International Biodeterioration 25 (1989) 87-95
The Application of Bioaugmentation to Waste Water
Treatment
N. C. A. Stevens
International Biochemicals Ltd, Galvin Road, Slough, Berkshire SL1 4DL, UK
ABSTRACT
The application of bioaugmentation is discussed. Biomass population
selection pressures are examined and reactionary measures which can be
taken to resolve effluent treatment problems are discussed. Two new case
histories on the use of bioaugmentation are presented.
INTRODUCTION
The successful operation of a biological waste water treatment plant is
dependent upon the biomass. This includes bacteria, fungi, protozoa,
rotifera, nemotoda and some higher forms (e.g. arthropods). Generally,
the basic trophic level is occupied by the bacteria (Hawkes, 1963; Pike &
Curds, 1971).
The genera of bacteria present are the function of the natural
population. Those able to survive in the environmental conditions will
persist in the system. The biomass selection pressures which exist in a
waste water treatment plant fall into three main categories:
(1) Those dictated by the nature of the influent
(2) Those resulting from the mode of operation of the treatment system
(3) Those which are determined by the design of the treatment system
For example, a toxic component could suppress the growth of certain
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International Biodeterioration 0265-3036/89/$03.50© 1989 Elsevier Science Publishers
Ltd, England. Printed in Great Britain.
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N. C. A. Stevens
species, or the lack of an adequate nitrogen source could favour the
growth of filamentous rather than fioc-forming organisms.
Alternatively, if an activated sludge plant is operated in the mode of
increased sludge wastage, there would be a selective pressure for faster
growing bacteria. As a result, ammonia removal may suffer as the slower
growing nitrifying bacteria are lost from the system.
Finally, the design of a treatment system can have an important
selective pressure for example much greater diversity of genera within
the biomass of a trickling filter compared to that of an activated sludge
system. Furthermore, changes to system design will affect operational
conditions and hence also have specific selective pressures (Daigger et
al., 1985; Jones & Franklyn, 1985).
However, despite the inherent ability of the bacteria within a waste
water treatment plant to adjust their composition under selective
pressures, many treatment plants cannot respond rapidly enough to
prevent them failing to produce the required standard of effluent. These
failures may be manifested as poor COD/BOD removal, turbidity in the
final effluent, poor sludge settlement, foaming, odour problems, loss of
nitrification or other effects. In such cases, there are four possible
measures which can be taken:
(1)
Modify influent characteristics (e.g. pH, nutrient addition, physical/
mechanical removal of solids, etc.).
(2) Modify mode of operation (e.g. alter sludge return or wastage rates,
alter aeration, change beds on alternating double filtration system).
(3) Change plant design (e.g. reorganise treatment units, build extra
capacity).
(4) Introduce new components to the biomass community (e.g. sludge
from another works, bioaugmentation).
The most common approach would involve either (1) and/or (2) and in
some cases this solves the problem, even if only temporarily. These
approaches involve increased operating costs, which could be excessive
in some cases. Option (3) would be reserved for problems such as
massive urban development, or factory expansion.
Option (4) is, in many cases, disregarded because of the lack of
understanding of waste water treatment biology. Although it is not
suitable in all cases, it has been possible to demonstrate significant
improvements in treatment plants which have utilised bioaugmentation
techniques (Thibault & Tracey, 1979; Chambers, 1981; Saunders, 1985,
1986). Bioaugmentation can often provide a cost advantage over the
other reactionary measures considered.
Bioaugmentation in waste water treatment
89
APPLICATIONS OF BIOAUGMENTATION
The development of selected and adapted bacteria, by high technology
techniques provides single species cultures which can degrade specific
target substrates. The cultures are harvested and preserved by freezedrying. The process utilises complex cryogenic protectants to ensure the
bacterial cell will remain intact ready for rehydration. These strains are
then blended to create mixed culture inocula.
The use of these cultures can provide benefits by:
(1) Providing an abnormally high growth rate.
(2) Giving an increased tolerance to toxic materials.
(3) Increasing the spectrum of bacteria available for natural selection.
(4) Increasing the concentration of desirable bacteria and thus reducing
their response time (lag phase) to specific substrates.
These traits can provide real benefits in aerobic waste water treatment
plants in the following areas:
(1) Plant start-up.
(2) Organic and hydraulic overloading.
(3) Toxic shock/problematic waste water.
(4) Poor sludge settlement.
DISCUSSION AND CASE HISTORIES
Plant start-up
The conventional means for biological commissioning of a new
effluent treatment plant is by means of tankering sludge from another
plant. This can have drawbacks since the influent characteristics may
differ from those of the 'parent' plant, producing a long acclamation
phase. Also, problems (i.e. poor sludge settlement characteristics) may be
inherited from the 'parent' plant and transport costs can be high,
particularly where large quantities and long distances are involved.
