Ventilated improved pit latrine: a theoretical evaluation of conventional design guidelines, user adaptations and prospects for improvement

Abstract

The ventilated improved pit latrine has the potential of meeting the sanitation needs of many households in developing countries and enhance the chances of attaining the Sustainable Development Goal (SDG) 6. However, some user adaptations of the technology appear to conflict with conventional design guidelines and may compromise the ventilation rate in the vent pipe. This would negatively affect the odour control function of the technology. This paper seeks to evaluate existing conventional design guidelines that are aimed at controlling odour and fly nuisance in the latrine to highlight their relevance and possible conflicts with existing and emerging user adaptations. It also identifies potential structural modifications that may be adopted to accommodate emerging user preferences without compromising the odour control mechanism. The review shows that, indeed, some construction practices such as provision of windows in multiple sides of the superstructure adversely affect the ventilation rate and could lead to odour problems. However, the effects of some suspected unfavourable user adaptations such as use of closed-top vent caps and ceramic seats with covers have not been investigated. Furthermore, recent studies have demonstrated the possibility of compensating for the negative effect of some user preferences with favourable environmental conditions such as high wind speed and structural modifications using a mathematical model. However, the existing model fails to account for some key design criteria and needs to be improved to make it useful for a wider application.