Don’t think of treatment plants: building factories to meet the sanitation SDGs

Rwanda  - Pivot fecal sludge treatment 1

Pivot Works factory in Kigali, Rwanda. From left to right: Fecal sludge receiving tank, flocculation tanks, mechanical dewatering machine. Photo: Ashley Muspratt

4,900 days from now, in 2030, the Sustainable Development Goals will expire.  If that feels like a long time, consider the work ahead.  And by work, I dare not attempt to wrap my head around all 17 goals; I refer specifically to the WASH goal – SDG #6 – and even more specifically to the sanitation targets.

From my admittedly invested perch – I run a sanitation company – the most exciting thing about transitioning from the MDGs to the SDGs is the belated inclusion of treatment.  There’s finally recognition that “improved sanitation” without treatment is not improved sanitation.  The WASH community’s new mandate: “halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally” (SDG 6.3).  But consider that the urban population still requiring “safely managed sanitation” today stands at 3.214 billion [1]. Serving them entails expanding safe management, i.e., some form of treatment, to 625,000 people each day for the next 4,900 days.  That’s basically a city a day.

How can we achieve such a massive expansion of safe fecal sludge and wastewater management?  For starters, let’s stop building treatment plants. Heresy? There’s a better way.

Safe management of human waste is an essential piece of the sanitation value chain. However, framing safe management as treatment implies a process that is costly and that exists for the sole purpose of rendering fecal sludge and wastewater safe for disposal – a “luxury” that most cities don’t think they can afford. What if we ventured to replace the word “treatment” with “manufacturing”?

The language we use to describe safe waste management has far-reaching implications for policy, budgetary decisions, and the design and operation of facilities.  Linguist George Lakoff argues that we understand particular words relative to our own unique “frames,” mental structures that shape the way we see the world and determine our notion of common sense [2]. So let’s change our frames. What gets you more excited (as either a sanitation nerd or government official): the burden of treatment or the opportunity of manufacturing?

Treatment, after all, is an antiquated approach to fecal sludge and wastewater management. With today’s technologies, human waste can be mined for a variety of forms energy, nutrients, and water. And the resource value of waste has potential to greatly exceed the cost of recovering those resources – and the cost of the so-called treatment.

Rwand - Pivot fecal sludge treatment products

Pivot Fuel, ready for shipping. Photo: Ashley Muspratt

At Pivot, we convert fecal sludge into an industrial fuel. And we deliberately use the term “factory” to describe our plants.  Factories take raw materials and convert them to value-added products that can be sold commercially.  Treatment plants, on the other hand, only convert hazardous material into a form that can be disposed.  Factories make money when well operated; treatment plants cost money even under the best of circumstances.

Imagine extending the language – the frame – of manufacturing to the design and construction of waste management facilities. The driving principle behind the design of Pivot Works factories is reuse – not treatment.  Reuse cannot be an afterthought in plant design, nor can it be undertaken without a hard look at the market demand for the end-product being considered. At Pivot Works factories, treatment is merely the byproduct of our manufacturing process – a fraction of our equipment serves the single purpose of treatment, while the majority serves to produce the highest quality industrial fuel possible from human waste.

Applying manufacturing framing to waste management is not just nuance, it pays real dividends.  The global cost of achieving the safe management component of SDG #6 is estimated at US$92 billion per year in capital costs, with annual O&M costs reaching US$120 billion by 2029.1 These estimates assume that improved management is met using 50% sewage with treatment and 50% fecal sludge management with treatment. I am confident that robust manufacturing plants can be installed and operated for far less than this estimate.

Pivot’s parent company, Waste Enterprisers Holding, recently commissioned a multinational engineering firm to independently review the lifecycle cost of a Pivot Works factory compared to three conventional wastewater and fecal sludge treatment process trains.  These ranged from waste stabilization ponds with sludge drying beds for pit sludge, to activated sludge with anaerobic digestion for waste activated sludge and pit sludge.  Compared to the conventional alternatives, the capital cost of a Pivot Works factory is 32 to 52% less expensive and annual operating costs are 90% less expensive. These savings are achieved through the radical reorganization of the conventional treatment process train and by maximizing revenue from fuel – by “treating” waste as a resource.

Pivot’s ultimate goal is to build plants for which operating costs are fully covered by revenue from fuel.  We estimate this is possible for plants processing over 500 m3 fecal sludge per day, and for volumes beyond that mark, the revenue model gets very interesting, opening up the prospect of revenue share with our client cities. One day soon, if not by 2030, cities will solve their sanitation crisis and profit from – not pay for – it too.

[1] Hutton, G. and Varughese, M. (2016). The Costs of Meeting
 the 2030 Sustainable Development Goal Targets on Drinking Water, Sanitation, and Hygiene, Water and Sanitation Program Technical Paper #103171. World Bank, Washington, D.C.

[2] Paraphrased from, Don’t Think of an Elephant! Know Your Values and Frame the Debate by George Lakoff, Chelsea Green Publishing, White River Junction, VT. Copyright 2004.

About the author

Ashley Muspratt is the Founder and CEO of Pivot and its parent company Waste Enterprisers. She earned her PhD from the Energy and Resources Group at the University of California, Berkeley with a focus on the engineering and economics of designing municipal scale wastewater treatment plants for reuse.  Ashley lives with her family in Kigali, Rwanda.

Pivot is currently operating in Kigali, Rwanda and beginning to explore pipeline opportunities in East and Southern Africa.  We are currently recruiting a Chief Technology Officer; to learn more about the position and other job openings see  Learn more about Pivot at

5 responses to “Don’t think of treatment plants: building factories to meet the sanitation SDGs

  1. IRC carried out research in Bangladesh on a business model for faecal sludge reuse from pit latrines. The conclusion was that it was only financially viable in the Bangladesh context if:

    • faecal sludge from individual pit latrines was processed in combination with agri-waste; or
    • 5-10 pit latrines were connected to a septic tank to reduce collection costs

    Would that not also be the case in Rwanda? The option you propose may be be cheaper than conventional wastewater treatment, but still not necessarily affordable.

  2. Thanks for your question. Let me respond with a couple of points:
    1. Pivot Works factories are designed to handle the ‘treatment’ component of the sanitation value chain. You’re right that revenue we generate from fuel will not cover the costs of sanitation all the way back to household-level extraction. When I talk about cost-recovery (or significant contribution to opex) I’m drawing my boundaries around the plant and assuming that FS is delivered to us. In sub-Saharan Africa, it’s typical for cities to have fleets of private exhauster trucks that service septic tanks but then dump it in non-functional or non-existent treatment plants.
    2. The Pivot Works factory benefits from scale — we’re not a rural or community-level solution. It’s at municipal scale, or upwards of 300,000 people, that we would be significantly less expensive than conventional treatment plants.

    In Bangladesh I’m curious if you looked at any non-agricultural endpoints?

  3. Thanks for the clarification. In the Bangladesh research project, there were two other end products besides agricultural fertiliser: electricity and heat (for hot water) generated from a gas engine fueled with biogas that drives the generator for the production of electricity.

  4. Very inspiring! You mentioned that this manufacturing is possible for plants producing about 500qm/d of fecal sludge or for municipalities with 300k+ inhabitants. Is it possible for you to share more detailed information about the whole setup and its investment costs? Greetings from Tanzania

    • Thanks for your interest, Joerg. The answer to your question is rather site specific but a typical full-scale plant will be between USD 3M and USD 5M. I’d be happy to discuss further offline. Fee free to contact me.

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