RO reject concentration
Shrink reject volume before final disposal or salt recovery.
- Municipal and industrial RO
- Packaged drinking water plants
- Boiler feed RO
RESEARCH PARTNERSHIP / 01
Developed withIndian Institute of Technology Bombay#3 in engineering, NIRF 2025
Operating in industryDelivered by Rispri Labs
Zero liquid discharge.
Without the steam bill.
Rispri Labs delivers rotating-disk evaporators, developed with IIT Bombay, that concentrate RO reject and industrial effluent using ambient air or low-grade waste heat. ZLD compliance with a fraction of the energy of steam-driven evaporation.
RESEARCH TO REALITYRispri Labs × IIT Bombay
IIT Bombay
What it means for you
Zero liquid discharge on air, not steam.
No steam
Your effluent evaporates using outside air or heat you already throw away.
No scale
Disks stay clean on salty reject, and are washed while the unit runs.
Modular
Add units as production grows, instead of buying a bigger evaporator.
Performance
Built for the economics of ZLD.
Steam for multiple-effect evaporators and dryers is usually the largest running cost in a ZLD plant. Our rotating-disk evaporator moves that work to ambient air and waste heat, with a very low fan load and surfaces that resist scale.
- <10Pa
- Air-side pressure drop per rotor stage
- 300–400m²/m³
- Wetted surface packed into every cubic metre
- 0.5–3L/G
- Liquid-to-gas ratio without flooding or dry spots
- TRL 9
- Proven in wastewater vaporisation in industry
Figures are from the research team's industrial installations and field data. Performance on your stream is confirmed in our laboratory before design.
Challenge and response
The problems this solves.
- 01The challenge
Steam for MEE and ATFD dominates ZLD operating cost.
How we solve itEvaporate with ambient air or low-grade waste heat instead of live steam.
- 02The challenge
High-TDS reject scales evaporator tubes and forces shutdowns.
How we solve itSlow-turning disks resist scale, and online jet cleaning keeps them working.
- 03The challenge
Spray towers and evaporation ponds lose droplets and drift.
How we solve itThin films on the disks give no droplet carryover.
- 04The challenge
A fixed-size plant cannot grow with production.
How we solve itModular rotor units add capacity as your flow increases.
How it works
The process, step by step.
- 1
Feed
Effluent or RO reject fills a shallow reservoir under the rotor.
- 2
Rotate
The circulating flow turns textured disks that sit partly submerged.
- 3
Evaporate
Air sweeps the wetted disks and carries away water vapour at very low pressure drop.
- 4
Concentrate
The brine thickens for final solids recovery, while the disks are jet-cleaned online.
Use cases
Where zero liquid discharge evaporation delivers.
Industrial ETP zero liquid discharge
Evaporate treated effluent that cannot be discharged.
- Textile and dyeing
- Pharma and chemicals
- Common effluent treatment plants
Front end for existing MEE
Remove most of the water before it reaches the steam evaporator.
- Smaller MEE for new plants
- Lower steam use in existing plants
- Debottleneck overloaded evaporators
Seawater and brine concentration
Concentrate seawater or brine for salt and mineral recovery.
- Salt works
- Desalination brine
- Mineral recovery
Aeration and VOC stripping
Use the same contactor to aerate or strip volatile compounds.
- Wastewater aeration
- VOC stripping from groundwater
- Odour control
Low-energy cooling towers
Cool process water using treated wastewater or seawater as make-up.
- Treated wastewater make-up
- Seawater cooling
- Evaporative condensers
Comparison
How it compares.
| Factor | Steam evaporator (MEE / ATFD) | Rispri solution |
|---|---|---|
| Energy source | Live steam from a boiler | Ambient air or low-grade waste heat |
| Scaling | Tube scaling needs regular acid cleaning | Disks resist scale; online jet cleaning |
| Carryover | Spray systems lose droplets | No droplet carryover |
| Scale-up | Fixed vessel size | Modular rotor units added as flow grows |
| Materials | Stainless or exotic alloys throughout | Mainly plastic disks; PP, PC, SS, Al or MS by duty |
Standards and regulations
Designed around the rules that apply to you.
We design each system to meet your consent conditions and the regulations for your sector, and our laboratory reports against them.
- CPCB ZLD guidelinesTechno-economic guidance on zero liquid discharge for water-polluting industries.
- Water (Prevention and Control of Pollution) Act, 1974Consent to operate conditions, including no-discharge clauses.
- Environment (Protection) Rules, 1986Discharge standards for effluent that is not taken to ZLD.
- Hazardous and Other Wastes Rules, 2016Handling and disposal of recovered salts and sludge.
Industries served
Built for the sectors that need it most.
- Textiles and dyeing
- Pharma and chemicals
- Dairy
- Glass manufacturing
- Common effluent treatment plants
- Power and refineries
Why Rispri
Institute science. Industrial delivery.
Institute-developed technology
Built on patented and peer-reviewed research from our partnership with IIT Bombay.
Tested on your stream
Our accredited laboratory characterises your water or waste before design and verifies results after.
Engineering since 1999
The team that builds ETPs, STPs and ZLD plants across India takes each solution from pilot to full scale.
One accountable partner
Design, supply, installation, commissioning, operation and testing under one contract.
Questions
Frequently asked questions.
Can the rotating-disk evaporator replace an MEE?
For many flows it can carry out most or all of the evaporation. In other plants it works as a pre-concentrator that shrinks the MEE and cuts its steam use. We decide after testing your effluent and, where needed, a site pilot.
Does it work in humid weather?
Evaporation rate depends on air temperature and humidity. Where ambient air alone is not enough, we add low-grade waste heat from compressors, DG sets or process cooling. Units are sized against your site's climate data.
How does it handle high-TDS reject without scaling?
The disks turn slowly through the liquid and are cleaned online with water jets, so scale does not build up the way it does inside evaporator tubes. The design limit is confirmed on your own reject in our laboratory.
Is the technology proven?
Yes. It has reached TRL 9 for wastewater vaporisation, and units have been operating in industry as effluent and seawater concentrators.
What maintenance does it need?
Very little. A low-head circulation pump drives the disks, there are no high-pressure parts, and cleaning is done online.
Research partnerships
More solutions from our partnerships.
THE NEXT STEP
Prove it on
your own stream.
Send us a sample or tell us about your site. We will test it, recommend a configuration and set up a pilot.
Request a pilot