Phosphate in swimming pools - the real cause of algae

Algae, like all plants require water and nutrients toeffectively bleaching the algae white and killing it.
grow, in a swimming pool there is little we can doThis is followed by a "floc" with aluminium salts,
about the water, however removal of thebefore vacuuming the settled dead algae to
nutrients - phosphate, you can keep yourwaste.
swimming pool algae free.Up until recently, none of the traditional
This summer has seen some of the highesttreatments for algae targeted the real cause of
recorded phosphate levels in swimming poolsthe algae problem. Chlorine has always been
across Australia and New Zealand. Some of thisrecognized as an effective algaecide, however
high level of phosphate has been attributed todoes nothing to treat the cause of the algae
summer drought related dust fallout, and anproblem.
increase in the phosphate levels of severalIn swimming pools there are two effective
common fertilizers. For many years phosphatechemical treatments for removing phosphate
and nitrate runoff from farms has been blamedfrom swimming pools: lanthanum compounds and
for the deterioration of our many lakes andaluminium compounds. In sewage and effluent
waterways, now the problem has crossed intotreatment ponds, iron compounds are used
our swimming pools.effectively, however these are undesirable in
For pool owners, the biggest concerns from highswimming pools due to the staining they cause.
phosphate levels are rapid chlorine consumptionAluminium compounds are more effective in pools
and stubborn, repeat algae problems.with a high level of phosphate build-up, in the
Removal of phosphate from pool water isrange of greater than 1000ppb (parts per billion);
important to help maintain healthy water quality.however they require vacuuming to waste after
Once it has been removed, regular maintenancetreatment. They will effectively remove
can prevent the level from becoming a problemphosphate down to 500ppb, but cannot remove
again and also aid in better chlorine performancephosphate below 100ppb which is required for
and efficiency, reduced chlorine consumption, andeffective algae control. Aluminium compounds are
no algae problems.relatively cheap, and therefore suitable for
Phosphate and nutrients are required by all livingremoval of a large percentage of phosphate
organisms, including algae, to survive and flourish.accumulated in the pools water.
It is well documented that raising the swimmingLanthanum products are a potent and specific
pools chlorine level will result in less algae problems.phosphate remover. They are best suited to
But how are they related, and what can be donemaintaining low levels of phosphate in pools where
to remove phosphate from swimming poolperformance and convenience are important.
water?They are easier to use and apply than aluminium
Phosphate is introduced to pool water from aproducts and do not require vacuuming to waste
variety of sources including runoff from lawns andafter their application. However they are more
gardens, pool fill water such as bores, dust, suntanexpensive and best suited for pools with less than
oils and leaves. With time, all of these sources will2000ppb accumulated phosphate. One of the main
cause a build-up and increase in the concentrationadvantages of lanthanum is that its ability to form
of phosphate in the pools water.lanthanum phosphate is not affected by the pools
Algae spores are continually being introduced towater balance.
the pool attached to dust and leaves. They onlyA small amount of lanthanum compound will cause
require nutrients and water to quickly multiply andthe phosphate level to drop below 100ppm, while
become a threat to the pools water quality dueconcentrations of below 10ppb are easy to
to rapid consumption/destruction of availablemaintain.
chlorine.Lanthanum compounds work by lodging in the
For decades chlorine has been used not just as apools filter media or cartridge, slowly dissolving to
pool sanitizer, but it is also effective as a shortlightly coat the filter media. As phosphate rich
lived algae killer.water passes over the lanthanum crystals, they
Traditional treatment has included "shock" dosingchemically attach themselves to the phosphate -
the pool with three to five times its regular dailyforming lanthanum phosphate. Lanthanum
chlorine dose; this is effective at killing off almostphosphate is not suitable as a nutrient, and binds
all visible algae.into larger particles so it can be removed by the
While this effectively kills the algae, it does not dopools filter medium. Lanthanum can be stored in
anything to address the condition that allowed thethe pools filter in large quanties without causing
algae to flourish in the first place. When thecloudy water.
chlorine level returns to normal to algae will beginTo conclude, phosphate removal is the secret to
growing again.maintaining algae free, quality swimming pool
Therefore preventing the algae from recurringwater, while allowing other chemicals to work at
requires that the chlorine concentration istheir optimal level.
maintained at the higher level, the water isAdditional algae insurance, is the use of a
removed from the pool, or water conditions arepreventative, "long life" copper based algaecide to
changed to become less favourable for algaebe used in conjunction with regular testing for
growth.phosphate.
Traditionally, phosphate levels have been ignored,While phosphate will accumulate in a pool naturally,
while attempting to remove dead algae bythere are steps pool owners can take to prevent
filtration. Given wet algae weighs 1000 times moreexcessively high levels.
than the phosphate needed to feed it, this is not- Do not allow runoff from gardens and lawns to
the most effective way to do this. Also as theenter the pool
algae are trapped in the filter, it releases a certain- Remove leaves from the pool regularly and
amount of trapped phosphate back into thepromptly
water.- Apply a lanthanum compound phosphate
The most effective traditional treatment is "superremover regularly
chlorination" or ten times the normal daily dose,- Have the pools water tested by a professional.