Alternatively, a new plant's biomass may be allowed to evolve
naturally without sludge addition by lengthy step feeding, but this
process can take months before the required treatment performance
parameters are met. It is not usually considered as a viable alternative.
The third approach is to consider the use of adapted and selected
bacteria to speed up the commissioning process by providing a high
performance biomass,
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N. C A. Stevens
This latter approach was that chosen by the South West Water
Authority (SWWA) for their Ipplepen Sewage Treatment Works (STW)
in South Devon. The effluent plant is a two rotor oxidation ditch system
with a volume of 835 m 3, designed for a m a x i m u m flow of 4300 m3/day
and a dry weather flow of 665 ma/day. The influent has a BOD of
191 mg/litre and TSS of 168 mg/litre with final effluent standards
required of 10 mg/litre BOD, 15 mg/litre TSS, and 5 mg/litre ammoniacal
nitrogen. The following was the seeding programme.
Days 1 and 2
Using mains water, the final settlement tanks and the oxidation basin
were filled to a depth of 1-8 m, a volume of 590 m 3. Over the following
14 h, the ditch was topped up with feed sewage to the lowest rotor setting,
producing a BOD load of 47 kg. Rotors and recycle pumps were operated
to bring dissolved oxygen levels to a m i n i m u m of 2 mg/litre and, at the
same time, the ditch was filled to a m a x i m u m level of 2.5 m. 15 kg of
commercially available, freeze-dried bacterial cultures were rehydrated
and added to the ditch.
Day 3
Without further changes, 7 kg of bacterial cultures were rehydrated and
added.
Day 4
Feed sewage (9 m3/h) was allowed to enter the ditch and 5 kg of bacterial
cultures rehydrated and added.
Day 5
A further 5 kg of bacterial cultures were rehydrated and added.
Day 6
The full flow of sewage was discharged to the oxidation ditch. Bacterial
cultures (5 kg) were rehydrated and added.
Days 7-9
Bacterial cultures (1 kg) were rehydrated and added per day.
Figure 1 shows the system achieved the required BOD of l0 mg/litre
w h e n the MLSS value reached 1000 on day 26. This was a satisfactory
buildup of the biomass, even though it was slower than normal because
of a period of wet weather and correspondingly low level of substrate.
However, the period involved would have been very m u c h longer had the
natural processes been allowed to follow their course.
Bioaugmentation in waste water treatment
91
Note :
The s y s t e m achieved
BOD and SS at
1 0 0 0 * M L S S arid
BOD. SS. NH3 over
2700 mg/I MLSS
- 3O
0
U3
~3
5 2ooc
20
•
g
.E
x
o
10
1000
Effluent
BOD
S
I
10
I
20
I
30
I
40
0
50
6O
Days
Fig. 1. S t a r t - u p o f l p p l e p e n S T W o x i d a t i o n
ditch.
Organic and hydraulic overloading
Overloading of treatment plants occurs across all industry sectors, but is
most c o m m o n in the food industry, where seasonal production and
consumer demand can exacerbate the situation. Bioaugmentation to
rectify a catastrophic plant failure and ensure that discharge limits could
be met even during continued overloading are discussed. This was the
situation at the Express Foods Group plant at Ruyton - - XI towns, near
Shrewsbury.
The extra extended aeration lagoon was originally designed to treat
350 m3/day ofinfluent carrying a total organic load of 1045 kg BOD/day.
The final effluent standard was 25 mg/litre B O D and 45 mg/litre TSS.
However, following the installation and commissioning of a new cheese
92
N. C. A. Stevens
processing line a n u m b e r of severe difficulties were experienced which
led to a massive increase in the hydraulic a n d organic levels of waste
materials received at the waste water treatment plant. Hydraulic volumes
increased from 350 m3/day to in excess of 500 m3/day whilst the organic
loadings rose from 1045 kg B O D / d a y to as high as 3000 kg BOD/day.
Sludge p r o d u c t i o n was initially high but problems arose with the
d e v e l o p m e n t a n d eventual p r e d o m i n a n c e of a filamentous biomass.
Dissolved oxygen levels fell to less than 1 mg/litre a n d the sludge volume
index rose to 225 ml/g. Final effluent BOD values of > 500 mg/litre were
typical. In an effort to reduce the loading on the treatment plant, a hired
tanker was brought in to remove a portion of the waste waters for
alternative disposal on to agricultural land. This h a d little impact on the
total effluent loading, and a remedial p r o g r a m m e utilising bioa u g m e n t a t i o n techniques was introduced. The objective was to establish
rapidly an active biomass which would be capable of responding to the
excessively high organic loadings a n d the reduced residence time of the
polluted waste waters within the treatment system. Additionally, such a
biomass would be required to have superior settlement characteristics,
that would enable adequate removal of s u s p e n d e d solids in the quiescent
zone of the treatment plant, prior to discharge into the river. This
requirement was more acute because of the reduced residence time in the
settlement zone caused by the 40-50% hydraulic overloading. Furthermore, because of the high cost incurred in the hiring of the tanker for the
removal of a portion of the effluent, it was important to achieve an
increase in plant efficiency as quickly as possible.
