High Performance Constructed Wetlands for Cold Climates

Abstract

In 1991, the first subsurface flow constructed wetland for treatment of domestic wastewater was built in Norway. Today, this method is rapidly becoming a popular method for wastewater treatment in rural Norway. This is due to excellent performance even during winter and low maintenance. The systems can be constructed regardless of site conditions. The Norwegian concept for small constructed wetlands is based on the use of a septic tank followed by an aerobic vertical down-flow biofilter succeeded by a subsurface horizontal-flow constructed wetland. The aerobic biofilter, prior to the subsurface flow stage, is essential to remove BOD and achieve nitrification in a climate where the plants are dormant during the cold season. When designed according to present guidelines a consistent P-removal of > 90% can be expected for 15 years using natural iron or calcium rich sand or a new manufactured lightweight aggregate with P-sorption capacities, which exceeds most natural media. When the media is saturated with P it can be used as soil conditioner and P-fertilizer. Nitrogen removal in the range of 40-60% is achieved. Removal of indicator bacteria is high and < 1000 thermotolerant coliforms/100 ml is normally achieved.

Filter bed systems treating domestic wastewater in the Nordic countries – Performance and reuse of filter media

“…The phosphorus removal shoved a very slow, but stable increase. This is consistent with earlier investigations of similar systems (Jenssen et al, 2005).…”

“…The total N-removal was in the same range as the N-removal in systems with biofilters and subsurface flow CW's as the final treatment step (Jenssen et al, 2005) despite that a lower removal could be expected due to the lack of plants (Zhu, 1998). The more advanced biofilters in this investigation having improved distribution systems (Heistad et al, 2001) that gives better distribution of the biofilm and a larger biofilm area as compared to the investigation of Jenssen et al (2005) may explain this.…”

“…This makes a statistical comparison of the results difficult. However, experience has shown that systems as in this paper have a very low variation in effluent water quality (Jenssen et al, 2005) and thus a few samples can still characterize the performance of the system.…”

Performance of six multi-stage hybrid wetland systems for treating high-content wastewater in the cold climate of Hokkaido, Japan

“…Moreover, hybrid systems have been in use since the 1980s (Vymazal 2011). Several important studies about the selection of filter media, the treatment performance at low temperature, and the recirculation effect have been conducted in cold climates (Poldvere et al 2009(Poldvere et al , 2010Jenssen et al 2005Jenssen et al , 2010Speer et al 2012). However, issues of clogging and freezing for treating high-content wastewater in cold climates still remain.…”

Management of Tundra Wastewater Treatment Wetlands within a Lagoon/Wetland Hybridized Treatment System Using the SubWet 2.0 Wetland Model

“…Constructed wetlands, as their name implies, refers to wetlands that are man-made and designed to specific dimensions, porosity, flow paths, hydraulic retention times, and related design features for the intended purpose of achieving predetermined levels of treatment [12,13,18]. The science regarding treatment processes, reaction rate constants, soil porosity, hydraulics, design options and management practices has been thoroughly investigated in the last two decades and is well documented [19][20][21][22][23][24][25][26].…”