This document discusses health issues related to waste reuse and presents strategies to reduce risks. It notes that in many African cities, population growth has outpaced sanitation infrastructure development. Various health risks from pathogens in waste are discussed for fecal sludge composting, wastewater irrigation, and aquaculture. The document then outlines approaches like composting, irrigation techniques, and wastewater treatment that can reduce pathogen levels and make waste reuse safer. It presents data on how these approaches lower bacteria and helminth egg counts.

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Water for a food-secure world
Addressing health concerns
of waste reuse
Philip Amoah (PhD)

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Outline
 Background
 Health issues in
 faecal sludge composting
 wastewater irrigation
 aquaculture
Risk reductions strategies

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Fecal sludge management
 In most cities in Africa, population growth outpaced the
development of sanitation infrastructure
 the management of urban waste (solid and liquid)
ineffective.
Background

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 Sewer networks in SSA are collecting only a small
percentage of wastewater generated.
 The few wastewater treatment plants are usually not
functional or overloaded.

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Current methods of waste reuse

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Waste is a potential vehicle for
pathogens in the food chain
 Bacteria : Salmonella spp. , E. coli etc…
 Viruses: Norovirus etc
 Protozoa: Cryptosporidium, Cyclospora, Giardia,
 Helminths: Fasciola spp., Taenia spp, Ascaris Lumbricoides

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Who is at risk?
Consumers
Farmers and their families

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Benefits of waste reuse

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Feedstock E. coli
(cfu/10g Dry wt)
F. coliform
(cfu/10g Dry wt)
Raw FS 4.2 x 106 ± 2.9 x 103 5.0 x 107 ± 2.6 x 105
Feedstock
E. coli
(cfu/10g Dry wt)
F. coliform
(cfu/10g Dry wt)
Dry FS 6.0x104 ±1.6 x103 5.9 x104 ± 7.0 x 102
Microbial populations in raw and
dry faecal sludge

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Day 1 after composting
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Turning compost (weekly)
Matured compost after 90 days
Heat generated during composting
kills pathogens
Compost temperature taking

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0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 97
Temperature
(dgrees
celcius)
Temperature changes during the
composting process.
Days

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A= FS + EFB; 1:1,
B= FS + CPH; 1:1,
C= FS+EFB+CPH; 1:1:1,
D= FS+EFB+CPH; 2:1:1,
E= FS+EFB+CPH; 2:2:1.
Changes in E. coli populations in compost piles during
composting.
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0 3 6 9 12
Escherichia
coli
in
log
units
Weeks after composting
A B C D E
FS = Faecal sludge; EFB= Empty fruit bunches; CPH= Cocoa pod husk

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Wastewater
generation
Consumer
Wastewater
treatment
Safe
produce
…
Multiple barrier approach from “Farm to Fork”
Wastewater
generation
Farmer/
Producer
Traders/
Retailers
Street food
kitchens
Consumer
Wastewater
treatment
Safe
Irrigation
Practices
Hygienic
Handling
Practices
Safe food
washing and
preparation
Awareness
creation
to create
demand for
safe produce
Policy recognition, safer farm land, tenure security,
market incentives, safe-food labelling,…
Wastewater Irrigation

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Safer irrigation practices
• Drip irrigation
• Furrow irrigation
• Avoiding soil splash
• Cessation of irrigation
• Avoid stirring up sediments
Farm level reduction by 2 - 4 log units

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Ponds trials – Sedimentation

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0
2
4
6
8
10
12
Karikari Gyenyase
Helminth
eggs
(No.
of
eggs/l)
Settled
Unsettled
Sediments
Indicator Organisms in ponds
under different conditions

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Improved use of watering cans
>1m, Uncapped >1 m, Capped 0.5-1.0m, Capped
Irrigation
height
(m)
Thermotolerant coliforms
(log MPN 100 g-1)
Capped Uncapped
Helminth eggs
(No.100 g-1)
Capped Uncapped
Dry
season
Wet
season
< 0.5
0.5 - 1.0
> 1.0
< 0.5
0.5 - 1.0
> 1.0
4.7 ± 0.1
5.4 ± 0.4
5.9 ± 0.4
6.5 ± 0.1
6.6 ± 0.1
7.7 ± 0.1
5.4 ± 0.3
5.7 ± 0.4
7.8 ± 0.4
7.5 ± 0.1
7.7 ± 0.2
8.47 ± 0.1
0.3 ± 0.2
1.0 ± 0.3
1.6 ± 0.3
0.7 ± 0.3
1.5 ± 0.4
1.4 ± 0.3
1.1 ± 0.4
1.6 ± 0.3
2.6 ± 0.4
1.4 ± 0.5
2.0 ± 0.4
2.9 ± 0.4
(n= 30 lettuce samples per height per season)

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Improving common salad washing practices
in homes and street food kitchens
 Common practices: 6 - 36% bacteria reduction
 Improved practices: 50-100% bacteria reduction
Challenges: Availability & price of e.g. chlorine tablets

