Sorption of active pharmaceutical ingredients in untreated wastewater effluent and effect of dilution in freshwater: Implications for an “impact zone” environmental risk assessment approach

Abstract

Evidence of ecotoxicological effects of active pharmaceuticals ingredients (APIs) has increased research into their environmental fate. In low and low-middle income countries (LLMICs) the main source of APIs to surface waters is from discharge of untreated wastewater. Consequently, concentrations of APIs can be relatively high in the "impact zone" downstream of a discharge point. Little is known about the fate of APIs in these impact zones. In this laboratory scale investigation, the effect of successive dilution of synthetic untreated wastewater (dilution factor 1 to 10) on the distribution of APIs was studied. The sorption was consistent with the chemical properties of each compound: charge, lipophilicity, and structure. Dilution increased desorption of the basic and neutral APIs (up to 27.7%) and correlated with their lipophilicity (R>0.980); the positive charge was of secondary importance. Anions did not significantly desorb (<10% loss). Increased concentrations of dissolved organic matter at dilutions of 8 and 10 times that of untreated wastewater coincided with lower dissolved API concentrations. The data showed a clear trend in the desorption process of APIs that may lead to higher exposure risk than anticipated. Therefore, it is suggested that these aspects should be accounted for in the development of dedicated environmental risk assessment approach for APIs in riverine impact zones of LLMICs countries.

Impact of the wastewater-mixing zone on attenuation of pharmaceuticals in natural waters: Implications for an impact zone inclusive environmental risk assessment

“…The APIs chosen for this study were the neutral acetaminophen (ACT), carbamazepine (CBZ), and nevirapine (NVR), the acidic diclofenac (DCF) and valsartan (VLS), and the basic acebutolol (ACE) and amitriptyline (AMI). These compounds represent APIs with different structure and functionalities (neutral, acidic and basic) which are commonly consumed in LLMICs (Bagnis et al, 2018a). The chemicals were purchased at the highest purity available, either from Sigma-Aldrich (acebutolol hydrochloride, amitriptyline hydrochloride, nevirapine, valsartan, and acetaminophen) or Fisher Scientific (carbamazepine and diclofenac sodium salt).…”

“…This results in serious pollution of a waterway to such a downstream distance that a combination of dilution and biogeochemical processes such as degradation, volatilisation and sorption render the anthropogenic discharges non-toxic. This area downstream of the DDUW has been defined as an "impact zone", beginning at the DDUW entry point and ending where easily measurable determinants such as biochemical oxygen demand (BOD), ammonia, and dissolved oxygen levels, critical to ecological health, have returned to environmental background concentrations (A.I.S.E./CESIO, 1995;Bagnis et al, 2018a). Whilst DDUW are known to contain high nutrient concentrations and BOD, the presence of emerging contaminants such as active pharmaceuticals ingredients (APIs) is of increasing concern (Keller et al, 2014).…”

“…Furthermore, current environmental risk assessment (ERA) guidance for APIs has been developed assuming that sewage is subject to treatment prior to discharge (EMA, 2006), and thus, given that the DDUW does not comply with this assumption, the environmental conditions in the impact zone require a dedicated ERA approach (Bagnis et al, 2018a). This can only be achieved by understanding the mechanisms of natural attenuation that APIs undergo, such as sorption and biodegradation, and the resulting degree of exposure within the impact zone boundaries and beyond.…”

“…A highly important factor often overlooked are the questions as to what the impacts of dilution are on other key processes, such as sorption and biodegradation, which are currently poorly understood but are critical to the derivation of a scientifically robust risk assessment or for use within the development of water quality models (Bagnis et al, 2018a;Hajj-Mohamad et al, 2017).…”

Water environmental risk assessment and regionalization in southeast coastal basins of China

“…Risk evaluation index system means making evaluation of damage of human health, social economy and environment caused by natural disasters which are induced by human collective economic activities. We can get basin environmental risk evaluation based on quantitative evaluation of several indexes in basin, which is essential for Integrated River Basin Management [1,2]. Currently, researches on basin's environmental risk evaluation are mainly divided into two types at home and abroad.…”