must manage.
TRANSPORTATION & ENVIRONMENT COMMITTEE
October 11, 2024
Subject: Nutrient Regulations & Impacts on the San José-Santa Clara Regional Wastewater Facility
Current load projections indicate one or more actions will be needed to meet the new limits. If no further action is taken to reduce loads, the RWF is projected to exceed the interim limit in the next five years. Actions to manage the RWF’s nitrogen loads to the Bay could include process treatment upgrades, expansion of non-potable reuse recycled water, or use of nature-based treatment systems such as engineered marshes or wetlands that sequester and beneficially use nitrogen.
Potential strategies and actions to reduce nitrogen discharges from the RWF Process Treatment upgrades – In anticipation of future nitrogen requirements, RWF staff initiated a comprehensive process optimization study in early 2020 to evaluate how the RWF could respond to future nutrient load limits and other regulatory requirements in a cost-effective and environmentally protective manner. The process optimization study identified upgrading the existing advanced secondary treatment as the best option to keep the RWF compliant with the anticipated nitrogen load cap until 2051. The plans for phasing in the upgrades and integrating them into the Capital Improvement Program was underway until the new, lower, nitrogen effluent limitations were imposed on the RWF. As a result of the lower nitrogen limitations in the 2024 Nutrient Permit, the initial phase of the upgrades has been paused so the upgrades can be re-evaluated against the lower limits in the adopted Nutrient Permit. This evaluation is underway as part of the Plant Master Plan Technical Update effort that is reviewing and updating the 2013 Plant Master Plan technical documents due to notable changes over the past 11 years.
Non-potable recycled water – Concurrent with the CIP evaluation of necessary upgrades to meet nitrogen requirements, the RWF participated in a regional study that evaluated the opportunities, costs, and benefits of nitrogen reduction by expanding recycled water. The study was closely coordinated with staff who manage the South Bay Water Recycling (SBWR) program and incorporated the anticipated expansion of non-potable recycled water over the next 20 years consistent with the SBWR Master Plan. The projected expansion approximately doubles the current non-potable recycled water delivery, reducing the nitrogen discharge to the Bay by nearly 1,000 kg/day, or about a 15% – 20% reduction of the RWF’s projected 2045 loads. If realized, this could provide significant flexibility in the timing and phasing of future treatment system upgrades. The anticipated expansion of non-potable recycled water is being incorporated into the Plant Master Plan Technical Updates evaluations.
Purified water for potable reuse – Purified water projects for either indirect or direct potable reuse provide very little to no reduction of nitrogen discharges to the Bay. This is because purified water projects produce a concentrated waste stream known as reverse osmosis concentrate (ROC), which contains most of the nitrogen and other pollutants remaining in the treated wastewater prior to purification. To date, purified water projects have envisioned managing the ROC by discharging it directly to the Bay, often combining or blending it with existing discharges. This practice reduces the cost of
TRANSPORTATION & ENVIRONMENT COMMITTEE
October 11, 2024
Subject: Nutrient Regulations & Impacts on the San José-Santa Clara Regional Wastewater Facility
disposal of the concentrated waste stream but presents challenges to managing nitrogen and toxic pollutant discharges, especially with large scale purification projects envisioned for potable reuse. As the nitrogen levels sent to the RWF increase with increasing population, projects that do not reduce pollutant levels and instead concentrate them, put additional cost and stress on existing treatment systems. The cost to manage ROC in purified water projects in a way that reduces the nitrogen and toxic pollutants in the concentrated waste stream should be incorporated into future large-scale purified water projects. Potable reuse projects are costly and present challenges but provide benefits by providing a reliable ongoing potable water supply that is resistant to drought. The regional study evaluating opportunities, costs, and benefits of nitrogen reduction by new or expanded recycled water also included conceptual evaluations of potable reuse projects. Because very little to no nitrogen reductions are achieved by purified water projects, the cost per unit of nitrogen reduction for purified water was multiple orders of magnitude more expensive than other nitrogen reductions strategies.
