The step of the cellular respiration pathway that can take place in the absence of O2 is glycolysis, glycolysis is an anaerobic that’s mean it’s does not require oxygen O2
The answer is: Glycolysis
Water pollution is the contamination of water bodies, usually as a result of human activities. Water bodies include for example lakes, rivers, oceans, aquifers and groundwater. Water pollution results when contaminants are introduced into the natural environment. For example, releasing inadequately treated wastewater into natural water bodies can lead to degradation of aquatic ecosystems.
It is water pollution, since you are polluting the river.
Hope I helped!