Effect Of Operational Variables On Nitrogen Transformations In Duckweed Stabilization Ponds

There is an urgent need to develop and improve low cost technologies for wastewater treatment. Simultaneously treating wastewater and producing duckweed in a pond system is, therefore, an attractive solution contributing to both environmental protection and food production. Duckweed has excellent qualities: a high protein content, a high growth rate and is an easy crop to handle. The small plant turns nitrogen from wastewater into a food source. This thesis reports on the effect of different operational variables, like anaerobic pre-treatment, the combination of algae and duckweed ponds and pond depth. Improved nitrogen removal was obtained through the combination of duckweed ponds with algae ponds. Duckweed pond systems could be designed with shallow depth without affecting nitrogen removal efficiency. This research is the result of the cooperative effort between the EIDENAR, Univalle, Cali, Colombia and the UNESCO-IHE Institute for Water Education in Delft, the Netherlands.

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.

Ecotechnologies for wastewater treatment (EWWT) have been used as a cost-effective alternative to conventional wastewater treatment methods for improving the removal of organic carbon, nutrients and pathogenic microorganisms from wastewater. However, due to biochemical transformations of organic matter and nutrients EWWT are net sources of CO2, CH4 and N2O greenhouse gases (GHGs), which may be transferred into the atmosphere contributing to global warming. Greenhouse Gas Emissions from Ecotechnologies for Wastewater Treatment provides scientific information about greenhouse gas, such as CO2, CH4 and N2O, generation and emissions from different municipal EWWT. The main EWWT considered in this book are anaerobic ponds, facultative ponds, duckweed-based ponds, and a freshwater natural wetland perturbed by anthropogenic activities such as wastewater discharge and nutrients from agricultural run-off. The book includes a full literature review of recent publications about GHGs emissions from EWWT. It also introduces the calculation of GHGs flux using a static chamber technique. Besides, the book presents information on the influence of environmental factors such as temperature, pH, DO, and nutrients on GHG emissions produced in EWWT under tropical conditions. This book will be a useful reference for researches and students interested in the broader area of water and climate change subjects. The publication may also be of interest to policy makers concerned with climate change, water sector planning, and wastewater treatment.

Natural and constructed wetlands play a very important role within the landscape and their ecological services are highly valuable. Water management, including flood water retention, biomass production, carbon sequestration, wastewater treatment and as a biodiversity source are among the most important ecological services of wetlands. In order to provide these services, wetlands need to be properly evaluated, protected and maintained. This book provides results of the latest research in wetland science around the world. Chapters deal with such topics as the use of constructed wetlands for treatment of various types of wastewater, use of constructed wetlands in agroforestry, wetland hydrology and evapotranspiration, the effect of wetlands on landscape temperature, and chemical properties of wetland soils.

Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.