Mature experimental constructed wetlands treating urban water receiving high metal loads.
The aim was to assess over 2 years the treatment efficiencies of vertical-flow wetland filters containing macrophytes and granular media of different adsorption capacities. Different concentrations of lead and copper sulfate (constant for 1 year each) were added to urban beck inflow water in order to simulate pretreated (pH adjustment assumed) mine wastewater. After 1 year of operation, the inflow concentrations for lead and copper were increased from 1.30 to 2.98 and from 0.98 to 1.93 mg/L, respectively. However, the metal mass load rates (mg/m(2)/d) were increased by a factor of approximately 4.9 for lead and 4.3 for copper. No breakthrough of metals was recorded. Lead and copper accumulated in the biomass of the litter zone and rhizomes of the macrophytes. Furthermore, microbiological activity decreased during the second year of operation. Bioindicators such as ciliated protozoa and zooplankton decreased sharply in numbers but diatoms increased. In conclusion, the use of macrophytes and adsorption media did not significantly enhance the filtration of lead and copper. Particulate lead is removed by filtration processes including straining. Furthermore, some expensive and time-consuming water quality variables can be predicted with less expensive ones such as temperature in order to reduce sampling costs.
Scholz
Miklas
M
The University of Edinburgh, School of Engineering and Electronics, Institute of Infrastructure and Environment, Crew Building, The King's Buildings, Edinburgh EH9 3JN, Scotland, United Kingdom. m.scholz@ed.ac.uk
Höhn
Patrick
P
Minall
Rowland
R
D019327:Copper Sulfate / Q000032:analysis; D005374:Filtration; D006863:Hydrogen-Ion Concentration; D007854:Lead / Q000032:analysis; D008670:Metals / Q000032:analysis; D014865:Waste Disposal, Fluid / Q000379:methods*; D014871:Water Microbiology; D014872:Water Movements; D018508:Water Purification / Q000379:methods*
D008670:Metals; D007854:Lead; C032722:lead sulfate; D019327:Copper Sulfate