development and adoption of solar-disinfection composting latrines in developing nations
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Development and Adoption of Solar-Disinfection Composting Latrines in Developing Nations. Craig Adams, Joe Rendall, Mario Medina, Mary Adams, Emily Robbins, Sarah Eberhart, Matt Williams University of Kansas. Presentation to University of Oklahoma International WaTER Conference - PowerPoint PPT PresentationTRANSCRIPT
Development and Adoption of Solar-
Disinfection Composting Latrines in Developing
Nations
Presentation to University of Oklahoma
International WaTER Conference
October 24, 2011
Craig Adams, Joe Rendall, Mario Medina, Mary Adams, Emily Robbins,
Sarah Eberhart, Matt WilliamsUniversity of Kansas
Water Supply and Sanitation Collaborative Council (WSSCC)
Unicef Progress Report
See unicef, Progress for Children, #5 (9/06)
Open Defecation• Unfortunately, very
common• Dangerous with
respect to spread of disease
• Simply providing latrines will not change behavior
Azacilo, Bolivia:A Small Aymaran
Village in Andes above La Paz
Working with Community
Ventilated Improved Pit (VIP)
http://tilz.tearfund.orghttp://www.accessgambia.com/information/small/latrine-vip.gif
Human Composting Latrines
The Humanure Handbook
Human Composting Latrines• Advantages over pit latrines and septic systems
– Creates valuable compost– Does not promote leaching into groundwater (as can septic systems and pit
latrines)
• Disadvantages:– Must be operated properly (e.g., addition of grass and ash)– Key issue is achieving full disinfection of human parasites (e.g., ascaris)
Prep4md.blogspot.com
Composting Latrines• Options– ECOSAN Toilet
• Dehydration approach (www.ecocan.co.za)– Below grade– Double vault composting latrine
– Solar disinfection composting latrine
Our Solar Composing Latrine Design
Disinfection Requirements• Time/temp
requirements for disinfection of Ascaris eggs.
• Ultimate goal is to achieve complete disinfection:• in one time
interval• Without
internal (composting) heat being required 0.1 1 10 100 1000 10000
20
30
40
50
60
70
80EnterovirusAscaris EggsSalmonellaShiggellaEntamoeba histolytica cystsTaenia eggsVibrio choleraeHr/D,Wk/Mo/YrSeries17
Hours
Tem
pera
ture
(C )
Pathogen disinfection data fit from Cairncross and Feachem 2nd Ed.
Approach to Our Solar Composting Latrine Research
• Two primary heat sources– Composting heat
• Best to insulate and keep all heat in– Solar heat
• Best to allow as much in as possible– What is best balance, and what design achieves this?
• Constraints– Local materials, building practices– Sustainable operation and maintenance– Material handling and usage
• Goal– Achieve complete disinfection regardless of
composting heat (so that all parts of pile are known to be disinfected).• Requires achieving critical “Time x Temperature”
everywhere in pile– Improve disinfection and compost quality
• Requires significant increases in temperatures
OBJECTIVES1. Develop and optimize solar composting latrines2. Develop design criteria and options for solar
compartments for various regions3. Calibrate and validate the thermal models
APPROACH• Phase 1: Non-insulated slab
– Simulated compost (to determine worst-case temps)
– What temperatures can be achieve at various depths?
– What are the temperature profiles?• Phase 2: Insulated slab
– Simulated compost (to determine worst-case temps)
• Phase 3: Insulated and non-insulated slab– Actual compost
Laboratory Studies• The lab experiment used to test different sustainable insulation materials.