The b i o a u g m e n t a t i o n p r o g r a m m e was based on a 14-day initial
inoculum, followed by a weekly m a i n t e n a n c e dose spread over 5 days.
However, prior to the introduction of the bacteria into the aeration
lagoon it was necessary to reduce the MLSS. The objective was to provide
some residual dissolved oxygen level, a n d to remove a percentage of the
highly filamentous biomass p r e d o m i n a t i n g within the lagoon.
The p r o g r a m m e c o m m e n c e d on 21 January with the removal of
sludge, bacterial cultures were a d d e d on 11 February, at which time the
residual dissolved oxygen level was 1.5 mg/litre a n d the MLSS was
2500 mg/litre. The dosing p r o g r a m m e was as follows:
Day 1
58 kg rehydrated microbial culture
Days 2-14 12 kg rehydrated microbial culture
Thereafter 12 kg per week spread over 5 days.
The microbial cultures were successful in bringing the performance of
this plant to a satisfactory level. F r o m the start of the p r o g r a m m e the
effluent B O D levels fell from 780 to 30 mg/litre within 25 days (see Fig. 2).
93
Bioaugmentation in waste water treatment
Commencement of programme
Point of application of biolyte system
- -
- -
Consent
discharge
80D
standard
Plant design loading (1045 kg/d)
Influent 80D kg/d
E f f l u e n t BOD mg/I
32001
3 000
2800
'1200
11100
2200
1000
c~ 2 0 0 0
0
m
1800
90O
Q)
_~ 1 6 0 0
_c
1400
800
700
1200
0
600 m
1000
o
500 2
800
400 w
600
300
400
200
200
100
5
10
15
20
25
30
35
Time
40
45
50
55
60
65
70
75
(days)
Fig. 2. Influent and effluent BOD 5 levels prior to and after commencement of BIOLYTE
SYSTEMS programme.
The influent BOD levels were variable but were on average 82%
(excluding three points) above the designed value. Hydraulic volumes
also maintained their excess level of 40-50% > design. The results may
be summarised as follows:
(1) Despite organic overloading of 180% of plant capacity, within 10
days of the introduction of the microbial cultures, removal
efficiency had improved from 80.6% at the commencement of the
programme to 98.1%.
94
(2)
(3)
N. C. A. Stevens
The sludge settlement characteristics improved, from SVIs of 276 to
76, within 7 days of introducing microbial cultures.
There was no need to transport a portion of the waste waters for
alternative disposal on the land and problems associated with
odour were overcome.
CONCLUSION
The two examples show that the application of bioaugmentation
techniques can e n h a n c e the efficacy of the natural biomass and give
measurable, cost-effective improvements in performance. The success of
the programme lies in correct problem definition and the selection of
bacteria to assimilate a given effluent stream. The cultures introduced in
this way must be able to actively compete for the available food and to
respond rapidly to a favourable growth environment - - adaptation and
selection techniques can ensure that the bacteria have this advantage.
The uses of bioaugmentation will obviously not replace the need for
sound engineering and process design, or for proper plant management,
but should provide another cost-effective option worth considering when
effluent problems occur.
ACKNOWLEDGEMENTS
I should like to thank the SWWA, and Express Foods Group for
permission to publish the data in the case histories.
REFERENCES
Chambers, J. V. (1981). Improving waste removal performance reliability of a
waste treatment system through bioaugmentation. Proceedings of 36th
Industrial Waste Conference, Purdue University, Indiana, USA.
Daigger, G. T. et al. (1985). The design of a selector to control low F/M
filamentous bulking. Journal WPCF,, 57 (3).
Hawkes, H. A. (1963). The Ecology of Waste Water Treatment. Pergamon Press,
Oxford.
Jones, G. A. & Franklyn, B. C. (1985). The prevention of filamentous bulking of
activated sludge by operation means at Halgon sewage treatment works.
Water Pollution Control, 84 (3).
Pike, E. B. & Curds, C. R. (1971). MicrobialAspects of Pollution, Soc. Appl. Bact.
Syrup. Academic Press, New York.
Bioaugmentation in waste water treatment
95
Saunders, F. J. (1985). Biotechnology and waste treatment. European Water and
Sewage, October 1985.
Saunders, F. J. (1986). A new approach to the development and control of
nitrification. Water and Waste Treatment Journal.
Thibault, G. T. & Tracey, K, D. (1979). Demonstration of a mutant bacterial
additive for enhancement of operation stability in oxygen activated sludge.
Proceedings of 34th Industrial Waste Conference, Purdue University, Indiana,
USA.