Extra efforts for less phosphorus

Although we remove 85% of the phosphorus present in the waste water on average each year, the level of phosphorus in Flemish watercourses is still constantly too high. In freshwater ecoystems, phosphorus stimulates the growth of algae as a result of which the oxygen level drops and light incidence is reduced. Both effects have a negative impact on certain species of aquatic organisms. 

A social debte within the Coordination Committee on integrated Water Policy (CIW) during which various measures were compared showed that the targeted dosing of iron and aluminium salts in the water treatment process is by far the most cost-effictive measure for reducing the phosphorus burden on watercourses. These are vulnerable streams and brooks that are close to the target water quality from te Water Framework Directive.

Aquafin currently rolling out the installation of phoshate analysers at 50 WWTPs. Based on continuous measurement, the right amount of chemicals is then added automatically in order to achieve the target value of 0.3 mg/l on an annual basis while the standard for most WWTPs is 2 mg/l. The new European Urban Waste Water Directive is expected to bring the standard to 0.5 mg/l for all WWTPs from a population equivalent of 10,000.

By rolling out this project each year about 70 tonnes of phosphorus less will be discharged in our watercourses.

Phosphorus that is removed during the treatment process accumulates in the sludge produced. The more phosphorus that is removed, the more will also be recoverable via sludge processing in the future.