Dear Sara  here are some ...

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Dear Sara 

here are some links

http://www.who.int/water_sanitation_health/monitoring/jmp2000.pdf

http://www.who.int/water_sanitation_health/publications/2012/globalcosts.pdf

 

you could find some data for USA on the following link 

http://www.asce.org/water_and_wastewater_report/

best regards

Marina