Occurrence of specific pollutants in a mixture of sewage and rainwater from an urbanized area

Abstract

Urban runoff appears to be a pathway for transferring new emerging pollutants from land-based sources to the aquatic environment. This paper aimed to identify and describe the groups of pollutants present in rainwater surface runoff as well as their mixture with wastewater in the combined sewer system from urbanized catchments and to determine the correlations between these pollutants. Four leading groups of new emerging pollutants have been identified that may be present in rainwater and municipal wastewater mixtures. The samples were tested for microplastics, phthalic acid esters, pesticides, and polycyclic aromatic hydrocarbons as well as basic parameters. The pilot site was Słupsk (northwestern Poland). We conducted nine sampling campaigns at three points. The results of the present study revealed that (i) polycyclic aromatic hydrocarbons were not present in the tested samples; (ii) the selected organochlorine pesticides were detected during one campaign in the dry season and therefore were not of critical importance; (iii) out of the 11 analyzed phthalic acid esters, five selected substances released from commonly used plastic products were present; and (iv) the number of microplastics contained in the tested samples ranged from 1,400 to 14,036 pcs/L and even occurred during pure rainfall.

Keywords: Microplastics; Micropollutant concentration; Phthalates; Stormwater quality; Urban runoff.

Figure 1

Concentrations of the analyzed pollutants in CSS: (a) di-2-ethylhexyl phthalate, (b) di-n-butyl phthalate, (c) dimethyl phthalate, (d) diethyl phthalate, and (e) di-n-octyl phthalate (roman numerals denote the month).

Figure 2

Amount of microplastic particles in CSS (expressed in pcs/L) (roman numerals denote the month).

Figure 3

Catchment area with the locations of the sampling and monitoring points (source: Google Maps).