A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Developement

Thesis (Ph.D.) - Asian Institute of Technology, 1985

The research programme on aquacultural treatment of nightsoil has been conducted at the Asian Institute of Technology (AIT) for about 10 years. This dissertation emphasizes only on the research in which nightsoil and biogas slurry are fed directly into single-stage, non-flow-through ponds for the production of algae and fish Tilapia (Oreochromis niloticus). The culture of herbivorous fish such as Tilapia in the same pond to graze on the algae is practical, in order to produce the fish protein biomass which is easily harvestable for animal (or human) food. Empirical and dynamic models describing the performance of septage and biogas slurry fed fish ponds were developed to simulate the temporal changes of various physico-chemical and biological parameters including dissolved oxygen, carbon dioxide, bacteria, algae, and fish growth. These models were based on the basic mechanisms and phenomena occurring in the ponds, and the simulated resul ts calculated from the Continuous System Modelling Programme (CSMP) computer package available at the AIT Regional Computer Center.