Flexcrevator: Safe & Hygienic Sanitation Services in Cities

Nearly two billion people depend on using pit latrines for sanitation needs. Over time, these latrines fill up with feces and need to be emptied. In many areas without solid waste infrastructure, the latrine is also the trash system, and plastic bags, rags, menstrual materials, and condoms clog vacuum systems that are used to empty full pits.

In these areas, unsanitary emptying of full pits by hand is the main option. NC State developed the Flexcrevator, the only all-in-one machine that simultaneously removes fecal sludge in the presence of high levels of trash, using a novel exclusion process. The device leapfrogs current practices by enabling fast, safe, and hygienic fecal sludge removal that is dignified and profitable. When scaled, the Flexcrevator will eliminate the practice of manual emptying and improve the lives of billions around the world by enabling profitable community-based sanitation service businesses in slums and poor urban areas.

An estimated 1.77 billion people use pit latrines for basic sanitation (Graham and Polizzotto 2013), and another half billion use septic tanks. Based on excreta production rates, 0.6 billion kg of feces and 2.1 billion kg of urine are deposited in pit latrines every day. These numbers are increasing as populations increase and open defecation rates decrease. Once pits and septic tanks are full, the fecal sludge has to be removed, transported, and treated for safe disposal or reuse. In addition to human waste, these pits are often filled with trash in the absence of strong solid waste management.

Due to trash in pits (up to 20-30% by volume; Still 2002), most latrines are emptied by hand, exposing workers to human pathogens (above). The pit emptiers also suffer from social stigmatization. Although mechanical methods for emptying pits and tanks exist, they are inefficient, too bulky, or too expensive for the average pit emptier to own. They also clog frequently due to garbage such as of rags, plastic bags, and bottles. Many vacuum truck operators choose not to empty household pits because of high trash concentrations. A dignified, safe, and cost-effective method for emptying pit latrines and septic tanks is needed. 

Our technology serves the ~4.5 billion people in low- and medium-income countries who are not connected to centralized sewer systems, and the millions of workers who empty pits and septic tanks. We work with local government, universities, businesses, and NGO partners in South Africa, India, Malawi, Kenya, Zambia, Rwanda, Madagascar, and Ghana.  Our design evolved over 8 years, based on field testing with our partners, and their continuous feedback and data ensure that the device reduces public health risks for communities, gives sanitation companies potential to earn profits, and improves the quality of life for manual emptiers.

Public health officials, international development agencies, and utility officials we have worked with expressed concerns that fecal sludge spills from manual emptying can spread enteric and diarrheal diseases. The Flexcrevator minimizes spills and exposure of workers and communities. Profitability for small businesses is key to widespread use, and we outfitted sanitation companies in Rwanda and Madagascar to test the device and develop business models using actual cost and profit data. Stakeholder satisfaction data are collected using interviews and surveys, and workers and households in Asia and Africa describe feeling proud that they are using a professional-looking machine, and rate the service very positively.

Our solution evolved over 8 years of rapid prototyping and lab- and field -testing in Africa and Asia. The innovation is trash exclusion - the ability to pump fecal sludge while excluding trash from the flow and leaving it inside the pit. The unique technology uses active clearing and screening, using augers and a small motor in a low-cost package (<$2500). This technology makes emptying faster and more hygienic than manual methods, professionalizes the pit emptying industry, and enables small private businesses to be profitable (based on our market and business study). This trash exclusion concept also gives regulators and service providers the opportunity, through new incentives and fee structures, to discourage users from leaving trash in pits. In addition to incentivizing behavioral change, fecal sludge without trash provides a number of downstream processing advantages that make treatment, reuse, or disposal of waste faster and cost effective. Thus the machine changes the regulatory/policy environment, incites behavioral change, and makes pit emptying businesses dignified and viable.

The complete Flexcrevator is the Excluder (right) and a Custom Vacuum System (top left). This setup is best suited for situations where pit latrines are hard to access, and barrels are currently being used. Sludge is pumped through the Excluder and into the Vacuum Tank in batches. When the tank is full, sludge is deposited into barrels for off-site processing and disposal. A gasoline engine fuels both the Vacuum Pump and the Excluder. Field testing shows that the Flexcrevator can effectively pump 2-4 L/s in wet pits and 0.5 L/s - 1.5 L/s in dry pits (88% moisture).

If access to the latrine is not an issue and a Vacuum Truck is available, an operator can connect the Excluder to a Vacuum Truck (middle left). Field testing in Kenya demonstrated that watery sludge can be pumped at up to 5.6 L/s in this setup. Without the Excluder, it would not have been possible to empty this pit because of the trash that would clog the vacuum line.

