and the Efficacy of Pit Latrine Additives - Water Research Commission

certain of the bio-supplements at the dosages applied are able to significantly increase COD and TSS
removal rates over those which occur naturally. However the dosages used in these experiments were far
beyond those that could be used in practice.
The second part of the experimental study involved using two of the bio-supplement products that had been
shown to be effective in removing COD and TSS in the first part of the experiment to treat real pit latrine
contents. The site of this part of the study was labourers’ toilet blocks at a rose farm in Magaliesburg. Three
blocks each containing 3 pits were isolated for the study. Two of the blocks were treated with each of the two
bio-supplement products and watered on a daily basis to simulate urine addition. The third block was treated
with the same amount of water as the other two blocks, but no bio-supplement was added. Researchers tried
to prevent the labourers from using any of these pits during the course of the study. The pits were open (did
not have pedestals or squat hole covers) and did not have vent pipes. Researchers removed sections of the
corrugated roof to discourage people from using the pits. Some reduction in pit contents was seen in the two
blocks where the toilets were treated with bio-supplement, and none was recorded for the control blocks,
however, the volume reduction was very little (a maximum of 22 cm over a period of 3 months when no
additional solid material was being added). It was noted that there was some improvement in fly and smell
problems in the pits treated with bio-supplements, but no improvement was noted in the control pits.
The authors of this study cautiously suggested that bio-supplements are able to reduce pit contents, but that
conditions in the field study were not optimal for achieving good solids reduction due to low temperatures,
and the presence of non-degradable objects in the vaults (Taljaard et al., 2003).
The second pit latrine additive study was reported at a Water, Engineering and Development Centre
(WEDC) conference in 1998 (Jere et al., 1998). In this study, a pit latrine additive, termed a bio-organic
breakdown compound consisting of spore-forming non-pathogenic bacteria was dosed to 4 pit latrines
weekly for four weeks. The compound was added to pits by injection through a perforated tube under
pressure to achieve mixing of the additive with the pit contents. This study showed that the treatment had a
significant effect on height of pit contents. Unfortunately, there was no control against which the results could
be compared. Decrease in pit height continued for 8 weeks after dosing was suspended indicating that the
treatment may have achieved long-term improvement in digestion rates in the pit. Chemical analysis data
were presented and showed a decrease in COD, BOD and Kjeldahl nitrogen concentrations, although it was
not clear how these values should be interpreted in terms of the load of COD, BOD and TKN load in the pit
contents. The authors cautiously concluded that the additives showed promise for reducing filling rates.
However, the results do not indicate the contribution to the decrease in pit contents height of the method of
application (injection under pressure through a perforated tube into the pit contents).
Although some work has been undertaken to test the efficacy of commercial pit latrine additives on
controlling filling rates, the work reported does not provide sufficient evidence to prove that additives
containing micro-organisms significantly increase the rate of degradation of pit latrine contents; however,
micro-organisms from pit latrine additives are clearly able to digest pit latrine contents.
4.2 Inventory of pit latrine additives
This section gives details of a number of pit latrine additives and their suppliers which have been to date
identified as being marketed in South Africa. This list is not exhaustive, but consists of those products that
were obtained and used in this study.
Most products are supplied with a Material Safety and Data Sheet (MSDS). From these and supporting
documentation supplied with the products or obtained from open source literature, most of the additives
consist largely of freeze-dried bacteria. Most seem to favour aerobic bacteria, though one claims to be
effective under both aerobic and anaerobic conditions. None of the micro-organisms are genetically
modified, but are cultures of naturally occurring micro-organisms that have been selected on the basis of
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