I promised to talk about some of the consequences of water pollution and one that is well known by now is eutrophication. For a quick summary watch the following video, if you want more details, just keep on reading
http://www.youtube.com/watch?v=UGqZsSuG7ao
Eutrophication is the exponential growth of algae and other waterplants. This growth is caused by high concentrations of fosfates and nitrates(starting from concentration of 0.2-0.3 mg/L N and 0.01-0.02 mg/L P) in the surface water. Because of the large growth all other life inside the water is suffocated. During the day the plants use fotosynthesis and large amounts of oxygen are produced, but at night this process is reversed. The plants keep on breathing and start using oxygen, as a result the concentration of oxygen can hit critically low values for fish life and other plants. When the algae die and are digested by bacteria, oxygen levels will decrease even more, but the nutriënt level(phosphates and nitrogen) will increase once more because of the degradation. These nutriënts will again increase the growth algae. By now you can see that it’s some sort of circle that keeps going and going.
Fish death due to water pollution
The average composition of algae’s biomass can be represented by the chemical formula C106H180O45N16P. The growth of celmaterial can be described as:
106 CO2 + 80,5 H2O + 16 HNO3 + H3PO4 + Energy —->C106H180O45N16P +149,75 O2.
Eutrophication is mainly a problem for slow waters like lakes and slow flowing rivers.
A way to keep eutophication from happening is by keeping the fosfate concentration low. Why?
Lowering Nitrogen concentration from pollution sources is good but most algae have the ability to take up nitrogen from the atmosphere when other sources are low. So inhibiting growth through low concentration of nitrogen won’t help. Also phosphate removal easier than nitrogen removal.
Sources of phosphates:
– Human feces and urine( 1,4 g P per inhabitant per day)
– Industries producing fosfates and bio-industries
– Water run off from fertilised grounds
– Some old detergents used peoples homes( 1,5- 2 g/inhabitant.day)
– Agriculture
Interesting: Adjusting the food for animals in agriculture could lower the amount of fosfates present. Fosfor is a vital component in the food of animals. Theoretically the amount of fosfor present in normal plant material should be enough to fulfill the needs of the animals eating those plants. But for pigs and chickens there’s an amount that’s not digestable, so farmers add extra fosfor to the the feed. The addition of an enzyme fytase to the feed, that degrades those hard to digest fosfates, could provide a solution to reduce fosfate levels in the feces of those animals.
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