The Flexcrevator can also use an in-line pump that pulls the sludge to a large collection tank. Pit emptying teams do not need barrels and pumps and hoses could be staged so that sludge can reach collection tanks potentially up to 100 m away. This configuration results in both speed and access at a cost much lower than the cost of a vacuum truck.

The Flexcrevator transforms the pit and septic tank emptying industry, a sector that affects billions of households and pit emptiers in poor and low-income countries. In developing a new class of sanitation device, NC State created the new concept of trash exclusion and set a new benchmark in portability and affordability. No other product can handle pits with trash and is as small or as portable: existing devices are large expensive trucks that cannot access many pits, or small vacuum systems that clog. No existing devices are able to automatically exclude trash, an approach that transcends the limitations of screening, macerating, or physical “fishing” of trash from dirty fecal sludge pits. Trash exclusion also leads to downstream benefits on treatment, and incentivizes behavior change in households and local governments.

The unit’s small footprint and modular design allows access to pit latrines and tanks in narrow alleyways that usually restrict vacuum trucks. Each component can be easily lifted for transport and storage. If access is not an issue, a vacuum truck operator has the option of connecting the trash excluder directly (below), allowing vacuum truck owners cleanly suck fecal sludge with very high trash concentrations. This was previously impossible, and changes the market of existing vacuum trucks.

The Flexcrevator has been shown in an exhaustive market/business study, using UN/WHO data and actual pit emptying fees, to be profitable. The payback period under realistic conditions is 1.5 years, and can lead to upward economic mobility of low-income entrepreneurs. 

The key innovation of the Flexcrevator is trash exclusion, where trash is left in the pit. We evaluated other processes like maceration, screening, and deflection, and determined that active exclusion is the best method to handle trash in fecal sludge pits. The other methods are too energy intensive or do not work in the complex mix of heavy trash levels in actual pits in S. Africa, Malawi, and Zambia.  Our team successfully integrated trash exclusion in the Flexcrevator through a patented unique clearing auger head (left) that attaches at the end of an Excluder (right).

Trash and sludge are pulled toward the Excluder under vacuum pressure. NC State’s clearing head consists of a perforated stainless steel pipe attached to the end of the rigid shaft to act as a screen for the trash. A separate auger attaches to the end of an Auger Mounting Disk and rotates around the perforated pipe. The spinning motion of the auger continuously clears the screen by pushing trash upward and away from the screen. We have optimized the hole sizes, hole placement, auger characteristics (pitch, diameter), and auger speed and tested extensively in Kenya and Rwanda. The clearing head allows for the continuous pumping of trash-less fecal sludge from pits. While the specific components are mostly off-the-shelf, the mechanism of action and specific designs for attachment and operation were the product of extensive ideation and prototyping, and covered by two US patents.

The Flexcrevator's ability to separate fecal sludge from trash results in several paradigm-changing effects. First, it allows service providers to charge for the removal of trash. This encourages behavioral change and dis-incentivizes customers from throwing trash in the pit latrine in the first place. The Flexcrevator also creates a safer, more dignified work environment for latrine emptiers as the workers have a reduced exposure to fecal sludge.

The Flexcrevator provides a pathway to regulating manual pit latrine emptying. Standardized regulations on how to perform clean, mechanized pit emptying do not yet exist. The issue of pit latrine emptying in urban areas continues to not get the attention it deserves- this is at least in part due to the fact that core stakeholders do not know of a hygienic way to approach this problem. This prevents stakeholders (donors, NGOs and the public sector) from making investments or developing capacity across the fecal sludge management chain as they cannot envisage the system that will exist. As long as the emptying process in manual – it will not be considered deserving of attention. Operating the Flexcrevator gives local officials the opportunity to observe how the Flexcrevator can vastly improve hygiene, sanitation, and human rights for not only communities but also sanitation workers. We know these effects are real because we have already heard from international donor agencies, local government units, utilities, NGOs, and pit emptiers who agree and believe this will work, and are excited about using the Flexcrevator at scale.

We estimate that the Flexcrevator currently benefits 1300 people and will benefit 10,000 people in one year’s time. In five years this will increase tenfold to 100,000 people. In ten to 15 years, the technology is expected to benefit millions as the Flexcrevator is brought to market.

