Question

which is a way that untreated sewage can enter the water?
faulty residential, municipal, or marina septic treatment systems
msds with closed (in - board position) y - valves
properly constructed municipal spray irrigation systems in approved soils
direct discharges from drinking water treatment plants

Explanation:

Faulty septic treatment systems can leak untreated sewage into water. Closed Y - valves in MSDs prevent discharge, properly - constructed municipal spray irrigation in approved soils is a controlled process and drinking water treatment plants do not discharge untreated sewage.

Answer:

Faulty residential, municipal, or marina septic treatment systems