Laboratory protocols for testing the efficacy of commercial pit latrine additives

Abstract

There is considerable national interest in the use of commercial microbially derived products for controlling the rate of accumulation of the contents of pit latrines. Manufacturers claim that some of these products can reduce accumulation rates, prevent the pit from ever filling up, or even result in decreases in pit contents volume. Prior to this research, there have been no scientific publications that have conclusively supported or refuted these claims. This project undertook to perform reproducible laboratory tests that would quantify the effect of commercial pit latrine additive products. Protocols were developed and tested on a range of different commercial products sold for their ability to control the rate of accumulation of pit latrine contents. The effect of commercial additives on mass loss from VIP sludge in 300 g honey jars was compared to mass loss from similar units subjected to no treatment and treatment with water. The purpose of these experiments was to separate and quantify the effect of microorganisms or enzymes originating from commercial pit latrine additives from the effect of natural processes within the pit latrine sludge (including digestion by microorganisms in the VIP sludge and dehydration) and the effects of other actions associated with treatment, such as the addition of water. Results indicated that insignificant mass loss occurred in all anaerobic test units, while significant mass loss occurred in all other test units. However, there was no statistically significant difference between any of the different treatments in the aerobic units. Investigation of analytical data from the test units indicated that mass loss in aerobic units was due to a combination of dehydration through evaporation of moisture and biological stabilisation processes, and that the latter were not significantly enhanced by the addition of commercial pit latrine products. It was concluded that there was no evidence to support claims that pit latrine additives could extend the life of a pit latrine.

An investigation of the effect of pit latrine additives on VIP latrine sludge content under laboratory and field trials

“…These results support the findings of previous studies (Sugden et al 2006;Foxon et al 2009) that pit latrine additives do not assist in reducing pit filling rates and sludge volumes. However, only two additives were tested, and there may be others which would return a different outcome.…”

“…In another laboratory study conducted by Sugden (2006) to investigate the efficacy of bio-additives designed to reduce sludge volumes in pit latrines and septic tanks by enhancing the anaerobic digestion process taking place, it was found that though all four stages of anaerobic digestion took place in all of the laboratory test units, there was no evidence to show that any of the bio-additives either enhanced or inhibited the anaerobic digestion process. Foxon et al (2009) also concluded from laboratory experiments that commercial pit latrine additives were unable to accelerate the biodegradation rate and mass loss from samples of pit latrine sludge.…”

Assessment of the influence of intrinsic environmental and geographical factors on the bacterial ecology of pit latrines

“…There have been a limited number of studies that have reported on decomposition within pit latrines, and only anecdotal evidence into factors that can slow down or speed up decomposition (Couderc et al ., ; Nwaneri et al ., ). Commercial (bio)additives, often based on nutrients, enzymes or bacteria, claim increased decomposition rates, reduced odour and longer pit life spans (Foxon et al ., ), though there is no scientific evidence that these products work, as was shown by a study conducted in South Africa (Buckley et al ., ). Regardless, microbial communities will play an important role in organic matter degradation within pit latrines, though little is known about the microbial communities present in pit latrines and their association with faecal decomposition within the pit environment.…”

Reducing Sludge Volume in Pit Latrines: Can Latrine Additives in Ghana Help?

“…Although there was mass loss in both trials due to treatment with commercial additives, the reduction was concluded to be statistically insignificant. In another study (Foxon et al, 2009), two laboratory trials were carried out to test the efficacy of commercial pit latrine additive in reducing sludge content in pit latrines. In trial 1, the effect of aerobic and anaerobic conditions was tested.…”