Start-up performance of a subsurface-flow constructed wetland for domestic wastewater treatment

Constructed wetlands have been shown to provide sufficient domestic wastewater treatment in temperate climates. However, the effectiveness of this technology, when subjected to severe temperature extremes during start-up conditions, is limited. Because of the growing interest in constructed wetland technology within smaller communities located in colder-climates, and the need for cost-effective treatment systems, this paper presents the performance of a constructed wetland system during the first two-years of operation under a variety of loading and operating conditions associated with northern climates. While the treatment performance of constructed wetland systems has been widely documented within the literature, documentation on performance during start-up stages has been limited. The results indicate that effective and sufficient constructed wetland seasonal removals of total suspended solids, volatile suspended solids, 5-day carbonaceous biochemical oxygen demand, chemical oxygen demand, and fecal coliform were achieved within the wetland cell during the first two-years of operation. Wastewater temperatures appeared to affect 5-day carbonaceous biochemical oxygen demand and chemical oxygen demand removal rates. Nitrogen and phosphorus reductions were not as effective and varied seasonally, as well as with wastewater temperature.