Projections are based on:

• Flexcrevators operating or soon to be operating in the field.
• Number of people needed to operate a Flexcrevator.
• Number of latrines and septic tanks across Zambia, Kenya, Malawi, Madagascar, Rwanda, South Africa and India that have been or will be emptied by a Flexcrevator.
• Average number of people that use a latrine or septic tank.

NC State aims to establish a non-exclusive license with at least 1 commercial partner working in developing countries by July 2020. The team will:

• Test 4 units with existing sanitation companies in Rwanda, Madagascar, and Ghana to validate performance and collect commercialization data. This information will help develop business model documentation within Africa, including supply chain, marketing, financing, and sales plan. A year-long demonstration site will be opened in Ghana to host demonstrations for interested commercial partners and allow them to observe the device
• Test at least 2 units to study gender impacts: how the device operation, access, and ownership/ operation, are affected by gender. The goal is to identify barriers to inclusive use of the device and define explicit ways to remove these barriers. This includes studies that consider the physiological differences between men and women. We will also ensure women-owned or operated emptying businesses are not excluded from accessing the systems and will consider giving preference to women owned or operated emptying businesses.

Support from MIT Solve would allow the team to replicate efforts in Africa and create a new demonstration and testing site in India. It also will give the opportunity to study how gender dynamics impact latrine emptying processes in a different region. After achieving the one-year objectives, the following 5 years will center on transferring technology to a commercial partner or support a commercial partner to bring the device to scale.

Broadly, the largest hurdle involves recruiting commercial partners to license the technology. Interested partners need a stable enabling environment (government regulations, buy-in and support of the local water and sanitation utility, a working treatment plant, and working financing models for customers) for them to be successful. Matching demand, supply chains, financing models, and all the other enabling environment factors in one city or country may not be possible, leading to non-ideal conditions for a commercial partner. In this case, additional support may be needed, or discussions with local governments need to be initiated.

From a cultural and a gender equity perspective, it is not yet known how regional gender dynamics prevent access to our device. Informal manual pit latrine emptying has been historically performed by men in different parts of the world. Although the Flexcrevator provides an opportunity for economic advancement for the world’s poorest, the Flexcrevator will continue to disproportionately benefit men if the team does not explicitly consider why the observed gender gaps exist and what barriers women face when participating in the sanitation value chain.

Lastly, a key barrier for scaling the Flexcrevator in the near term is that sanitation companies are not yet familiar with the device. While we have partners operating the Flexcevator, we need to have a platform to showcase its benefits. Addressing commercial partner recruitment, gender barriers, and bringing more exposure will be key in increasing the technology’s impact.

Demonstrations to private companies and facilitating organizations alike will be necessary to drive wide adoption of the Flexcrevator. In the first year, these demonstrations will be at field sites. We currently target countries where there is already a strong enabling environment for improved pit emptying services and where NC State already has a strong in-country partner. The Bill and Melinda Gates Foundation has provided funding to test the device in Rwanda, Madagascar, and Ghana and work with a cultural anthropologist to study gender and pit emptying in Ghana. The team will collaborate with partners in Africa to develop business, marketing, and supply chain plans for the Flexcrevator. Funding from the Bill and Melinda Gates Foundation also allows us to host partners at a demonstration site in Ghana.

Financial support from the MIT Solve Challenge greatly increases the scope of our project by allowing us to partner with existing sanitation companies in India and set up local demonstration hubs for Asian partners. We have chosen India due to its strong capacity to build devices domestically. The NC State team also has previous testing experience within India, and the country’s ambitious program to end open defecation nationwide (Swachh Bharat) demonstrates political will for improved sanitation services.

NC State University is a Research 1 University in the US with over 34,000 students, 2,300 faculty, and an annual budget of over $1.4 billion dollars. We are a team based in the Civil, Construction and Environmental Engineering Department of North Carolina State University. The university first received funding from the Bill and Melinda Gates Foundation to develop, test, and optimize the innovative pit emptying device in 2011.

NC State filed two patents for Flexcrevator: one on the principle of trash exclusion, and another on the design of the Trash Excluder’s clearing auger screen.  Since the Bill and Melinda Gates Foundation primarily funded the project’s development, the device is subject to the Foundation’s Global Access Policy. This means that while the university will hold and maintain intellectual property associated with the Flexcrevator, the Global Access Policy compels us to ensure that the technology is made available to stakeholders within LMICs at an appropriate price point, quantity and quality.  

