A few related points
No central repository of livestock-related pollution problems exists, but federal agency studies, state water quality assessments and reports of pollution incidents all point to significant and growing threats to water resources from confinement agriculture. The increased risk of water pollution, says the U.S. Department of Agriculture (USDA), is linked to "ever-growing numbers of livestock and poultry per farm and per acre."
Today, U.S. livestock production generates an estimated 500 million to 1 billion tons of manure annually, with a significant portion of that waste coming from a relatively small number of large-scale operations that the Environmental Protection Agency (EPA) calls Concentrated Animal Feeding Operations (CAFOs). In contrast, municipal wastewater treatment plants annually treat 18 million tons of human fecal material.
The report has a number of good real life examples, of water pollution caused by livestock farming.