The effects of substrate particle size, depth and vegetation on ammonia removal in a vertical flow constructed wetland

The four cells of the second stage of a vertical flow reed bed, had different combinations of vegetation, sand particle size and sand depth. Analysis of the correlation between cell surface area and sand volume showed NH3-N removal more closely correlated to volume than to cell surface area. Hydraulic conductivity and NH3-N removal were also shown to be correlated in vegetated cells. Reliability of NH3-N removal was seen to be dependent upon the: absence of continuous pending on the cell surface. It was concluded that, on highly loaded systems, inadequate oxygen transfer rates were more likely to limit nitrification than substrate surface area availability. Differences in ammonia removal rates between vegetated and unvegetated cells are discussed. The effects of manipulation of the dosing:resting ratio upon ammonia removal were also demonstrated.