Bulking and Foaming Filamentous in Modified Bardenpho Process

2nd International Conference on Chemical, Environmental and Biological Sciences (ICCEBS'2013) March 17-18, 2013 Dubai (UAE)
Bulking and Foaming Filamentous in Modified
Bardenpho Process during Hot Season
Ahmet Aygun, Sezen Kucukcongar, Zehra Gok, Merve Sogancioglu, Esra Yel,
and Murat Kucukhemek
liquid separation in the final clarifier [2]. Filamentous bulking
and foaming are among the most important problems
preventing effective solid-liquid separation. Although these
problems have been known for more than half a century, no
final or comprehensive solutions are available [3].
Filamentous bulking sludge, a term used to describe the
excessive growth of filamentous bacteria, is a frequent
problem in activated sludge process that has severe effects on
operational performance and increase the treatment cost [4].
A better understanding of the phenomena behind the bulking
appearance is essential for treatment plant management and to
preserve the effluent quality. Some factors responsible for
filamentous bulking sludge are oxygen deficiencies, nutrient
deficiencies, presence of reduced sulphur compounds,
decrease in food/micro-organism ratio (F/M) and wastewater
composition [5].
Wastewater composition is one of the significant factors
affecting filament formation, as it has been found that slowly
degradable organic material and especially lipids favour the
growth of both M. parvicella and Nocardia which are the
most common foam causing filament types [6,7]. Although,
these two are very common, they are not the only types,
several other filamentous species are also causing foaming.
Within the normal ambient temperature range found in
activated sludge aeration basins (8 to 25 0C), in can be
generally stated that filamentous organisms grow more rapidly
as the temperature increases within this range [8].
Research using classical microbiological techniques, such
as microscopic observation and culture-based enumeration,
has demonstrated a link between the predominance of
filamentous microorganisms and instances of foaming in
laboratory, pilot and full-scale wastewater treatment plants [6,
9,10]. The diversity of filaments in foam and identification
difficulties may have contributed to the lack of understanding.
To help resolve these issues, population shifts of putative
foam-causing organisms before, during, and after foaming
need to be quantified.
The environmental conditions encountered by the organism
in the N and P removal system (advanced biological treatment
system) are very different to those in conventional fully
aerobic systems. Nevertheless, the N and P systems did not
appear to be exempt from filamentous bulking problems.
Indeed it appeared that these systems had a propensity to
Abstract—The hot season filamentous species in wastewater
samples weekly taken from oxic and anoxic zones of the two parallel
aeration basins at Konya WWTP were identified and associated with
the operational conditions of the plant. Primarily, N. Limicola II, III,
Types, 021N, 0092, 0041/0675, 0581, 0803, M. Parvicella and
Nocardia found to dominate, which represents the biodegradable
industrial discharge, high θc and low F/M. In order to avoid the
bulking/foaming problems, specific control measures should be
preferred to non-specific ones. Operational condiditons were more
critical. Type 0092, M. parvicella, N. limicola III were determined as
the most dominant species in all basins and zones with their rate
above 75% observation frequency. When it is compared with the
aeration basins whether added or not added antifoaming and different
zones (oxic and anoxic) of basins, it was observed that different
species were dominant.
Keywords—Activated sludge, bulking, filamentous bacteria,
foaming, temperature.
I. INTRODUCTION
A
CTIVATED sludge is a commonly used biological
process in the treatment of domestic and industrial
wastewaters. Activated sludge represents a complex microbial
ecosystem containing a large variety of microorganisms, such
as bacteria, protozoa, fungi, metazoan, viruses and algae, as it
is a rich source of organic matter and nutrients. Despite the
diversity of microorganisms entailing activated sludge,
researchers have always been focused on bacteria [1]. The
performance of this process relies on a great deal on solid–
Ahmet Aygun is with the Environmental Engineering Department, Selcuk
University, Konya, 42075, TURKEY (Phone: +90 332 2231999; fax: +90
332 2410635; e-mail: [email protected]).
Sezen Kucukcongar is with the Environmental Engineering Department,
Selcuk University, Konya, 42075, TURKEY (Phone: +90 332 2232076; fax:
+90 332 2410635; e-mail: [email protected]).
Zehra Gok is with the Environmental Engineering Department, Selcuk
University, Konya, 42075, TURKEY (Phone: +90 332 2231964; fax: +90
332 2410635; e-mail: [email protected]).
