Modelling the fate of micropollutants in integrated urban wastewater systems: Extending the applicability to pharmaceuticals

Assessing city-wide pharmaceutical emissions to wastewater via modelling and passive sampling

With increasing numbers of chemicals used in modern society, assessing human and environmental exposure to them is becoming increasingly difficult. Recent advances in wastewater-based epidemiology enable valuable insights into public exposure to data-poor compounds. However, measuring all >26,000 chemicals registered under REACH is not just technically unfeasible but would also be incredibly expensive. In this paper, we argue that estimating emissions of chemicals based on usage data could offer a more comprehensive, systematic and efficient approach than repeated monitoring. Emissions of 29 active pharmaceutical ingredients (APIs) to wastewater were estimated for a medium-sized city in the Netherlands. Usage data was collected both on national and local scale and included prescription data, usage in health-care institutions and over-the-counter sales. Different routes of administration were considered as well as the excretion and subsequent in-sewer back-transformation of conjugates into respective parent compounds. Results suggest model-based emission estimation on a city-level is feasible and in good agreement with wastewater measurements obtained via passive sampling. Results highlight the need to include excretion fractions in the conceptual framework of emission estimation but suggest that the choice of an appropriate excretion fraction has a substantial impact on the resulting model performance.

Characterization of urban sources of antibiotics and antibiotic-resistance genes in a Dutch sewer catchment

A one year study was conducted in the city of Nijmegen, The Netherlands, to characterize various urban sources of antibiotics and antibiotic resistant genes (ARGs) in wastewater within a single sewer catchment. Prevalence of ermB, tet(W), sul1, sul2, intl1, and 16S rRNA gene was determined at 10 locations within the city. Sampling locations included a nursing home, a student residence, a hospital and an industrial area, among others. Wastewater concentrations of 23 antibiotics were measured using passive sampling. Additionally, excreted loads of 22 antibiotics were estimated based on ambulatory prescription and clinical usage data. Genes sul1 and intl1 were most abundant across most locations. Ciprofloxacin and amoxicillin together contributed over 92 % of the total estimated antibiotic selective pressure at all sampling points. The present study highlights the prominent role that hospitals can have in the prevalence and proliferation of ARGs in urban wastewater. Furthermore, results suggest that even short-term changes in the therapeutic regimen prescribed in hospitals may translate into shifting ARG abundance patterns in hospital wastewater. The methods applied present an opportunity to identify emission hotspots and prioritize intervention options to limit ARG spread from urban wastewater to the environment.

Contaminants of emerging concern in the urban aquifers of Barcelona: Do they hamper the use of groundwater?

Urban aquifers are an alternative to obtain freshwater, but they are frequently polluted by contaminants of emerging concern (CECs). Therefore, there is a need to ascertain whether CECs are a water management challenge as they might limit the use of groundwater as safe drinking water even at ng L-1 concentration levels. To answer this question, it is required to evaluate human health-risk effects of measured CECs in the groundwater and to understand their behaviour at a field-scale. This study compiles data about the presence of CECs in the aquifers of Barcelona and its metropolitan area, evaluates health risk effects of measured CECs in the groundwater and presents approaches implemented to identify and quantify the coupled hydro-thermo-chemical processes that govern their fate in the subsurface. Some CECs might be harmful to humans, such as 5-methyl-1H-benzotriazole and the pharmaceuticals azithromycin valsartan, valsartan acid, lamotrigine, gabapentin, venlafaxine and lidocaine, which show very high to intermediate health risk effects. The number of harmful CECs and the level of their hazard increase from the groups of adults and 14-18 years old teens to the groups of 4-8 years old and 1-2 years old children. Thus, some CECs can limit the use of groundwater in Barcelona as potential drinking water source. Finally, knowledge gaps in understanding the integration of these processes into urban water resources management plans are identified, which will help to define groundwater potential uses and to assure the adequate protection of the human health and the environment.

