The role of a hybrid phytosystem in landscape water purification and herbicides removal.

Abstract

The performance of a hybrid phytosystem in landscape water purification and herbicides removal was investigated. The phytosystem operating in an arboretum is located in the Minhang Campus of Shanghai Jiao Tong University, China. The phytosystem is composed of two purification stages: sedimentation Stage 1 without external air supply; and Stage 2 with an external air supply. Stage 2 is also vegetated with three major kinds of plants, namely Pontederia cordata L., Typha latifolia L. and Cyperus alternifolius L. The system's hydraulic loading rate (HLR) was maintained at 1.632 m/day between December 2013 and November 2014. Sedimentation, filtration and adsorption by filter media, combined microbial processes in the rhizosphere (nitrification-denitrification) and plant uptake of the pollutants were all responsible for water purification in the phytosystem. The biological and physical parameters analyzed were total dissolved nitrogen (TDN), nitrate (NO3-N), nitrite (NO2-N), ammonia (NH3-N), total dissolved phosphorus (TDP), dissolved organic carbon (DOC), turbidity, chlorophyll-a and algal cells number. Highest removal efficiencies for TDN, TDP, turbidity, DOC, chlorophyll-a and algal cells were 56.9%, 73.3%, 92.4%, 29.9%, 94.3% and 91.0%, respectively. When the phytosystem was considered for herbicides removal, removal efficiencies of more than 25% were noted for all the herbicides.