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.
Storm sewer water usually goes straight into the waterways without any
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
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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Update: June 2012