How to Make Wastewater Treatment Plants Affordable?

Since ​wastewater ​treatment is ​expensive and ​cities ​engineering was ​not properly ​planned, ​industrial and ​municipal ​wastewater ​usually gets ​discharged into ​the nearby ​water bodies, ​here in ​Ethiopia.  ​

This has ​extremely bad ​effects on the ​environment.​  ​

How could I ​minimize the ​cost of ​water ​treatment ​plants so that ​they are ​affordable for ​investors and ​municipalities?​  ​

Suggesting how ​to best recycle ​this water may ​also greatly ​help.