Water & Wastewater Asia January/February 2022

ENVIRONMENTAL REPORT
Contact was up to 10 minutes.
Ozone was effective against all the
micropollutants analysed, including
Atenolol, Atenololsaure, Benzotriazol,
Carbamazepine, Clarithomycin,
Diclophenac, Gebapentin,
Hydrochlorothiazid, Levetriazepam,
Mefenamisnaure, Methyl-benzotriazo,
Sulfamethoxazol, Trimetoprim,
Valsartan, and Venlafaxin. Doubling
the contact time made minimal
difference in effectiveness.
MULTI-BARRIER TREATMENT
APPROACH TO CEC
As seen in the examples above, we
know ozone alone can effectively
oxidise target pollutants. When ozone
is combined with a biologically active
filter (BAF), the result is a multi-barrier
advanced bioactive filter process that
provides several additional process
benefits.
Instead of the complete oxidation of
the targeted organic compounds with
ozone alone, the De Nora Tetra ABF
bioactive filter uses a lower dose of
ozone to partially oxidise and break
the long chain recalcitrant carbon
into smaller biodegradable organic
compounds. The smaller chain organic
compounds are then removed in the
downstream BAF. This process allows
for lower ozone doses, and lower
capacity ozone equipment versus
conventional ozone only treatment.
This, in turn, may reduce capital costs
and energy consumption. In addition,
the ABF process does not require
upstream reverse osmosis (RO) or UF
membranes commonly used with other
types of direct and indirect water reuse
schemes.
The synergy created by combining
ozone and BAF treatment has proven
effective in removing common DBPs
and provides a biologically stable
effluent by oxidising assimilable
organic carbon (AOC) generated by
ozonation alone. This may reduce the
risk of downstream biofilm growth in
the filter.
ABF USED FOR TOC REMOVAL
AND DBP REDUCTION
In the summer of 2019, a 9 MGD
water treatment plant in Pennsylvania
commissioned a De Nora pilot to
evaluate the use of ozone and BAF
to treat settled surface water. They
were hoping to improve their TOC
removal and achieve significant DBP
reduction without adversely impacting
current water quality performance.
The existing plant has six filters at
576sf/filter designed for 16 MGD.
Media is 4-inch anthracite on top
of 1-inch sand. A containerised
ABF pilot was deployed featuring a
20-foot-long, high-cube container with
ozone generation equipment having
a capacity of 20g/h, and two 8-inch
diameter BAF with capacity to handle
a total flow of 6gpm. The system is
operated automatically, with remote
control and monitoring capability
through cellular communication.
Specific objectives for the pilot were
to achieve close to a 50% reduction in
raw water TOC that could be reliably
and consistently achieved with the full
combined treatment train throughout
the year. In 2017, raw water TOC
reached 10mg/litre. With respect to
DBP reduction, the pilot goal was to
achieve a 25% reduction of the mean
TTHM value and a 25% reduction of
the mean HAA5 value. Additionally,
all other regulated parameters would
show no significant increase as
compared to the plant values of the
pilot testing period.
The pilot ran for six months and the
ABF effluent averaged 47% greater
TTHM removal than current plant
performance, exceeding pilot objective
of 25%. Pilot control anthracite had
2.2 times higher effluent TTHM than
ABF. The percentage of TOC removal
in the ABF pilot relative to raw water
decreased by 45%.
SUMMARY
As the chemical load in the waterborne
waste stream increases
in volume and diversity due to
contaminants of CECs, DBPs, and
other micropollutants, water utilities
are challenged to find solutions to
ensure water quality and safety.
New pollutants require new
approaches.
By combining two technologies, ozone
generation and BAF, the De Nora tetra
ABF bioactive filter offers a costeffective
approach to today’s treatment
challenges. The De Nora Tetra ABF filter
is designed to target micropollutant
and DBP reduction for both direct
and indirect water reuse plants and
DBP reduction at drinking water
treatment plants, offering measurable
improvements in water quality and
operational efficiency.
Alex Bettinardi is global product manager, ozone, De Nora
Water Technologies; and Stanley Shmia is global product
manager, filtration, De Nora Water Technologies.
WATER & WASTEWATER ASIA | JANUARY/FEBRUARY 2022 27