ABSTRACT
The effect of baffles on algal-bacterial biofilm structure and composition of
Chapter 2
The effect of baffles on algal-bacterial biofilm structure and composition of
zooplankton in wastewater stabilization ponds
Abstract
Nitrifier biomass in the water column of wastewater stabilization ponds is low and this
reduces nitrification rates. For this study, baffles were installed as attachment surface for
nitrifiers. Four pilot scale wastewater stabilization ponds were constructed in Kampala,
Uganda; pond 1 was control while ponds 2, 3 and 4 had baffles of the same total surface
area but different configurations. The ponds were operated for two periods i.e. under an
(period 1) and an influent BOD
(period 2, achieved by covering facultative pond). The
objective of this study was to investigate biofilm biomass and, distribution and composition
of algae on the baffles. The diversity and biomass of zooplankton in the pond water column
was also investigated. Dry weight of biofilm was determined gravimetrically while the wet
weight of the algae in the biofilm were determined using the bio volume method. The
results showed that the algal-bacterial biofilms grew rapidly within 2-3 weeks and after
that, the thickness did not increase. The algal-bacterial biofilm dry weights at 5cm depth of
all ponds during period 1 were higher than those of period 2. This is probably due to the
contribution of influent algae and heterotrophic biomass. As the facultative pond during
period 1 was not covered, more algae entered the maturation ponds forming thick biofilms
on the baffles, the algae in the deeper layers died forming a layer of detritus material.
