Suitability of select micro-green, ornamental and legume plants for use in green walls: a novel brewery wastewater treatment option

Green walls are increasingly popular in urban settings with demonstrated beneficial use as vertical gardens, building envelops, and uniquely orientated green space to improve urban biodiversity and air quality. This research evaluated the suitability of green wall plants for the preliminary treatment of wastewater generated by food and beverage makers, quantifying suitability with plant growth metrics. Edible micro-green, ornamental, and legume plants were planted in perlite filled pots and irrigated continuously with untreated brewery wastewater or a control of Hoaglands solution. Plants receiving wastewater had less growth than the control. Stem growth for microgreen and legume plants that were started from seed was 798% and 253% less, respectively, when irrigated with 100% brewery wastewater. The stem growth of established ornamental plants was 26% less when irrigated with the wastewater. Wastewater irrigated plants with the highest rates of growth and survivability included the mustard plant (Brassica juncea), and ornamental plants Epipremnum aureum (Golden Pothos) and Chlorophytum comosum (Spider Plant). Growth metrics for wastewater irrigated legumes were higher for plants inoculated with rhizobia, than plants without the inoculation, which suggests low available nitrogen concentrations, rather than toxicity of the wastewater, limited plant growth. The results suggest that ornamental plants such as Epipremnum aureum and Chlorophytum comosum can be sustained, without the addition of supplemental nutrients, in a green wall utilized to treat brewery wastewater.