The parameter total suspended solids (TSS) is often used to evaluate the need for stormwater treatment or to assess the effectiveness of treatment measures. The purpose of this study is to analyze the value and the limitations of this approach using metals as an example. They are of major concern due to their accumulating effects in the environment. Data of a monitoring campaign at a stormwater treatment facility is evaluated. TSS, organic matter and the associated metals (Cr, Cu, Zn, Cd, and Pb) were analyzed in four different particle size fractions (<63 µm, 63–125 µm, 125–250 µm, and 250–2000 µm). While the highest event meant concentrations for all metals were found in the smallest fraction, a rather uniform particulate bound metal concentration (mass of metal per mass of particulate matter) over the first three particle size fractions was detected. Total metal loads correlated well with TSS even better with TSS < 63 µm. However, the removal efficiency in terms of the reduction of the total metal load was not reflected sufficiently by the TSS or TSS < 63 µm removal efficiency.

Effluent of a municipal wastewater treatment plant (WWTP) was treated on-site with the UV/chlorine (UV/HOCl) advanced oxidation process (AOP) using a pilot plant equipped with a medium pressure UV lamp with an adjustable performance of up to 1 kW. Results obtained from parallel experiments with the same pilot plant, where the state of the art UV/H₂O₂ AOP was applied, were compared regarding the removal of emerging contaminants (EC) and the formation of adsorbable organohalogens (AOX). Furthermore, the total estrogenic activity was measured in samples treated with the UV/chlorine AOP. At an energy consumption of 0.4 kWh/m³ (0.4 kW, 1 m³/h) and in a range of oxidant concentrations from 1 to 6 mg/L, the UV/chlorine AOP had a significantly higher EC removal yield than the UV/H₂O₂ AOP. With free available chlorine concentrations (FAC) in the UV chamber influent of at least 5 mg/L (11 mg/L of dosed Cl₂), the total estrogenic activity could be reduced by at least 97%. To achieve a certain concentration of FAC in the UV chamber influent, double to triple the amount of dosed Cl₂ was needed, resulting in AOX concentrations of up to 520 µg/L.

This study shows how a combination of denitrification and pesticide removal is possible. A reactor with granulated poly-ε-caprolactone (PCL) was operated in an upflow-mode with nitrate and α-endosulfan containing water. The polymer was used as a substrate for denitrification and simultaneously as sorbent for the pesticide α-endosulfan. The experiments showed that nitrate was removed at high denitrification rates and without accumulation of nitrite. α-endosulfan, which was added to the influent, was not found in the effluent. Doubts that the pesticide could interfere with the biological process were not justified here.