WC134 JanFeb 2024 - Magazine - Page 12
WASTEWATER
Left to Right: DuPont OxyMem MABR module being lowered onto receiving steelwork at Elmira Wastewater Treatment Plant. Low pressure oxygen is supplied to the
MABR modules using small process blowers, attached by rubber pipes and camlocks.
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WATER C AN ADA • JANUARY/ FEBRUARY 2024
sumption can be more than 75 per cent lower than alternative
attached-growth systems often considered for plant upgrades—a
significant saving considering that more than a third of the
energy consumed by municipalities may be attributable to water
and wastewater treatment.
Consistent year-round performance
Most operators and owners of suspended biomass wastewater
treatment plants know that colder temperatures and varying seasonal process loadings can pose a significant challenge. Winter
conditions slow the growth rate and metabolism of microorganisms within the treatment basin, often making nitrification harder to achieve, especially on plants where solids may be washed
out due to high flows.
The MABR has been put to the test around the world, with
modules demonstrating that they can continue to efficiently target pollutants throughout winter, even when water temperatures
reach 10°C, and during peak summertime loads. For example,
one installation in Spain using DuPont OxyMem MABR modules provided additional capacity for the plant during the wine
crushing season when the COD load to the plant was 370 per
cent higher than the design load. As a result, the plant was able
to achieve the target effluent COD concentration throughout
the year.
High volumes of rain and molten snow also risk potentially
washing away valuable nitrifiers at conventional plants. Mean-
WAT E R C A N A D A . N E T
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The fundamentals of MABR technology
As with a conventional activated sludge plant, the MABR is a
biological treatment process which achieves nutrient and pollutant removal using microorganisms. Where conventional plants
rely on a suspended biomass, the MABR makes use of a robust
biofilm attached to membranes within self-contained modules.
Typically, the MABR is offered in two basic configurations:
Where the MABR works alongside a suspended biomass (MLSS
present) the arrangement takes the form of an advanced integrated fixed film activated sludge (IFAS) system, and where MABR
operates alone without the presence of suspended growth, a pure
biofilm system. In either instance, hollow fibre membranes within the MABR module receive air carrying oxygen at low pressure,
supplied by process blowers. The oxygen diffuses across the
gas-permeable membrane wall, and a biofilm grows on the outer
surface after the module has been deployed. As a result of the
optimal growth environment, a nitrifying biofilm is established
within a few weeks.
The gas-permeable membrane and attached biofilm arrangement enables superior oxygen transfer efficiency, allowing the
microorganisms to achieve a higher rate of nutrient and pollutant
removal compared to conventional systems which tend to rely on
bubbles for the transfer of oxygen into a bulk liquid; the MABR
aeration efficiency is therefore commonly three-to-four times
more than fine bubble diffused aeration systems. In addition to
the improved biological treatment performance, energy con-