Nature-based solutions – The RWF participated in a second regional study that evaluated the opportunities and benefits of implementing nature-based solutions to reduce nitrogen inputs to San Francisco Bay. A nature-based treatment system beneficially utilizes natural processes to reduce pollutant levels in wastewater. The systems evaluated for treating wastewater are hybrid systems that include engineered elements such as pumps, levees, and water control structures, but have a foundation in marsh or wetland habitats. They are located along the edges of the Bay and incorporate shoreline resiliency, flood protection, and water treatment. Nature-based solution opportunities in the Bay Area include horizontal levees (a levee with a gentle sloping marsh plain into the Bay), open-cell wetlands, and vegetated open-water treatment systems. The RWF has opportunities for nature-based systems in its inactive biosolids lagoons and along the future flood control levee along the southern border of Pond A18.
Combined, the identified opportunities total 199 acres, and initial estimates could result in roughly a 900 kg/day reduction of nitrogen discharges to the Bay.
Nature-based solutions opportunities present a possible option for managing ROC concentrated waste from purified water projects and additional treatment of remaining tertiary treated wastewater. Nature-based systems provide additional treatment of nitrogen and other pollutants, so they can be a tool to meet multiple regulatory requirements. In addition, these systems provide secondary benefits by enhancing existing habitat, creating new habitat, and providing shoreline and habitat resiliency.
While the evaluation of nature-based systems indicates nitrogen management potential, no near-term plans to implement a nature-based solutions project exist.
TRANSPORTATION & ENVIRONMENT COMMITTEE
October 11, 2024
Subject: Nutrient Regulations & Impacts on the San José-Santa Clara Regional Wastewater Facility
Comparison of nitrogen management strategies
The different strategies to manage and ultimately reduce nitrogen discharges to the Bay have varying costs, reliability, nitrogen reduction potential, and uncertainty associated with each of them. Some strategies such as water recycling and nature-based solutions have additional benefits such as reducing the discharge of other pollutants, enhancing or creating new habitats, and benefiting water supply.
Of the various strategies, treatment upgrades represent the highest level of certainty for reducing nitrogen and meeting future discharge requirements. Capital upgrades to existing nitrogen removal systems can be expensive with preliminary estimates in the hundreds of millions of dollars at full scale. Expansion of non-potable water recycling is the next most certain and is a cost-effective means of reducing nitrogen discharges to the Bay. Increasing non-potable reuse alone to projected volumes will not enable the RWF to remain below its future nitrogen limits. However, it is an attractive option because it could lessen the urgency of future treatment upgrades and provide flexibility with construction timing, budgeting, and regulatory requirements. Expanding nonpotable water recycling also reduces other pollutant discharges to the Bay, which provides additional regulatory flexibility beyond nitrogen reduction requirements. As a secondary benefit, non-potable water recycling also provides a reliable water supply that can reduce the demand for potable water. Both the identified treatment process upgrades and expansion of non-potable water recycling are being explicitly incorporated into the Plant Master Plan Technical Update effort. Once the Technical Update is completed, any identified strategies (such as treatment upgrades or recycled water expansion) requiring additional budget to implement will be requested in the appropriate future budget proposal process.
A purified water project as a stand-alone project provides the benefit of increased potable water supply but does not provide a meaningful reduction in nitrogen or other pollutants. Preliminary estimates of the cost per kilogram of nitrogen reduced from nature-based systems indicate that costs for this strategy are similar to non-potable water recycled. The nature-based solutions strategies evaluated for the RWF provide an overall nitrogen reduction that is about the same as reductions from projected nonpotable water recycling expansion. This may make them an attractive option, either as a stand-alone project or a project that could be paired with a future purified water project to achieve nitrogen reductions, water supply benefits, and habitat enhancement.
COORDINATION
This report has been coordinated with the City Attorney’s Office and the City Manager’s Budget Office.
TRANSPORTATION & ENVIRONMENT COMMITTEE
October 11, 2024
Subject: Nutrient Regulations & Impacts on the San José-Santa Clara Regional Wastewater Facility
/s/
LORI MITCHELL P.E
Acting Director, Environmental Services
For questions, please contact Eric Dunlavey, Deputy Director Regulatory Affairs and Purified Water, Environmental Services at [email protected] or (408) 635- 4017.