Current Progress – Onsite Treatment

Pasteurization system performance data from Kenya ~ July, 2017

The ADPL's microcontroller delivers temperature and flow data from Kenya in real time.

  • The green line indicates the heater (pasteurization) temperature.
  • As the digester effluent flows through the heat exchanger on its way to the heater, it is heated from the ambient temperature (red line) to those indicated by the blue line.
  • As the pasteurized effluent flows from the heater through the heat exchanger on its way out of the system, it gives up its heat to the incoming effluent as indicated by the difference between the purple line and the yellow line.
  • More efficient heat exchange is now possible thanks to a more consistent flow pattern throughout the day, reducing the biogas required to achieve reliable pasteurization.


System Upgrades Installed in Kenya ~ June, 2017

Significant enhancements to the pasteurization system which had been designed and tested in the lab at Duke were installed on two working systems in Eldoret, Kenya in late June.

  • An effluent filter was added to the digester to capture large particles in a 1/2" mesh and prevent them from entering the downstream pasteurization system.
  • A custom-designed pinch valve was installed after the filter basket to deliver a more constant flow of effluent to the pasteurization system, improving its efficiency.
  • The insulation on the heater and heat exchanger were upgraded, reducing heat losses.
  • An improved control box was installed to support the pinch valve, improve operator maintenance and troubleshooting and improve reliability.


Prototype Filter Basket ~ April, 2017

A prototype filter basket designed to prevent clogging in the ADPL is currently being tested with fecal sludge simulant in the lab. The filter basket uses a removable mesh perpendicular to the effluent flow to capture large particles (such as pieces of newspaper) that exit the digester before they can clog the downstream pasteurization system. A handle outside the box allows the mesh to be scraped off without exposing the operator to contact with fecal matter. A ball valve is being added to allow for the occasional flushing of settled solids.


Introducing Dr. Forbis-Stokes ~ March, 2017

Aaron Forbis-Stokes successfully defended his PhD thesis titled "Anaerobic Digestion Pasteurization Latrine – Self-sustaining Onsite Fecal Sludge Treatment for Developing Countries” on March 30, 2017. Congratulations, Aaron!


Journal Article Published ~ November, 2016

 In the special issue 'Innovative Global Solutions for Bioenergy Production', the journal 'Enivronmental Engineering Science' published our paper titled 'On-Site Fecal Sludge Treatment with the Anaerobic Digestion Pasteurization Latrine' in November. Aaron Forbis-Stokes is the primary author. The paper gives a detailed account of the pilot ADPL units in Eldoret, Kenya. It is open access and can be found at:


New ADPL systems installed in Cebu ~ June, 2016

Two new ADPL systems were built and commissioned in the Sagay and Subayon districts of Cebu, Philippines in collaboration with the Tesari Foundation. The new digesters were inoculated, and tipping buckets, solar panels and microcontrollers were installed with the pasteurization systems. Duke environmental engineering student, Nicki Willis conducted on-site research to evaluate social barriers to system adoption. System operation and maintenance will be performed by local residence, with support from the Tesari Foundation and Duke.


Additional system upgrades in Eldoret ~ May, 2016

After installing new digesters in our field units in Kenya, a tipping bucket and new microcontroller was installed at each site. The tipping bucket enables us to measure the flow through the system. The new Particle Electron controller will provide remote, real-time monitoring of system temperatures and flow. The controller will also operate a gas valve and automated flame ingitor to help maintain heater temperatures 68<T<72 °C.

New Baffled Anaerobic Digesters For Eldoret ~ April, 2016

Two fixed dome anaerobic digesters designed by Aaron Forbis-Stokes using computational fluid dynamics were manufactured by Specialised Fibreglass in Nairobi and installed at the Eldoret North and Central sites. The new baffled design will improve average residence times and reduce solids in the effluent stream going into the heater and heat exchanger.  The new digesters have four chambers and sampling ports for taking core samples and assessing solid deposition levels.


First Journal Article Published ~ December, 2015

Our paper, 'Anaerobic digestion of undiluted simulant human excreta for sanitation and energy recovery in less-developed countries' was published in the Journal 'Energy for Sustainable Development'. The paper’s lead author is Joan Colón. Aaron Forbis-Stokes and Marc Deshusses are co-authors.

To open the article, click on the image.


Funding from the Bill & Melinda Gates Foundation ~ November, 2015

Duke was awarded a new grant to expand the monitoring of existing field units, identify and implement system enhancements and lay the groundwork for expanded field testing. Aaron Forbis-Stokes who has been working on the project for several years will finish his PhD in 2016 and continue his work as a postdoctoral researcher. Kathy Jooss and Brandon Hunter joined the team, Kathy as Project Manager and Brandon as graduate student researcher.

ADPL Research Began at IIT Madras, India ~ November, 2015

An ADPL processing system was built on the IIT Madras campus for simulated testing of ~50 users. The digester is made up of a fixed dome digester and a floating dome collector in series and is fed with waste diverted from the universities sewer system. Professor Ligy Philip is leading the research in India.  Students from her group monitor the system daily and test samples regularly.

UNC Water & Health Conference ~ October, 2015

Aaron Forbis-Stokes presented a poster at the University of North Carolina's Water & Health Conference on October 28, 2015 titled 'Anaerobic Digestion Pasteurization Latrine - Two Year Study of An Innovative Sewage Treatment System in Eldoret, Kenya.' Click on the image to view the poster.


Tesari Foundation Installation in Cebu, Philippines ~ July 2014

The Tesari Foundation, with help from Aaron Forbis from Duke, built an ADPL toilet at their facility in Toledo City, Cebu, Philippines. The system is designed for about 10 users, but is being used for testing and is being fed with swine waste manure. The digester is made up of two digesters in series, a fixed dome and a floating dome. Rolf Rivera is the local project lead in the Philippines.



Three ADPL toilets Installed in Eldoret, Kenya ~ July 2013

Three ADPL toilets, each with three stalls were built in Sogomo Estate in Eldoret, Kenya.  The Central location has ~35 users, the South location, ~27 users and North, ~18 users. All three use floating dome digesters. Patrick O’Meara is the local project lead on the ground in Kenya. University of Eldoret students assist with daily monitoring and data collection.