Effect of amended filler fold-flow bioretention system on nitrogen and phosphorus reduction in rainwater

The study on the amended bioretention systems was conducted in view of the instability and even the negative removal of N, P in rainwater by the bioretention tanks. By constructing two systems of straight-flow and fold-flow bioretention, traditional fillers and hydroxy-aluminium vermiculite sludge particle (HAVSP) were filled respectively. Three simulation test device columns were set up, of which 1^# was a traditional filling straight-flow bioretention column, 2^# was a modified filling straight-flow bioretention column, and 3^# was a modified filling fold-flow bioretention column. The removal effect of nitrogen and phosphorus in rainwater under three simulated experimental devices was compared, and the improvement effect of HAVSP on bioretention filler was discussed. The results showed that the reduction effect of nitrogen and phosphorus in HAVSP amended filler fold-flow bioretention system was more obvious than that in conventional filler and amended filler straight-flow bioretention system, and had the best effect on nitrogen and phosphorus reduction when the outflow height was 350 mm, with total nitrogen and nitrate-nitrogen removal rates up to 76% and 77%, respectively.