Coordination among wastewater treatment plants could save rate payers money
Treating polluted water flowing into San Francisco Bay to meet regulatory requirements is going to cost ratepayers money. Exactly how much depends, in large part, on whether the region's wastewater treatment plant operators are willing and able to coordinate infrastructure construction and operation to meet these requirements, according to a Stanford University study published Sept. 24 in Nature Water.
The paper features a framework that calculates the most cost-effective way for multiple treatment facilities to jointly plan, build, and operate infrastructure to remove excess nitrogen from wastewater before it is discharged to the bay. Applied to three Bay Area treatment plants within a few miles of each other, the tool found that coordination could cut total capital and operating costs by up to 48 percent, a savings of $268 million over 30 years compared to the cost of building infrastructure independently.
"If you don't coordinate, each facility has to build and finance small infrastructure projects on its own,” said study lead author Sinan Abi Farraj, a PhD student in civil and environmental engineering in the Stanford Doerr School of Sustainability and School of Engineering. “The coordinated solution reduces how much infrastructure gets built and how much that infrastructure costs."
In response to algal blooms, fish kill events, and other damaging impacts of nitrogen pollution, regulators have ordered a 40 percent reduction in nitrogen discharges into the San Francisco Bay by 2035. Meeting those limits the conventional way, with each of the region's 37 plants independently upgrading its own facilities, is projected to cost more than $10 billion and require annual sewer rate increases of roughly $200 per household.
Until now, utilities and planners have had no reliable way to calculate how much coordination could actually save them. Existing tools are designed to optimize upgrades within a single facility, not across multiple plants sharing a watershed. This leaves utilities largely dependent on inconsistent models created by consultants to estimate potential savings from working together.
The researchers point out that nitrogen removal doesn't have to happen at each plant individually. Construction costs don't scale proportionally with capacity. If a larger facility can remove nitrogen more cheaply than a smaller one, it makes economic sense for the larger plant to handle more of the load while the smaller one builds less or nothing at all.
"Regional facilities rarely coordinate their decadal capital improvement plans or monthly operation because independent agencies monitor them and issue separate discharge permits," said study senior author Meagan Mauter, a Stanford professor of civil and environmental engineering. "We have developed a transparent framework that reveals the magnitude of the cost savings that coordinated infrastructure design and operation unlocks for the Bay."
The framework models monthly capital and operational decisions over thirty years across multiple facilities simultaneously, identifying the lowest-cost portfolio of upgrades across a watershed rather than within any single plant's fence line. The researchers found that a staged scenario in which plants delay construction until it's needed, rather than building in advance of permit deadlines, generated meaningful savings. However, the largest gains came from staged and full coordination: jointly deciding what to build, where, and when across all three plants.
Timing matters too. The analysis found that beginning coordination now would save an additional 32 percent compared to waiting until 2045, by which point many plants will have already locked in their infrastructure decisions and their debt.
Several Bay Area utilities are in conversations about forming a regional coordination effort, according to Abi Farraj, but most are waiting for regulators to approve an official coordination framework before committing.
"The only way you convince a plant to coordinate is to show them exactly how much their ratepayers will save and give them confidence that they will still be able to maintain regulatory compliance," said Abi Farraj. "That's what this tool is designed to do."
The study grew out of a project that received early funding from the Stanford Woods Institute for the Environment’s Realizing Environmental Innovation Program. A separate study informed by the project showed how water systems, such as desalination plants and wastewater treatment facilities, could help enhance grid stability and create new revenue streams.
Study co-author Akshay Rao is a PhD student in civil and environmental engineering, a joint department of the Stanford School of Engineering and the Stanford Doerr School of Sustainability.
Mauter is also a senior fellow at the Stanford Woods Institute for the Environment and the Precourt Institute for Energy, both in the Stanford Doerr School of Sustainability. She is also an associate professor of photon science and, by courtesy, of chemical engineering.
The research also received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) Postgraduate Scholarship-Doctoral (PGS D) award.
Journal
Nature Water
Article Title
Valuing regional coordination of nutrient discharge management
Article Publication Date
24-Sep-2026
Waste bullrush transformed into copper-enhanced material for dye removal from wastewater
Using an ecofriendly technology, researchers have developed a reusable adsorbent capable of removing harmful synthetic dyes from industrial wastewater
image:
Schematic illustration of the green, single-step co-pyrolysis process for preparing the ZVCu@BAC composite from bullrush weed biomass and copper precursor without hazardous chemical reducing agents.
view moreCredit: Mr. Asif Ali, Professor Michiaki Matsumoto, and Professor Yoshiro Tahara from Doshisha University, Japan https://www.sciencedirect.com/science/article/abs/pii/S2213343726034962 Copyright © 2026 Elsevier Ltd.
Industrial activities, such as textile manufacturing, paper production, leather processing, and food processing, can generate wastewater containing synthetic dyes. Because many synthetic dyes are chemically stable, difficult to biodegrade, and environmentally persistent, their release into water bodies can pose risks to aquatic ecosystems and human health.
To address this challenge, researchers at Doshisha University, Japan, devised a single-step co-pyrolysis strategy to valorize agricultural waste into an amphoteric adsorbent that can effectively remove synthetic dye contaminants. This ‘green’ solution to the synthetic dye-driven ecological crises was put forward by Mr. Asif Ali, PhD Student (MEXT Scholar); Professor Michiaki Matsumoto; and Professor Yoshiro Tahara at the Department of Applied Chemistry, Graduate School of Science and Engineering, Doshisha University. This study was made available online on August 19, 2026, and was published in Volume 14, Issue 5 of the Journal of Environmental Chemical Engineering on October 01, 2026.
