Which of the following is not a system used for treatment and disposal of animal wastes?

The correct answer is based on understanding the various treatments and disposal methods for animal waste. Bio-filtration typically refers to a method used to treat wastewater, often utilizing living plants and microorganisms to filter out contaminants. While it can be part of a broader wastewater treatment system, it is not a distinct system specifically designed for the treatment and disposal of animal wastes.

In contrast, field spreading and aerated lagoons are well-established systems used for managing and treating animal waste. Field spreading involves applying waste directly onto fields where it can fertilize crops and return nutrients to the soil. Aerated lagoons use aeration to promote microbial digestion of waste materials, often functioning as part of a larger waste management system for farms.

Understanding the characteristics of each method clarifies why bio-filtration does not fit within the category of systems specifically engineered for animal waste treatment and disposal.