There is water pollution issue in Thailand. Water pollution is caused by dumping waste into rivers selfishly. The disposal of garbage down the river is causing foul odor bad weather and dirty water. (Often the government was going to solve a problem.) To cure the polluted water bodies. (They are supposed to throw the rubbish into the bin)and (they are supposed to think about the consequences after throwing that waste irresponsibly.) Finally, place some posters which persuade people not to throw rubbish into the water. Which include the penalty for those who do not follow.

I want to use was/were going to and to be supposed to
I don’t know how to use it. Could you help me,please?