ABSTRACT
Wastewater treatment performance of solid-matrix, constructed wetland systems has been investigated during the design, operation, and maintenance of seven large-scale units at Richmond, Australia over a 3.5-year period. Performance models were developed by treating the systems as fixed-film bioreactors. Systems consisted of lined trenches planted with Typha orientalis or Scirpus validus in gravel and a floating macrophyte, Myriophyllum aquaticum, growing in open water with no solid matrix. System performance varied in response to variations in influent application rate and makeup, local temperature variation, system size and design, and macrophyte type and cover. Enumeration of microbial populations present in macrophyte systems during application of secondary effluent demonstrated that most of the total microflora and nitrifier populations were associated with gravel particles and root mass regions. Improved models are being developed through examination of removal data from discrete compartments in the systems and/or analysis using removal kinetics of increased complexity.
