Artificial road runoff water treatment by a pilot-scale horizontal permeable treatment zone

Runoff water from urbanized areas, including roads and related objects may be a source of micropollution. One of the methods limiting its migration to surface- and groundwater receivers may be the application of horizontal treatment zones enhancing natural attenuation of the soil-water environment. The aim of the presented small-scale field tests was testing the utility of mixtures of zero valent iron - ZVI, activated carbon - AC, zeolite - Z, limestone - LS, and silica spongolite - SS as reactive materials. During the 11-month experiment, runoff water samples were collected from three treatment zones and subjected to physical and chemical analyses (pH, EC, Eh, Cl−, Fe2+, Cd2+, Cu2+, Ni2+, Pb2+, Zn2+, NH4+, NO2−, NO3−, COD, ƩPAH, PEE). Additionally, the change of the hydraulic conductivity of the mixtures was systematically controlled. During the experiment, the highest mean values of removal efficiency of Cl− (13%) and COD (82%) were observed for ZVI/AC/Z; Ni2+ (94%), Zn2+ (99%) and NH4+ (82%) for ZVI/AC/LS; and PEE (70%) for ZVI/AC/SS. Cadmium (98%), copper (100%) and lead (100%) were removed with the same intensity by all three systems. ƩPAH were removed with the same intensity at 97% by ZVI/AC/SS and ZVI/AC/LS. However, the contact of runoff water with both mixtures resulted in increased emission of NO2− and NO3−. The experiment showed also that the hydraulic conductivity of the mixtures decreased to a minimal value of 3.2 · 10−5 m/s for ZVI/AC/Z.

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