There is an urgent need to develop and improve low cost technologies for wastewater treatment that are within the economic and technological capabilities of developing countries. Simultaneously treating wastewater and producing duckweed in a pond system is therefore an attractive option to contribute to both environmental protection and food production. Duckweed has excellent qualities, like high protein content, high growth rate and is easy to handle. The small plant turns nitrogen from wastewater into are source, therefore research is needed to manage the nitrogen conversions in duckweed ponds.
This thesis reports on the effect of different operational variables, like anaerobic pre-treatment, the combination of algae and duckweed ponds and pond depth. Anaerobic pre-treatment was found to contribute to the reduction of area requirements for the duckweed ponds and enhanced biomass production. Denitrification was found to be the most important nitrogen removal mechanism in duckweed ponds, followed by biomass up-take. 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 was carried out with financial support of the Dutch government within the framework of the SAIL funded project, entitled "Education in the Field of Sanitary and Environmental Engineering" and is the result of the cooperative effort between the EIDENAR, Univalle, Cali, Colombia and the UNESCO-IHE Institute for Water Education. A substantial part of the research was implemented in and with support from the Ginebra Wastewater Research Station of Acuavalle, Cali, Colombia.