Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation (Duke University, USA)

  • kathyjooss
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Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation (Duke University, USA)

Below is an overview of the grant we received in April, 2013 in the third round of the Reinvent the Toilet Challenge of the Bill & Melinda Gates Foundation. We recently issued a press release and set up our website.

Title of grant:

Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation

Subtitle: Employing Supercritical Water Oxidation (SCWO) to treat sewage waste and recover clean water

Name of lead organization: Duke University

Primary contact at lead organization: Marc Deshusses, Primary Investigator

Grantee location: Durham, North Carolina, USA

Developing country where the research will be tested: South Africa, India or Ghana

Start and end date: April 4, 2013 – March 31, 2016 (extended to March 2017)



Short description of the project:

Engineers at Duke University and the University of Missouri are designing a unit that addresses the treatment of human waste and possible reuse of the system’s byproducts. It will sanitize the collected waste of approximately 1000-1200 people — a neighborhood-scale solution.

The technology being employed, supercritical water oxidation (SCWO), is promising because it works quickly and generates energy in the forms of hot water and steam from the treatment of human waste. It does not require prior dewatering or drying of fecal sludge, and it effectively eliminates all types of harmful organisms. SCWO technology has already been implemented in research and commercial applications to treat waste products including polychlorinated biphenyls (PCBs), chemical weapons and sewage sludge.

Goal(s):

Duke University and the University of Missouri seek to demonstrate that both SCWO and supercritical water gasification (SCWG), a related technology, have prominent roles to play in solving the world’s sanitation challenges.

Objectives:

The objective of this project is to produce a demonstration unit that fits into a 20 ft. shipping container and quickly and safely turns fecal sludge into sterile water and harmless byproducts. An economic model that quantifies and optimizes the economic, environmental and social benefits of the unit is also under development. A successful design will deliver economic opportunity to operators at a local level in developing countries.


Grant type: Reinvent the Toilet Challenge (RTTC) Round 3, with a value of US$ 1,749,595.

Funding for this research currently ongoing (yes/no): Yes

Research or implementation partners: University of Missouri

Our website:

sanitation.pratt.duke.edu/home (includes current status and a list of FAQs)

University of Missouri video:



Questions or comments welcome here on the forum.

Regards,
Kathy


On our website we have compiled a list of frequently asked questions (FAQ)( sanitation.pratt.duke.edu/frequently-asked-questions ) and a timeline updated with current status ( sanitation.pratt.duke.edu/current-progress ).

Kathy Jooss
Project Manager,Pratt School of Engineering
Duke University, Durham, North Carolina, USA
This email address is being protected from spambots. You need JavaScript enabled to view it.
www.sanitation.pratt.duke.edu
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  • JKMakowka
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Re: Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation (Duke University, USA)

Very interesting research, those supercritical fluids are amazing stuff!

I am wondering though how you want to ensure a sustainable oxygen supply, as even hospitals are struggling with that here in Uganda...or you plan to include an pressure-swing-adsoption air-separator? But, maybe it is sufficient to use compressed air?

Your FAQ is also a bit misleading in regards to external (electrical!) energy supply needed. Either it will need is quite constantly if you plan to do continuous process (to pre-pressurize the feedstock), or in very regular intervals if it is a batch process. Your FAQ makes it sound like you only start it once and then it runs all by itself (which the breakdown process itself obviously does), or am I overseeing something there?

I also think you are very optimistic in regards to it being competitive from a price point of view. Realistically it should be compared to a medium sized DEWATS, biodigestor or professionally run composting site and not a full sewerage and WWTP combination (as the service level is not comparable).

I could imagine it to be a very interesting solution for a diary farm though: Treat the manure and at the same time produce process heat to pasteurize the milk.

Microbiologist & emergency WASH specialist
WASH news aggregator at: news.watsan.eu
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Re: Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation (Duke University, USA)

Uhmm, one other idea:

Could the alternative supercritical water gasification process be run with concentrated solar energy? That would be a neat way of treating waste and the same time produce/store energy in the form of methane.

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  • kathyjooss
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Re: Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation (Duke University, USA)

Hi Julius,

Thank you for your questions and comments. You’ve hit on some of our key areas of investigation.

We are planning to use compressed air as an oxidant source for our prototype, and we’ll be conducting experiments over the next several months to confirm our assumptions. We have looked into air-separators, but capital cost and energy requirements would likely be prohibitive.

I apologize if the FAQ was misleading with regard to the energy requirements of the unit. From a heat-energy perspective, it will be advantageous to run the unit in continuous mode since system start-up requires the temporary use of a furnace to heat the feedstock to the kindling temperature. How often the system will need to be restarted will depend on several factors including the reliability of feedstock supply and maintenance requirements. Even in continuous mode, however, we do require electrical energy to pressurize the water, feedstock and air coming into the reactor. We can recover some electrical energy from the steam produced, but our most recent calculations estimate a small negative energy balance.

As we get further along in the development process, we will be able to continue to improve our cost estimates. At this stage, we are focusing on successfully adapting the technology and optimal prototype design.

We’re open to specialized applications for SCWO technology. I am not familiar with the need for on-the-farm milk pasteurization in developing countries. In the U.S. most milk is transported to pasteurization centers.