Merve Sogancioglu is with the Environmental Engineering Department,
Selcuk University, Konya, 42075, TURKEY (Phone: +90 332 2231971; fax:
+90 332 2410635; e-mail: [email protected]).
Esra Yel is with the Environmental Engineering Department, Selcuk
University, Konya, 42075, TURKEY (Phone: +90 332 2232091; fax: +90
332 2410635; e-mail: [email protected]).
Murat Kucukhemek is with the Konya Metropolitan Municipality, Konya,
42000 TURKEY (Phone: +90 505 2162321; fax: +90 332 2410635; e-mail:
[email protected]).
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2nd International Conference on Chemical, Environmental and Biological Sciences (ICCEBS'2013) March 17-18, 2013 Dubai (UAE)
produce generally poorer settling sludge than their more
conventional short sludge age fully aerobic counterparts [11].
Antifoaming agents have been utilized for foam control in
activated sludge units. The chemical structure and the
antifoaming mechanism of most of the commercial
antifoaming agents are not clear. They can either remove foam
by destroying the foam causing microorganism, or simply by
destroying the foam physically.
The aim of this study was to identify the hot season period
filamentous species in activated sludge aeration basin
KonyaWWTP, to associate them with the operational
conditions of the plant, to compare the species observations
for anoxic and oxic zones, and to compare the basins that
antifoaming agent was added or not.
smear was stained for 1 min with ammonium oxalate-crystal
violet solution. The slide was rinsed in tap water and drained
of excess; Lugol’s solution was applied for 1 min. The stained
slide was rinsed in tap water and decolorized for
approximately 15-30 s with acetone alcohol. It was
counterstained with safranin for 15 s, rinsed with tap water
and dried.
As the second staining method, the Neisser staining
protocol was used for the same samples [13]. Another smear
of activated sludge sample was deposited on a different glass
slide. The slide was thoroughly air dried and fixed by passing
slide through a flame. A freshly made mixture of 2 part
solution A (methylene blue, glacial acetic acid and ethanol
solution) and 1 part solution B (crystal violet and ethanol
solution) was placed onto the slide for a contact period of 1015 s. Afterwards the excess dye was rinsed with tap water and
the slide was stained with solution C (chrysoidin Y solution)
for a contact period of 45 s. The slide was rinsed with tap
water and dried.
Gram- and Neisser-stained glass slides were examined
under oil immersion at 100X magnification with direct
illumination with Olympus BX51T-32P01 microscope
equipped with a color camera.
Filamentous bacteria were characterized to genus or to a
numbered “type” using the dichotomous key suggested by
Jenkins et al. [8]. At assessment period, available filamentous
species’ percentage distribution and filamentous bacteria’s
frequency of observation were determined. The rank of
filaments was recorded by using a scale ranging from 0
(filaments absent) to 3 (dominant). Determining the dominant
species, the operating conditions that caused foaming and
bulking were investigated.
II. MATERIAL AND METHOD
A. Material
Description of Konya WWTP
Konya WWTP (Qavg: 0.2 Mm3/d) includes preliminary
treatment, modified Bardenpho for organic carbon and partial
nitrogen degradation, disinfection, thickener and anaerobic
sludge digestion. Bardenpho aeration basins consist of 4
subsequent zones ordered as: anoxic-oxic-oxic-anoxic. Same
operating conditions were applied at aeration basins (T1 and
T2) that worked as two parallel lines in Konya WWTP. 4
mg/L water-based antifoam was added intermittently in 1st
aeration basin (T1). Wastewater samples were taken from the
first (anoxic zone) and the third (oxic zone) each week
between April and July 2012. The working period wastewater
influent and effluent water quality data were given in Table 1.
TABLE I
KONYA WWTP INFLUENT SAMPLE AND EFFLUENT WATER QUALITY
Average value
Parameter
Influent
Effluent
COD, mg/L
816
77
BOD 5 , mg/L
415
29
SS, mg/L
414
28
TP, mg/L
13
5
NH 4 -N, mg/L
66
51
TN, mg/L
96
69
III. RESULTS AND DISCUSSION
After Gram and Neisser staining procedures, sample
photomicrographs are indicated as in Fig 1(a) and 2(b) for
wastewater samples, respectively. While purple-blue species
in Gram staining are gram positive, pink or reddish species are
gram negative. Similarly, blue-colored species were neisser
negative while neisser positive species are yellow-brown in
Neisser staining (Fig. 1(a) and 2 (b)). During the period
between April and July 2012, observation frequency
percentages of observed filamentous bacteria in all basins and
zones are given in Figure 1.
