Mitigating Biofouling in Cooling Water System: Actibromide® to Combat Perna viridis Infestation and environmental impact

Heavy settlement and fouling of green mussels were observed in the process seawater heat exchangers (PSWHX) and conduits at the Madras Atomic Power Station (MAPS), despite the use of a continuous low-dose chlorination (CLDC) regime. This regime involved maintaining total residual oxidant (TRO) levels at 0.2 ± 0.1 mg/L and performing twice-weekly booster dosing at 0.4 ± 0.1 mg/L. To enhance the efficiency of these heat exchangers, supplemental targeted dosing of Actibromide® was considered. The efficacy of this biocide on adult green mussels was evaluated to determine the appropriate in-plant concentrations (0.2, 0.5, and 1.0 mg/L TRO). The results showed 100% mussel mortality after 12 days at 0.2 mg/L, 7 days at 0.5 mg/L, and 4 days at 1.0 mg/L. Actibromide® exerted toxic effects on mussels by generating reactive oxygen species (ROS), which inhibited cellular processes in various tissues, including the gills, mantle, digestive gland, and foot. The highest ROS generation was observed in the digestive gland compared to other tissues. Hydrogen peroxide (H2O2) production increased in a dose-dependent manner under Actibromide® stress, and superoxide dismutase (SOD) and catalase (CAT) activity were highest in the digestive gland. DNA damage, expressed as % tail DNA in a comet assay, indicated that even the lowest dose of Actibromide® (0.2 mg/L) induced significant DNA damage (34%). Additionally, acetylcholinesterase (AChE) activity, a sensitive biomarker for neurotoxic stress, showed reduced activity (80–91%) at all tested biocidal concentrations. This study clearly demonstrates that Actibromide® penetrates green mussels at the cellular level, causing severe damage to the gills and digestive glands, reducing feed consumption, and inducing both neurotoxic and genotoxic effects. Therefore, supplemental targeted dosing of Actibromide® (0.2 to 0.5 mg/L) is recommended for effective green mussel control in PSWHX systems.