“…Moreover, data concerning operational features (e.g., HLR, fouling rate, surface area) also varied across articles and were sometimes not available, making it difficult to correlate CGGT performance and design features. On top of that, only a few articles reported data concerning other relevant topics beyond treatment performance, such as, for example, potential oxidation by-products (Chen et al, 2011), energy requirements (Talekar et al, 2018;Bakheet et al, 2020;Robles et al, 2020;Talekar and Mutnuri, 2020) and costs (Bakheet et al, 2020;Robles et al, 2020). Finally, due to the novelty of the topic, no article dealt with simulations/modelling using secondary data.…”