Identification of sewage markers to indicate sources of contamination: Low cost options for misconnected non-stormwater source tracking in stormwater systems.

There has been increasing research focusing on the detection and occurrence of wastewater contamination in urban water systems. To find suitable markers to indicate industrial and domestic sewage flows inappropriately entering storm drains, this study investigated the occurrence and fate of 52 chemical markers through wastewater treatment facilities of manufacturers of agricultural and sideline products, beverage products, and pharmaceutical products, which are also consumed in our daily life. Of the 52 candidate markers, sodium, chloride, potassium, isomalto-oligosaccharide, acesulfame, theanine, glycerol, and clarithromycin were found to be conservative markers, with an average change in concentrations through the wastewater treatment processes of <30%. These markers are useful in identifying industrial and domestic sewage flow contamination in urban sewers. Specially, sodium, chloride, potassium, isomalto-oligosaccharide, acesulfame, and clarithromycin exhibited higher concentrations in blackwater than in greywater, with detected average concentrations of 43.8 mg/L, 189 mg/L, 37.3 mg/L, 123 µg/L, 37.2 µg/L, and 0.99 µg/L in blackwater, respectively. In contrast, theanine and glycerol were observed with higher concentrations in greywater than in blackwater (average 10.1 µg/L and 19.5 µg/L in greywater, respectively). The benchmark concentrations to discriminate between industrial and domestic sewage were also presented. A study in a storm drainage system of downstream Taihu catchment, China demonstrated the usefulness of the markers as low-cost options to trace and quantify misconnected wastewater entries into storm drains, while denoting priority areas for misconnected entries correction.