Effect of the ebb-and-flow constructed wetland operation, media type and celery (Apium graveolens L.) growth on nutrient removal from a pre-treated brewery effluent

Abstract

Breweries face a high cost of wastewater treatment to meet environmental discharge standards. Constructed wetland (CW) design and operation have been optimised for sustainable wastewater treatment. An ebb-and-flow CW was used to investigate the effect of media on nutrient removal from a brewery effluent. Eight media (clay pebbles, clay bricks, sand, bioballs, recycled plastic and gravel sizes), either alone or mixed, were tested. A 2:1:1 ratio of each media, pine bark and granular activated carbon, respectively, was used for mixed treatments. A uniform celery planting density of eight seedlings per m2 and 12-min effluent retention time was used. There were significant differences between unmixed and mixed media on nutrient removal (p , 0.05). The unmixed media of clay pebbles had the highest mean COD reduction of 7.5% and ammonia 8.1%. Mixing resulted in better overall mean removal efficiency of nitrite-N (7.6%), nitrate-N (15.3%), total inorganic nitrogen (29.9%), orthophosphate (12.7%) and plant biomass (11158.5 gm 2 ) than unmixed media. Media porosity, surface area and chemical composition and celery plant enhance nutrient removal through synergistic interactions. The study recommends unmixed clay pebbles, bioballs and 19-mm gravel for improved ammonia-N removal and mixed media for multiple pollutant removal and celery productivity.