Vol.:(0123456789) 1 3 Modeling Earth Systems and Environment https://doi.org/10.1007/s40808-018-0523-0 ORIGINAL ARTICLE Optimising ventilation to control odour in the ventilated improved pit latrine Peter A. Obeng 1  · Sampson Oduro‑Kwarteng 2  · Bernard Keraita 3  · Henrik Bregnhøj 3  · Robert C. Abaidoo 4  · Esi Awuah 2  · Flemming Konradsen 3 Received: 18 June 2018 / Accepted: 29 September 2018 © Springer Nature Switzerland AG 2018 Abstract The rate of ventilation through the vent pipe of a ventilated improved pit latrine is the main technical factor that determines its efciency in odour control aside the maintenance and cleaning practices of the users. Even though the factors afecting the ventilation rate have been well researched, they have not been previously related in a mathematical model to quantify the relative efect of the various factors on the ventilation rate. The objective of this paper is to develop such a model that could be used to optimise and predict the ventilation rate as a function of relevant design criteria and weather conditions. The ventilation rates produced by various design modifcations in an experimental ventilated improved pit latrine were measured under monitored weather conditions. A linear regression model was used to assess the relative efect of the various design modifcations and the elements of weather on the ventilation rate. It was found that the diameter of the vent pipe is the most important factor which accounts for 53% of variations in the ventilation rate, followed by the external wind speed, which accounts for 25% of changes in ventilation. The provision of windows in other sides of the superstructure other than the windward side leads to a reduction of 32% in the ventilation rate and accounts for 9% of the variations in the ventilation rate. A regression model developed in this study could be used to optimise and predict the ventilation rate based on a set of design criteria and meteorological data. Keywords VIP latrine · Ventilated improved pit · Ventilation rate · Dry sanitation technology · Modelling Introduction Dry on-site sanitation technologies are the most widely used among households in low-income communities (Obeng et al. 2015). With proper design and construction, they qualify as improved sanitation technologies (Karnib 2014). They are especially popular in communities where the use of septic tanks with water closet and other water-dependent systems is technically unfeasible due to inadequate water supply, lack of motorable access roads to empty tanks or some other site constraints (Brikké and Bredero 2003; Paterson et al. 2007). In such situations, even households that could aford the more convenient and ‘prestigious’ water closet system are compelled to rely on dry sanitation technologies. For instance, Obeng et al. (2015) reported that some households in a Southern Ghana community had abandoned their septic- tank-with-water-closet systems and resorted to ventilated improved pit (VIP) latrines due to irregular water supply to the community. Consequently, the study reported that 70% of the residents depended on dry sanitation systems. * Peter A. Obeng pobeng@ucc.edu.gh Sampson Oduro-Kwarteng sokwarteng@gmail.com Robert C. Abaidoo abaidoorc@yahoo.com Esi Awuah esiawuahrt@gmail.com Flemming Konradsen fko@sund.ku.dk 1 Water and Sanitation Unit, Department of Chemistry, University of Cape Coast, Cape Coast, Ghana 2 Civil Engineering Department, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana 3 Department of Public Health, University of Copenhagen, Copenhagen, Denmark 4 Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana