Lake Erie and algae.

[BruceF]

The algae are fed by phosphorus, the same chemical that American and Canadian authorities spent billions to reduce — for good, they believed — in the 1970s and ‘80s. This time, new farming techniques, climate change and even a change in Lake Erie’s ecosystem make phosphorus pollution more intractable.
Like plants, algae thrive on a phosphorus diet. Decades ago, some 64 million pounds of phosphorus flowed into Lake Erie each year from industrial and sewer outfalls, leaky septic tanks and runoff from fertilized lawns and farms.
The United States and Canadian governments responded by capping household detergent phosphates, reining in factory pollutants and spending $8 billion to upgrade lakeside sewage plants. Phosphorus levels plunged by two thirds, and the algae subsided. But in the mid-1990s, it began creeping back.
http://www.nytimes.com/2013/03/15/sc...-erie.html?hpw

[wastewater]

Thanks for sharing... interesting article. Had the pleasure of working on a few water pollution control projects around the Cleveland area about four years ago. Compared to the condition of this Lake in the 1970's, Lake Erie's water quality has really improved within our modern times. Ohio has also tightened their belt over the years with stringent regulations/and oversight of enforcing regulations (especially in regards to stormwater management).

From what I read within the NYtimes article is the mention (more than once) of rain-algae-phosphorus. Sounds like stormwater run-off is one of the main culprits. Stormwater management can be a tough one to tackle. There are many solutions that can be applied to help correct the problems, but unfortunately (many times) the results take a long time to transform into a positive.