Experimental and Modeling Studies of Horizontal Subsurface Flow Constructed Wetlands Treating Domestic Wastewater

Abstract

Cyperus papyrus, commonly referred to as papyrus, belongs to the Cyperaceae family and is one of the most prolific emergent macrophytes in African subtropical and tropical wetlands. Botanical studies have shown that stands of papyrus are capable of accumulating large amounts of nutrients and have a high standing biomass. Its C4 photosynthetic pathway makes C. papyrus highly productive with dry weight biomass generation rates of up to 6.00 kg m-2 y-1 and nutrient uptake rates of up to 7.10 kg ha-1day and 0.24 kg ha-1day of, respectively, nitrogen and phosphorus. C. papyrus plants take about 6 - 9 months to mature with a highly reliable natural re-growth and replenishment on a site after harvesting. Studies featuring side by side investigations with unplanted controls, show that C. papyrus has mostly a positive effect on the treatment of wastewater, i.e. it supports higher treatment efficiencies for the removal of organics (COD, BOD5), pathogens, heavy metals and nutrients such as nitrogen and phosphorus. The ability of C. papyrus to use nutrients from the wastewater and the incorporation of heavy metals and organics into its phytomass, added to its easy management by regular harvesting, make it one of the most suitable plants to be used in wastewater phytoremediation in tropical areas. Therefore, it continues to be an excellent candidate for application as a macrophyte in the constructed wetland wastewater treatment technology. As such, determining the potential scope of the performance of C. papyrus is vital for the optimal application and design of C. papyrus based constructed wetland systems. This work collates growth, productivity and performance information from various independent studies incorporating the C. papyrus macrophyte in constructed wetlands for wastewater treatment