Treatment wetlands of the far north

Abstract

Wetlands form an important part of wastewater treatment systems used in small, cold, far northern communities in North America. Natural wetlands are used, which abound in sparsely populated cold regions. Numerous recent studies have shown that cold region treatment wetlands (CRTW) are remarkably effective at treating lagoon effluent. They function only for a few weeks during the short summers, and storage is required during the balance of the year. They differ in many important ways from the temperate and tropical treatment wetlands due to their unique climatic setting. Performance reflects distinctive climatic conditions; complex topography, hydraulics and hydrology; and the arctic biological regime. Over three dozen systems operate in permafrost areas. They display a median nominal detention time of 21 days, and function at water temperatures of 5–15 °C. Median reductions are 59% for TSS, 92% for CBOD5, 96% for ammonia nitrogen, 85% for TP, and 2.3 log10 for E.coli. This is appropriate technology for hamlets isolated from the free flow of goods and services of populous warm climates, because of the minimal reliance upon mechanical equipment and operational complexity.