This study presents an interesting approach to mixotrophic denitrification using an iron sulfide-polylactic acid biofilter, but a few points could use clarification. The results indicate that the biofilter achieved nitrate and phosphate removal rates of 98.04% and 94.12%, respectively. Were these efficiencies sustained over a longer operational period, or were there signs of performance decline due to biofilm clogging or material degradation?
Additionally, in Table 2, the operational conditions for different phases are outlined, but it would be helpful to clarify whether the influent COD and nitrogen levels were adjusted dynamically based on system performance. If so, were any control mechanisms implemented to maintain stable conditions?