As shown in Figure 1, Type 0092, M. parvicella, N.
limicola III were determined as the most dominant species in
all basins and zones with their rate above 75% observation
frequency, while Spirochaetae, Type 411, Spirillum,
Beggiatoa and Streptecocus were determined the least with
their rate below 25% observation frequency. The first and
second basin (T1 and T2) were operated under the same
conditions, the only difference was water-based antifoaming
agent which was added in T1. In addition to application of
antifoaming, in anoxic zone, Type 1863, Type 0411, Type
0581, Type 1851, Type 021N, S. natans and N. limicola II
B. Method
Bacteria in aqueous medium on the slide were hardly seen
under the light microscope due to their structural features.
These microorganisms were merely made more apparent by
staining and increasing their concentration at their location.
Gram and Neisser staining were applied to obtain more
reliable imaging procedures in wastewater samples weekly
taken from oxic and anoxic zones of the two parallel aeration
basins at Konya WWTP between April and July 2012.
The Gram Hucker staining protocol was used according to
Standard Methods [12]. A smear of activated sludge sample
was deposited on a glass slide. The slide was thoroughly air
dried and fixed by passing slide through a flame. First, the
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2nd International Conference on Chemical, Environmental and Biological Sciences (ICCEBS'2013) March 17-18, 2013 Dubai (UAE)
were lesser observed in samples. Besides this, after
antifoaming addition, Type 0803 and Streptococcus was never
observed. Depending on antifoaming addition in oxic zone,
Type 0803, Type 1701, Type 0581, H. hydrosis, Type 1851,
Type 021N and Thiotrix II species were lesser observed.
Similar to that of in anoxic zone, Type 0411, Fungi, Beggiatoa
was never observed after antifoaming addition.
The dissolved oxygen deficiency is one of the most typical
factors that cause most filamentous bacteria in activated
sludge process. Increasing dissolved oxygen concentrations
approximately 2 mg/L or even more is the effective method to
avoid filamentous bulking [4].
Independent from application of antifoaming species were
observed alterations between both of two basins’ oxic and
anoxic zones of the two basins.
Fig. 1(a) Sample Gram stained smear image
A
B
C
D
Fig. 1 Percentage of observation frequency of filamentous species in
Konya WWTP aeration basin
(A: 1st basin anoxic zone; B: 1st basin oxic zone; C: 2nd basin anoxic zone; D:
2nd basin oxic zone).
While Type 0803, Type 1701, H. Hydrosis, Type 0914,
Type 0041, Type 21N, Spirochaetae, Fungi, S. natans,
Thiothrix II and N. limicola I species, taken from the samples
in oxic zones, were observed higher; they were observed rare
in anoxic zones. Concordantly with this, with increasing
dissolved oxygen, Type 1863, Type 0411, Type 0581,
Zooglea, Streptecocus and Thiothrix I were observed lesser.
Filamentous bacteria are normal components of activated
sludge but they may compete successfully with the flocforming bacteria under specific conditions. Percentage ratios
of filamentous bacteria in the overall observations were
determined and dominant species generated by operating
conditions were presented in Figure 2. N. Limicola III (9%);
M. parvicella and Type 0092 (7%); Type 0041 and 021N and
N. Limicola II (6%); Type 0581, 0914 and 0675 and Nocardia
(5%); Type 0803 and 1851, S. natans, Thiothrix I and
Thiothrix II (4%) were the dominant filamentous
microorganisms in the 81% of the samples taken at time of hot
season period. The F/M and θc were 0.07-0.20 and 11.2 days,
Fig. 1(b) Sample Neisser stained smear image
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2nd International Conference on Chemical, Environmental and Biological Sciences (ICCEBS'2013) March 17-18, 2013 Dubai (UAE)
respectively during this period.
