ENVIRONMENT
PHOSPHORUS
REDUCTION
IN WASTEWATER TREATMENT
Phosphorus, usually
in the form of
phosphates, originates
from sources such
as human and animal
waste, detergents
and food residues.
Food and beverage
processing plants
will very often have
phosphate inputs from
all of these sources.
column as the dead algae cells
decompose, leading to anoxic
conditions that can result in mass die
offs of fish and other aquatic life. As
the algae and other dead organisms
decompose, the organic form of
phosphorus bound in the dead
organic matter can be converted to
orthophosphate, making phosphate
available to aquatic plants and algae
once again. So in effect, internally
recycled phosphorus can fuel
another algal bloom, and this cycle
can be continually perpetuated.
Phosphorus
removal
The effectiveness of phosphorus
removal during wastewater
treatment can vary, depending on
the available equipment and the
treatment methods used. Only
wastewater treatment plants that
employ specialised phosphorus
removal techniques will normally be
able to remove phosphorus to the
desired levels
Many food processing plants
ultimately treat their wastewater by
Wastewater treatment
systems that are
commonly used in the
food and beverage
industry typically manage to reduce
biological oxygen demand (BOD)
and nitrogen effectively, but very
often are not as effective at reducing
phosphorus to acceptable levels.
In order to protect the environment,
industrial wastewater treatment
plants are tasked with reducing the
discharging it to aerated settling
ponds where the organic waste is
broken down by aerobic bacteria.
Upstream of this aerobic biological
process there may be some primary
treatment process such as a DAF
or perhaps and anaerobic pond,
however neither of these stages
of treatment provide a satisfactory
reduction in phosphorus loads if any
at all.
There are two methods of removing
phosphorus from wastewater:
biological removal and chemical
removal. Biological phosphorus
removal can be achieved by
cycling the activated sludge in
anaerobic and aerobic conditions
which can build up a population of
microorganisms that are capable of
storing phosphorus intracellularly
as polyphosphate. If these specific
microorganisms exist in sufficient
numbers, then the phosphorus will
be removed along with the waste
activated sludge.
However, to establish and maintain
biological conditions for effective and
continuous phosphorus removal has
proven to be quite challenging for the
levels of contaminants including
phosphorus, so that the treated
effluent meets environmental
standards before it is discharged into
a local water body.
Environmental
impacts of
phosphorus
Phosphorus is a naturally occurring
nutrient found in soil and rocks that
is required by all living organisms.
Phosphorus (phosphates), together
with nitrogen (nitrates), is an essential
plant nutrient that is readily taken
up by plants for growth. However,
when these nutrients are available in
unwanted excessive amounts, they
can fuel rapid plant growth - which
is why they are used extensively in
fertilisers.
High levels of phosphates in aquatic
environments can fuel algal growth,
resulting in algal blooms that can
potentially lead to eutrophication
as the thick algal mats block out
sunlight causing the algal cells to
die off.
Oxygen is stripped from the water
16 MAY 2019