Full-time staff (2)

• Dr. Francis de los Reyes (Principal Investigator)
• Jocelyn Tsai (Project Coordinator)

Part-time staff (2)

• Walt Beckwith (Technical Staff)
• Giovanna Portiolli (Student)

Contractors (2)

• Tate Rogers (Technical Contractor)
• Dr. Nicola Greene (Market Specialist) 

Principal Investigator Dr. Francis de los Reyes spearheads this project and directs NC State’s Water, Sanitation and Hygiene (WaSH) Cluster. This unique cross-disciplinary set of faculty catalyzes and conducts transformational research and education to serve the water, sanitation, and hygiene needs of marginalized people. Dr. de los Reyes has published over 260 papers/book chapters/conference papers on topics relating to water treatment, wastewater and sanitation, including papers on characterizing pit latrines in peri-urban areas, trash removal from pit latrines, and desludging fecal material from pits. Dr. de los Reyes’s lab regularly collaborates with companies, universities, and government entities in Europe, Asia, and Sub-Saharan Africa. 

The team at NC State prioritizes continuous improvement through learning from field testing. NC State has partners in Malawi, South Africa, Zambia, Rwanda, Kenya, Madagascar, Ghana and India for multiple rounds of field testing and creates new iterations after each visit.

Field Testing Site Partners

Pit Vidura is a pit emptying business performing field testing for the Flexcrevator in Rwanda. Committed to providing safe pit latrine emptying for its customers and workers, this woman-owned business has emptied over 850 latrines to date.

Madacompost is a social enterprise testing the Flexcrevator in Madagascar. This is a sanitation company that uses vacuum trucks, in line pumps, and also manual emptying teams to manage fecal waste in the Mahajanga region.

Both companies will report the impact of the Flexcrevator on business operations and profits at the end of existing field testing trials.

Demonstration Site Partner

Sama Sama is a social business catalyzing sanitation and hygiene markets by integrating the entire sanitation value chain in Ghana. Sama Sama “establishes and aggregates networks of local entrepreneurs to provide access to quality, affordable, and sustainable sanitation and hygiene solutions”. They will be testing the Flexcrevator next year and will host local partners for a week-long demonstration.

Technical and Market Consulting

Triangle Environmental is an international sanitation consulting company that performs market assessment of the Flexcrevator and serves as a technical advisor. The lead consultant, Tate Rogers, co-invented the device at NC State in 2011. 

Our key customers include local government units (LGUs), NGOs, and private sector groups.

LGUs and NGOs will want pit latrines emptied safely for reasons beyond profits:

• Improved population health through reduced indiscriminate disposal of waste or overflowing of unemptied pits.
• Improved operator health through reduction of exposure to sludge during emptying.
• Service delivery goals –the drive for providing adequate safely managed sanitation in their area of operation.

The Flexcrevator’s ability to contain fecal sludge through its design, minimize direct contact by eliminating unhygienic “fishing” for trash during emptying, and allow for the quick emptying of pits to prevent overflows satisfies all of these goals.

For the private sector groups, the Flexcrevator drives higher profits by:

• Widening the customer base – accessing new customers that were previously unreachable due to access or trash.
• Generating more profit from each job carried out – working more efficiently and generating a higher margin on each job completed.
• Doing more jobs in one day – from 1 pit a day with manual emptying to 3-5 pits a day with the device.

The Flexcrevator is an affordable mechanized method of emptying pits. The current price of the device is 10-20x cheaper than a vacuum truck. At commercial production levels, this price will likely fall to nearly 40x cheaper than a vacuum truck. The annual profit estimates indicate that the Flexcrevator has the potential of earning a team a profit of up $32,965 a year per depending pits emptied per day and transport costs.

NC State will pursue grants and competition prize money to cover expenses for field testing, prototype manufacturing, training and outreach. Successful launches of new technology require successive rounds of capital, training and marketing activities. The core goal of these activities is to find an appropriate commercial partner or partners to bring the device to low income regions with the most need for clean pit emptying technology. Our technology is new and serves the poorest. Funds and support will be needed to lower risk for a Flexcrevator-based business.

When we identify an appropriate manufacturing, distribution, and operational partner we will shift from grants to generating revenue from licenses. The studies that we are funding with private pit latrine entrepreneurs like Pit Vidura, Madacompost and Sama Sama allow us to get insight on what revenue models work best. Possible models include rentals, group-owned systems, selling to manual emptiers, or pit latrine owners. Proven models will in turn help support businesses purchasing and distributing Flexcrevators that can help sustain new environmentally- and socially-oriented services, sustaining the demand and need for licenses. 