Heat Flux of Wood and Concrete Block Base Materials
Field StationNelson Environmental Study Area – KU Experimental Field Station
Field Station• 10 slabs• Data
– Outside parameters:• Ambient temperature (shade)• Ground temp (@ 4”)• Total solar radiation (at angle of lids)
– Compartments all instrumented with:• 10 Thermocouples in soil (5 readings)• 2 Thermocouples in compartment air
– Selected compartments also have• Slab temperatures• Cover interior surface temperature• Soil moisture• Additional Thermocouples
• Data collection– Agilent 34980A Logger– 60 channels collected (of 120 available) at 5 min
intervals• Meteorological station also on site
“Energy Generation in Compost” Locascio, Katinka; Wolfson, Richard
Experimental Matrix(47 permutations)
• Baseline– Mounded compost pile (covered with Black & Translucent
6 mil plastic sheet)• Sides:
– Single and Double Wood, – Concrete, – Single and Double ¼” PC
• Covers– Single and Double 1/16” PC (corrugated)– Single and Double ¼” PC (flat)– Unpainted and Black Metal (corrugated)– 6 mil Translucent plastic sheet– White fiberglass (corrugated)
• Insulation– None vs. Hay
• Moisture– Dry (10%) vs. 30-50%
• Internal Heat– None vs. 100 W/compartment (~ 200 W/m2)*
• Interior Walls– Uncovered vs. Al-foil covered
Thermally Inert Soil Assumption• Typical composting heat generation: 200 W/m2 (Cornell Univ.)
0 6 12 18 0 6 12 18 00
5
10
15
20
25
30
35
40
700 ml of Baked Soil in a Mason Jar 700 ml of Unbaked Soil in a Mason Jar
Time of Day
Tem
p (C
)
Reproducibility in Designs
0 6 12 18 0 6 12 18 020
25
30
35
40
45
Compartment 1Compartment 2Compartment 5Compartment 6Compartment 4Compartment 7Compartment 8Compartment 9
Time of Day
Tem
p (C
)
• Comp. 1 & 2: Straw Insulated Concrete• Comp. 5 & 6: Straw Insulated Double Wood• Comp. 4 & 7: Uninsulated Double Wood• Comp. 8 & 9: Single Sided Wood
Temp. Profile of Uninsulated Concrete w/ Dbl 1/16” PC Cover~28°C DAY
0 2 4 6 8 10 12 14 16 18 20 22 005
1015202530354045505560657075808590
0
400
800
1200
1600
2000
2400
2800
3200
3600T-Internal AirT-4" MidT-4" NE CornerT-6" MidT-8" MidT-8" SW CornerT-Top of Slab (ave)T-External AirSolar Radiation (W/m2)
HOUR
Tem
pera
ture
(C )
Sola
r Rad
iatio
n (W
/m2)
0.1 1 10 100 100020
30
40
50
60
70
80
90EnterovirusesAscaris EggsSalmonellaShigellaEntamoeba histolytica cystsTaenia eggsVibrio cholerae0" (>Air)4"6"8"
Hours of Sustained Temperature
Com
post
Tem
pera
ture
(C )
at D
epth
P18: Uninsulated Double Wood -Single 1/16” Clear PC
Date: 8/25/2011Max Solar Radiation: 8.01 kWhr-m2
Max ambient T: 28.2 °C (82 °F)
Uninsulated Wood – Single 1/16” PC (DRY)
Infiltration issues
Discussion• Building materials
– Insulated wood and concrete both effective. Infiltration should be prevented.• Cover Materials
Double Clr PC > 6mil Plastic sheet ~ Single Clr PC > White Fiberglass > Black Metal > Metal
• Moisture– Moisture required for composting– Moisture decreased temperatures by ~5C (evaporation)
• Reflective interior (foil)– Increased soil temps ~3C
• Clear sides– Increased solar heating– Increased solar heating may be offset by increased heat losses– May be impractical
Discussion• Internal heat generation
highly beneficial• Infiltration and exfiltration
potentially significant heat loss mechanism
• Turning piles – Lower parts of pile cycled
up to top of pile to be disinfected
– Can not assure that parts of pile aren’t left on bottom
– Requires increased handling – health implications
Acknowledgements• Funding – DOD ARO, Constant DP funds• Matthew Maksimowicz, Jay Bernard, Jim Weaver• Aurelien Jean • KU Exp. Field Station / NESA: Dean Kettle, Bruce Johanning• Many EWB-KU students who have contributed to building
latrines working with Azacilo, Bolvia• EWB-USA• Sumaj Husai and Engineers-In-Action• People of Azacilo, Bolivia
• Questions/Comments/Discussion?