Summer School on
Wastewater Treatment Plants and Management
Eng. Dr. Erich Kellner
Lector of Civil Engeneering Department of São Carlos
Federal University (UFSCar)
November, 7 th – 2012
São Carlos - Brazil
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Stabilization ponds:
Figure 1: Stabilization ponds – Lins (SP) - Brazil
Stabilization ponds are biological treatment systems in which stabilization of organic material is carried out by bacterial oxidation and/or photosynthetic reduction of algae.
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Basic Configurations of
Wastewater Treatment Systems by Stabilization Ponds:
Figure 2: Configurations of wastewater treatment systems by stabilizations ponds
Source: adapted from von Sperling (2000)
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•
•
•
Pros and Cons of using stabilization ponds:
PROS CONS
Simplicity to built, operate and maintain;
Low operational cost;
Good quality on effluent;
• Need large areas;
• Limited and dependent on weather;
• Quality of effluent varies;
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:
Figure 3: Anaerobic Pond– São Carlos (SP) - Brazil
• Basins of 3m to 5m (10 feet to 17 feet) depth receiving continuous organic load of wastewater so that anaerobic conditions are met.
• Sedimentation pond.
• High waste water loading – depletes all O
2.
• Solids settle at bottom of the to pond.
• Anaerobic digestion of sludge occurs at the bottom of the pond.
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Anaerobic Ponds:
Figure 4: Metabolic process in anaerobic digestion
Source: adapted from Pescod (1995)
Hydrolysis - Complex organics
(proteins and fats broken down to simpler compounds by various bacteria
Acidogenesis (Fermentation) –
Fatty acids and alcohols oxidized
,amino acids and carbohydrates fermented, produce volatile fatty acids and hydrogen
Acetogenesis – conversion of complex fatty acids to acetic acid
Methanogenesis - conversion of acetic acid to methane and CO
2 and CO
2
,H
2 to methane
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Anaerobic Ponds - Design Criteria:
Design is highly empirical – based on volumetric load (g BOD/m 3 /day) and
Hydraulic Detention Time (day)
•Time of Hydraulic Detention (q) = between 4 to 6 days for the final plan
•Liquid depth = between 4 to 5m
•Volumetric organic load ( l v
) = 0.08 and 0.4 kgDBO/m 3 pond.
day
•Superficial organic load( l s
) > 1000 kgDBO/ha.day
•Sludge accumulation = 0.01 to 0.03 m 3 /inhab.year
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Anaerobic Ponds - Design Criteria:
Table: Expected efficiency to reduce DBO due to average air temperature in the coldest month
Average Air Temperature
Coldest Month
( o C)
Removed DBO
(%)
<10 40
10-25
>25
2.T + 20
70
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Facultative Ponds:
Figure 5: Facultative ponds – Barretos (SP) - Brazil
• Basins of 1.5m to 2m depth.
• To have clear water, light penetration and photosynthetic production of oxygen to decompose organic material take place easier
• Part of the solids present in the wastewater settle and are biodegradable in an anaerobic process
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Facultative Ponds:
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Facultative Pond Interactions:
Figure 6: Definition of interactions occurring in a facultative pond
Source: Tchobanoglous and Schroeder (1985)
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Facultative Ponds - Design Criteria:
PRIMARY FACULTATIVE PONDS:
•Superficial application rate limit* ( l
S
) = 20.T – 60 kgDBO/ha.day**
• Expected efficiency to reduce DBO (Empirical equation based on complete mixture model)*: let e be the efficiency (%); l s superficial application rate (kgDBO/ha.day)
Notes:
• Refers to half depth in the area
• Average air temperature in the coldest month ( o C).
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Facultative Ponds - Design Criteria:
SECONDARY FACULTATIVE POND:
14.T – 40 < 200 kgDBO/ha.day** p/T >17 o C
•Superficial application rate limit* ( l
S
) =
350. (1,107-0,002.T) T-25 kgDBO/ha.day** p/T
<17 o C
• Expected efficiency to reduce DBO (Empirical equation based on complete mixture model)*: let e be the efficiency(%); l s superficial application rate (kgDBO/ha.day)
Notes:
* Refers to half depth in the area.
** Average air temperature in the coldest month ( o C).
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Maturation Ponds:
Figure 7: Maturation ponds – Barretos (SP) - Brazil
• Basins of between 0.8m and
1.5m depth. Normally, 1.0 m depth is used.
• The main objective of maturation ponds is to remove pathogenic microrganisms present in the wastewater, which occur mainly due to sunlight in the water column.
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Maturation Ponds - Design Criteria:
•Superficial organic load ( l s
) < 50 kgDBO/ha.day
•HDT for each pond ( q m
) > 7 days, with at least 3 maturation ponds in sequence.
•Decrease of pathogenic microrganisms:
Ne

