Some obstacles presented themselves during the time I was in South Africa. Unfortunately, the
technology I was supposed to test was not working. Many technical difficulties were encountered
when trying to operate the viscous heater (VH). The timeframe to get the VH working, was about
6-8 weeks, which by that time I would have already been gone. Instead, I focused on the second
part of my project, which was assessing storage conditions of fecal sludge with and without black
soldier fly larvae (BSFL). BSFL can be grown on fecal sludge and are currently being used as a
source for animal feed because of their high protein content.
To evaluate the potential for microbial regrowth in the finished product, storage of the fecal sludge
was tested with two different conditions: fecal sludge with BSFL, and fecal sludge without. The
fecal sludge without BSFL served as the control. Each container was filled with 500 grams of fecal
sludge. 500 BSFL were grown in each designated container with the fecal sludge. Although, it is
expected take a total of 10 days for the larvae to grow to their largest size, experiments were
conducted from initial growth of the larvae to 14 days. The fecal sludge served as the feed for the
larvae. To get the sludge ready for the larvae, I manually sieved the fecal sludge. Once the sludge
was prepped, and the larvae was ready, I placed the larvae in the sludge. To assess the inactivation
of in situ bacteria, I tested for heterotrophic bacteria and E.coli and Total Coliform bacteria using
the 3M Petrifilm Plates, as shown in Photo 7.
Although it was unfortunate that the technology wasn’t working, it just went to show that in
research you never know what’s going to happen. Luckily, I was able to learn more on BSFL, and
see how human waste can be reused in that regards.
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| Photo 5. Manually screening the sludge through a sieve |
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| Photo 6. Larvae in 500 grams of VIP sludge |
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| Photo 7. Heterotrophic Bacteria Plates using 3M Petrifilm Plates |
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