N o v e m b e r 4 , 2 0 2 4
Transportation and Environment Committee
(D) 2. Nutrient Regulations Impacts
to the San José-Santa Clara
Regional Wastewater Facility
Eric Dunlavey
Mariana Chavez-Vazquez
▪ Operating since 1956
▪ Largest tertiary treatment
wastewater facility in West
▪ 167 MGD capacity
▪ Serves
▪ 1.5 million people
▪ 17,000 businesses
▪ 8 cities & County
▪ Subject to multiple regulatory
discharge permits
2 Regional Wastewater Facility
▪ RWF is subject to multiple federal (NPDES) Clean Water Act permits
▪ Permits are reissued and updated every 5 years
▪ Individual NPDES Permit governs O&M and most water
quality requirements for the RWF
▪ Regional issue-specific Permits (mercury, PCBs, nutrients) 3 RWF Clean Water Act Permits
▪ SF Bay has much higher
nitrogen levels than other
large urban Bays
▪ 2/3 of Bay’s nutrients from
wastewater treatment
plant discharges
▪ Group Nutrient Permit
since 2014
4 Nutrient Permit
▪ Elevated nutrients can lead to excess algae growth
▪ Excess algae growth can:
5 Why Nutrients Matter
Lower dissolved oxygen, suffocating fish
Despite high nutrients, San Francisco Bay has been
resistant to these effects until…
Elevate levels of toxin producing algae (HABs)
Photo credit: Darwin BondGraham
▪ Heterosigma akashiwo
– Toxic effects
– Brown or red water
6 The August 2022 Red Tide
Engesmoa et al 2019
8/16/2022
8/4/2022 8/11/2022 8/16/2022 8/20/2022 8/25/2022
Photo Credit: James Ervin
Conditions didn’t degrade in Lower South Bay like they did in South and Central Bays.
7 Lower South Bay Bloom Conditions
Healthy and abundant fish in
Lower South Bay August 2022.
Green (not brown)
water. H. akashiwo
present but at lower
concentrations.
Photo Credits: James Ervin
8 Regulatory Consequences of Bloom
$2.2M/year
$$
$2.2M/year
$$$
9 Regulatory Consequences of Bloom
▪ Two dry-season nitrogen limits imposed by regulators:
1. Interim Limit from 2024 – 2034 (current performance).
2. Final Limit from 2035 onward (40% reduction regionally). ▪ Active Permit negotiations Jan 2024 – May 2024.
RWF limits in first draft
Interim Limit 5,400 kg/day
Final Limit 3,700 kg/day
RWF negotiated limits
Interim Limit 6,400 kg/day
Final Limit 5,000 kg/day
10 Regulatory Consequences of Bloom
▪ Permit imposes two limits on RWF:
1. Interim Limit of 6,400 kg/day nitrogen 2024 – 2034.
2. Final Limit of 5,000 kg/day nitrogen by 2034 onward. ▪ The Challenges for RWF:
▪ Nitrogen received at RWF will increase over time.
▪ Improved solids handling will eliminate existing nitrogen removal pathway. ▪ Increased nitrogen removal efficiency will be necessary to meet fixed limits. ▪ Removing more nitrogen presents challenges and requires additional nitrogen management actions.
11 Nutrient Management Options
Treatment Process Upgrades
Water Recycling
Photo Credit: Amanda Suutari
Nature-based Solutions
Conclusion – Ongoing Actions
▪ Continue engagement in development of nutrient regulations – Positions taken are science-based
– Goal of certainty and stability in future targets
▪ Evaluate process upgrades through Master Plan update
– Necessary to meet regulations long term
– Progress required by Permit and demonstrates commitment ▪ Explore and implement alternative nutrient management actions – Significant Costs to implement modifications to the treatment process at RWF – Non-potable recycled water expansion provides flexibility to future capital upgrade timing
– Nature-based treatment is a potential tool for providing additional flexibility or pairing with purified water projects with partner agencies 12