(
1

No
K
T
 q m
) n
K
T

( ) T  20
Continuously
Stirred Tank
Reactor (CSTR)
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Hydrodynamic Test:
FP1
AP
FP2
Figure 8: Stabilization Ponds in Novo
Horizonte (SP)
Source: Moreira (2006)
Figure 9: Rodamina B injection in FP1
Source: Moreira (2006)
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Hydrodynamic Test:
7,00
6,00
5,00
4,00
3,00
2,00
1,00
0,00
0,0 0,5 1,0 1,5 2,0 t/t m
Figure 10: Non-dimensional concentration curve of Rodamina B in function of measured time in FP1 exit
Source: Kellner, Moreira & Pires (2009).
2,5
• Theoretical hydraulic Detention Time teórico was 164 hours.
• Real hydraulic Detention Time resulted in 55 hours, with dispersion number(d) equal to
11.034.853.603 !!!.
• Active volume of 33.6% (3.5h) and recuperation of dye mass of 95.6%.
Source: (Kellner, Moreira & Pires, 2009).
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Influence of Thermal Stratification in the Distribution of
Rodamina B in the Water Column of FP1
Temperature ( o C)
Concentration ( m g/l)
[Animation done from results presented by Kellner, Moreira & Pires (2009).]
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Thermal Stratification of a stabilization pond affects…
…the useful volume,
…the dispersion number,
…the HDT, etc.
According to Kellner & Pires (2000), temperature gradient
0.6
o C/m, in stabilization ponds with temperature of 25 o C, can lead to a thermal stratification state.
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Design and Operational Problems:
Figure 11: Facultative Pond built in shaded area
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Design and Operational Problems:
Figure 12: Infiltration problem in anaerobic pond
22

Design and Operational problems:
Facultative Pond with red brown colour
Possible causes:
• Organic material overload
• Presence of photosynthetic bacteria that oxidates sulphyte and does not produce oxygen does not contribute to reducing BOD
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Design and Operational Problems:
Facultative Pond withmilky green colour
Possible causes:
• The pond is in an autofloculation process due to increase in pH and temperature
• Precipitation of hydroxide magnesium or calcium dragging algae and other microrganisms with it
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Design and Operational Problems:
Facultative Pond with yellow green colour
Possible causes:
• Growth of rotifers, protozoas or crustaceans which feed on algae;
• There could be a significant decrease in the DO and possibly a bad odor from the anaerobic decomposition of OM.
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Design and Operational Problems:
Facultative Pond with green blue colour
Possible causes:
• Significant growth of cianobacteria;
• Appearance of native certain species which decompose easily, causing bad odors, reducing the penetration of sunlight and diminishing oxygen production.
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Design and operational problems:
Facultative pond with grey colour
Possible causes:
• Overload of organic material and/or short detention time
• Fermentation in sludge layer incomplete.
27

Design and operational problems::
Absence of Grit Removal System
Not having desanders can cause silting in the ponds
28

Design and operational problems::
Absence of Grit Removal System
…is able to change the flow and wastewater in the ponds
29

Anaerobic pond – Problems of bad odor
Free surface makesexchange of gases easier (CH
4 for the atmosphere
, H
2
S,…)
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Anaerobicpond - Problems with bad odor (possibility of using methane)
31

Sludge:
32

Sludge conditioning (Solution or Environmental passivity?)
Sludge conditioning in materia lsacks can make it passive.
Figure: Sludge conditioning 33

E-mail: erich.kellner@ufscar.br
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