Optimising cost and value.
Whether reuse makes sense in any given place depends on two things: how much it costs to deliver the water, and how much that water — and anything recovered with it — is worth.
Cost of infrastructure
What it takes to deliver the water
Extent
How much new infrastructure is needed
Complexity
How clean the water must be made
Value of the product
What the water (and recovery) is worth
End use
What the water replaces or supplies
Recovery
Energy, nutrients and minerals
Reuse is attractive when value exceeds cost.
The cost spread
The outrageous range of reuse costs.
Differences in the scope and complexity of projects mean that there is a three orders of magnitude difference in the per cubic metre of product water cost of water reuse projects. Geography explains a lot of these differences: labour costs and permitting requirements are lower in some countries than others. Extent and complexity explain the other costs. In some cases a reuse project may involve no more than directing a pipe into an irrigation canal. In others it might involve multiple advanced oxidation processes and long distance conveyances.
Boxes show interquartile range (25th to 75th percentile); thick line is the median. Whiskers extend to 1.5 × IQR; dots are outliers beyond.
Source: GWI Reuse Project Tracker; excludes China.
Industrial reuse economics
Industrial reuse economics
On-site industrial water reuse enjoys a much lower standard deviation in unit cost than municipal reuse systems, but the economics of water reuse in industry is much more complex. It is inextricable from overall production economics. It is also complicated by regulation. The more times water is used in a plant the more contaminants are likely to build up (reducing process efficiency), but the more contaminated a wastewater stream becomes, the more troublesome it is to dispose of. It leads to the “dilute to pollute” phenomenon whereby it is often cheaper to dilute a waste stream with water to within permitted limits than to save the water and produce a concentrated waste stream that might violate regulations. Changing the economics of industrial water reuse will involve improving the economics of treatment and finding more value in waste streams as an alternative to disposal.
What goes into the cost
The anatomy of a reuse project cost.
The six stages of the treatment train are where project-to-project variation lives. Some projects need every stage built from scratch; others need just one. Within each stage, the technology chosen can swing the cost by an order of magnitude.
Total project cost
Construction
The treatment train and pipes
Non-construction
Soft costs and finance
Water reuse infrastructure
Collection
Sewers, pump stations, lift stations
Primary
Screening, grit removal, sedimentation
Secondary
Biological treatment, clarification
Disinfection
Basic pathogen removal
Polishing
Advanced treatment to spec
Distribution
Pipes, pumps, storage, conveyances
Polishing technology options
used in combination, depending on end use
Other value recovery
value pulled out alongside the water
Sludge
Processing and energy recovery
Nutrients
Removal and recovery
Materials
Other value recovery
Non-construction costs
- Project development
- Planning
- Design
- Permitting
- Public outreach
- Insurance
- Project management
- Contractor overhead & profit
Financing costs
- Capital amortisation
- Interest cost
Often the largest line item
Variation comes from which stages are built, and how far the polishing has to go.
Case study
Napa Purified Water — two alternatives at 10 MGD.
The Napa Sanitation District's potable reuse feasibility study (Carollo) is one of the few public DPR programmes with a fully itemised cost stack. Both delivery alternatives share the same 37,850 m³/d advanced water purification facility — only the conveyance and storage infrastructure changes. It is the clearest available view of where treatment money actually goes.
Alt 3 — Treated water augmentation
$7,136 per m³/day
Alt 6 — Raw water augmentation
$7,919 per m³/day
Napa treatment breakdown — same for both alternatives ($6,251 per m³/day)
Treatment unit-process splits estimated from comparable California DPR studies; neither project publishes a public itemised breakdown of the sub-processes within the AWPF.
Source: Napa Sanitation District Potable Reuse Feasibility Study (Carollo). Costs in USD per m³/day of installed capacity.
Case study
Pure Water Southern California — anatomy of a $9 billion programme.
The Metropolitan Water District of Southern California and Los Angeles County Sanitation Districts' Pure Water Southern California (PWSC) project is one of the world's largest planned potable reuse schemes — roughly 150 MGD (568,000 m³/day) of purified water for groundwater recharge and indirect potable reuse.
Capacity
~568,000 m³/d
150 MGD at full build-out
Total project cost
~$9 billion
Range $8–10 bn
Unit cost
~$15,800
per m³/day capacity
Composition
Breakdown ($4.5bn treatment)
indicative split — see footnote
Sub-process splits are estimated from comparable California DPR programmes; the PWSC programme has not published a public itemised breakdown.
Annual operating cost (~$415M / yr, range $300–500M)
dominated by energy, membranes, chemicals, staffing
Sources: PWSC program material; Napa DPR feasibility study (Carollo); comparable California IPR/DPR engineering studies. Figures are indicative mid-points within published ranges.
Comparison
Advanced treatment costs benchmarked.
Cost per m³/day of installed capacity, by unit process, for the two California reuse programmes. Different scales — Napa at 10 MGD, PWSC at 150 MGD — yet the per-process unit costs land in remarkably similar territory. Reverse osmosis and membrane pretreatment dominate in both.
Reverse Osmosis (RO)
Microfiltration / Ultrafiltration (MF/UF)
Buildings
Ozone / Biological Activated Carbon (BAC)
Ultraviolet Disinfection / Advanced Oxidation (UV / UV-AOP)
Residuals
Chemicals
Napa figures from the District's Potable Reuse Feasibility Study (Carollo). PWSC per-process figures derived by dividing indicative treatment line items ($bn) by 568,000 m³/d nameplate capacity. Both breakdowns are best-available estimates; sub-process splits are not publicly itemised by either programme.
Part 2 — Levellised cost per m³ of delivered water
The price the water actually sells for — for comparison.
