This document describes experiments conducted to optimize liquid treatment processes for a sustainable sanitation system. Sonication at 20 and 60 kHz was found to reduce particle size and chemical oxygen demand of effluent. Ultraviolet exposure showed potential for disinfection, with the smallest diameter dish proving most effective. Testing electrochemical cell treatment at 50-60°C found disinfection rates were not significantly different, but energy use was reduced by 15.5% at 60°C. The experiments aim to determine effective and efficient liquid disinfection methods for application in developing world sanitation solutions.

1.  Funding was provided by: A grant from the Bill and Melinda Gates Foundation,
Reinvent the Toilet Challenge
Toilet System
 We assume 0.5L urine and 1.5 L flush water per urine flush
 Each fecal flush contained approximately 200 g of wet feces, 1.5 L of flush water
and 0.5 L of urine.
 Flush Water
 Urine and feces collection methods were approved by RTI’s institutional review
board.
Experimental Design
Sonication
Sonication was essentially explored to determine the effect particle size has on
chemical oxygen demand and the efficiency of electrochemical treatment.
Samples of effluent pulled from the Beta system were sonicated at the following
frequencies: 20, 40 60 khz.
Figure 2. The effect of sonication on
turbidity of effluence at various
khz frequencies.
20 and 60khz provided the greatest
particle size reduction and were chosen
for the conduction of chemical oxygen
demand(COD) testing.
Chemical Oxygen Demand and Sonication
COD levels between different particle size ranges was an area of exploration.
Sonicated effluent was passed through filters ranging from 2.7um to .2um, and
COD readings were taken at each interval. Effluent sonicated at 20 and 60khz
had greater reduction in COD levels after each filtration when compared to
unsonicated material.
Ultraviolet Exposure
Exposure to ultraviolet (UV) light proved to have potential for disinfection when
tested in stationary batches, in a quartz dish under 250nm wavelength. This result
prompted construction of two smaller diameter dishes, of which the smallest (1in
in diameter) proved most effective at bacterial termination. The diameter testing
allowed for the calculation of optical constraints on the amount of effluent able to
undergo disinfection in a flow-through system.
Electrochemical Cell Treatment + Heat
The use of an electrochemical cell (EC) to disinfect effluent has already been
established however, the addition of heat offers a potential for increased efficiency.
EC was tested on preprocessed effluent at temperatures of 50 and 60 degrees
Celsius using a 24 volt power source. Upon review no significant discrepancy
appeared in disinfection rates between the two temperatures, possibly due to
fluctuation in the heating system. Repeated testing of the 60 degree run proved a
reduction in average time required to reach the disinfection threshold. Moreover
testing revealed a 15.5% reduction in total energy use.
Figure 3. Comparative analysis of control to 60C electrochemical treatments.
Global Sanitation Improvement
Continuing the development and optimization of the toilet system will allow for the
expansion of sustainable sanitation solutions across the developing world. Following
the parameters set forth by the Bill and Melinda Gates Foundation, fosters the
development of a sanitation system with the potential for real world application.
These parameter include: having a facility cost of less than five cents per person per
day
 Providing hygienic and affordable methods of waste disposal
 Treating excreta in unconnected, decentralized locations
 Providing toilets requiring no:
 piped-in water,
 sewer connections
 outside electricity
A system that is applicable to the Developing World consumers allows for the practical
application and implementation of the product. Benefits of improved sanitation
include but are not limited to.
 Reduced exposure to bacterial
 Reduction in cases of diarrheal diseases
 Reduction in the loss of life related to diarrheal diseases
 Improved overall health of the community
 Ability to combat community issues
 Increasing education
 Improved economic standing
Sonication Ultraviolet Exposure
Sonication has a plethora of potential that still requires exploration. Our initial next
step will be to acquire membranes for particle size distributions in the area of
kilidaltons. Once the sonicated effluent is distributed in particle ranges, the effect
on COD will be compared to that of unsonicated effluent.
Ultraviolet Exposure
Ultraviolet exposure on effluent has the potential to increase disinfection efficiency,
especially when coupled with other disinfection mediums. Our next step is to
identify the thickness and flow rate at which effluent can travel past an UV source in
a flow through model and result in disinfection. If the disinfection efficiency
outweighs the energy consumption, the combination of ultraviolet and sonication
will be explored.
Electrochemical Cell Treatment + Heat
Electrochemical cell disinfection will undergo a variety of future tests with the aim of
finding optimal operating conditions. Tests at various other temperatures will be
completed to find the most energy efficient option. Additionally discovering the
average time of disinfection under various EC treatment conditions will add another
factor of efficiency to the overall system.
Moreover, EC testing using two electrochemical cells, running at the same time is
currently under exploration. The current system utilizes EC at 24 and 32 Volts
running at separated stages of the liquid disinfection loop. Variables within this
exploration include, energy efficiency, time of disinfection, and variation in voltage
and current in each cell.
1A Better Toilet. (n.d.). Retrieved July 22, 2016, from http://abettertoilet.org/
2Dwyer, L., & Teninbaum, J. (2014, April 9). If You Live in One of These 16 Countries, Your 'Bathroom' Is Probably Outdoors.
