21.  Penalty should be given to those who pollute water or waste water.

22.  With the development of industry, more and more fresh water is needed, and a lot of fresh water is polluted by the waste water from the factory .

23.  And worst of all, fresh water is being pollouted by waste water and garbage.

24.  So many people waste water without being blamed for it.

25.  At the same time, we can purify the waste water and sea water.

26.  Secondly, we should call on people not to waste water, and protect the water resources.

27.  At last , we should pourify the waste water and reuse it.

28.  For example, the reuse of the waste water.

29.  If every one can do this, it will save much waste fresh water to use.

30.  First, we should control the increasing of population, and purify the waste water before it is drained from the factory.