Tracking the Logistics of Fecal Sludge Collection in Kigali, Rwanda
“If we have data, let’s look at data. If all we have are opinions, let’s go with mine.”- Jim Barksdale. Our growing R&D team at Pit Vidura has been working hard on transforming our routinely collected data into important insights that improve the quality and affordability of our waste management services. As always, we’d love to share our learnings with you!
Here in Kigali, like other rapidly urbanizing areas, there is no sewer system — everyone uses a pit latrine or septic tank. When these systems fill, moving the fecal waste from a house to a disposal site entails removing the waste from a pit or septic tank and then transporting it to a disposal site via truck. When a pit latrine or septic tank is full, households request an emptying service from one of many private service providers. But many of these service providers are too expensive for low-income households. While we are proud of being Kigali’s most affordable waste collection service, we know that we have a long way to go before every single household can afford our services and we are constantly iterating on new ways to drive down our costs and meet every household’s ability to pay.
Left to right: Pit Vidura’s vacuum truck which is used to empty septic tanks near to the main road; Loading barrels onto a flatbed truck which is used to serve low-income clients in informal settlements
The duration of an emptying job is an important component of the price of our fecal sludge emptying service — the longer a job takes, the more costly it is for us. Thus, reducing the overall duration of emptying jobs can help pass on savings to low-income households. We conducted a time and motion study to identify bottlenecks within the emptying process. We used data collected routinely by our service delivery teams on the duration of each task for 925 jobs completed over 13 months. Ultimately, this exercise will enable us to focus our design and engineering efforts on addressing identified bottlenecks and making our service more efficient and affordable.
Left to right: Trash fishing process used to remove trash deposited in pit latrines in low-income areas, Pumping waste from a pit to barrels using eVac.
Each emptying job consists of: preparing the worksite with our tools, removing trash from the waste containment system (pit or septic tank);moving sludge from the pit to the truck’s tank via direct pumping or barrels; cleaning the workspace. In aggregate, these tasks can take on average 3 hours for exhauster trucks and 4.7 hours for the flatbed truck.
We found that trash fishing and pumping make up more than 60% of the total process time per job.
Another learning from our study is that emptying process times vary according to the type of sanitation facility. According to our data, the duration of a pit latrine emptying job is 30% longer than the soak pit and 50% longer than septic tank emptying. This variation is associated with the high volumes of trash, viscous sludge, and a lower degree of process mechanization for emptying pit latrines. Due to limited road access in many low-income informal settlements, barrels and portable pumps are necessary to remove waste from some household facilities, especially pit latrine users. In fact, only 39% of our pit latrine jobs were serviced by vacuum trucks. The high cost of serving low-income pit latrine users in inaccessible areas explains why many vacuum trucks rarely serve such low-income areas — despite the huge market potential, jobs in these areas are statistically time-consuming and more cumbersome due to the high volumes of trash deposited in pits. The presence of high trash volumes in fecal sludge can clog or damage pumps, and cause costly delays. As pit latrines are the most common form of sanitation in developing countries, reducing the duration necessary to empty these types of sanitation systems is an emerging priority for our team.
Moving forward, we hope to act on our findings and make our service more efficient by:
Developing or sourcing improved pumping technologies that are capable of handling sludge with low moisture and high solid waste contents,
Develop and implement practical concepts that reduce the amount of solid waste in pit latrines, such as the promotion of Lixil SaTo Pans, sensitization campaigns, and a pricing structure that provides an incentive for low amounts of solid waste in pits
Reducing the amount of manual labor by using mechanized pit to road transportation technologies especially in informal settlement areas without access roads (e.g. use of Dovac),
Automating data collection using remote sensing and monitoring technologies. This will help in optimizing logistics and operations processes as well as tracking progress accurately.
Stay tuned as we work on improving our process. We won’t stop until safe and affordable sanitation is available for all!