1. Explain how water is filtered and cleaned in a city for drinking.

Reverse osmosis (RO) is a filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane
http://en.wikipedia.org/wiki/Reverse_osmosis

2. Explain how sewer water is treated and returned to the river or lake.

Water is filterd by removing waste from water and turning it into solid form. Process includes procesess of physical, chemical, and biological. Waste is in solid form
matt

3. 2 good questions to ask tomorrow.

1) What process does the water have to go through to be filtered?

2) How long does it take to filter a gallon of water?