A new aquaculture technology that recycles wastewater within fish farming systems could reduce water use by up to 94 percent while lowering environmental pollution, according to a new study by researchers at the Freshwater Institute in the United States.
The study, published in the journal Aquacultural Engineering, examined the use of multi-vessel membrane bioreactors (MBRs) integrated into recirculating aquaculture systems (RAS) used for rainbow trout farming.
Researchers found the technology dramatically reduced the amount of freshwater required without affecting fish growth or survival.
Recirculating aquaculture systems are land-based fish farming operations where water is continuously filtered, treated and reused. Although these systems already use less water than traditional fish farming methods, they still require regular water replacement to maintain water quality and remove waste.
The newly tested membrane bioreactor system treats wastewater generated from drum filter backwash and solids flushing before returning the cleaned water into the production system.
According to the researchers, the innovation reduced daily make-up water requirements from about 2,004 litres to only 129 litres. Water exchange rates also fell sharply from 21 percent to 1.4 percent.
The technology combines membrane filtration with aerobic and anoxic treatment zones that help remove solid waste while supporting nitrification and denitrification processes necessary for maintaining water quality. Researchers said the treated systems maintained stable production conditions throughout the four-month trial.
Scientists say the findings could help address growing concerns over water consumption and nutrient pollution associated with aquaculture, one of the world’s fastest-growing food production sectors.
Global aquaculture production reached 94.4 million tonnes in 2022, according to previous studies, increasing pressure on freshwater resources and surrounding ecosystems.
Experts note that improving water efficiency has become increasingly important as fish farming expands to meet rising global demand for seafood. New technologies such as advanced filtration systems, biofloc systems, integrated multitrophic aquaculture and digital monitoring tools are being explored to make aquaculture more sustainable.
The study’s findings also come as countries seek ways to reduce environmental impacts linked to aquaculture, including nutrient discharge, disease transmission and depletion of freshwater resources.
Researchers involved in European aquaculture projects have previously highlighted that smarter water reuse technologies can significantly lower pollution while improving fish welfare and farm productivity.
The technology may also hold promise for emerging aquaculture markets in Africa, where affordable recirculating systems are being tested to improve fish production while conserving water.
A recent feasibility study in Kenya’s Nyeri County found that affordable recirculating aquaculture systems reduced water use by between 27 and 40 percent compared to conventional fish ponds.
Researchers say wider adoption of membrane bioreactor systems could support more sustainable fish farming, particularly in regions facing water scarcity and tightening environmental regulations.
