Plankton composition, distribution and significance in a tropical integrated pilot constructed treatment wetland in Uganda

The importance of the plankton community in wastewater treatment has been under-estimated for a long time, simply because of its biomass accumulation resulting in final release of organic matter back into the system after decomposition. In a two-year 3-month periodical study on a tropical integrated wastewater treatment constructed wetland, the phytoplankton role was tested and it has been shown that, through harvesting, the phytoplankton community plays a significant role in municipal wastewater treatment. The high phytobiomass, which was dominated by green algae (Chlorophyta), enhanced high levels of dissolved oxygen and high pH within the open ponds, and because of this, the system was found to be highly efficient in BOD₅ (81%) and NH₄⁺-N (93%) removal. The high pH enhanced ammonia volatilization within the open ponds. Regression statistics between the plankton community composition and some of the physico-chemical parameters (BOD, NH₄⁺-N, DO, pH) within the wetland system show a significant relationship. In conclusion, open treatment wetlands provide a wide variety of planktonic organisms as water quality improvement systems through the provision of oxygen and alteration of the pH for BOD₅ and ammonium reduction respectively.