This document discusses the performance of reed bed or wetland treatment systems in cold climates and freezing winter conditions. It explains that treatment is driven by bacterial activity, not plant growth, and that wetland systems can operate year-round in cold climates if designed properly. Specifically, the key points are: 1) Treatment wetlands have been successfully used around the world, including in areas where temperatures remain below freezing for extended periods. 2) Maintaining a stable environment for bacterial growth and accommodating slower bacterial removal rates are important for performance in winter. 3) Insulation methods like ice/snow blankets, reed litter, mulch or peat can maintain water temperatures above freezing even when air