Kansas
River and violations of the plant’s NPDES permit.
In the second, primary basin effluent from the excess-flow
storage basin was pumped and treated by the ballasted
flocculation basins. Each basin was operated for
6 hours at a 23,000-m3/d (6-mgd) flow rate, and
microsand pumps were operated during the entire
period. Ferric chloride, polymer, and microsand
were used in the ballasted flocculation basins (polymer
and ferric chloride were dosed at 2 mg/L and 100
mg/L, respectively). The flow was disinfected with
sodium hypochlorite and dechlorinated with sodium
bisulfite in the excess-flow chlorine contact basin.
The flow was then blended with treatment plant effluent
and discharged to the Kansas River. Both testing
phases evaluated the following items:
..• influent flow
rates for each ballasted flocculation system;
..• operating
sequences, normal startup and shutdown,
and emergency stopping;
..• operation
of each component of the ballasted flocculation
system;
..• operation
of each treatment train;
..• microsand
and solids recirculation pump flow;
..• hydrocyclone
underflow rate; and
..• ferric chloride
and polymer feed rates.
After satisfactory completion of mechanical startup
testing, field optimization and process performance
test-
ing were conducted. Each train was tested during
a 6-hour period for 2 consecutive days. During testing,
which was similar to the latter part of mechanical
checkout, primary basin effluent was stored in the
excess-flow storage basin.
The
project team provided temporary pumping at a 76,000-m3/d
(20-mgd) flow rate, and flow was discharged at the
excess-flow splitter—screening facility. After
fine screening, primary basin effluent flowed by
gravity to the ballasted flocculation basin for
treatment (polymer and ferric chloride were dosed
at 1.5 mg/L and 100 mg/L, respectively).
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After
treatment, flow was disinfected with sodium hypochlorite
and dechlorinated with sodium bisulfite. The flow
was then blended with the normal plant effluent
and discharged to the Kansas River. During the process
performance test, wastewater flow was maintained
at 3800 m3/d (1 mgd) to each process treatment train
to maintain normal operations. In addition, the
following items were recorded:
• microsand and solids recirculation pump flow;
• hydrocyclone underflow rate; and
• ferric chloride and polymer feed rates.
Grab samples of influent and effluent flow to
the ballasted flocculation system were collected
every hour and analyzed for
• total suspended solids;
• BOD, soluble BOD, and carbonaceous BOD;
• chemical oxygen demand and soluble chemical
oxygen demand;
• fecal coliform count;
• turbidity;
• water temperature;
• water pH; and
• iron.
A
Problem with Foam
During mechanical startup testing, the project team
noted that white foam developed where the flow discharged
into the ballasted flocculation basin’s effluent
weir troughs and into a common effluent flume before
discharging to the excess-flow chlorine contact
basin.
At the troughs, the flow falls about 4.3 m (14 ft).
Foam was also noticed at the discharge of the excess-flow
chlorine contact basin effluent box, where flow
falls about 3 m (10 ft). During the first day of
optimization and process performance testing, white
foam appeared at these two locations after the first
hour of operation. Foam also appeared at the plant’s
dechlorination structure, where the excess flow
facilities’ flow blended with the plant’s
effluent flow. Here, the excess flow falls about
3 m (10 ft) before being blended with plant effluent.
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