Wpływ miąższości reaktywnej warstwy drenażowej na odpływ fosforanów z zielonego dachu

Abstract

The green roof runoff may be contaminated with phosphorus. The source of P pollution can be a substrate layer. The research was carried out to determine an optimal ratio of P-reactive drainage layer (RM) to substrate layer (S) in a green roof construction. The main goal of conducted column experiment, was to examine P-removal efficiency of drainage layers in different thickness. The green roof material used in the experiment is a commercially available substrate for intensive roofs. It has been confirmed that the substrate can act as a source of phosphorus occurring in leachate from green roofs. It has been found that the P-reactive drainage layer of Polonite® in thickness of 2 and 5 cm reduces phosphate load in runoff. The load of phosphorus discharged from the columns amounted to 0.091; 0.032 and 0.02 mg P-PO4 for K1 (S:RM=10:1), K2 (S:RM=10:2) and K3 (S:RM=10:5). Layer of the substrate relative to reactive material layer of 10: 2 was considered as an optimal solution. In relation to the quality of water supplied an increase of pH and conductivity in runoff was observed. The P-reactive drainage layer and its thickness had no effect on these parameters. All the columns reduced water outflow by approximately 40% compared to the volume of simulated precipitation.