Module 4.10 Ecosan versus conventional sanitation How can dry UD ecosan system be compared with a conventional systems (open defecation, latrine pit, water-borne)?
Post on 27-Mar-2015
218 Views
Preview:
Transcript
Module 4.10Ecosan versus conventional
sanitation
How can dry UD ecosan system be compared with a conventional
systems (open defecation, latrine pit, water-borne)?
4 Swedish systems with nutrient recovery compared
1. Reference. Conventional system. N & P removal in WWTP. Effluent: 8 mg N & 0.24 mg P/l. Sludge incinerated, ash landfilled.
2. Urine. 80% of urine diverted & recycled as fertiliser. Rest = reference
3. Blackwater. Vacuum toilets. Collected blackwater anaerobically digested, sanitised & recycled as fertiliser. Rest = reference
4. Sludge. Sludge recycled as fertiliser. Rest = reference
Recycled plant available NPKS
0
10
20
30
40
50
60
70
80
Reference Urine Blackwater Sludge PhoStrip KREPRO BioCon
Rec
ycle
d pl
ant
avai
labl
e N
PK
S (
% o
f to
t) N P K S
Energy use
0
100
200
300
400
500
600
700
800
900
1000
Reference Urine Blackwater Sludge PhoStrip KREPRO BioCon
Ene
rgy
use
(MJ/
pers
, yr
)
Pumping Treatment Transports P-recovery Spreading Chemical fertiliser
Total use non-renewable
0
100
200
300
400
500
600
Reference Urine Blackwater Sludge
No
n-r
en
ew
ab
le r
eso
urc
e u
se (
10
e-1
6/p
ers
on
, yr
)
P,K,S Oil, gas Electricity
Other studies of sorting systems
• Many systems analysis have found same results:
• Urine diversion – decreases water emissions – gives lots of useful fertiliser– saves chemical fertiliser– saves energy
Recycled NPK vs degree of diversion
0,0
0,5
1,0
1,5
2,0
2,5
3,0
NConv
N40%
N100%
PConv
P40%
P100%
KConv
K.40%
K100%
Rec
ycle
d N
PK
[kg
/p,y
r] Urine
Sludge
Water emissions vs degree of diversion
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
N Conv N 40% N 65% N 100% P Conv P 40% P 65% P 100%
Wat
erem
issi
ons
[kg/
p,ye
ar] Sew plant
Field
Landfill
Chemicals
Energy usage vs degree of diversion
http://www.stockholmvatten.se/pdf_arkiv/english/Urinsep_eng.pdf
0
50
100
150
200
250
300
350
Conv 40% Urine 65% Urine 100% Urine
Ene
rgy
usag
e [M
J/p,
year
]
Fertiliser
Oil
Electric
Energy usage vs transport distance
0
50
100
150
200
250
300
350
400
Conv. 1 kmUrinetruck
33 kmUrinetruck
100 kmUrinetruck
200 kmUrinetruck
1 kmUrine
t+t
33 kmUrine
t+t
100 kmUrine
t+t
200 kmUrine
t+t
Ene
rgy
usag
e [M
J/p,
yr]
Fertiliser
Oil
Electricity
System boarders
• What to include and what to exclude?• UDD
– Solid organic waste– Energy production– Fertiliser production
• Food production– Delivered sanitational function
• Greywater• Drinking water• Other waste
Productive Sanitation
N=2.8kgP=0.4kgK=0.5 kg
N=2.8kgP=0.4kgK=0.5 kg
Nutrient flow per person and year
FoodExcreta
Fertiliser
Value of fertiliser - urine• 2.8kg N = 6kg Urea 0.5€/kg = 3€• 0.4 kg P = 2kg TPS ~0.4€/kg = 0.8€• 0.5 kg K = 1kg KCl ~0.4€/kg = 0.4€• Total value 4.2€ per person and
year = 0.012€ per person day• Value per jerry can 20L ~ 0.23€• Can at least pay for transport and
spreading• Non-subsidised
Cost for ecosan• Pour flush toilet 1900 INR (35€)• EcoSan toilet 4200 INR (77€)
Fertiliser per family
Nutrients Fertiliser Amount, kg Difference4 persons NPK 10-5-20 160 kg
N 18,2 10,0% 16,0 2,2P 2,32 2,2% 3,6 -1,2
NPK 10-5-20 Indian, price 5.5 INR/kg (0.1€)
Value 880 INR/year (16€)
Present value years 2-10: 5070 INR! (93€)
Conclusion
• Pour flush toilet cost: 1900 R• EcoSan toilet cost: 4200 R
– Income from fertiliser: 5080 R• Fertiliser can pay for toilet in 10 years, not just
additional cost!Additionally• Less hazard to ground & surface water
– Saves on drinking water– Protects health
Cost sharing• Having no toilet has lowest investment &
direct running costs!• Only type of toilet where the investment can
directly pay off• The cost of Ecosan is compatitive compared
with any other ecological solution• The cost is largely paid by household when
building – no risk for corruption at municipal level – higher cost acceptance
• More private enterprise – more competition – saves taxes
top related