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Obstacles and new research - Daniela Peguero

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.

Photo 5. Manually screening the sludge through a sieve
Photo 6. Larvae in 500 grams of VIP sludge

Photo 7. Heterotrophic Bacteria Plates using 3M Petrifilm Plates

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