poster - International Conference of Agricultural Engineering

After the assembly of the experimental apparatus, a 25 mg.L -1 (2% w/v) coagulant solution
prepared from the seeds of Moringa oleifera was added to the system according to the
procedure described by Arantes (2010). The unit was turned on and intervals of fast and
slow mixing were conducted, being programmed for a stirring velocity gradient at 400s -1 for
15 seconds and 40s -1 for 1800 seconds, respectively. After this interval of mixing, Jar Test
equipment was adjusted to recover the maximum volume of sample to the filtration. The
upper output was sealed and another output was placed at 1.5 up from the bottom of the
jars. In addition, the jar was suspended so that the homogenization blades reach the bottom,
and thus prevent the floc sedimentation. After the jars were suspended, the homogenization
occurred until the end of filtration of the sample.
The samples were directed into a single output which was connected by rubber hoses. This
output was directed towards the filtration system, which employed a simple filter system in
PET (polyethylene terephthalate) bottle, with the filter medium composed by 5 layers of nonwoven
synthetic fabrics with a thickness of 4 mm each, and a gramature of 600 g/m 2 . The
filtration rate was 4 m 3 / (m 2 .day), within the values established by Di Bernardo (2003). Other
characteristics of slow filtration was not adopted because the proposed system operated at a
bench scale, with a limited flow conditioned to operate in a total of 4 hours and a half,
approximately.
Samples were collected after an interval of mixing (fast and slow) in the jars, after leaving the
filter every 30 minutes for a total period of 240 minutes (4 hours). Samples were sent for
turbidity determination and separation by vacuum filtration followed by the mechanical
extraction, according to procedures carried out for the extraction of Cryptosporidium oocysts
employed by Hong et al. (2001). In the case of microspheres, there was no need to add the
reagent Fluorescein Isothiocyanate (FITC), since they have its own fluorescence
(CEQUEIRA, 2008). At the end of the process, the slides of microspheres were obtained and
the counts were performed in the epifluorescence microscope (Motic Mod BA410) with 100-
fold increase lens.
The negative control test (without inoculation of microspheres) was performed both to
demonstrate the possibility of contamination between the tests and indicate the presence of
false positives results in the positive control test (without addition of Moringa oleifera
coagulant solution). The positive control test was conducted to check the amount of recovery
of polystyrene microspheres, especially because there is no Moringa oleifera coagulant
solution added to this test.
3. Results and Discussion
The results showed that the coagulation with Moringa oleifera followed by filtration in
synthetic non-woven fabrics retain polystyrene microspheres throughout the filtration, with
removal efficiency of 99% and 100% removal in some sampling intervals.