Types 0092, 0675/0041, M. parvicella proliferate under low
F/M ratios (long sludge age), and/or nutrient deficiency
conditions [8]. Type 0803 dominates in case of industrial
influent and anaerobic supernatant recycle [13], which was the
case during the study period. S. natans, Types 1701, 021N,
1851, Thiothrix spp., H. hydrossis, N. limicola II, III increases
with biodegradable industrial effluents. Konya sewerage
system receives wastewaters from a number of small and
medium scale industries distributed to the several regions of
the city. Most of these are working on food processing and
automotive spare part production/maintenance. The ambient
temperature varied between 14.8-22.2 ºC (avg 19.3 ºC). The
seasonal variation of the filamentous population is primarily
attributed to the temperature effect on the population size of
M. parvicella and Type 0092 [14,15]. Operational conditions
and influent variations affect the dominating filaments. The
complementarities of the dominance of these filamentous
microorganisms are strong evidence that they compete for the
same substrate. It was hypothesized that increasing
temperatures are responsible for foam formation as growth
rate increases with increasing temperature in the growth range
[14]. M. parvicella is dominant at the temperatures below 15
ºC and Type 0092 is dominant at temperature above 15 ºC [8].
Nocardia appears to be favored at higher aeration basin
temperatures and M. parvicella at lower aeration basin
temperatures. This phenomena not observed in this study.
Filamentous growth is not only temperature-dependent.
Therefore, the operational conditions should be strictly
followed and controlled to prevent filamentous growth.
was dominant specie. While the most dominant N. limicola III
with the rate 11% and M. parvicella, Type 0041 and Type
0092 became dominant also. In anoxic zone of basin 2, N.
limicola III was the most dominant specie, but in oxic zone,
Type 0092 and Type 021N became dominant also.
Recently antifoaming agents have been produced and utilized
at aeration basins as temporary solution to foaming problems.
This study was performed hot season, when excessive amount
of Nocardia had been expected.
TABLE II
DOMINANT FILAMENTOUS SPECIES AND PERCENTAGE DISTRIBUTION
T1-Z anox
T2-Z anox
7%
8%
7%
Nocardia*+
9%
N. limicola III
M. parvicella
M. parvicella N. limicola III
Type 0092
Type 0092
Type 021N*+
Type 0581*
+
Type 0675*
T1-Z ox
T2-Z ox
7%
6%
7%
M. parvicella
M. parvicella
11%
Type 0092
N. limicola III Type 0041
Type 0803*
N. limicola III
Type 0092
N. limicola II*
Type 021N*
Type 0041
*Difference between T1 and T2 basins (antifoaming agent added or not)
+
Difference between Anoxic and Oxic zone
As seen in Table 2, as the most abundant filament type, N.
limicola III was observed at all zones. This indicated that the
utilized antifoaming agent was either only destroy Nocardia
or can destroy the foam physically without any adverse effect
to the other filamentous microorganisms. The number and
types of filamentous species differ slightly in anoxic and oxic
zones. In antifoaming agent added basin (T1) the number of
filamentous species was higher, whereas, number of observed
types was lesser in the oxic zone of T2.
IV. CONCLUSION
N. Limicola II, III, Types, 021N, 0092, 0041/0675, 0581,
0803, M. Parvicella and Nocardia dominated in Konya
WWTP in hot season. Operational conditions and
biodegradable influent characteristics had higher influence.
Specific control measures, i.e. creating environmental
conditions in the plant to inhibit or suppress the growth of the
filamentous organisms are suggested in this study. Due to the
variety of types of species, non-specific measures (e.g. the use
of chemicals which selectively control the excessive growth)
are not suggested. Presence of more than one condition,
forming bulking and foaming in Konya WWTP, resulted in
lower percentage distribution of different filamentous
bacteria. To resolve present problems in this plant, it is
suggested that controlling of the industrial wastewater
discharge, F/M rate and regulation of sludge age, setting
desired value of dissolved oxygen and removal of nutrient
deficiency.
Fig. 2 Observed filamentous species percentage relative to each
other in Konya WWTP modified Bardenpho unit during 2012 hot
season.
Species and percentage distribution of dominant
filamentous species observed in each zone, were compared in
Table 2. When T1 (antifoaming agent was added) and T2,
(antifoaming agent was not added) were compared in terms of
distribution of dominant filamentous bacteria, it was observed
that different species were dominant. For example, in anoxic
zone of basin, while Type 0092 and N. limicola III were more
dominant, whereas, in anoxic zone of basin 2, N. limicola III
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2nd International Conference on Chemical, Environmental and Biological Sciences (ICCEBS'2013) March 17-18, 2013 Dubai (UAE)
ACKNOWLEDGMENT
This study was technically supported by Konya Metro po
litan Municipality, Konya Water and Sewerage Ad mini strati
on (KOSKI).
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