Absolutely true, that's why there is a dead zone at the bottom of the mississippi. However there are literally tons of ammonia flowing out of places with high

Absolutely true, that's why there is a dead zone at the bottom of the mississippi. However there are literally tons of ammonia flowing out of places with high density and where that high ammonia still ends up in water ways after passing through a sewage system. In particular this has been true in Western Europe, and there are issues in various areas around the country here (Great Lakes, Chesapeake Bay, SF bay is weird so for now we seem to be not as affected on this particular front). In the US human sewage is thought to contribute 11% of the problem and in Europe 25%. Not everything, but surely it'd be nice to solve the problem. Also some of these technologies could be applied to other sources such as manure if treatment standards were imposed on agriculture. Runoff is harder for sure, but there we can maybe look at more targeted application of fertilizers. It helps nobody to pay for fertilizer that ends up in a river and not growing more food. Useful Source: http://www.wri.org/our-work/project/eutrophication-and-hypoxia/sources-eutrophication http://www.wri.org/our-work/project/eutrophication-and-hypox...