Waste Contamination in Water - Eutrophication
By Patricia Lopes
The degree of eutrophication in water bodies depends, mostly, on the concentration of nutrients usually phosphorus in the water,. Calculations show that because of the increase of population growth and urbanization, the world input of phosphorus into the rivers will have reached 2.56 million tons per year by the end of the 20th century. Also, an additional 0.6 million tons, are added mainly due to agricultural and livestock farming. The increase of eutrophication is mostly in rivers, lakes, water reservoirs, and coastal marine waters. The world rivers total phosphorus concentration has increased by four times. These facts clearly show that something has to be done about this problem and solutions to curb eutrophication need to be taken into actions. "For every complex problem, there are many solutions that are complicated, messy and right." H.L. Mencken
Essential macronutrient elementsSymbolEssential micronutrients (trace elements)Symbol OxygenOIronFe
Several approaches have been developed to solve the eutrophication phenomenon. Nevertheless, first one has to figure out what type of nutrients needs to be removed. Then one has to determine how to remove these nutrients. On the side is a list of chemical elements that are essential for the plants to grow:
1) The Tertiary Treatment:
Aluminum sulfate (alum) [Al2(SO4)3] when added to lake water removes phosphates through precipitation. It forms aluminum ions, which are hydrated (combined with water) as follows: Al+3 + 6 H2O ⇄ Al (H2O)63+
In a series of chemical hydrolysis steps, hydrogen ions are liberated, which may lower the water pH, and ultimately forms aluminum hydroxide (Al(OH)3), which is a solid precipitate: Al3+ + H2O ⇄ intermediate reactions ⇄ Al(OH)3(s) + H+ The solid precipitate forms flocculent material (floc) that has a high capacity to adsorb phosphates. The aluminum hydroxide blanket separates the sediment from the water column. The sediments are heavier than water. This floc then settles to the bottom of the lake and creates a barrier that slows down sediment phosphorus release. 2) The Biological Treatment:
Biological removal uses the ability of some microorganisms to take up phosphorous in excess of their instant requirements for nutrients and store it within the cells in the form of polyphosphates Wastewater operators prefer Biological phosphorus removal since it lowers process costs and reduces the problem of eutrophication 3) Physical Treatment:
Physical Treatment is the best know treatment in removing the nutrients from the water. Using this method, one is preventing the nutrients to enter the water in the first place. This can occur by restricting phosphorus products or starting committees to help recycle, and allow people to treat their lakes in their community.
The best known case of recovering a lake from eutrophication with this method is in Great Lakes basin, in North America. To solve the problem of eutrophication in the Great Lakes, measurements had to be made of nutrients entering and leaving each lake from all sources. The GLC (Great Lake Committee) set goals on how much phosphorus can be entered in the lakes. Through pollution prevention, they are using less polluting products and recycling more, so that less pollution is released and less has to be cleaned up later.
Cleanup measures have been mostly, but not completely, successful. Finish phosphorus removal measures started in the mid-1970s and have targeted rivers and lakes polluted by industrial and municipal discharges. These efforts, which involved removal of phosphorus, have had 90% removal efficiency. Still, some targeted point...