Fecal Sludge Management
What is fecal sludge management and why is it important?
More and more people around the world are purchasing, or being provided with, pit latrines, communal toilets, or other improved sanitation solutions. While this is vital to reduce transmission of diarrhoeal diseases, questions arise about how to deal with the pit latrine waste management.
Latrine pits need to be emptied periodically and in many densely populated, urban environments it is simply not feasible to dig a new pit every time they fill up. The lack of resources available to serve such populations means that faecal waste management is often the responsibility of residents themselves. Not surprisingly many individuals delay this unpleasant task which can often result in toilets overflowing. Many others are likely to opt for their easiest means of disposal, sometimes illegally dumping the sludge into nearby open drains and rivers. This has significant public health and environmental consequences with the whole community potentially being exposed to untreated human waste.
Our key contributions and reserach in this area:
One potential solution to the problem of faecal waste management may come from the research the group is conducting into black soldier fly larvae (BSFL). The idea behind BSFL human waste management is to use the larval stage of a non-disease spreading, non-nuisance fly species (Hermetia illucens) to feed on pit latrine waste. As the larvae develop on the faecal material, they increase in size, reducing the mass of the waste, and converting the dangerous pit material into a potentially useful soil conditioner or fertiliser. Once the larvae have developed into prepupae, they can be harvested. These prepupae are high in fat and protein and have an economic value. Previous studies have showed that BSFL fed on animal manure are a suitable replacement for conventional protein sources in animal feeds.
It is proposed that pit latrine material is fed to BSFL, which can then be harvested, safely processed to remove any possible pathogens, and sold as an animal feed. A correctly managed, decentralised, community based system could help improve sanitation in developing countries which lack suitable waste management solutions. Giving the pit material a value could reduce the cost of pit emptying, and encourage local entrepreneurs. The overall aim of this research is to improve sanitation in developing countries, and in doing so reduce the incidences of diarrhoeal disease.
Our current projects in this area:
Ian Banks conducted his MSc thesis on the “Determination of physical and biochemical changes of human faeces, of different dietary origins, and black soldier fly larvae (Hermetia illucens) as feeding occurs”. This research demonstrated that BSFL can develop successfully on fresh human faeces, and grow to a larger size than when fed animal manure. It showed how BSFL can successfully develop on vegetarian and omnivore human faeces, implying that a BSFL human waste management system could be implemented in many countries in the world, not dependant on peoples dietary habits.
Assessing the impact of BSFL on faecal reduction in pit latrines
The research currently underway at LSHTM on BSFL consuming pit material is the PhD work being conducted by Ian Banks, entitled; “To assess the impact of black soldier fly (Hermetia illucens) larvae on faecal reduction in pit latrines”. Currently in the analysis and write-up stage, the work aims to determine which pit latrine characteristics, i.e. total solids, chemical oxygen demand, ammonium, are important in the development of BSFL on pit material. The research also aims to discover what affects factors such as feeding rate, moisture content of food, and larval density, have on the waste reduction and larval development of BSFL. Finally the research aims to look at how the presence of common cleaning chemicals affects the development of BSFL.
Full list of publications related to fecal sludge management:
- Banks, I.J., Gibson, W.T. & Cameron, M.M. (2014). “Growth rates of black soldier fly larvae fed on fresh human faeces and their implication for improving sanitation.” Tropical Medicine & International Health19(1): 14-22.
- Clasen TF, Bostoen K, Schmidt WP, Boisson S, Fung ICH, Jenkins M, Scott B, Sugden S, Cairncross S 2008. Interventions to improve excreta disposal for the prevention of diarrhoea. (Protocol for a Cochrane Review). In: The Cochrane Library, Issue 2, 2008.
- Cairncross, S. 1990. Use of sewage and sludge in agriculture. Editorial, Lancet (i) 635‑636.