Answer:
Municipal of sewage in water
Explanation:
The municipal sewage water has a large number of microbes present in it that leads to lower level of oxygen in water. The reduction of oxygen in water occurs due to decomposition of algae present in water by microbes. Algae is responsible for the production of oxygen from the process of photosynthesis. When they are removed from an environment then no more oxygen will be produced which leads to decrease of oxygen in water.
