Membrane Bioreactors
CONTINUED
FROM
P R E V I O U S PA G E
while the main constituents of
mixed liquor suspended solids
(MLSS) remain outside the
membrane and are wasted to
another treatment plant for
processing.The reuse water
drawn through the membrane
walls is then further disinfected
to ensure that it meets Class
A+ requirements.
By installing membranes,
wastewater plants can handle a
much higher concentration of
MLSS, since the systems require
no secondary clarifiers or filters.
Normal mixed liquor at a conventional activated sludge plant,
depending on the facilities,
is 2,000 to 4,000 milligrams
per liter (mg/l). An MBR plant,
however, can handle concentrations as high as 10,000 or even
15,000 mg/l. As a result, MBRs
can reduce a facility’s required
tankage size by about 40 percent.
This space efficiency is
making it possible to double
Randolph Park’s capacity on its
existing footprint.The plant was
previously equipped with a primary clarifier, two secondary
clarifiers and two aeration
basins.“We are reusing every
cubic inch of the existing
Membrane Bioreactor Flow Diagram for the Treatment Process
Anoxic
Zone
From
Headworks
and Sewer
Aeration
Zone
Membrane
Cassettes
Reclaimed
Water
Waste Sludge
to Collection
System
Air
Return Liquid
Return Sludge
basins,” explains Melodee Loyer,
supervising engineer and lead
engineer on the project.“Since
we don’t need the existing clarifiers, we’ll add a third aeration
basin of the same size and turn
the existing clarifiers into anoxic zones.”
The right system
at the right price
Because there is only one qualified MBR manufacturer in the
United States, Brown and
Caldwell and the client
(PCWWM) traveled to the
United Kingdom to visit wastewater treatment plants designed
by another manufacturer. They
opted to compare two membrane manufacturers, Zenon and
Kubota, that are qualified in the
United States and around the
world.“This is the first U.S.
project to involve competitive
bidding from the two leading
ach day, on a newly opened
stretch of freeway, thousands
of Phoenix-area commuters
drive past approximately 200
acres of industrial brownfields
located in the heart of Tempe,
Ariz. A developer is currently
working with the City of Tempe
to transform this barren landscape of auto salvage yards,
landfills and industrial operations
into an attractive area of commercial businesses, multi-tenant
housing and hotels.
To facilitate the planning
and redevelopment process,
Brown and Caldwell has created
a multifunctional, interactive
database that includes detailed
environmental data and infrastructure information for every
land parcel in the site. Linked to
a high-resolution aerial photograph of the redevelopment
E
16
SPRING 2002
To Disinfection
Before Reuse
vendors,” Loyer adds.“MBR is
a hot technology in the industry
and will be the future of water
reclamation in areas with
stringent water quality requirements and land scarcity, as
well as in plant expansion
projects that seek to minimize
capital expenditures.”
area, it makes the data easily
accessible to potential buyers
and investors, the public and
environmental regulators.
“It’s a pretty slick tool,” says
database developer Mike Simms
of Brown and Caldwell’s Phoenix
office. Users can navigate through
the high-resolution aerial photo
of the brownfields area and
zoom in to examine details.
Clicking on a particular parcel
displays specific environmental
and infrastructure data for that
site, as well as additional photographic views.
“The project is still in
the early stages,” adds Project
Manager Kevin Hebert,“but
this database will speed efforts
by the developer to turn this
site into a visually pleasing,
productive tax base for the
City of Tempe.”