A low-cost method of sterilising ballast water to help prevent the migration of potentially invasive species from port to port has been developed by scientists in the Philippines.

Ballast is a heavy material used to provide stability to structures. Onboard ships, water is pumped in or released to maintain stability by acting as a counterweight to cargo loaded into the holds.

As ships move around the globe, water taken onboard in one location is often discharged in another. When released, the water may carry with it bacteria, microbes, plankton, larvae, and other aquatic species alien to the new environment.

The risk is that these organisms compete with native species for resources and affect local habitats. Invasive species can also have serious impacts on human health and local economies. For instance, consumption of shellfish contaminated by toxic algae – some species of which are transferred to new areas in ballast water – can cause severe illness and death.

The biological invasion of parts of south-east Asia by Mytella strigata, an invasive mussel species native to the Western Atlantic, costs the Luzon aquaculture industry in the Philippines about US$5.4 million a year.

The prototype of the sterilising system uses a combination of UV rays and mechanical methods to reduce the number of invasive species in ballast water. It is funded by the Philippine Council for Industry, Energy & Emerging Technology Research & Development.

According to Benjamin Vallejo, marine biology professor at the Institute of Environmental Science & Meteorology, University of the Philippine Diliman, it is significantly cheaper than other available methods.

“The [Philippine] model costs US$300,000, as compared to US$1 million to 5 million in the market,” he said.

While some shipping companies can afford to have sanitation systems installed on their ships, others opt for shore and barge based systems available at certain ports. The new Philippine prototype is port-based, though it is possible to make a ship-based version, according to Vallejo.

Shipping is vital to intercontinental trade and over 50,000 merchant ships ply international waters. Ships releasing untreated ballast water are a major threat to ecological and economic well-being, says the International Maritime Organization.

By 8 September 2024, all ships meet a new standard set by the BWM Convention which specifies the maximum amount of viable organisms harmful to human health that can be discharged.

The original version of this article was produced by SciDev.Net’s Asia & Pacific desk.