Structural diversity of organic contaminants in sewage sludge: a comparison of sewage fingerprints from Germany and China

Abstract

Sewage sludge is formed during wastewater treatment and in recent years, the amount of sewage sludge increased rapidly all over the world. This sewage sludge is attractive for usage in agriculture as an inexpensive nitrogen and phosphorus fertilizer. However, there is only very limited knowledge about the spectrum of organic pollutants that might occur in sewage sludge and is probably posing a threat to the environment. We therefore conducted GC–MS based non-target screening analyses in order to identify a wide spectrum of organic contaminants in sludge samples from several wastewater treatment plants and to figure out corresponding finger-prints of pollution. The plants are located in Germany and China and have various capacities ranging from 35,000 to 1.1 million population equivalents. The special focus was to reveal information on the structural variety of individual organic compounds in sludge samples from the two countries. Several emerging pollutants including some fragrances, pharmaceutical educts, vitaminoids, technical additives were identified accompanied by compounds of biogenic origin. Some of these compounds have rarely been reported as constituents of sewage sludge to date and, consequently, are relevant candidates for more specific assessments including the ecotoxicological long-term effects. Based on the results of this study, it seems mandatory to establish non-target screening analyses on a regularly base as a tool for a comprehensive identification of the variety of anthropogenic organic constituents. Following, such contaminant spectrum can act as basis for further environmental risk assessments as well as to provide individual fingerprints for evaluation of impacts on ecosystems.

Quantitative Non-targeted Screening to Profile Micropollutants in Sewage Sludge Used for Agricultural Field Amendments

“…Figure 3. Comparison between the concentration of confirmed compounds in this study and previously reported values (the reported concentrations were taken from Spain,10 Germany and China,14 Sweden,12,55 Scotland,56 and Slovakia54 ).…”

“…10,24,54,55 Figure 3 demonstrates the comparison between the concentrations of confirmed micropollutants in the studied sludges and those previously reported from different countries. Many of the identified compounds have already been discovered in sludges from different countries e.g., citalopram and venlafaxine from Spain, 10 tris(2-chloro-iso-propyl) phosphate and triphenyl phosphate from Germany and China, 14 and miconazole and methyl benzotriazole from Sweden. 55 In general, concentrations for many of the compounds obtained in the current study were on an order of magnitude similar to previously reported values.…”

“…As a result, some proportion of such and other compounds are retained by the sewage sludge through physicochemical processes such as absorption through hydrophobic and electrostatic attraction. − Here, the properties of the sewage sludge such as microbial community composition (biodegradation abilities), pH, and adsorption capacity also play an important role in the retention of micropollutants that are not degraded in the treatment process. Consequently, the sewage sludge contains all insoluble or adsorbed impurities from influents and is recognized as a sink of moderate to high lipophilic micropollutants. , Nevertheless, to reduce the cost of running WWTPs and increase agricultural production, sewage sludge serves as a source of soil nutrients, especially nitrogen, phosphorus, and organic matter, and thus is widely applied in agricultural practices. − …”

“… 10 , 11 Nevertheless, to reduce the cost of running WWTPs and increase agricultural production, sewage sludge serves as a source of soil nutrients, especially nitrogen, phosphorus, and organic matter, and thus is widely applied in agricultural practices. 12 − 14 …”

Sewage sludge pretreatment: current status and future prospects

“…The pretreatment methods of sewage sludges are used to support the process of methane fermentation (Patinvoh et al 2016 ; Wluka et al 2021 ; Nguyen et al 2021 ; Machnicka and Grübel 2023 ). Methods used for the pretreatment of biomass for biogas production on a large scale are chemical, or physical, including thermal and mechanical.…”