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City
of Hayward – Disinfection
Facilities
The City of Hayward selected WBA to replace its disinfection systems
with sodium hypochlorite. Both the effluent disinfection system
and the plant wash water facilities required conversion. The
plant’s average flow was about 9 MGD and peak hydraulic
capacity was about 40 MGD. The City originally had hoped to use
the existing chlorine storage building slab for the hypochlorite
facilities and build a new building. WBA evaluated the foundation
conditions and determined that the bay mud underlying the slab
would be subject to liquifaction during an earthquake. Based
on our recommendations, the City authorized the design of a new
building. WBA provided the plans and specifications for installation
of the sodium hypochlorite equipment. WBA provided construction
period office engineering and assistance to the City in their
application to the Federal Emergency Management Agency to fund
half the project costs.
WCWD – Disinfection
Facilities
The West County Wastewater District (WCWD) retained WBA to rehabilitate
its effluent disinfection system by converting from gaseous chlorine
to sodium hypochlorite. The plant’s average flow was about
12 MGD and peak hydraulic capacity was about 33 MGD due to its
ability to store excess flows in flow equalization basins. Shortly
after initiating the design, the District experienced a severe
wet weather event necessitating diversion of treated effluent
through an abandoned outfall. Since the outfall had been abandoned,
the District had no regular means of dechlorinating the effluent
prior to discharge. For the duration of the winter, they used
a rented bisulfite system. As a result of that experience, they
amended the WBA design contract to include installation of a
bisulfite feed system. We were able to use space in an existing
chemical building by replacing an abandoned caustic tank with
a new bisulfite storage tank. WBA completed contract documents
to complete all these tasks.
Oro
Loma Sanitary District – Disinfection
Facilities
The Oro Loma Sanitary District decided to rehabilitate its
effluent disinfection system by converting from gaseous chlorine
to sodium
hypochlorite. The plant’s average flow was about 12 MGD and
peak hydraulic capacity was about 100 MGD. The District had decided
to expedite the project by using in-house staff to design the base
slab and elected to pre-purchase the bulk storage tanks and the
chemical feed pumps. The District retained WBA to do the process
design, review the structural design and modify it to accommodate
pipe chases for the piping. WBA provided the pre-purchase specifications
and the plans and specifications for installation of the sodium
hypochlorite equipment. The process design was complicated by the
fact that some of the effluent was used for golf course irrigation.
The plant had a separate contact tank for the irrigation water
that needed additional chlorination and WBA’s design allowed
the District to disinfect the irrigation water with the same feed
pumps as was used for the other effluent.
USD – Odor
Scrubber Upgrade
The Union Sanitary District (USD) retained WBA to develop design
documents to modify its 17 chlorine mist type scrubbers to use
liquid-only spray nozzles in place of the existing liquid and
air spray nozzles. By eliminating the use of compressed air,
the District
avoided the capital cost of replacing its existing maintenance
intensive compressors, and will realize significant savings by
not operating the four 200 hp compressors.
The design consists of developing a distribution system to deliver
the concentrated sodium hypochlorite to all scrubbers, new control
panels to control the addition of concentrated sodium hypochlorite
to each scrubber, and modification to the scrubber nozzles and
feed piping to deliver the sodium hypochlorite solution to the
scrubber ducting.
The above projects are representative of our experience in this area.
If you
would like additional information on these, or other projects that
we
have completed, please contact us.
For detailed descriptions
of representative projects in our other areas of expertise,
click below on the category you are interested in:
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