11.   There are also rather expensive countertop, under-sink or basement systems that cleanse water by a process called reverse osmosis.

12.   These areas play important roles in filtering and cleansing water, in serving as a reservoir for flood water, and in harboring fish and shellfish populations.

13.   To help cleanse the water, sludge was dredged from the bottom and dumped into one particularly contaminated corner of the bay to make reclaimed land.