Phosphates are present in many soaps, detergants, and commercial household products. They are also found in many fertilizers, and are used as animal feed supplements for their nutritive qualities. They are used in pharmaceuticals and industrial chemicals as well.
High phosphate concentrations in surface waters is often an indicator of fertilizer runoff, domestic waste discharge, or the presence of industrial effluents or detergents. Although phosphates from these sources are usually organically bound, all will degrade to "ortho" or reactive phosphates with time. In water containing high concentrations of phosphates, algae and other aquatic plant life will flourish, eventually resulting in the accelerated decay of organic matter, causing decreased dissolved oxygen levels in the water, and thus suffocating fish, and other water bound life forms.
You can help reduce the amount of phosphates entering our water supply by reading lables on your household products, and choosing to use those that are phosphate free.
There are a few recipes for eco-friendly alternatives in previous posts, and here is another one for a water friendly oven cleaner...
simply use baking soda, salt and water mixed into a paste!