Preliminary Study on the Potential Use of Fly Ash as a Ventilated Improved Pit Latrine Additive

Abstract

<jats:p>This study describes the results of a series of laboratory experiments on aimed at developing of a protocol for the use of fly ash as a pit additive in the ventilated improved pit latrines (VIPs) in South Africa. Model VIP vaults were prepared in the laboratory and filled with synthetic faecal sludge; and dosed with fly ash in amounts ranging from 5 to 20 % (w/w). The maximum leachable chemical oxygen demand (COD) accounted for 3.2 % of the total organic matter, while the maximum leachable ammonium accounted for 1.4 % of the leachable ammonium present in the synthetic faecal sludge. All phosphate in the synthetic faecal material was leachable. Mixing of the 20 % dose of fly ash into the synthetic faecal sludge resulted a minimum 98.9 % reduction (or about two log units) in the faecal coliform concentration after 28 days of incubation. As a result, addition of fly ash can decrease microbial threats to public and environmental health threats from the VIP faecal wastes, but can cause environmental contamination with phosphate. The fly ash dose and the duration of the faecal sludge treatment require further optimisation. Relationship between the chemical composition of the fly ash used as an additive to stabilise the VIP faecal sludge and the leaching of phosphorus from the sludge will also have to be investigated further.</jats:p>

Disaster Risk Management, Ventilated Improved Pit Latrines, and Sanitation Challenges in South Africa

“…This indicates that the fly ash treatment could pose a viable option to treat the VIP faecal sludge. This is further supported by the findings of Collings et al, who reported that there were no detectable and culturable bacteria on the fly ash from South Africa [93]. This, along with the pH values between 10 and above in the synthetic faecal sludge after fly ash addition [90], indicated the antimicrobial activity of the coal-fly ash.…”

“…In situ treatment could still be achieved, and the relevant Ri effectively managed using different additives, such as fly ash. In 2019, Collings et al reported on the application of the untreated fly ash in the elimination of 92% of the initial concentration of faecal coliforms from the synthetic faecal material under the ambient conditions and within 3 weeks of incubation at ambient temperatures [93]. Modification of the coal fly with sodium hydroxide resulted in the production of an additive that has been shown to decrease the concentration of faecal coliforms below 545 colony-forming units per gram of synthetic faecal sludge [94].…”

“…This would require personal protective equipment, which is equivalent to working with the microbiological laboratory with biosafety level 2 (see page 24 in reference [112]). The mixing of the modified fly ash into the bulk of the VIP faecal sludge would have to be accomplished for adequate treatment [93,94].…”

“…The coal-fly ash modification would require energy requirements in the hydrothermal treatment, and this could pose practical problems as well. However, unmodified fly ash could still be used as a pit latrine additive and stabilisation could be accomplished in the order of weeks [93,94]. The implementation of any successful VIP faecal sludge treatment will require a policy and end-user engagement.…”