Chapter 02 · Nature, land & waterWater, Waste & Pollution
Brine
Definition
Water with a high concentration of dissolved salts, produced in large volumes as the residual concentrate of desalination, oil and gas extraction, and salt-flat mineral processing. Desalination brine can reach roughly twice the salinity of seawater and carries residual treatment chemicals; its disposal — typically to sea — is a major environmental concern for marine ecosystems.
References
Brine as desalination residual (~2× seawater salinity); discharge impacts on marine ecosystems; brine mining and recoverable minerals (Li, Mg, Ca, K); Lithium Triangle extraction.
Disposal best practice (diffusers, dilution, siting away from sensitive habitats).
Overview
What it means
Brine embodies a classic pollution-to-resource transition. As waste, poorly managed discharge can raise local salinity, deplete oxygen and harm benthic life; responsible practice uses multi-port diffusers, dilution and siting away from reefs and seagrass beds.
As resource, "brine mining" treats the stream as a process current: lithium is extracted from continental brines in the South American "Lithium Triangle", and desalination concentrates can yield magnesium, calcium, potassium and other minerals, turning disposal cost into revenue and reducing discharge volumes.
How it is used
Regulation of brine discharge features in desalination permits and marine-pollution frameworks; direct lithium extraction (DLE) technologies target geothermal and oilfield brines; circular-water strategies couple desalination with mineral recovery and zero-liquid-discharge systems.
Why it matters
Global desalination capacity is growing with water scarcity; whether its brine stream is managed as pollution or mined as a resource will shape both coastal ecosystems and critical-mineral supply chains.