GENERATION OF ADDITIONAL REVENUE

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22 Φεβ 2014 (πριν από 3 χρόνια και 7 μήνες)

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POTENTIAL FOR

GENERATION OF ADDITIONAL REVENUE
FROM PRODUCTS OF

WASTEWATER TREATMENT



Dr. Damjan Nemec

(
B.Sc.Chem.Eng
.
)

Wastewater treatment in general


Process of
removing contaminants
from collected sewage


Household sewage


Industrial sewage



Nature of
contaminants
:


physical (TSS)


chemical (COD)


biological (BOD)



Objective is to produce an
environmentally
-
safe effluent

Wastewater treatment in general


Basic process steps









Usually regarded as
the black sheep
of utility services


High operating costs
and rarely appreciated by the public

Preliminary

(physical)



Screening



Grit removal



Grease removal





Efficiency:


-

TSS =


-
10%


-

COD =


-

5%


-

BOD =
-

5%

Primary

(physical, chem.)



Sedimentation







Efficiency:


-

TSS =


-
50%


-

COD =


-
20%


-

BOD =
-
20%

Secondary

(biological)



Aeration



Sedimentation






Efficiency:


-

TSS =


-
95%


-

COD =


-
90%


-

BOD =
-
95%

Tertiary

(advanced)



Nutrient removal



Filtration



Adsorption



Disinfection




Efficiency:


-

TSS
>



-
99%


-

COD
>



-
99%


-

BOD
>

-
99%

Wastewater

treatment

in Mombasa

Wastewater

treatment

in Mombasa

Kipevu


WWTP

Kizingo


WWTP






Kipevu

WWTP

influent

Kipevu

WWTP

effluent

a
eration

tanks

s
ludge


thickeners

s
creens


&
grit

removal

s
ludge

drying

beds

sludge

settling

tanks


Plant

capacity
:


196.000 P.E.



17.100 m
3
/d


9.580 kg/d BOD


Electricity consumption







Overall cost


5.606.400 kWh/a
×

20
KSh
/kWh = 112.128
.000

KSh
/a

Kipevu

WWTP


Equipment

No. of units

kW per unit

kW total

h/d

daily (kWh)

annual (kWh)


Aerators

16

45

720

20

14.400

5.256.000



Settlers

4

1,5

6

24

144

52.560


Return sludge pumps

4

5

15

24

360

131.400


Excess sludge pumps

2

5

5

12

60

21.900


Sludge thickeners

2

2,5

5

24

120

43.800


Screw pumps

2

15

15

4

60

21.900


Washout pump

1

4

4

24

96

35.040


General

1

10

10

12

120

43.800


Total





780



15.348

5.606.400

influent

Kipevu

WWTP

effluent

a
eration

tanks

s
ludge


thickeners

s
creens


&
grit

removal

s
ludge

drying

beds

sludge

settling

tanks

Digester #1

Digester #2

Biogas cleaning

Biogas storage

Flare

CHP
unit

Sludge

Thickened

sludge

Biogas

Biogas

Biogas

production

from

sludge


Nett production of electricity


7.635
-

1.455 = 6.180 kWh/d


2.255.700 kWh/a
×

20
KSh
/kWh = 45.114.000

KSh
/d

(40%)




Overall investment


1.826.000


(~ 5,3 years of payback)



41% less sludge to dispose!



Biogas production from Kipevu WWTP sludge






Kipevu

WWTP

Expanding services


Biogas plant has space for additional substrate


Food waste from hotels can be collected as extra service


~100 hotels, ~6.500 tourists


~
0,5 kg of food waste per tourist => 3,5 t/d of energy rich waste

Biogas storage

Flare

CHP
unit

Food

waste

Digester #1

Digester #2

Biogas cleaning

Sludge

Substrate

Biogas

Biogas

Biogas

production

from

sludge


Nett production of electricity


8.670
-

1.510 = 7.160 kWh/d


2.613.400 kWh/a
×

20
KSh
/kWh = 52.268.000
KSh
/d

(47%)




Overall investment


1.923.000


(~ 4,8 years of payback)



37
%
less sludge to dispose
!


Biogas production from Kipevu WWTP sludge

influent

Kipevu

WWTP

effluent

a
eration

tanks

s
ludge


thickeners

s
creens


&
grit

removal

s
ludge

drying

beds

sludge

settling

tanks


Can be treated further with advanced methods and reused:


Urban reuse:


Irrigation of public parks, landscapes and golf courses


Vehicle washing and decorative water features


Connecting to fire hydrants for fire protection


Industrial reuse:


Cooling water


Boiler make
-
up water


Industrial process water


Agricultural reuse


Can even be purified to potable water standards!


Reuse of treated water from WWTP


Reuse of treated water from
Kizingo

WWTP


For irrigation of the golf course and local parks


Only filtration and disinfection required


Nutrient removal not required, their presence is beneficial!




Limited extra investment


Plant is located beneath the golf course!


After treatment the water is discharged into the sea


17.100 m
3
/d



Focus on cooling water requirements of the local industry


Usually the largest use of reclaimed water


High quantities and moderate quality required


Numerous petroleum refineries in the US that practice this


Reuse of treated water from
Kipevu

WWTP






Kipevu

WWTP


Potential treatment required for cooling water standard



Corrosion concerns (filtration)


Removal o
f

dissolved solids



Biological concerns (disinfection)


Removal of microbiological organisms (may deposit on surface)


Removal of nutrients (may contribute to microorganism growth)



Scaling concerns (chemical treatment)


Removal of Calcium, Magnesium, Phosphate and Sulphate



Reuse of treated water from
Kipevu

WWTP


Wastewater treatment…


…is required to protect the environment (for today and tomorrow)


…can be very expensive, especially if plants are under capacity


…plants should be maintained regularly with skilled staff



The cost pressure can be reduced…


…by “exploiting” the potential of wastewater treatment products


Sludge for energy (biogas)


Expanding the services to collecting other energy rich waste (tipping fees)


Reuse of treated water will be gaining in importance in the coming years



Concrete results on the assessment will be made available

Current conclusions

Thank you for your attention!




damjan.nemec@gmail.com