Heather N. Bischel Postdoctoral Research Scientist Laboratory of - - PowerPoint PPT Presentation

Hygiene considerations for source-separated urine collection, storage and processing into a marketable fertilizer

Heather N. Bischel

Postdoctoral Research Scientist Laboratory of Environmental Chemistry Swiss Federal Institute of Technology, Lausanne (EPFL)

Simon Schindelholz, Manfred Schoger, Tamar Kohn

September 15, 2016

Kwazulu- Natal province

Urine separation & Struvite production

>80K Urine-Diverting Dry Toilets (UDDTs) in rural/peri-urban areas

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Population: 3.5M

Durban Valorisation of Urine Nutrients in Africa (VUNA)

Struvite production: Add Mg2+, gentle mix, Cotton bag Filters MgNH4PO4·6H2O Drying outdoors under cover

Hygiene Considerations

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Source-separated urine is not sterile! Human pathogens detected in source-separated urine in Durban

~106 viral pathogens 106 -108 bacterial pathogens 104 protozoan cysts or oocysts 10–104 helminth eggs

Feachem et al, 1983

Diarrheal Bacteria Human viruses E.g.,: Shigella spp., Vibrio spp.,

• E. coli 0157:H7

E.g.,: Rotavirus, Adenovirus, Hepatitis A Virus 1g of fresh feces from an infected person can contain:

Bischel et al, Wat. Res. 2015

Characterize and optimize hygiene of urine storage and recycling

Overall Objectives

Fertilizer application Urine Storage Struvite Production & Drying Excretion in feces / urine Pathogens:

• 1. Which hazards

are there?

• 2. How can we mitigate them?

Inactivation Kinetics and Mechanisms

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• Anticipate short-term urine storage for process scale-up or in dense locations
• Which microbial targets to evaluate? Pathogen indicators and in situ bacteria
• Manual struvite production in the field: Variable temperature and humidity

Challenges

• 3. Health risk

implications?

Inactivation Potential During Urine Storage

(Höglund, Stenström et al. 1998; Vinneras et al. 2008; Schonning 2001; Höglund, Ashbolt et al. 2002. Decrey et al. 2015, 2016) and others

BACTERIA: VIRUSES:

Inactivation depends on:

• Organism (e.g., gram negative/positive bacterium; viral genome type)
• Urine storage temperature
• Ammonia concentration (urine dilution and storage conditions)
• pH (ammonia speciation)

e.g., E. coli and Salmonella e.g., Rotavirus e.g., C. perfringens spores: Little to no reduction Rapid die-off T90 < 5 d at ~20°C Slower inactivation T90 ~ 35 d at 20°C, 1:2 dilution Viable bacteria present after long-term storage And even urine treatment (Lahr et al, 2016) Inactivation during fertilizer production important after short-term urine storage

Inactivation during Struvite Precipitation & Drying

• Inactivation of virus and helminths during

controlled struvite drying ↑ inactivation with ↓ moisture content ↑ inactivation with ↑ temperature

• Degradation of struvite with T > 55˚C

Laboratory-made Struvite Cake

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• Evaluate:
• Retention of bacteria in

struvite cake

• Bacteria inactivation in

lab (controlled) and field

• How to increase inactivation

without heat treatment?

(Decrey et al. Wat. Res. 2011)

0.1 1 10 100 1000 0.1 1 10 100 1000 FL1 (Green) FL3 (Red) 1600 0.1 1 10 100 1000 0.1 1 10 100 1000 FL1 (Green) FL3 (Red) 1600

Methods: Bacteria Inactivation during Struvite Precipitation & Drying

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Targeted health-relevant bacteria:

Enterococcus spp. Salmonella typhimurium

Heterotrophic plate counts: Total viable bacteria by flow cytometry:

(Live) (Dead)

~1010 viable bacteria per gram of struvite!

Struvite

In situ measurements by Flow Cytometry

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• 2,5
• 2
• 1,5
• 1
• 0,5

0,5 20 40 60 Log C/C0 Time (hrs) Live Dead 35˚C/40% RH 0 hrs

(Live) (Dead)

FL3 (Red) FL1 (Green)

24 hrs

FL3 (Red) FL1 (Green)

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R² = 0,9186 7 8 9 10 11 12 3 4 5 6 7

Total Live Cells: Log C (Counts/g ww) Heterotrophs: Log C (CFU/g ww)

48 hrs

FL3 (Red) FL1 (Green)

Isothermal Struvite Drying

log10(C) = log10(𝐷0) − (𝑢 δ)𝑞

• S. typhimurium
• 5
• 4
• 3
• 2
• 1

1 200 400 600 Log C/C0 Time (hrs)

Low Relative Humidity

• 5
• 4
• 3
• 2
• 1

1 200 400 600 Log C/C0 Time (hrs)

High Relative Humidity

• Tailing can result from, e.g.:
• Reduced probability of lethal hit
• Evaporative cooling at low humidity
• Dehydration tolerant subpopulation

Low Humidity p < 1 (Tailing) High Humidity p > 1 (Shoulder) Retention of moisture for continued inactivation (followed by desiccation) Weibull Model: Distribution of resistances to inactivation

• Shape param. (p) captures tail or shoulder
• δ is the time for first-decimal reduction

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• 4
• 3
• 2
• 1

1 2

• 4
• 3
• 2
• 1

Log(C/C0) Relative Moisture Content, Log(θ/θ0)

Controlled Lab Conditions

eThekwini Batch Swiss Batch 1

• 4
• 3
• 2
• 1

1 2

• 4
• 3
• 2
• 1

Log(C/C0) Log(θ/θ0)

Field Conditions

Nylon Filters Cotton Filters

In situ Heterotrophic Bacteria Inactivation

Dynamic Field conditions: Oscillating temperature and relative humidity

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Recommendations for inactivation of pathogens during struvite production

Addabbo et al 2010

Soil Solarization

http://www.ipm.ucdavis.edu/

struvite degrades T > 55˚C Inactivation dependent

• n relative humidity

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Minimum temperature (35˚C) required for helminth inactivation Wet-heating for enhanced inactivation of bacteria Desiccation: reduce moisture content for virus, helminth, & bacteria inactivation

Characterize and optimize hygiene of urine storage and recycling

Summary & Next steps

Quantitative microbial risks assessment: during urine collection, handling and struvite production

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• 1. Which hazards are there?

Source-separated urine is not sterile!

• Contains fecal pathogens –

including persistent viruses

• Recommend: Personal protective

equipment; sealed storage

• 2. How can we mitigate them?

Struvite Production

• Bacteria retained in filtered struvite
• Field inactivation consistent with lab
• Recommend: initial retention of moisture

followed by desiccation Fertilizer application Urine Storage Struvite Production & Drying Excretion in feces / urine Pathogens:

Acknowledgements

• Tamar Kohn, Laboratory of Environmental Chemistry
• Kai Udert & Bastian Etter, Eawag/VUNA
• Teddy Gounden, EWS Field staff
• Chris Buckley, Sara Rhoton, Nicola Rodda, UKZN
• Simon Schindelholz, Manfred Schoger, Loic Decrey

Funding: US and Swiss NSF Bill & Melinda Gates Foundation Rotary Foundation EPFL, EWS and Eawag Contact Info After April 2017: Heather Bischel, Asst Prof University of California, Davis hbischel@ucdavis.edu