In Vitro Assessment of the Inhibitory Effect of Sludge against Fusarium oxysporum f. sp. cubense (Smith) Synder et Hansen

Sludge production is a major challenge for wastewater treatment plants and is expected to exceed10,000 tons per day worldwide. Inadequate management of sludge can result in treatment and disposal issues, necessitating the need for effective sludge disposal strategies. Recent studies have shown that sludge may be effective in controlling soil-borne pathogens, but the underlying mechanisms and potential applications of this property in local environments remain unclear.To address this knowledge gap, this study investigated the physico-chemical properties of sludge from a sewage treatment plant and its inhibitory activity against the fungal pathogen Fusarium oxysporum. Sludge samples produced at various drying rates were tested, and the percent relative inhibition zone diameter (% RIZD) was measured. Potential bacterial species with inhibitory properties were isolated from the sludge and identified, and correlational analysis was carried out. The results show that sludge extract, after two months of drying, had the highest % RIZD(78.29 ± 5.7%, p < 0.05) – which correlated positively with the total bacterial count, total nitrogen, potassium, and microbial respiration. These results indicate that the biotic components may have a positive effect on the sludge's inhibitory potential against F. oxysporum. Although sludge has been found to have the potential to inhibit fungal pathogens, further treatment is necessary to meet regulatory standards (PNS/BAFS 40:2016) and avoid environmental contamination. This study provides a baseline for future research on sludge reuse and management policies.