Chemical Engineering September 2015 - 61

Table 4. advanTages and disadvanTages of The biological aeraTed filTer
(baf)
BAF Advantages
1. Applicable to limited spaces
2. Lower power consumption
3. Handles temperature variations
4. Very small footprint
BAF Disadvantages
1. Requires clarification, disk filtration and/or multimedia
filtration
2. Does not handle influent variability
3. Ultrafiltration needed for demineralization system
4. Backwash needs to be dewatered or thickened
further
isting baF. makeup for the demineralized
water-treatment system is
secondary-treated municipal wastewater.
this water undergoes further
processing at the industrial plant
(in this example, a power plant), including
biological treatment primarily
to remove ammonia and disk filtration
to remove suspended solids.
however, the cartridge filters for the
reverse osmosis and electrodeionization
(Ro/edi) system were severely
fouled because of submicron
particles (<1 µm) passing through
the disk filter. an ultrafilter was proposed
to be installed to protect the
Ro/edi system.
there are two ways to handle the
sludge generated from the treatment
process: (1) discharging the
thickened sludge to the Potw,
and (2) landfilling the thickened and
filter-pressed sludge. in the current
case, a parallel-plate gravity-settler
unit was designed to precipitate
suspended solids from equalized
filter backwash wastewater and the
plate settler sludge was pumped
back to the Potw. an additional
thickener and filter press were proposed
to process the plate settler
sludge. the produced cake from
the dewatering system can be
landfilled at a nearby facility.
the proposed dewatering system
utilizes a solids gravity thickener followed
by a sludge conditioning tank
and a filter press. the solids thickener
will process residuals continuously,
while the sludge conditioning
tank and filter will operate on a batch
basis (as needed).
■
Edited by Dorothy Lozowski
Acknowledgments
the authors thank mike mcmenus,
brian clarke, and brad buecker of
Kiewit engineering and design co.
for providing valuable comments to
this article.
References
1. Morton, Robert and others, Advanced Water Treatment
of Non-nitrified Secondary Effluent with Tertiary
Membrane Bioreactor and Reverse Osmosis Processes,
WEFTEC 2013 Conference Proceedings,
86th Annual Water Environment Federation Technical
Exhibition and Conference, Chicago, October 5 to 9,
2013. http://weftec2013.conferencespot.org/55109wefb-1.1182180/
t -022-1.1185426/5221.1185475/a-485-1.1185494
2.
Bartels, Craig and others, Operational Performance and
Optimization of RO Wastewater Treatment Plants, Hydranautics,
Technical Papers. http://www.membranes.
com/index.php?pagename=tech_papers
3. Morton, Robert, and others, Pilot Study of Advanced
Treatment Processes to Recycle JWPCP Secondary
Effluent, Proceedings of the Water Environment Federation,
WEFTEC2011: Session 41 through Session 50,
pp. 2979-2994(16). http://www.ingentaconnect.com/
content/wef/wefproc/2011/00002011/00000014/
art00046?crawler=true
4. U.S. Environmental Protection Agency (EPA), " Water:
Effluent Guidelines, " http://water.epa.gov/scitech/
wastetech/guide/
5. UN Water website, The United Nations Inter-Agency
Mechanism on all Freshwater Related issues, Including
Sanitation, http://www.unwater.org/statistics/en/
Authors
Behrang (Ben) Pakzadeh is a licensed
P.E. (California), and a senior
process engineer with Kiewit
Engineering & Design Co. (9401
Renner Blvd., Lenexa, KS 66219;
Email: behrang.pakszadeh@kiewit.
com; Phone: 916-689-4016). He
has over 10 years of experience in
power, upstream oil-and-gas, and
municipal water and wastewater
industries. Pakzadeh serves on the Water Environment
Federation (WEF) Industrial Wastewater Committee. He
has contributed over 20 presentations and technical
articles for various conferences and journals. He has a
Ph.D. in civil and environmental engineering from the
University of Nevada - Las Vegas, an M.S. in environmental
engineering from the Technical University of
Denmark, and a B.S.C.E. from Sharif University of Technology
(Iran).
Raymond Eric Zbacnik is a senior
process engineer with Kiewit
Engineering & Design Co. (Address
same as above; Email: raymond.
zbacnik@kiewit.com, Phone: 913689-4213).
Zbacnik has about 40
years of chemical process engineering
experience, which includes
13 years with Babcock & Wilcox, 6
years with HDR: Cummins & Barnard
and 11 years with Foster Wheeler. Zbacnik holds a
B.S.Ch.E. from Purdue University, and an M.E.Ch.E. from
Manhattan College. He is a member of the AIChE,
IChemE, ACS and AWMA.
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