## 1 Introduction  
Human health, conservation of the ecosystems and biodiversity and socioeconomic development strongly depend on water quality. In the last century, freshwater consumption has increased remarkably. According to the World Health Organization (WHO), more than 13,000 people die every day due to the onset of diseases related to water unavailability or contamination [1; 2]. Climate change also contributes to the water crisis by altering water flows, with the increase in rainfall and extreme meteorological phenomena in some geographical areas in contrast to long periods of drought in other regions. Moreover, urbanization, economic development and the increase in industrial production, especially in the pharmaceutical, electronic and energy sectors, results in a considerable amount of urban and industrial wastewater which, combined with agricultural activities, degrades the quality of water and leads to the pollution of many water resources worldwide [3]. In particular, potentially toxic elements (PTEs) and contaminants of emerging concern (CECs) are conveyed to the environment by multiple routes, making targeted actions to treat contaminated water essential [4; 5]. The term CECs includes a wide range of organic molecules, such as pharmaceuticals and personal care products, artificial sweeteners, endocrine-disrupting compounds, etc. The list of compounds belonging to this registry of recalcitrant pollutants is constantly evolving and, consequently, most of them are not yet regulated by legislation due to the lack of exhaustive data on toxicity, mode of action, bioaccumulation capacity and reactivity. Most of these compounds share an incomplete removal during the conventional wastewater treatment plant process as the treatment plantswere not designed to treat these kind of pollutants, and as a result they are discharged into the environment [6; 7]. Conversely, the toxicology and the related environmental problems of PTEs such as arsenic, mercury, lead and cadmium are in most cases well known so that many regulations governing their release into the environment exist; PTEs are ubiquitous and persistent and may be toxic to biota even at low concentrations. Despite this, many industrial activities such as mining operations, electroplating industries, metal plating activities, and especially battery manufacturing, release PTEs into the waste produced and, if not properly treated, into the environment. They are inherently non\(-\)biodegradable and can bioaccumulate in fish and biomagnify along the food chain with resultant negative health effects in humans [8; 9]. As a consequence, the increasing presence of PTEs in water systems has not only affected the quality of the water but has also influenced the food sector including the aquaculture industry. In the last few decades, aquaculture has been the fastest growing food-producing sector worldwide and it is expected to be the only way to meet the increasing demand for aquatic food in the future. In this context, recirculating aquaculture systems became a valid alternative to traditional open systems thanks to the higher production per unit of surface area and the lower needs of land and water [10; 11]. However, one of the main drawbacks in these systems is the accumulation of unpleasant tastes and odors in the fish meat: the most common are earthy and moldy ones, mainly caused by two saturated bicyclic terpenoids, geosmin and 2-methylisoborneol (MIB), semi-volatile compounds that can be absorbed by fish and accumulate in lipid-rich tissues. Although they are not toxic to humans at the concentrations usually detected, they can be perceived by our senses even at extremely low concentrations and their presence can make fish unsuitable for commercialization and human consumption, so their removal becomes essential [12; 13]. In addition, water used for aquaculture can also be subject to incoming contamination by CECs and PTEs with the subsequent negative impact on the quality of the fish produced.