Metal accumulation from leachate by polyculture in crushed brick and steel slag using pilot-scale constructed wetland in the climate of Pakistan.

Abstract

The temperate climate of Pakistan has enhanced the performance of macrophytes grown in crushed brick and steel slag in constructed wetland for removal of heavy metals from leachate. Two pilot-scale constructed wetlands [constructed wetland 1 (CW1) and constructed wetland 2 (CW2)] were planted with a polyculture of Phragmites australis and Typha latifolia in crushed brick and steel slag, respectively. These wetlands were located in the National University of Sciences and Technology, Islamabad campus, and operated for 15 months for treatment of leachate with climatic variations of Islamabad. The metal accumulation in a polyculture of Phragmites australis and Typha latifolia and in substrates was analyzed in the laboratory of Institute of Environmental Sciences and Engineering located near wetland site. Despite the high temperature in summer season, removal of Cu, Zn, and Pb was efficient due to the synergistic combination of macrophytes and substrates in both wetlands. Substrates acted as a primary sink of metals and enhanced metal accumulation in the plant's roots which resulted in poor translocation of Cu, Zn, and Pb to shoots. Despite the variation in precipitation and temperature during summer and winter seasons, the average removal of copper, zinc, and lead was 95%, 91%, and 89% by polyculture in crushed brick in CW1 and 97%, 95%, and 91% in steel slag in CW2, respectively. A The variation in climate has a negligible effect on the sorption of metals by both substrates in CW1 and CW2. Furthermore, Phragmites australis with crushed brick in CW1 was efficient for removal of Zn and Typha latifolia was performing better with steel slag in CW2 for significantly high removal of Cu and Pb in the climate of Islamabad,Pakistan.