Fill a bucket with water. The water represents the streams and rivers that service wildlife, organisms that live in water and the human population.
Pour three to four bags of tea in the bucket of water. The tea represents urine that is produced from toilets.
Pour 1/2 cup dry dog food in the bucket. The dry dog food represents fecal matter produced by animals and the human population.
Throw other types of material in the bucket to represent other items that make up sewage. Students should put paper, sticks, vegetable oil and food coloring in the water. Mix the substances and use it to demonstrate how a sewage plant would treat the sewage.