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Name: Amanda
Status: Student
Age: 11
Location: N/A
Country: N/A
Date: N/A 

I was wondering,... when you spray your lawn with chemicals and it rains the chemicals get washed away. They go in the sewers. how do you purify the water?

The path of chemicals from residential and agricultural run-off is a major problem, that poses many difficult questions. Some of the chemicals such as weed killers are decomposed by bacteria in the soil, while others are not. Some run-off such as nitrates and phosphates from fertilizers contribute to algeal blooms that can kill fish. Such run-offs are often not treated at all and may contain harmful bacteria. Unfortunately, there is no easy answer to your question, and it is one that will be with us for sometime to come.

Vince Calder

Storm sewer water usually goes straight into the waterways without any treatment.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois

Hi Amanda,

It depends on what chemicals you add. If it is fertilizers, plants can be grown in the water to use up the nutrients. If it is pesticides, it takes more advanced treatment methods (such as the charcoal filtration used in fish tanks and many pitcher water purifiers), which are often difficult to do on a large scale. It is generally better to not use the chemicals or use as little as possible. Although your lawn might not look as perfect as a golf course, it's better for the environment.

Donald Yee Ph.D.

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