All-in cost per cubic metre once finance and operations are spread over delivered volume. The three Californian potable reuse projects sit at the top. Beneath them, nine Saudi independent sewage treatment plant tariffs show what competitively procured non-potable reuse costs at scale. Two recent large seawater desalination plants anchor the bottom of the chart.
California potable reuse
Pure Water Southern California
150 MGD · IPR · $2,900/AF
$2.35Napa Alt 3
10 MGD · DPR/TWA · $3,000/AF
$2.43Napa Alt 6
10 MGD · DPR/RWA · $3,200/AF
$2.59
Saudi Arabia — non-potable reuse (ISTP tariffs)
Jeddah Airport 2
2019 · no conveyance
$0.24Taif
2019 · no conveyance
$0.29Madinah 3
2021 · no conveyance
$0.32Dammam West
2019 · no conveyance
$0.34Arana
2025 · 41 km conveyance
$0.36Buraydah 2
2021 · no conveyance
$0.38Tabuk 2
2021 · no conveyance
$0.38Al-Haer
2023 · 32 km conveyance
$0.52Hadda
2025 · 38 km conveyance
$0.63
Large seawater desalination
Soreq II
Israel · 548,000 m³/d · PPA
$0.41Hassyan
Dubai · 818,000 m³/d · PPA
$0.37
What the comparison shows
- Californian potable reuse delivers water at $2.35–$2.59 per m³. Large modern seawater desalination delivers it at $0.37–$0.41 — roughly six times cheaper.
- Saudi Arabia's competitively-procured non-potable reuse plants land in the same band as desalination, at $0.24–$0.63 per m³. Treatment to irrigation rather than potable spec, large scale, and competitive PPP procurement do most of the work.
- Within the Saudi cluster, the three most expensive projects (Al-Haer, Hadda, Arana) all include long-distance conveyance — 32 to 41 km. The six cheapest have no conveyance burden at all. Even on a 30¢/m³ baseline, getting the water from where it's made to where it's used adds real cost.
- Years of competitive price discovery in the Middle East desalination market give us a very clear idea of what the price of desalination should be. We are still a long way from understanding what the cost of reuse should be.
PWSC: MWD lifecycle unit cost, 150 MGD, 100% debt at 4% over 30 years. Napa: Carollo feasibility study (2024), 12-month operation. SWRO and Saudi ISTP figures are published 25-year PPA / BOT tariffs at preferred bidder award.
Sources: MWD official programme material; Napa Purified Water Feasibility Study; GWI DesalData; Saudi Water Partnership Company tender data.
The economics page so far has been about cost. But cost is only half the picture. Whether a project gets built — and whether the water it produces commands a price that covers its cost — depends just as much on what the water is worth to whoever uses it. And reused water is not all the same product. A litre delivered to a farm and a litre delivered to a chip fab are valued in entirely different worlds.
The value of water
A cubic metre of water is not a cubic metre of water.
What reused water is worth depends entirely on what it replaces or supplies. Water to irrigate a hectare of farmland and water to feed a semiconductor fabrication line are both, literally, cubic metres of H₂O. Their economic value differs by a factor of fifty or more. Migrating reuse capacity towards higher-value applications is one of the two main ways to improve the economics of reuse.
- Industrial process water is the most valuable on average. The low end of the industrial range ($0.80) is already above the high end of irrigation ($0.40). It reflects the fact that industrial users need a higher quality of water than agricultural water users.
- The value of water is always a function of the alternatives. Communities which can source raw water for potable use for less than $0.50 per m³ are unlikely to consider a potable reuse project.
- Most of today's reuse capacity is supplied at the bottom of the value scale. Irrigation, environmental flows, and other non-potable uses dominate the global reuse mix — and almost none of it is paid for at anywhere near the price reflected here. Most reclaimed water is supplied free of charge to farmers.
Value ranges represent typical willingness-to-pay and avoided-cost benchmarks across each application class. Within each range, value varies substantially by location, alternative supply costs, and end-user characteristics.
Source: GWI analysis; industry benchmarks.
Both sides of the economic ledger can move. Cost can come down — through innovation, scale, and smarter procurement. Value can go up — through migrating capacity towards higher-value applications and through reforming how water is priced. The two levers don't pull against each other; they pull together. The next section is about how.
Changing the economics
How do we change the economics of water reuse?
Scale
Reuse is still a cottage industry, with each project feeling like the first of its kind. As the industry scales, projects will become more standardised and easily replicated. There will also be more economies in the production of the basic components of the treatment train. That is why we call this the Scaling Reuse Initiative.
Innovation
Water reuse projects involve a huge range of treatment processes, all of which can be improved to bring down the cost of reuse. Ensuring that the R&D community is focused on the right challenges is what our Tech Innovators Working Group is all about.
Public attitudes
A huge amount of the cost of water reuse arises from the fact that the public is unfamiliar with it and concerned about the potential risks. We need to turn the argument around so that reuse is welcomed as the most sustainable source of water. That is part of what our Cities, Utilities and Communications Working Group is tasked with doing.
Regulation
The value of reuse is very much a function of regulation. Under-regulation creates unnecessary obstacles to reuse projects, while over-regulation can make them prohibitively expensive. Our Policy and Regulation Working Group aims to promote fit-for-purpose enabling regulation for water reuse.
Finance
Water reuse has a double or triple value proposition: wastewater treatment, product water sales, and energy/materials recovery. It should be an excellent investment. Our Finance Working Group is dedicated to opening up that opportunity and developing easily replicable models.
Industry
The most valuable opportunity in water reuse is probably in partnerships between industrial water users and municipal wastewater utilities. We need to unlock this potential by bringing the two sides together. That is part of the purpose of our Industry & Supply Chain Working Group. The other part is exploring and promoting best practice in on-site reuse so that it is as widely adopted as possible.
