Zero Liquid Discharge Patents: Leaders & Filing Trends 2026
- Filing has cooled since its 2021 peak. 92 families published that year against 21 so far in the most recent (partial) year — activity is flat to declining, not accelerating.
- Claims cluster in wastewater treatment and separation. C02F and B01D together cover the large majority of records, while salt-chemistry subclasses like C01D and C01F carry a fraction of that volume.
- The assignee base is thin at the top. Co-assignee pairs number only ten across the whole dataset, and momentum in the latest year is near zero for every organisation tracked, including past filers.
Filing growth compares 2021 (92 records) with 2024 (50) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 1,145 records in scope (CR5), not by the ranked leaders only.
What the zero liquid discharge patent record shows
Zero liquid discharge (ZLD) and brine minimization patents describe systems that recover water and solid salts from industrial or produced wastewater rather than discharging brine. The corpus behind this page spans 1,145 patent families published between 2015 and mid-2026, indexed against claims that combine ZLD or brine-minimization language with salt recovery, water recovery or selective salt crystallization. Filing offices are led by the United States, followed by WIPO/PCT filings and national offices in India, Europe, Australia and Canada at comparable volumes to each other.
Because publication typically lags filing by around 18 months, the most recent year's count of 21 understates true filing activity for that period. Even allowing for that lag, the trend line from the 2021 peak of 92 down through the 2022 midpoint of 64 points to a genuine slowdown rather than an artifact of reporting delay.
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Filing trends and technology composition
Two views of the same 1,145-family dataset: how filing activity has moved year over year, and which IPC subclasses carry the claim volume.
A peak in 2021, then decline
Filings rose from 81 in 2017 to a peak of 92 in 2021, then fell to 64 by the 2022 midpoint and down to 21 in the latest partial year. Read against the typical 18-month publication lag, the last two years still trend downward rather than merely appearing low.
Water treatment and separation dominate the IPC mix
C02F (water and wastewater treatment) appears in 756 records and B01D (separation processes including filtration) in 606, together accounting for most of the corpus. Salt-chemistry classes — C01D for alkali-metal compounds at 136 and C01F for alkaline-earth, aluminium and rare-earth compounds at 45 — sit well behind, alongside E21B well-drilling applications at 82 and B01J catalysis/process claims at 71.
Shares are the percentage of the 1,145 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Zero Liquid Discharge Resource Recovery with Eureka
This page is one run against one query. Ask Eureka your own question about zero liquid discharge resource recovery and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records and a representative filing
Industrial wastewater recovery apparatus aiming at zero liquid discharge (ZLD)
The application describes an apparatus that pre-heats wastewater through a spiral coil pipe using two heat exchangers to conserve heat, agitates the wastewater surface to raise evaporation rate, and condenses distilled water in two stages while monitoring water quality in real time. The design also includes automatic cleaning of internal components during operation.Filed by Meghanathan, Dharmendra; published 2020-01-09.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US20060060532A1 | Water desalination process and apparatus | 196 |
| 2 | US20040055955A1 | Production of purified water and high value chemicals from salt water | 132 |
| 3 | US7083730B2 | Production of purified water and high value chemicals from salt water | 127 |
| 4 | US20100163471A1 | Water desalination plant and system for the production of pure water and salt | 125 |
| 5 | US20190077686A1 | Zero-discharge technique for separating sludge and salt from desulfurization wastewater | 115 |
| 6 | US20060196836A1 | Process and apparatus for the treatment of saline water | 108 |
| 7 | US20120160753A1 | Water desalination plant and system for the production of pure water and salt | 97 |
| 8 | US20080110630A1 | Method for Production of High Pressure Steam from Produced Water | 94 |
| 9 | US20120267307A1 | Osmotic separation systems and methods | 91 |
| 10 | US7459088B2 | Water desalination process and apparatus | 89 |
Citation counts favour older records simply because they have had longer to accumulate references within the searched corpus; treat them as markers of influence on subsequent filings, not as a ranking of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers mean for filing strategy
Three patterns stand out once family counts, IPC composition and citation data are read together.
Growth has stalled, not accelerated
The 2021 peak of 92 families gave way to a midpoint of 64 in 2022 and just 21 in the most recent partial year. Even adjusting for an 18-month publication lag, this is a technology area past its filing high point rather than one still building.
The bottleneck is treatment and separation, not salt chemistry
Water and wastewater treatment (C02F) and separation processes (B01D) together dominate the IPC mix. Selective salt crystallization and alkali/alkaline-earth chemistry — C01D and C01F — carry far less filing density, suggesting the process engineering around ZLD is well claimed while the downstream chemistry is comparatively open.
