Thesis (M. Eng.) - Asian Institute of Technology, 1995

A thesis submitted m partial fulfilment of the requirements for the degree of Master of Engineering.

The study evaluated the applicability of the integrated biomass model of Polprasert and Agarwalla (1994) to water hyacinth pond (WHP) and waste stabilization pond ( WSP) systems. The hydraulic characteristic of the ponds was determined by tracer and dye studies. The dispersion numbers of WHP and WSP operated at hydraulic retention time (HRT) of 5 days were 0.01 7 and 0.016 respectively, and photographs from the dye study showed no apparent vertical mixing which supported the tracer study results. Batch kinetic experiments were performed to determine the first-order rate coefficients of suspended and attached biomass from the pilot-scale WHP and WSP units. The overall first-order rate coefficients of the pilot-scale units based on COD removal performance were computed using the integrated biomass and plug-flow equations. The values of overall effective rate coefficients computed from specific biomass activities were greater than the overall rate coefficient derived from pond performance . The integrated biomass equation was modified incorporating the additional COD introduced into the reactors from decaying organic matter (e.g. plants and detritus) for use with the simplified biomass-specific overall effective rate coefficient equation. The modified equations w~re validated using first-stage full-scale and pilot-scale WHP and WSP data conducted in AIT. The median effluent COD concentrations for both units were predicted better than the unmodified integrated biomass and plug flow equations. Simplified charts for the design and operation of WHP systems were prepared and demonstrated the significant influence of pond depth on reactor sizing.