Sharing their motivation for this study, the first author Mr. Asif Ali says, “An alarming 20% of toxic, recalcitrant textile wastewater is discharged untreated causing severe damage to aquatic life and human health. So far, no single wastewater treatment method is universally suitable.” Conventional treatment methods, including membrane separation and advanced oxidation, can be constrained by high energy requirements, secondary products, fouling, maintenance, and operational costs. Activated carbon provides an effective alternative for dye removal; however, commercial activated carbon can require costly production and regeneration, while some metal-modification approaches require additional chemical reducing agents.
To overcome these technical and environmental hurdles, the research team used bullrush agricultural waste as the sustainable carbonaceous precursor, while copper (II) nitrate trihydrate and potassium hydroxide (KOH) facilitated the in-situ growth of zero-valent copper nanoparticles (Cu0) within a mesoporous framework. In a single-step co-pyrolysis strategy, by harnessing the biomass's own in-situ volatile reducing gases (CO and H2) to reduce copper precursors, they fabricated a zero-valent copper nanoparticle-enhanced bullrush activated carbon composite, namely ZVCu@BAC, without using secondary chemical reductants.
To comprehensively characterize the composite, the team used advanced imaging techniques like SEM, TEM, EDX mapping, FTIR, BET, and XRD. They found that unlike the unmodified BAC, which formed an amorphous, highly porous structure, the ZVCu@BAC composite, with a high surface area of 984.5 m2/g and a total pore volume of 0.615 cm³/g, exhibited a mesoporous architecture, achieved a uniform, non-agglomerated distribution of needle-like Cu0 structures securely anchored across the carbon matrix. The characterization also included TGA/DTA.
Next, the research team conducted comparative batch adsorption experiments to evaluate the removal profiles of cationic Methylene Blue (MB) alongside anionic Methyl Orange (MO) and Sunset Yellow (SY). Benefiting from an amphoteric interface (pHpzc ≈9.0), the ZVCu@BAC composite achieved superior broad-spectrum removal for both cationic (MB, qm = 62.31 mg/g) and anionic dyes (MO, qm = 56.37 mg/g; SY, qm = 35.76 mg/g). The equilibrium data were best described by the Langmuir isotherm, while pseudo-second-order kinetics indicated that chemisorption played a major role in the rate-controlling process. Thermodynamic evaluations established that the adsorption processes were highly spontaneous (ΔG∘ < 0) and fundamentally exothermic (ΔH∘ < 0). The adsorption was supported by a multi-pathway mechanism involving electrostatic attraction, π─π stacking, pore-filling, and coordinate bonding with metallic Cu0 sites.
Further characterization showed that the composite exhibited excellent structural integrity and durability, retaining 90.6% MB removal efficiency and 88.0% MO removal efficiency after six regeneration cycles using a simple 0.1 M KOH/acetone eluent. Taken together with an estimated production cost of only ~¥1800 JPY/kg, these insights position the bullrush-derived ZVCu@BAC composite as a highly cost-effective, sustainable, and scalable candidate for industrial wastewater treatment.
This composite could potentially be explored for simultaneous mixed-dye removal during industrial wastewater remediation, with the wide operational pH tolerance expanding its applicability. Further, solvent-based cyclic regeneration capability may help reduce composite replacement requirements.
Emphasizing the significance of their findings, Prof. Matsumoto says, “Our study findings present the opportunity to advance a circular economy: valorizing invasive, zero-cost bullrush weed biomass into a functional carbon framework through an ecofriendly, single-step co-pyrolysis route.”
This study brings us one step closer to keeping rivers and streams clean, protecting our valuable water resource.
About Dr. Asif Ali from Doshisha University, Japan
Dr. Asif Ali received his PhD degree in Engineering from Doshisha University in September 2026. He was a MEXT Scholar at the Graduate School of Science and Engineering, Doshisha University. His research focuses on the development of advanced functional materials for removal of pollutants in water through adsorption, and for use in energy storage applications such as batteries and super capacitors. Dr. Ali’s research expertise in environmental chemistry has led to publication of 14 research articles.
About Professor Michiaki Matsumoto from Doshisha University, Japan
Dr. Michiaki Matsumoto is Professor at the Department of Applied Chemistry, Doshisha University. He received his Master of Engineering from the Department of Synthetic Chemistry, School of Engineering, Kyushu University in 1980. Soon after, in 1982, he received his Doctor of Engineering degree from the same department at Kyushu University. Professor Matsumoto joined Doshisha University in 2008, and has established his expertise in bioreaction engineering, separation technology, extraction, and membrane separation. He has published over 230 research articles and has received awards for his achievements.
Proposed synergistic adsorption mechanisms of cationic (Methylene Blue) and anionic (Methyl Orange, Sunset Yellow) dyes onto ZVCu@BAC, highlighting electrostatic attraction, π− − π stacking, hydrogen bonding, pore filling, and localized coordination with metallic Cu0 active sites.
Credit
Mr. Asif Ali, Professor Michiaki Matsumoto, and Professor Yoshiro Tahara from Doshisha University, Japan https://www.sciencedirect.com/science/article/abs/pii/S2213343726034962 Copyright © 2026 Elsevier Ltd.
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Journal of Environmental Chemical Engineering
Article Publication Date
1-Oct-2026
COI Statement
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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