High-COD, high-TDS industrial effluent
Treat organics and salt in one step.
- Pharma and chemicals
- Textile and dyeing
- Food processing reject
RESEARCH PARTNERSHIP / 14
Available for pilot projectsDelivered by Rispri Labs
Microbial desalination cell.
Bacteria that clean and desalinate.
Rispri Labs offers microbial desalination cells, an emerging technology now available for pilot projects. Electroactive bacteria break down the organic load in wastewater and generate a current that pulls salt out of a saline stream, while hydrochloric acid and caustic soda are recovered as by-products.
RESEARCH TO REALITYRispri Labs research collaborations
What it means for you
Treat the organics, remove the salt, recover the chemicals.
70–85%
COD removal on complex, high-TDS effluent (design figure).
HCl + NaOH
recovered as by-products instead of a waste brine.
5 KLD
modular field-scale units for industrial effluent and seawater.
Performance
One cell, five chambers.
High-COD, high-TDS effluent is the hardest stream in many ZLD plants: the salt defeats biology and the organics foul RO and evaporators. A microbial desalination cell uses the organics as fuel. The bacteria release electrons, and the current they make drives salt ions out of the saline chamber into recovery chambers.
- 70–85%
- COD removal on complex high-TDS effluent (design)
- 5KLD
- Modular field-scale unit size
- 2by-products
- Hydrochloric acid and caustic soda recovered
- <3.5kWh/m³
- Target: below the 3.5–5 kWh/m³ of conventional seawater RO
These are design figures. The microbial desalination cell is available for pilot projects: each pilot runs on your own effluent, and our NABL-accredited laboratory measures the results before any scale-up.
Challenge and response
The problems this solves.
- 01The challenge
High salt stops biological treatment in a normal ETP.
How we solve itSalt is moved out of the stream electrically while bacteria treat the organics.
- 02The challenge
High-COD reject fouls RO membranes and evaporators.
How we solve itBacteria remove 70–85% of COD (design figure) before the stream goes further.
- 03The challenge
ZLD leaves a mixed salt that is hard to dispose of.
How we solve itAcid and alkali are recovered as HCl and NaOH, moving towards near-ZLD.
- 04The challenge
Seawater RO uses 3.5–5 kWh for every cubic metre.
How we solve itThe cell is powered by the organic load itself and aims to use less.
How it works
The five chambers, step by step.
Each cell has five chambers separated by ion-exchange membranes.
- 1
Anode
Electroactive bacteria oxidise the organics in the wastewater and release electrons.
- 2
Acid recovery
Chloride ions collect here and leave as hydrochloric acid (HCl).
- 3
Desalination
Saline water or effluent loses its salt as ions move out under the current.
- 4
Alkali recovery
Sodium ions collect here and leave as caustic soda (NaOH).
- 5
Cathode
Electrons complete the circuit, closing the current that drives the salt out.
Two reactor designs
Tubular or stacked flat-plate.
Both designs run the same five-chamber process. The choice depends on flow, space and how the units are serviced.
Cylindrical tubular
A compact cylindrical reactor with the five chambers in a tubular layout.
Modular stacked flat-plate
Flat-plate chambers built as stacked modules, so capacity grows by adding stacks.
Feed basis for industry
Industrial units are designed on a field feed of 8–10 g/L COD and 10–20 g/L TDS, and confirmed on your effluent.
Use cases
Where a microbial desalination cell fits.
Coastal seawater desalination
Desalinate seawater using the energy in wastewater.
- Coastal industry
- Island supply
- Port facilities
Near-ZLD with acid and alkali recovery
Recover HCl and NaOH instead of a mixed waste salt.
- ZLD front end
- Reject treatment
- Chemical reuse
Decentralised plants for coastal industry
Modular 5 KLD units close to the source.
- Industrial estates
- Coastal clusters
- Remote sites
Start with a pilot
A pilot unit runs on your own effluent before any commitment.
- Sample characterisation
- On-site pilot
- Measured results
Verified by our NABL lab
COD, TDS and by-product quality are measured independently.
- COD and TDS
- HCl and NaOH strength
- Energy use
Comparison
How it compares.
| Factor | Conventional route (RO / MEE) | Rispri solution |
|---|---|---|
| Organics | Removed separately before RO | 70–85% COD removed in the cell (design) |
| Salt removal | High-pressure RO or steam evaporation | Ion migration driven by bacterial current |
| Energy | 3.5–5 kWh/m³ for seawater RO | Aims to use less, powered partly by the organic load |
| By-products | Mixed waste salt | HCl and NaOH recovered |
| Scale | Large central plant | Modular 5 KLD units |
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 guidelinesGuidance on zero liquid discharge for water-polluting industries.
- Water (Prevention and Control of Pollution) Act, 1974Consent conditions, including no-discharge clauses.
- Environment (Protection) Rules, 1986Discharge standards for treated effluent.
- Hazardous and Other Wastes Rules, 2016Handling of residues and recovered chemicals.
Industries served
Built for the sectors that need it most.
Why Rispri
Proven technology. Industrial delivery.
Field-proven technology
A proven, field-tested technology from our research collaborations with IIT Bombay, IIT Kharagpur and ICT Mumbai.
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.
What is a microbial desalination cell?
It is a reactor in which electroactive bacteria break down the organic load in wastewater and generate an electric current. That current pulls salt ions out of a saline stream, so the same unit treats organics and removes salt.
How does it remove salt?
The cell has five chambers: anode, acid recovery, desalination, alkali recovery and cathode. Under the current made by the bacteria, chloride ions move to the acid chamber and sodium ions to the alkali chamber, leaving the middle stream with less salt.
What is recovered?
Hydrochloric acid (HCl) and caustic soda (NaOH) are recovered as by-products, which supports near-ZLD operation instead of producing a mixed waste salt.
Which effluents suit it?
Complex effluent with both high COD and high TDS. Industrial units are designed on a field feed of 8–10 g/L COD and 10–20 g/L TDS, with a design COD removal of 70–85%.
How much energy does it use?
It is designed to undercut the 3.5–5 kWh/m³ used by conventional seawater RO, because part of the energy comes from the organic load itself. The figure for your stream is measured in the pilot.
What sizes are available?
Modular 5 KLD field-scale units for industrial effluent and seawater, in cylindrical tubular or stacked flat-plate designs.
Is it available now?
Yes, for pilot projects. It is the newest technology in our portfolio, so every project starts with a pilot on your own effluent, and our NABL-accredited laboratory measures COD, TDS and by-product quality before any scale-up.
Research partnerships
More solutions from our partnerships.
THE NEXT STEP
Prove it on
your own effluent.
Send us an analysis of your high-COD, high-TDS effluent or saline stream. We will assess it and propose a pilot.
Request a pilot