Constructed wetlands in cold-climate regions: performance, challenges, and opportunities: a review

Untreated wastewater discharges into polluted bodies of water jeopardize the availability of water for human consumption. For that reason, constructed wetlands (CWs) are a sustainable and ecological technology commonly used in marginalized communities as an alternative wastewater treatment method, with low installation and maintenance costs. CWs use endemic vegetation for wastewater treatment, similarly to natural wetlands. Pollutants are removed from wastewater through biological, physical, or chemical processes. Additionally, CWs include deep wells, filter medium, and macrophytes. The radicular system of macrophytes decreases pollutant concentration by interacting with microorganisms associated with their roots. Macrophytes are especially important to CWs because they transport oxygen. For this reason, this review outlines the current state of CW technology and its operational challenges under extreme climate conditions, such as cold weather or winter. The operational conditions of CW systems are analyzed, mainly design modifications, macrophyte selection, and environmental conditions. The analysis is based on case studies and the background of CW systems installed in cold-climate regions or operating during the cold season. The review analysis was conducted using “Methodi Ordinatio”, which systematically analyzes the information with a specific purpose. Overall, CW systems operating in cold climates are an effective, sustainable, and adaptable technology for wastewater treatment. Effective modifications, such as design adaptations, plant species, and CW type, are essential to optimal operation and to maximize their efficiency.