In-Lake Mechanisms for Manganese Control—A Systematic Literature Review

An elevated concentration of manganese (Mn) in lakes is a common water quality problem faced by many water utilities. Thermal stratification is a natural phenomenon that influences the Mn concentration in lakes and can exacerbate Mn accumulation in surface water without external loading sources. While several treatment methods can be utilized to treat Mn in drinking water treatment plants, in-lake control mechanisms can be a proactive and efficient strategy for Mn control by reducing water treatment complexities and costs. Despite previous research pointing to the benefits of in-lake Mn control, the feasibility and effectiveness of the various in-lake Mn control mechanisms in lakes in different environmental conditions remains unclear. To identify and consolidate the existing research on the topic, a comprehensive, systematic literature review (SLR) was conducted. The SLR identified case studies of in-lake Mn control mechanisms in thermally stratified lakes. The identified case studies were grouped into three categories based on their goals: identification of Mn behaviour in lakes, built engineering implementations and digital solutions for process optimization and anticipation. It is critical that a site-specific understanding of Mn dynamics is obtained before implementing any built or digital solutions, because lake specific dynamics can significantly impact a solution’s performance. While most reviewed mechanisms were successful in decreasing high Mn concentrations, a lack of financial and environmental cost–benefit analyses for most in-lake Mn control mechanisms was observed, which is crucial for their adoption by water authorities. The rationale of this SLR provides a summary of the benefits and limitations of the most common in-lake Mn control mechanisms, the enabling the conditions for their implementation, and the knowledge gaps and future direction for research on the topic, being valuable to support informed decision-making by water authorities managing waterbodies with high Mn concentrations.