OsmoFlux

Desalination supplies drinking water to 300 million people — and returns 142 million cubic meters of hypersaline brine to the sea every day, where it sinks onto the coastal ecosystems that can least afford it. Only 0.5% of Earth’s water is usable freshwater, and over four billion people live in water-stressed regions, so the world’s 22,000 plants are not optional. Yet their brine, most of it discharged straight to the sea, is enough to bury Florida a foot deep every year. At nearly twice the salinity of seawater, it spreads across the seafloor, draining oxygen at the base of fragile coastal ecosystems, every day the plant runs. In 2022 a $1.4 billion California plant was denied its permit partly over brine.

OsmoFlux offers desalination plants a new way to get an engineering answer to the brine question. Reverse electrodialysis (RED) is a membrane technology studied mainly as a way to generate electricity. OsmoFlux is a screening tool for plant engineers to evaluate RED to dilute discharge while recovering power. A plant enters its own flows, brine chemistry, and permit limits, and OsmoFlux returns the optimal RED stack design for meeting that limit, along with what it costs to build and run.

• What the model found: the load that maximizes power and the load that minimizes concentrate salinity are different. Across 4,353 stack designs, operating at 90 % of peak power raises salt transfer by a median 21.5 % while lowering concentrate salinity by 1.20 g/L, because water leaves the concentrate along with the salt and offsets much of the salinity gain.
• Where treatment comes from: adding membrane or dilute water outranks rearranging the same resources into stages.
• What it changes: selecting hardware and load together meets the same outlet duty with 23 cell pairs instead of 36–37, and lowers the avoided-treatment value needed to justify the stack by 34 %, even when the stack imports electricity.
• A real feed: a module case built from the Carlsbad Desalination Plant’s published feed and permit data shows the same hardware saving (29–33 %). When dilute water is scarce, the dilute outlet becomes the binding condition and the preferred load adjustment reverses.

OsmoFlux offers desalination plants a screener to explore optimal design configurations. A plant would set the two outlet limits, the dilute-supply ratio, the membrane budget and the retained-power rule. OsmoFlux checks water feasibility from conservation, looks up the design in the survey, reports the fewest pairs that meet both limits, and ranks the four levers - power, water, membrane, rearrangement - by the benefit provided.