## 4 Discussion and Conclusions  
The CW WWTP of Cecchi winery fully respected the limit for discharge for the whole monitored period (two and a half monitoring years), not only confirming in general [1; 2; 3; 4; 5; 6; 7], but evidencing the suitability in long-term (up to 10 and a half years after upgrade, 18 and a half years including upgraded plant) of CW technology for the treatment of winery wastewater. For the last two and a half years, the efficiency of the CW WWTP is also demonstrated continuously with a sampling rate of half an hour for all the days. A similar monitoring campaign is quite unique in the Constructed Wetlands sector and in the available published literature. This work further evidenced the suitability of the FRB as 1 st for the treatment of winery wastewater. The mean COD removal efficiency observed from the FRB 1 st stage of the Cecchi CW WWTP was 70%, slightly lower but in agreement with the range registered from several FRB 1 st stage for domestic and municipal wastewater in France. [PERSON] et al. [10] report an average COD removal efficiency of the FRB 1 st stage of 77% \(\pm\) 2% from 250 monitored CW WWTPs (oldest 30 years old), while [PERSON] et al. [9] refer to a mean COD removal efficiency of 80% \(\pm\) 13% from 169 monitored CW WWTPs (oldest 12 years old). The proper functioning of the FRB 1 st stage can be attributed to a correct load in terms of the organic loading rate (OLR). Indeed, the Cecchi CW WWTP was loaded with a mean OLR of 62 \(\pm\) 33 g\({}_{\text{COD}}\) m\({}^{-2}\) d\({}^{-1}\) (range 8-145 g\({}_{\text{COD}}\) m\({}^{-2}\) d\({}^{-1}\)), in agreement with value reported from previous monitored periods [5; 6]. Therefore, the FRB 1 st stage of the Cecchi CW WWTP worked with sufficiently conservative OLRs, since FRB 1 st stages are usually designed with an OLR of about 100 g\({}_{\text{COD}}\) m\({}^{-2}\) d\({}^{-1}\) for municipal wastewater treatment [21]. On the other hand, the hydraulic loading rate (HLR) significantly differed from the usual values, due to different characterization of winery wastewater. Due to a very high organic load, the Cecchi CW WWTP worked, during the presented monitoring period, with a mean HLR of 0.05 \(\pm\) 0.02 m\({}^{3}\) m\({}^{-2}\) d\({}^{-1}\) (range 0.02-0.10 m\({}^{3}\) m\({}^{-2}\) d\({}^{-1}\)). These values are one order of magnitude lower than the suggested ones for the design of FRB 1 st stage for the treatment of municipal wastewater [21]. Consequently, the feeding scheme must be adapted to the different condition when FRB 1 st stage is designed to serve wineries; in this case, the designers have opted for a shorter resting period (6 h) in comparison to the values used for municipal applications (usually seven days [21]). Therefore, the feeding and resting periods for FRB 1 st are design variables to be properly addressed, especially for the design of CW WWTPs, which are expected to work under not common OLR and HLRs. At the same time, the optimal feeding scheme for an FRB 1 st stage treating winery wastewater is still an open technical and scientific question deserving to be further studied in the near future. The good performance of FRB 1 st stage was fundamental for the proper functioning of the subsequent HF 2 nd stage. Indeed, the high COD removal of the FRB 1 st permitted to feed the HF 2 nd stage with a mean cross-sectional organic loading rate of 279 g\({}_{\text{BOD5}}\) m\({}^{-2}\) d\({}^{-1}\) (assuming a COD/BOD\({}_{5}\) ratio of 2), in the range suggested by book and guidelines to avoid HF clogging, i.e., between 250 g\({}_{\text{BOD5}}\) m\({}^{-2}\) d\({}^{-1}\)[22] and 500 g\({}_{\text{BOD5}}\) m\({}^{-2}\) d\({}^{-1}\)[23]. Consequently, the HF 2 nd still not evidenced relevant clogging issues up to now, i.e., after 10 years of operation (excluding the pre-upgraded plant), confirming the suitability of HF CW technology in long-term recently evidenced by [PERSON] [9]. Despite the good performance of HF 2 nd stage, the FWS 3 rd stage played an important role.