Soil and construction materials
Filter medium and a variety of sludges, such as carbon and coagulation sludge, can be reused as soil or as fill or embankment material in infrastructural works; for example, in a noise barriers or as road substrate. These applications are subject to the Soil Quality Regulations. Materials that meet the regulatory quality requirements can, upon certification, be used as soil, dredging spoil or construction material. This generally involves residuals with a waste material status; the certification does not change this status, even if in a couple of respects different (more flexible) requirements apply compared to those for waste materials.
We strive to have as few residuals as possible used as construction material in infrastructural works, because this is a low-value application which is not considered recycling under the waste hierarchy. Whenever possible, we recycle the residual in applications that spare the use of primary raw materials. Reuse as (clean) soil is in effect a form of recycling.