Analysis of the particle size specific effectiveness of rainwater treatment systems with a particle counter

Supplementary option for the determination of fine particulate substances (AFS63)

Abstract

Filterable substances (AFS), which is closely equal with the parameter total suspended solids (TSS), is used as indicator parameters for the contamination of stormwater-runoff and for the effectiveness assessment of stormwater-runoff treatment systems. Worksheet DWA-A 102 (DWA/BWK,
2020) recommends the fine fraction of filterable substances (AFS63) for assessing the contamination of stormwater-runoff and the water pollution caused by discharge. AFS is defined as all sink, suspended, and floatables retained by a filter with a pore size of 0.45 µm. The fine fraction AFS63 summarizes the suspended solids of the size range 0.45 µm to 63 µm. However, the influencing variables and conditions for determining the AFS63 parameter are complex. This begins with the taking of a representative sample and continues through to the determination of the parameter. While the determination of AFS is regulated in standards, the mandatory determination of AFS63 is currently under discussion. In view of the fact that the parameter AFS63 is used to prove the effectiveness of treatment plants, a correct determination for balancing the contamination of influent and effluent is of particular importance. A comparatively simple and representative determination with a particle counter has turned out to be a useful supplement to the previous determination method.