auma assessed thedischarge of reject water from a desalination unit at a marina on the Costa Brava: what effect the brine actually has on the receiving marine environment and under what conditions the discharge is acceptable.
Project overview
| Client | Marina facility (confidential) |
| Market | Utilities |
| Practice area | Water · Environment |
| Location | Costa Brava |
| Services | Discharge assessment report |
| Year | 2025 |
The challenge
Desalination solves a water availability problem and creates another at the outlet: what to do with the concentrated stream it produces.
- High salinity: the reject water is far more concentrated than the receiving environment.
- Sensitive seabed: the Mediterranean coast hosts habitats especially vulnerable to increased salinity.
- Small scale, same requirements: a modest facility must justify its discharge with the same technical rigour.
The auma solution
The report focuses on what governs acceptability: actual dilution at the discharge point.
- Characterisation of the flow and composition of the reject water relative to the receiving environment.
- Analysis of the discharge plume behaviour and its dilution under the conditions at the point.
- Assessment of potential effects on the marine environment and the conditions that make the discharge acceptable.
The result
- Technical report setting out the discharge assessment and its acceptability conditions.
- A documentary basis for dealing with the authority responsible for marine discharges.
- An objective basis for operational decisions about the facility.
For a discharge to the sea, the relevant question is not how much is discharged, but how it dilutes and what it falls on.
Frequently asked questions
What is desalination brine?
The reject stream of the desalination process: the water left with a far higher salt concentration than the original once the product water is separated. Every reverse osmosis process generates it.
Why is brine discharge a concern?
Because a local rise in salinity can affect sensitive marine communities, particularly Mediterranean seagrass meadows. The impact depends on flow, depth, currents and above all on the dilution achieved.
What permit does a marine discharge need?
Authorisation from the competent authority, with effluent characterisation and justification of compatibility with the receiving environment. If the setting is a protected site, a specific impact assessment is also required.
Do you need to justify a discharge before the authorities?
We characterise the effluent, analyse its dilution and defend the discharge conditions on technical grounds.
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