Chemical Engineering October 2013 - 43

STEP 1.
Obtain
STEP 2.
wastewater
characteristics
and other plant
information
Evaluate and
summarize the
information
obtained
STEP 3.
Is the
wastewater
biodegradable?
STEP 4.
YES
Evaluate an
appropriate
biological
treatment
approach
NO
FIGURE 17.
Understanding
wastewater characteristics
is crucial
to selecting the
proper biological
treatment process
Consider
non-biological
treatment
methods
NO Can pretreatment
increase the
biodegradability
of wastewater?
YES
Add pretreatment
to make the
wastewater
biodegradable
and continue on
process selection
clear. This process was deemed an appropriate
potential approach for the
wastewater.
Further studies showed that when
the sludge from the fungal MBBR
reactors was removed before the
bacterial MBBR treatment, the system
exhibited more effective COD
and toxicity elimination. Therefore,
a clarifier was added in front of the
two-stage bacteria MBBR reactors
to remove the excess sludge from the
previous fungal MBBR reactors.
Step 5: Determine the most
appropriate treatment process
Based on the laboratory test results,
both Option 4 and Option 9 showed
similar COD removal results (90-95%).
Option 9 resulted in far better toxicity
removal, which could be the result
of the longer HRT in the MBBR process.
Option 8 showed that adding two
MBBR reactors did not improve COD or
toxicity removal for the effluent of Option
4. It was thought that the fungal
MBBR reactors of Option 9 improved
the toxicity removal. According to these
results, Option 9 was chosen as the
most appropriate biological wastewater-treatment
process for this specific
wastewater. Pilot tests conducted later
confirmed the laboratory test results.
In the full-scale installation, activated
carbon was also introduced after the
biological treatment steps to remove
any remaining toxicity in the effluent
from Option 9.
A complex, yet simple solution
This case study illustrates the capability
of an MBBR system to utilize
microbial populations that can target
specific constituents in complex
wastewater. This capability is a distinct
advantage over other biological
processes. However, most industrial
wastewater is not as complex as the
example given here, and the steps to
finding the best process for any particular
application are as basic as following
the steps in Figure 17.
That said, the methods of ensuring
that a full-scale MBBR system is designed
to operate optimally are properly
evaluating the wastewater biodegradability
and correctly developing
the design parameters of the system,
such as the appropriate process, loading
rates and air supply. The simplicity
of the operation of an optimized
system leads observers to believe that
filling an aerated tank with plastic
media would suffice, but as the AstraZeneca
example demonstrates, expertise
is gained only by experience.
Concluding remarks
As noted above, cost is almost always
a concern when developing or expanding
an industrial wastewater-treatment
process. In that regard, MBBR
has several advantages, as follows:
1. Because of the high surface area of the
media, the MBBR process has a very
small footprint as compared to an activated
sludge system of similar treatment
capacity. The smaller footprint
can result in lower installation costs
and can provide the solution for plants
with space constraints.
2. The treatment capacity of MBBR
plants can be expanded by simply
adding more media to the existing reactors
to enable them to treat higher
hydraulic and loading rates when
manufacturing facilities increase production.
3.
The process is flexible in its ability to
accept variations of flow and loading.
4. A sludge recycle system is not needed
in an MBBR process, thus simplfying
operations.
5. Without the need for recycling sludge,
the MBBR system has more options
for solid/liquid separation.
Instead
of a conventional clarifier, an MBBR
system typically uses small-footprint
solid/liquid separation technologies,
such as dissolved air flotation, discfilters
or sand-ballasted clarification,
reducing the overall system footprint
by about 60%.
6. MBBR technology is available in a variety
of configurations and materials
of construction.
7. As in this case study, specific microbial
populations can be developed to
address difficult-to-treat wastewater,
if required.
■
Edited by Mary Page Bailey
References
1. Ghorpade, A., others; Novel Treatment for
Challenging Pharmaceutical Waste,
Proceedings
of Microconstituents and Industrial
Water Quality Conference, Water Environment
Federation, Baltimore, Md, 2009.
Acknowledgements
The author would like to acknowledge Brandy
Nussbaum and Michael Johns of AnoxKaldnes,
as well as Nathen Myers and Carla Robinson of
Veolia Water Solutions & Technologies for their
contribution to this work.
Author
Li An is a senior application
engineer at
Water Solutions &
Veolia
Technologies
(250 Airside Drive,
Moon Township, Pa. 15108;
Phone: 412-809-6673; Email:
li.an@veoliawater.com; Website:
www.veoliawaterstna.
com;).
She has extensive experience
with multi-discipline
projects that include biological,
physical and chemical
processes, with particular expertise in Veolia's
AnoxKaldnes Moving Bed Biofilm Reactors. An
was educated at Tongji University in China, where
she earned a B.S. in Water Supply and Sewerage
Engineering, and M.S. and Ph.D. degrees in Environmental
Engineering. Prior to joining Veolia,
she taught at Tongji University and worked for
consulting firms in both the U.S. and China.
CHEMICAL ENGINEERING WWW.CHE.COM OCTOBER 2013 43
STEP 5.
Select the
optimal
biological
treatment
approach
http://www.veoliawaterstna http://WWW.CHE.COM
Chemical Engineering October 2013

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