Nature-based solutions at the Torreele/St-André Water, Belgium

Since 2002 Aquaduin, based in Koksijde (Belgium), applies Indirect Potable Reuse (IPR) based on multiple barrier approach. The main treatment steps are submerged ultrafiltration (UF), reverse osmosis (RO) at WPC Torreele and finally Managed Aquifer Recharge (MAR) in the dune aquifer of water catchment St-André.

To improve the water quality of the RO concentrate, beginning 2022 Aquaduin took a Nature Based Solution (NBS) into operation. The concept of this NBS  is a horizontally constructed wetland (7.500 m²) combined with short rotation coppice using willows.

In the first 3 years of operation the results were very consistent. The concentration of total nitrogen dropped 31% on average. Most of the ammonia and nitrite was removed. The BOD content is removed by almost 100%. The removal capacity for COD and organic carbon is lower, respectively  7,5 and 10,9%. VITO also analyzed the removal capacity for organic micropollutants, as part of the NBRACER project. Compounds, like atenolol and gabapentine, are removed up to 80% on average. Others like diclofenac are not removed.

The scheme is also part of the CircSyst project. The first part of the research aims to compare different substrates and their ability to treat the concentrate. The second part of the research will be a pilot test using nanofiltration (NF) to treat the effluent of the NBS willow field. The purpose of this test is to investigate if the NF filtrate could be reused and treated directly with RO to increase the overall capacity of WPC Torreele.

Aquaduin will also perform tests with biochar produced out of harvested willows. The aim of these tests is to investigate the capacity of biochar as replacement of activated carbon for removal of organic micropollutants, e.g. PFAS.

Author:

Emmanuel van Houtte
Geologist