poster - International Conference of Agricultural Engineering

TABLE 1: Average count of microspheres in the sampling intervals and efficiency (%) of
treatment.
Sampling
Average count of
Efficiency (%)
Intervals (min)
microspheres
0 3000 99.85
30 2000 99.9
60 1500 99.925
90 500 99.975
120 2500 99.875
150 500 99.975
180 3500 99.825
210 0 100
240 0 100
Total filtrate
(240 min) 12000 99.4
The retention capacity of polystyrene microspheres is entirely due to the use of Moringa
oleifera coagulant solution. Ndabigengesere et al. (1995) showed that the coagulation active
agents in aqueous extracts are dimeric cationic proteins and the clotting mechanism can be
represented by adsorption and neutralization of colloidal charges. The microspheres adhere
to the surface of the floc formed during the process. This adhesion may be explained by
means of mechanisms that occur during the flocculation step.
In the filtration process, the floc is almost fully retained in the first and second layer of the
non-woven synthetic fabric, and white sediment is formed on the surface layer as a result of
the adhered flocs. The adhesion of the microspheres on the floc and the material retained in
the fabric can be seen in microscopic image (FIGURE 1).
A
B
Figure 1: A - Microscopic image of post-test non-woven synthetic fabric with microspheres
and Moringa oleifera. B - Post-test image of non-woven synthetic fabric visible to the naked
eye.
The negative control test showed that there was contamination in some sampling intervals,
but these values are considered minimum to detect in slides, presenting 1% contamination
only for the sampling intervals at 30, 60, 120 and 240 minutes.