On the Efficacy of H(2)O(2) or S(2)O(8)(2−) 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, H(2)O(2) and S(2)O(8)(2−), as (pre-)treatment options for algae-laden waters. Anabaena sp. and Vibrio alginolyticus have been selected as target microorganisms. With the objective of activating H(2)O(2) or S(2)O(8)(2−), additional experiments have been performed with the presence of small amounts of iron (18 µmol/L). For the cyanobacterial case, H(2)O(2)-based processes demonstrate greater efficiency over that of S(2)O(8)(2−), as Anabaena sp. is particularly affected by H(2)O(2), for which >90% of growth inhibition has been achieved with 0.088 mmol/L of H(2)O(2) (at 72 h of exposure). The response of Anabaena sp. as a co-culture with V. alginolyticus implies the use of major H(2)O(2) amounts for its inactivation (0.29 mmol/L of H(2)O(2)), while the effects of H(2)O(2)/Fe(II) suggests an improvement of ~60% compared to single H(2)O(2). These H(2)O(2) doses are not sufficient for preventing the regrowth of V. alginolyticus after 24 h. The effects of S(2)O(8)(2−) (+ Fe(II)) are moderate, reaching maximum inhibition growth of ~50% for Anabaena sp. at seven days of exposure. Nevertheless, doses of 3 mmol/L of S(2)O(8)(2−) 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.