On the Efficacy of H2O2 or S2O82- at Promoting the Inactivation of a Consortium of Cyanobacteria and Bacteria in Algae-Laden Water

Harmful algal blooms in coastal areas can significantly impact a water source. Microorganisms such as cyanobacteria and associated pathogenic bacteria may endanger an ecosystem and human health by causing significant eco-hazards. This study assesses the efficacy of two different reagents, H2O2 and S2O82-, as (pre-)treatment options for algae-laden waters. Anabaena sp. and Vibrio alginolyticus have been selected as target microorganisms. With the objective of activating H2O2 or S2O82-, additional experiments have been performed with the presence of small amounts of iron (18 mu mol/L). For the cyanobacterial case, H2O2-based processes demonstrate greater efficiency over that of S2O82-, as Anabaena sp. is particularly affected by H2O2, for which >90% of growth inhibition has been achieved with 0.088 mmol/L of H2O2 (at 72 h of exposure). The response of Anabaena sp. as a co-culture with V alginolyticus implies the use of major H2O2 amounts for its inactivation (0.29 mmol/L of H2O2), while the effects of H2O2/Fe(II) suggests an improvement of similar to 60% compared to single H2O2. These H2O2 doses are not sufficient for preventing the regrowth of V alginolyticus after 24 h. The effects of S2O82- (+ Fe(II)) are moderate, reaching maximum inhibition growth of similar to 50% for Anabaena sp. at seven days of exposure. Nevertheless, doses of 3 mmol/L of S2O82- can prevent the regrowth of V alginolyticus. These findings have implications for the mitigation of HABs but also for the associated bacteria that threaten many coastal ecosystems.

Automated summary

Harmful algal blooms in coastal areas can impact water sources, and this study evaluates the effectiveness of H2O2 and S2O82- reagents in treating algae-laden waters. The results show that H2O2-based processes are more efficient in inhibiting cyanobacterial growth compared to S2O82-. However, S2O82- can prevent the regrowth of bacteria, while H2O2 doses alone are not sufficient.