Retrieved July 22, 2016, from http://www.takepart.com/article/2014/04/08/top-countries-without-sanitation
3Gleick 2002; irty Water: Estimated Deaths from Water-Related Diseases 2000-2020. Pacific Institute for Studies in
Development, Environment, and Security
4Reinvent the Toilet. (n.d.). Retrieved July 22, 2016, from http://www.gatesfoundation.org/What-We-Do/Global-
Development/Reinvent-the-Toilet-Challenge
5UN-water global analysis and assessment of sanitation and drinking water (GLASS) 2014 report: Investing in water and
sanitation: Increasing access, reducing inequalities
6World Bank, 2013; ESMAP 2013 Annual Report. . Washington, DC
6. Potential for Impact
Improving Global Sanitation:
Liquid Toilet Systems
Author1, Author2 • 1RTI International, Research Triangle Park, NC; 2Affiliation
References
More Information
*Presenting author: Tess Rogers
000.000.0000
terogers@rti.org
RTI International
ATB 203,
RTI International is a registered trademark and a trade name of Research Triangle Institute.
3. Methods Acknowledgments (if any)
4. Findings or Results 8. Next Steps
Sonication
 Sonication at 20 and 60 Khz
 Reduces effluent turbidity
 COD reduction
 Third level bullet — PPT level 4
Ultraviolet Exposure
 Stagnant exposure at 250nm wavelength
 1in Diameter quartz dish has highest power density
 May correlate to higher disinfection potential
 Data justifies the on-going flow through experimentation
Electrochemical Cell Treatment + Heat
 EC at 6 degrees Celsius
 Run with 24 volt power source, reduces disinfection time
 Statistically significant time reduction when compared to room temperature EC
 Addition of heat to EC reduces the necessary kJ/L required for disinfection.
5. Conclusions or Summary
Laboratory Limitations
 The laboratory setting constrains a field based project
 Material availability
 Prioritization of experiments
 Fecal and urine donation
 Inability to perfectly mimic field conditions
 Deviations in field and laboratory fecal samples, and operational use
Project Constraints
 Reinvent the Toilet Initiative has set operational goals
 Off-grid
 Low energy consumption
 Less than .05cents [US] per day per user
 Low to zero maintenance requirements
 No piped in water use
 All operational waters must be recycled and pulled from the system
These constraints promote the development of a sanitation system that will not only
disinfect but be sustainable in regards to energy and the economic standing of the
consumer market.
7. Limitations (if any)
Alpha system launched 2015, Ahmedabad – CEPT University
 User studies identifies areas for liquid system optimization
 Decreasing energy of liquid disinfection process
 Need o achieve in country discharge standards
This study is meant to determine which processes, or combination thereof, can be utilized to enhance
efficiency of liquid disinfection process.
Current exploratory variables include:
 Effluent is sonicated in attempts to reduce particle size, increasing the oxidation of material during
electrochemical, and reducing the chemical oxygen demand.
 Ultraviolet light sources were tested on stationary and flow through apparatuses to determine optimal
disinfection versus energy use.
 Effluent was raised to various degrees of heat them treated with a twenty-four volt electrochemical cell
to determine the effect of temperature on electrochemical effectiveness and bacterial termination.
Sanitation: A Global Problem
Figure 1. Explanatory map of global sanitation deprivation. Illuminated numbers reveal the
millions of people lacking sanitation access in particularly plagued countries.
 “2.5 billion people worldwide lack improved sanitation facilities3.”
 Lack of public waste management systems leads to open defecation2.
 Facilitates the spread of disease in the developing world4.
 Nearly 1 million children die each year from diarrhea1.
 Without intervention, as many as 135 million people could dies from preventable
sanitation-related diseases.
 The most underserved populations are those in rural areas and where
implementation of solutions is complicated by lack of access to dependable
electrical and clean water infrastructures required for modern sanitation facilities.
RTI Contribution: “Reinvent the Toilet Initiative”
 The Bill and Melinda Gates Foundation launched the “reinvent the Toilet Challenge”
(RTTC) aimed at:
 Developing and implementing sustainable sanitation facilities
 RTI has developed a toilet that converts human waste into burnable fuel and
disinfected liquid1
1. Introduction or Background
2. Objectives or Purpose
10L Reaction
Vessel
EC
Cell
8L Stimulated Effluent
Leads to power
supply 20 Khz
Mounted
Sonicator
55 mL
Effluent
Test Tube
Stabilizer
Power
Source
UV
Power
Output
UV
Effluent
Heated
stainless steel
coil
Ultraviolet
Exposure
Electrochemical
Treatment Sonication
Figure 2: Modular toilet designed for low income
countries (A.) Squat plate user interface (B.) Solid-
liquid separator (C.) Liquids are diverted through a
series of baffle tanks to allow any remaining solid
particulate to settle out. (D.) The settled liquid is then
sent to a holding tank until the desired volume is
collected. (E.) The collected the volume is moved to
a new tank where it is electrochemically treated
(F.)The treated liquid is finally transferred to a holding
tank until needed for recycle. (G.) Solids are
processed and burned. The heat from burning is used
to generate electricity through the use of thermo-
electrics.