Chemical Engineering September 2020 - 43

Table 4. ulTraFilTraTioN sysTem DesigN
Number of membrane trains
Number of cassettes per train
Number of cassette spaces per train
Number of modules per train
Total number of installed cassettes
Total number of installed modules
Spare space
MLSS design
Dimensions per each membrane tank (W x L x H)
Average operating volume per each membrane tank
Total membrane tank operating volume
Table 5. eFFlueNT QualiTy
Parameter
Biochemical oxygen demand (cBOD5) (mg/L)
Chemical oxygen demand (mg/L)
2
4
4
168
8
336
12.5%
10,000 mg/L
10 ft x 28.8 ft x 12 ft
19,400 gal
38,800 gal
Values
Daily Average
≤ 27
≤ 190
food-to-mass ratio (F/m) of 0.2.
the two uF membrane trains contain
four cassettes per train, which
are installed in 316 l stainless-steel
membrane tanks. membrane filtration
is designed to treat average and
peak flows, including when one train
is off-line (n-1 condition). the mlss
concentration within the membrane
tank is 10,000 mg/l, as indicated in
table 4.
the mBr permeate quality parameters
for cod and Bod, expressed
in daily average and peak flows, are
shown in table 5.
the waste activated sludge (was)
from the mBr package is sent to
a bio-sludge treatment unit for settling
and dewatering. Further settling
is achieved by a thickener, wherein
polymer is added to create large settled
solids. this sludge is scraped off
the bottom of the tank and pumped
to a holding tank where an aeration
grid prevents the solids from settling
and becoming septic. From there,
sludge is pumped to a continuous
belt press for dewatering and hauled
offsite for disposal.
Plant startup and commissioning
once startup and commissioning of
the wastewater treatment plant commenced
in october 2018, stable operation
was achieved around two months
into the project. the initial " mechanical
checkout " and hydraulic guarantees
of the systems and equipment were
Daily Peak
≤ 75
≤ 520
performed for
each unit. internal
inspections of the
dnF units included
the following steps:
* Checking the
vessels and the
pressurization
tanks
* Verifying that
the sprayer headers
and nozzles
were correctly
installed
* Examining the
bottom-sludge
and floatingsludge
scrapers,
as well as the
weirs for each
train
after the coagulation and flocculation
mixers were inspected,
water was fed from the equalization
tanks through dnF train a
to test the nitrogen pressurization
tank and controls. the system is
now running at 80 psi with a 150gal/min
recycle rate (25% recycle
at a 600-gal/min flow design).
Jar tests were performed to test
and optimize the chemicals needed
for coagulation and flocculation
in the de-oiling process. subsequently,
train a went into service
and the effluent tank control was
changed to level control based on
the flow coming from each dnF
train, as well as the combined flowmeter
from the dnF effluent pumps.
during the acclimation period,
the mBr system was operated
without permeation and the mBr
aeration blowers were operated
continuously in manual mode.
the return activated-sludge (ras)
pumps were run continuously in
manual mode while dosing with
urea
and
phosphoric
acid,
as
necessary. the cod loading was
maintained using ethanol. samples
were taken daily to monitor
cod loading, urea and phosphoric
demand, as well as mlss and
mixed-liquor
volatile
suspended
solids (mlvss) concentrations.
once the minimum mlss levels
were reached, wasting was initiChemiCal
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