## 1 Introduction  
Constructed wetlands (CWs--also known as treatment wetlands) are nowadays recognized as reliable nature-based solutions not only for the treatment of domestic and municipal wastewater, but also for industrial wastewater. This is confirmed by numerous review works [1; 2; 3] and a book fully dedicated to the presentation of successful experiences in using CW for different kinds of wastewater [4]. Among the many industrial wastewater applications included in the review works, CWs for the treatment of winery wastewater seem to be one of the most promising and ready-to-the-market applications. [PERSON] et al. [5] reviewed the topic in detail: (i) discussing the peculiarity of the winery wastewater and why CWs are suitable to treat it; (ii) reporting experiences from different countries and different types of CW technologies, from simple horizontal subsurface flow systems (HF) to multistage CWs, as well as a combination of both technological and nature-based solutions. [PERSON] et al. [6] further investigated the topic, comparing three complex treatment schemes using different solutions to manage the high organic load driven by winery wastewater (nature-based French Reed Bed (FRB) in comparison with technological solutions, i.e., anaerobic and sequencing batch reactors) in order to identify the pros and cons of different approaches. Practical information for the application of CW for winery wastewater was also reported within the recent IWA book \"Wetland Technology\" [7]. In order to spread the use of CWs, one of the first \"false myths\" that was needed to be answered was their supposed short lifespan due to clogging issues. Despite that design guidelines to avoid clogging failures have been well-known among the CW designers since the early 90s, the monitoring of a successful full-scale CW wastewater treatment plant (WWTP) in the long-term period remains the best way to reply to these \"false myths\". Good examples come from the most diffused application of CWs, i.e., the treatment of domestic and municipal wastewater. For instance, [PERSON] [8] reported the high treatment efficiencies of HF systems in the Czech Republic that were more than 20 years old. Other examples are available also for more innovative CW solutions, since FRBs have been shown to maintain high performances from 12 [9] up to 30 [10] years of functioning. The importance of reporting long-term performance of CW systems is starting to be considered also for other applications, such as agricultural runoff treatment [11]. On the other hand, long-term experiences of CW for industrial wastewater treatment are rare, also due to the relatively more recent application of CW to this field. The capability to properly treat highly fluctuated influent loads is another useful point to increase the confidence in CW technology for industrial wastewater treatment. Although this peculiarity is well-known in the literature (e.g., [12]) and often reported in technical guidelines, it is usually based on single samples, and recent modeling studies are starting to request a better understanding of this feature [12; 13; 14; 15]. In order to confirm the capability of CWs to face variable influent loads, online sensors can be useful tools. Although online sensors are nowadays available on the market, their use for monitoring CW treatment performance is a relatively novel research field. Few experiences are available in the peer review literature; this is probably linked to the common small-scale application of CWs. [PERSON]' et al. [16] tested the reliability and the economic feasibility of using online sensors, instead of manual samples, for monitoring CW performance on HF pilot plants. In order to set an operating protocol for obtaining reliable data, [PERSON] et al. [17] studied the results from online monitoring of nitrogen compounds effluent from tertiary CWs in France (15,000 population equivalent (PE) WWTP). [PERSON] et al. [18] investigated the use of a microbial fuel cell as a low-cost sensor for CWs.