Effect of aluminum sludge filler improved bioretention tank on runoff pollutant reduction

In view of the poor effect of traditional filler bioretention tank on the reduction of nitrogen, phosphorus and other pollutants, the study on improving the bioretention tank with different proportions of aluminum sludge filler was carried out. The bioretention tanks with aluminum sludge and zeolite ratio of 3:2 (low ratio) and 4:1 (high ratio) were set up to study the permeability and removal effect of simulated rainwater with high, medium and low concentrations. The results showed that compared with the low proportion aluminum sludge filler bioretention tank, the high proportion aluminum sludge filler bioretention tank had stronger permeability, and with the growth of the operation cycle, its permeability decreased slowly. The high proportion aluminum sludge filler could improve the service life of the bioretention tank; by increasing the aluminum sludge filler ratio, it could significantly improve the removal efficiency of pollutants of high concentration rainwater. Especially, the removal rates of TP, COD, TN and NH₃-N could reach 89.0%, 62.4%, 66.4% and 68.0%, respectively. There was no significant difference in the removal efficiency of low concentration rainwater pollutants by high or low aluminum sludge ratio.