A vertical flow constructed wetland for the treatment of winery process water and domestic sewage in Ontario, Canada: Six years of performance data

•We assessed a vertical flow constructed wetland treating winery wastewater.•Effective removal of COD, CBOD, TSS, TP, TKN, and NH4+-N.•Little seasonal variation in treatment despite the cold climate of Ontario, Canada.•TP removal decreased overtime suggesting saturation of adsorption sites. Wine production is a growing industry in the Canadian province of Ontario. Due to the high organic loads and large amount of suspended solids found in winery process water it is important for wineries to adopt sustainable water management practices. Constructed wetlands (CW) have been shown to be a viable option in the warmer climates of the Mediterranean and the western USA but little research has examined their feasibility in the cold climate of Ontario. The purpose of this paper was to assess six years of performance data from a vertical flow CW treating winery process water and domestic sewage at a winery in the Niagara region of Ontario with an average hydraulic loading rate (HLR) of 22.3mmd−1 and an average chemical oxygen demand (COD) surface loading rate (SLR) of 34.0gm2d−1. The CW has four cells, each 101m2, and was designed to treat 16,620Lday−1 of wastewater consisting of winery process water and domestic sewage. The performance data were separated by season to determine the effect of temperature on treatment performance during the colder months. There was little variation in seasonal performance and the average treatment efficiencies over the six-year period were: 99% for COD, 99% for carbonaceous COD, 98% for total suspended solids, 83% for total phosphorous, 94% for total Kjeldahl nitrogen, and 85% ammonium. Effluent nitrate, total coliforms, and Escherichia coli concentrations were also monitored and consistently met the regulatory standards for discharge to a subsurface leaching bed. The CW system proved to be an option for treating winery wastewater.