19. Photo:
David
Brazier/IWMI
Photo
:Tom
van
Cakenberghe/IWMI
Photo
:
David
Brazier/IWMI
Photo:
David
Brazier/IWMI
Method Use Contact
time
Mean log10 FC levels before
and after treatment
Log
reduction
Before After
Running tap I
I
3-4 sec.
2 min.
5.5
6.1
5.2
3.9
0.3
2.2
NaCl7
NaCl23
NaCl35
NaCl7
NaCl23
NaCl35
I
I
I
I
I
I
3 – 4 sec.
2 min.
5.5
5.5
5.5
6.1
6.1
6.1
5.0
4.7
4.4
4.7
4.6
4.0
0.5
0.8
1.1
1.4
1.5
2.1
NaCl7 + Vin6818 I 3-4 sec.
2 min.
5.5
6.1
5.2
4.7
0.3
1.4
Vinegar6818
Vinegar12500
Vinegar21400
I
C
C
3-4 sec.
2 min.
5 min.
10 min.
5 min.
10 min
5.5
6.1
3.7
3.7
4.7
4.7
5.3
5.1
1.9
0.0
0.0
0.0
0.2
1.0
1.8
3.6
4.7
4.7
Efficacy of common methods at different exposure times
(N= 10 for each treatment)

20. Mean log10 FC
levels
Method Use Contact
time
Before After Log
reduction
Removal of outer leaves
(Vinegar 12500)
C
C
5 min.
10 min.
4.3
4.3
3.8
3.4
0.5
0.9
Laundry Omo™
(Detergent)
C
C
5 min
10 min
4.3
4.3
1.7
1.9
2.6
2.4
Eau de javel™
(I65μS/cm)
Thick Bleach™
(248μS/cm)
Power Zone™
(223μS/cm)
I
C
C
C
C
C
5 min
10 min
5 min
10 min
5 min
10 min
6.4
6.4
6.3
6.3
6.3
6.3
4.0
3.5
3.8
3.8
4.1
3.3
2.4
2.9
2.5
2.5
2.2
3.0
KM100
KM200
I
C
3-4 sec
2 min
5 min
10 min
5.5
6.1
6.4
6.4
4.8
4.9
4.4
3.9
0.7
0.6
1.0
2.5
CL tabs100 C
C
5 min
10 min
6.4
6.4
4.1
3.7
2.3
2.7
Efficacy of common methods Continued

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0
2
4
6
8
10
12
14
1 2 3 4 5 6 7 8
Washing methods
Number
of
helminth
eggs
100g-1
wet
weight
1) Unwashed, 2) Light washing in a bowl, 3) Washing in salt solution(7 ppm)
4) Washing in salt solution (23 ppm), 5) Washing in salt solution (35 ppm)
6) Washing under running water, 7) Vinegar solution 6818 ppm
7) Salt/vinegar solution (7 ppm/6818 ppm)
Efficacy of common washing method on
helminth egg contamination

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Wastewater treatment plant
(e.g. WSP, anaerobic/aerobic reactors )
$ $
consumers
$
aquaculture
farmers/labor, inputs
Aquaculture

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Stabilization ponds (maturation) in
Kumasi

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Microbiological quality of C. gariepinus
(CFU/g) raised in WFP and NWFP
Fish tissue Pathogen NWFP WFP
Skin
Total coliform 1.3 x 104 6.8 x 105
E. coli 2.1 x 103 4.2 x 105
Salmonella spp ND ND
Helminth eggs ND ND
Flesh
Total coliform 3.7 x 102 4.2 x 102
E. coli ND ND
Salmonella spp ND ND
Helminth eggs ND ND
Gut
Total coliform 2.0 x 102 1.2 x 103
E. coli 1.4 x 102 3.6 x 103
Salmonella spp ND ND
Helminth eggs ND ND

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Heavy metals concentration (mg/l) in
pond water
Heavy Metal Concentration (mg/l) Guidelines
NWFP WFP WHO FAO
Fe 1.37±0.22 2.05± 0.07 0.30 5.00
Cu 0.04±0.01 0.05± 0.02 2.25 0.20
Zn 0.27±0.04 0.39± 0.21 5.00 2.00
Mn 0.03±0.01 0.05± 0.01 0.50 0.20
Pb 0.05±0.01 0.06± 0.01 0.05 5.00
Cd 0.02±0.00 0.03± 0.01 0.01 0.01
 Apart from iron heavy metals in gills, muscle
and liver were below permissible levels

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Emerging contaminants
S. Asem-Hiablie et al., (2013) Serum estrogenicity and biological responses in
African catfish raised in wastewater ponds in Ghana . Science of the total
environment
Biological effects of reusing water in
aquaculture tested
 Similar body indices in catfish from both freshwater and
treated municipal wastewater
 Suggests that municipal wastewater may be amenable
for use in aquaculture in some cases.

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Thank you
Email: p.amoah@cgiar.org