After nearly a decade of prototyping and learning, NC State is excited to bring the Flexcrevator to commercial partners around the world. While NC State already has a growing network with sanitation companies in Ghana, Madagascar and Rwanda, the Flexcrevator has the potential to improve the lives of over one billion globally. Participating in the MIT Solve Challenge gives NC State opportunity to showcase the device to a variety of international companies beyond Africa through its pitch and networking events.

Not only will global exposure benefit our work, but we look forward to building and learning from a strong peer network. As a group committed to advancing gender equity we are especially interested in working with equally dedicated companies that have applied to the Innovation for Women Prize. We also have a lot to learn from previous winners of the 2018 MIT Solve competition in the Women and Technology group. If selected, we are eager to collaborate with the 2019 cohort of businesses focused on promoting gender equity in LIMCs.

In addition to promoting our technology and working with other companies with similar goals, we want to expand awareness of current, unacceptable pit latrine emptying methods. Although programs such as Bill and Melinda Gates Foundation’s Reinvent the Toilet Challenge highlighted emerging toilet technologies, there has been less focus on the current state of pit emptying along with the need for safe emptying methods.  Exposure through global media and social media will reinforce urgency in addressing this long-standing international problem. 

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India is rapidly urbanizing with a staggering number of pit latrines that need to be emptied safely. Using data from the 2017 Joint Monitoring Programme (JMP), we estimate that India alone has 39 million pit latrines . Other parts of Asia also have a huge need for pit emptying, with an estimated total of nearly 140 million pit latrines in China, Bangladesh, Indonesia, Vietnam and Sri Lanka combined.

To expand the global impact of the Flexcrevator, we need exposure and partners in India and other Asian countries. The range of organizations that would be of interest would be local manufacturers, sanitation companies, testing partners, and social entrepreneurial organizations interested in cultivating entrepreneurship on the ground. We have a few examples below but they are not exhaustive.

• GK Manufacturing: A small to mid-scale prototyping and manufacturing house.
• India Institute for Human Settlements:A non-for-profit organization that performs interdisciplinary research in urban informal settlements. This includes latrine and septic tank emptying.
• Banka Bioloo: A company that performs pit and septic tanks
• iDE Vietnam and iDE Bangladesh: Country branches of iDE Global, a non-for-profit organization that supports local entrepreneurship. 

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Funding from this prize and MIT Solve will allow us to reach the Indian market and open doors within Asia. The primary goal is to establish a partnership with a sanitation company in India to test the Flexcrevator and document how the group grew their business. The new site will also serve as a demonstration site for partners from other high need countries like China, Sri Lanka, Bangladesh, and Vietnam.

The initial $10K from MIT Solve will be used to manufacture Flexcrevator units for the Indian market while the Innovating Together for Healthy Cities Prize would fund the rest of the effort. A sanitation company will receive support funds ($20K) to buy auxiliary equipment, try new processes and business models with the Flexcrevator, and report how the device impacts their profits. After half a year of testing pit latrine emptying in India, we will invite regional commercial partners to a week-long demonstration. Up to 10 commercial partners from other Asian countries will have housing, food, and domestic transportation covered for a week from the prize money ($10K).

Travel funds ($10K) are included to allow NC State to visit the site and meet with commercial partners directly during the demonstrations held in India. Contractor support from Triangle Environmental will be used to train partners, and refine market strategies ($20K). The remainder of the Innovating Together for Healthy Cities Prize will support work to coordinate and interface with partners ($15K).

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Ensuring that men and women can access the device is a primary focus of this project. The Flexcrevator has the potential to improve the working lives of people in the sanitation chain, but there might be gender barriers that limit participation in the chain. For this reason we will examine the following:

• How are women currently participating in the value chain in pit emptying, and what are the drivers and barriers for their success?
• What opportunities exist from the end users’ perspective for increasing the demand of improved pit emptying?
• What approaches work for increasing women’s participation in pit emptying?
• To what extent does expanding women’s participation in the sanitation value chain correlate with changes in improved pit emptying?

NC State is already partnering with Sama Sama, a Ghana-based company that has studied how gender impacts the business of owning and maintaining a toilet. To answer this question in an Indian context we would partner with similar organization familiar with gender and pit emptying in the region ($15K). We also would hire a cultural anthropologist to travel directly ($10K) to the site and perform structured interviews on the ground with women and stakeholders along the pit emptying chain ($10K). Materials and supplies ($10K) would be set aside to design and implement changes to make Flexcrevator more accessible to women. Funds for publishing our findings in open access papers ($10K) would help us disseminate this information widely. The final portion of funds ($20K) would be used to fund oversight for the project.

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