analysis of a pilot-scale anaerobic baffled reactor treating domestic ...

pathogens and parasites, which may present a potential health risk to humans and water supplies.
These results indicate that outflow produced by a baffled septic tank or ABR would not be safe for
discharge to water course or for agricultural use without a post-treatment step for the removal of
pathogenic contaminants.
Table 5.5: Phase III: Pathogen indicator organism concentrations in inflow and outflow from
the pilot-scale ABR
Average/
Median
Std Deviation Number of
observations
117
Min. Max.
Total Coliforms In 7.3 25 7.0 7.7
[log(cfu/100mℓ)] Out 6.6 25 5.8 7.1
E. Coli In 7.7 25 7.2 8.1
[log(cfu/100mℓ)] Out 6.8 25 5.9 7.3
Coliphage In 4.1 24 3.6 4.8
[log(pfu/100mℓ)] Out 3.5 24 2.0 4.2
Ascaris spp. In 772 341 13 347 1 500
[Number eggs/ℓ] Out 17 15 13 2 56
Mean HRT: 22 h Total flow treated: 352 658 ℓ
5.7.2 Microbial community studies
Two Master level student projects were undertaken to investigate microbial community structure and
dynamics on the pilot-scale ABR.
• During Phase III, Lalbahadur undertook a MTech research project through Durban Institute of
Technology (DIT, now Durban University of Technology, DUT) looking at quantifying
different classes and genera of micro-organisms in sludge taken from each of the
compartments using a variety of microbial techniques (Lalbahadur, 2005).
• In Phase III and Phase IV, Pillay investigated microbial community structure by examining
dispersed and granular sludge taken from different compartments by scanning electron
microscopy (SEM) and epi-fluorescence microscopy (EFM) as part of his Master of Science
dissertation through the School of Conservation and Biological Sciences at the University of
KwaZulu-Natal. (Pillay, 2006)
The main findings of these projects are summarised in this section.
5.7.2.1 Characterisation of microbial communities using molecular techniques
Three molecular techniques were used for the identification and enumeration of microbial consortia in
the samples. The details of the methods for these techniques may be found in Lalbahadur (2005). The
three methods were
• total cell counts using 4’6-diamidino-2-phenylindole (DAPI) staining: binds with intact DNA,
thereby providing an indication of the density of intact micro-organisms (although this
technique does not indicate the activity of these organisms).