From market to environment - consumption-normalised pharmaceutical emissions in the Rhine catchment

Direct and indirect threats by organic micropollutants can only be reliably assessed and prevented if the exposure to these chemicals is known, which in turn requires a confident estimate of their emitted amounts into the environment. APIs (Active Pharmaceutical Ingredients) enter surface waters mostly through the sewer system and wastewater treatment plants (WWTPs). However, their effluent fluxes are highly variable and influenced by several different factors that challenge robust emission estimates. Here, we defined a dimensionless, theoretically consumption-independent 'escape factor' (k_esc) for estimating the amount of APIs (expected to be) present in WWTP effluents. The factor is determined as the proportion of marketed and actually emitted amounts of APIs. A large collection of German and Swiss monitoring datasets were analyzed to calculate stochastic k_esc values for 31 APIs, reflecting both the magnitude and uncertainty of consumption-normalised emissions. Escape factors provide an easy-to-use tool for the estimation of average API emissions and expected variability from numerous WWTPs given that consumption data are provided, thereby supporting simulation modeling of the fate of APIs in stream networks or exposure assessments.

Modelling and prediction of the effect of operational parameters on the fate of contaminants of emerging concern in WWTPs

Wastewater treatment plants (WWTPs) provide a barrier against the discharge of contaminants of emerging concern (CECs) into the environment. The removal of CECs is highly WWTP-specific and the underlying mechanisms are still poorly understood, hampering the optimization of biological treatment steps for their removal. To fill this knowledge gap, we assessed the influence of four operational parameters of activated sludge biological treatment, namely total suspended solids, temperature, pH and redox conditions, on the sorption and biodegradation of four CECs under controlled laboratory conditions. Design of Experiments was used to better address the factors influencing CECs removal and interactions among operational parameters. The derived statistical models showed results in concordance with previous studies and indicated how sorption and biodegradation of the investigated CECs depend on most tested parameters and few of their interactions. The predictions of the developed models have been compared with literature values, indicating how the tested parameters are responsible for most of the variability of sorption, while they could not reliably generalize biodegradation rates. The developed models were also implemented as an extension of a mechanistic biological treatment model, successfully describing the dynamic behaviour of a large-scale WWTP, which was observed during a three-day continuous monitoring campaign. Compared to a traditional modelling approach, the one including the developed models showed on average almost a three-fold uncertainty reduction, favouring its use to aid WWTP managers and regulators for improved assessment of CEC fate and removal. Finally, the models highlighted that, while higher temperatures and solids concentrations generically favoured CECs removal, removal efficiency vary significantly due to operational parameters and no globally optimum conditions for CECs removal exist. The use of these models opens the door to the combined dynamic management of both traditional contaminants and CECs in WWTPs.

The role of the sewer system in estimating urban emissions of chemicals of emerging concern

The use of chemicals by society has resulted in calls for more effective control of their emissions. Many of these chemicals are poorly characterized because of lacking data on their use, environmental fate and toxicity, as well as lacking detection techniques. These compounds are sometimes referred to as contaminants of emerging concern (CECs). Urban areas are an important source of CECs, where these are typically first collected in sewer systems and then discharged into the environment after being treated in a wastewater treatment plant. A combination of emission estimation techniques and environmental fate models can support the early identification and management of CEC-related environmental problems. However, scientific insight in the processes driving the fate of CECs in sewer systems is limited and scattered. Biotransformation, sorption and ion-trapping can decrease CEC loads, whereas enzymatic deconjugation of conjugated metabolites can increase CEC loads as metabolites are back-transformed into their parent respective compounds. These fate processes need to be considered when estimating CEC emissions. This literature review collates the fragmented knowledge and data on in-sewer fate of CECs to develop practical guidelines for water managers on how to deal with in-sewer fate of CECs and highlights future research needs. It was assessed to what extent empirical data is in-line with text-book knowledge and integrated sewer modelling approaches. Experimental half-lives (n = 277) of 96 organic CECs were collected from literature. The findings of this literature review can be used to support environmental modelling efforts and to optimize monitoring campaigns, including field studies in the context of wastewater-based epidemiology.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11157-022-09638-9.