Effects of Algal Biofilms and Operational Conditions on Nitrogen Transformations and Removal in Waste Stabilization Ponds UNESCO-IHE PhD Thesis

Discharge of nutrient rich wastewater causes eutrophication of surface water; therefore wastewater treatment before discharge is required. Wastewater stabilization ponds are low cost technology used by developing countries but not effective in nitrogen removal due to low nitrifier biomass in the water column. Introduction of surface area for attachment of nitrifiers has therefore been proposed. This thesis reports the performance of pilot scale wastewater stabilization ponds fitted with baffles. The effect of baffles on nitrogen removal under tropical and two operational conditions was investigated. Under TKN/BOD ratio of 0.67, the baffled ponds performed better in nitrogen removal than the control pond. Total nitrogen mass balances showed that nitrification-denitrification, algal uptake and sedimentation were principle nitrogen removal mechanisms in biofilm waste stabilization ponds This study shows the potential of biofilms in improving nitrogen removal in wastewater stabilization ponds. The BOD and TSS concentrations were sufficiently low to permit for reuse in irrigation. If the objective is reuse and optimization of resources, the effluents from the ponds had sufficient nitrogen content for use in agriculture.

1. Introduction 2 The effect of baffles on algal-bacterial biofilm structure and composition of zooplankton 3 Comparison of hydraulic flow patterns 4 Nitrification in bulk water and biofilms 5 Nitrification rates of algal-bacterial biofilms 6 Effect of operational conditions on the nitrogen removal 7 Nitrogen mass balances for pilot scale biofilm stabilization ponds under tropical conditions

Mohammed Babu was born on March 21st 1973 in Mbale, Uganda. He holds an Msc Environmental Science and Technology and aPhD from UNESCO-IHE, Delft, The Netherlands. Currently, he is lecturing at the department of Environmental Science at the Islamic University in Uganda. His major research interests include water quality, pollution monitoring, wastewater research, wetland ecology, limnology and solid waste management. He has researched on the use of biofilms in improving nitrogen removal in waste stabilization ponds. His studies have shown that biofilms have a potential to improve nitrogen removal in wastewater stabilization ponds.