Incorporating solar energy is beyond the scope of our project at this time, but there are RTTC grantees looking into it. Maybe somewhere down the road we’ll be able to leverage that expertise!

Best Regards,
Kathy

Kathy Jooss
Project Manager,Pratt School of Engineering
Duke University, Durham, North Carolina, USA
This email address is being protected from spambots. You need JavaScript enabled to view it.
www.sanitation.pratt.duke.edu
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Re: Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation (Duke University, USA)

Hi Kathy,
It is very interesting to read about your project. If you don’t mind, I also have couple of questions to you.
It is written on FAQ that "The value proposition of a SCWO sewage treatment unit includes equipment and operating costs, the local value of sewage treatment services and the revenue-generating potential of the output byproducts, like hot water and steam". Could you please write the percentages of the various costs which are included in the value proposition of a SCWO sewage treatment unit?
What are the maintenance requirements for your system and what kind of operator staff is needed? Also, in FAQ section, it is written that “SCWO requires sophisticated equipment, high pressure pumps and control. It is very unlikely that a miniaturized household system would be economical”. What is the minimum planned size (for how many people? 100? 1000?)? Is the idea to have a full-time operator per unit, or one operator for several units?
Thank you in advance,
Gökce

M.Sc. Gökce Iyicil
Research Assistant
Technical University of Munich
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Re: Sanitation in South Africa- A Preliminary Evaluation of Barriers and Opportunities

Below is attached a preliminary evaluation of the technical and economical feasibility to apply Supercritical Water Oxidation (SCWO) as a means to manage waste in the South African context.

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  • kathyjooss
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Re: Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation (Duke University, USA)

Hi Gökce,

Thank you for your posting. I don’t have a simple answer to your question, but I will try to explain why. The key components affecting the economics of our unit vary depending on the local sanitation market under consideration. The cost of procuring the equipment and hiring local labor will differ by location, the price customers are willing to pay to get rid of their sludge (e.g. ‘tipping fee’) will vary based on the regulatory environment and other factors, and the revenue potential of the steam and hot water produced also depends on the specific location (e.g. is hot water required for laundry or is steam needed for sterilization?). In addition, we are still in phase I of the project, and don’t yet have a prototype in operation. By next summer, our capital and operating costs will be much more accurately defined.

We are working on a cost model that outlines all of these factors and uses their inputted values to determine the economic proposition of the solution. We expect to have that model available at the end of 2013. We will then begin to run scenarios using data from specific cities.

The system we are designing would treat the sewage produced by ~1000-1200 people. The number of operators needed will depend on how the feedstock is transported to our holding tank (e.g. are trucks coming and going or is it piped continuously?) and operational safety and security requirements. If our unit is located in a secured compound, for example, one operator may be sufficient. Once the control technology and design have been fully engineered, a full time operator may not be required, but initially we envision one or possibly two operators, not necessarily dedicated, depending on the location.

Best Regards,
Kathy

Kathy Jooss
Project Manager,Pratt School of Engineering
Duke University, Durham, North Carolina, USA
This email address is being protected from spambots. You need JavaScript enabled to view it.
www.sanitation.pratt.duke.edu
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  • kathyjooss
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Re: 2015 Fecal Sludge Management (FSM3) Conference Presentation

In January, 2015, Dr. Marc Deshusses presented the neighborhood-scale sewage treatment system under development at Duke University at the FSM3 conference in Hanoi, Vietnam.


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Note by moderator (EvM):

You can also watch Marc's presentation here:



Or see here and scrol forward to time 9 min. 45 s:



A link to the pdf file of the presentation:
www.susana.org/images/documents/07-cap-d...-3-2-3-Deshusses.pdf

Presentation title was: "Omni Processor for Fecal Waste Sanitation for the urban poor using supercritical water oxidation (SCWO)"

Kathy Jooss
Project Manager,Pratt School of Engineering
Duke University, Durham, North Carolina, USA
This email address is being protected from spambots. You need JavaScript enabled to view it.
www.sanitation.pratt.duke.edu

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Re: Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation (Duke University, USA)

Hi Kathy, I am also a Kathy. How do I go about finding out about the possibilities of a Supercritical Oxidation pilot plant for a 'new' sustainable / business UNusual / Better living /social housing project that I am busy with in South Africa. We are currently in the planning phases with implementation for 2018. We are looking for a treatment system with small footprint (leaves more area for housing)using High Tech solutions (education / technology is a key aspect of this project)that will produce water for irrigation (urban agriculture) and amenity purposes.
Regards, Kathy
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  • kathyjooss
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Re: Neighborhood-Scale Treatment of Fecal Sludge by Supercritical Oxidation (Duke University, USA)

Hi Kathy,
Thank you for your message. Your project sounds very interesting. It is too early for us to consider specific test sites at the moment as we are still focused on assessing the technical feasibility of our system. I will make note of your interest though and would be happy to contact you when we are at the point of considering field trials.

Best Regards,
Kathy J.

Kathy Jooss
Project Manager,Pratt School of Engineering
Duke University, Durham, North Carolina, USA
This email address is being protected from spambots. You need JavaScript enabled to view it.
www.sanitation.pratt.duke.edu
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