Initial design and construction costs may be significant, ranging into tens of thousands of dollars. Unlike chemical treatment, however, wetlands are passive systems requiring little or no continuing maintenance. This is a relatively new treatment technology with many specific mechanisms and maintenance requirements not yet fully understood. Optimum sizing and configuration criteria are still under study. Seasonal variations in metals removal efficiency have been noted with lesser amounts removed in cold weather.
Wetlands are generally more effective in removing iron than manganese.
The greatest utility of wetlands appears to be in the treatment of small flows of a few gallons per minute. Leasing may be considerably cheaper.