Final answer:
Filtration and Aeration are key nonchemical methods for reducing contamination in drinking water, removing physical particles and unwanted gases respectively.
Step-by-step explanation:
The nonchemical methods often used to reduce contamination in animals' drinking water are Filtration, UV radiation, Boiling, and Aeration. Filtration involves passing water through various media such as sand, gravel, and charcoal to physically remove particles, bacteria, and viruses. Aeration is the method of bringing air into contact with water to exchange certain components and remove substances such as volatile organic compounds, hydrogen sulfide, and ammonia. Both of these methods are essential in ensuring water safety without the use of chemicals.