Very little joint filing
Only ten co-assignee pairs appear across 1,145 families, and the strongest of these link a handful of filings each. Most patent activity in this space happens inside a single organisation rather than through joint ventures or co-development filings.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to zero liquid discharge resource recovery, with the prior art for and against each one.
| Assignee | Co-assignee | Shared families |
|---|---|---|
| Evoqua Water Technologies LLC | EVOQUA WATER TECH CANADA LTD | 5 |
| Oasys Water, Inc. | MCGINNIS ROBERT | 4 |
| General Electric Company | BL Technologies, Inc. | 4 |
| University of South Carolina | DAVIS THOMAS A | 4 |
| Water Technologies International LLC | SCHOEN RICHARD M | 3 |
| Water Technologies International LLC | MINNICH KEITH R | 3 |
| Water Technologies International LLC | KARLAPUDI RAMKUMAR | 3 |
| Water Technologies International LLC | TIWARI CHANDRAKANT | 2 |
Where co-assignment does occur, it links water-technology specialists to equipment or academic partners rather than spanning multiple large filers — a sign that cross-company R&D partnerships are the exception here, not the norm.
Who holds the claims, and where filing has gone quiet
Recent-year momentum is low across every organisation tracked in this dataset, including the assignees with the largest historical portfolios.
Even the most active recent filer is filing once
The single organisation with any latest-year activity in the tracked set recorded just one filing in that period; every other tracked assignee, including established water-technology and industrial names, shows zero in the same window.
Joint filings are the exception
Strongest pairings link a water-technology specialist to a Canadian affiliate, an ocean-systems firm to an academic collaborator, and an industrial conglomerate to its technology subsidiary — each at only a handful of shared filings.
Filing is US-anchored with broad international spread
The United States receives the largest single share of filings, with WIPO/PCT applications and national filings in India, Europe, Australia and Canada following at broadly comparable volumes to one another rather than one clear second market.
| Assignee | Recent year | YoY |
|---|---|---|
| Brisa International LLC | 1 | — |
| Water Technologies International LLC | 0 | — |
| Oasys Water, Inc. | 0 | — |
| Aquaporin Technology Ltd. | 0 | — |
| General Electric Company | 0 | — |
| Battelle Memorial Institute | 0 | — |
| EasyMining Sweden AB | 0 | — |
| Evoqua Water Technologies LLC | 0 | — |
Where to take this
The dataset points to a mature, slowing filing environment concentrated in process engineering rather than salt chemistry.
Check freedom to operate against the top-cited prior art
The highest-citation records in this corpus date from the mid-2000s to late-2010s and concern core desalination and purified-water recovery processes. Any new filing touching evaporation, crystallization staging or combined water/salt recovery should be checked against these first.
Run a freedom-to-operate searchScope claims around the under-claimed branches
Selective crystallization sequencing and alkaline-earth by-product recovery sit well behind the core treatment and separation classes in filing density. That gap is where a first claim has more room to stand without crowding existing art.
Explore white space in EurekaCommon questions about ZLD resource recovery patents
In this dataset, a ZLD patent is a filing whose title, abstract or claims combine zero liquid discharge, ZLD or brine-minimization language with salt recovery, water recovery or selective salt crystallization terminology. That combination captures process and apparatus claims for recovering usable water and solid salts from industrial wastewater rather than discharging brine to the environment. It excludes general desalination filings that do not address the recovery or valorisation side of the process.
The corpus shows filings rising from 81 in 2017 to a peak of 92 in 2021, then falling to 64 by 2022 and to 21 in the latest partial year. Because publication lags filing by roughly 18 months, the very latest year is always undercounted, but the multi-year decline from 2021 through 2022 predates that lag and reflects a real slowdown in new filing activity. This pattern is consistent with a technology area where core process claims are already well established and fewer new entrants are filing foundational patents.
C02F, covering water and wastewater treatment, appears in 756 of the 1,145 records, and B01D, covering separation processes such as filtration, appears in 606 — together these dominate the corpus. Salt-chemistry classes including C01D for alkali-metal compounds and C01F for alkaline-earth, aluminium and rare-earth compounds appear far less often, at 136 and 45 records respectively. That gap suggests the evaporation, filtration and separation engineering is heavily claimed, while the downstream salt-chemistry side has comparatively more open space.
The dataset tracks a handful of organisations with historical portfolios in this space, but recent-year momentum is low across all of them — the most active tracked assignee in the latest year recorded only a single filing, and every other tracked organisation recorded zero. Co-assignee pairings are also rare, with only ten pairs identified across the entire 1,145-family corpus, most linking a single specialist firm to an affiliate or academic partner rather than reflecting broad industry consolidation.
Filing density is comparatively thin in areas such as selective salt crystallization sequencing, alkaline-earth by-product valorisation, and waste-heat integration for evaporator stages, especially relative to the dense C02F and B01D core. Produced-water applications tied to well drilling (E21B, 82 records) and catalytic pretreatment of brine streams (B01J, 71 records) also carry lower volume than the core treatment classes. These are the branches worth scoping first for a new filing, since they sit adjacent to crowded claim territory without being buried in it.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.