Water pollution is a topic that comes up when talking about the hog-raising industry in the United States. Over the past 50 years, a significant change has been made in how and where hogs are produced. Before, pigs were just raised on pasture systems but now they are housed in concentrated animal feeding operations. The U.S. Environmental Protection Agency noted that low consumer prices, and therefore low producer prices, have resulted in larger, more efficient operations, with many smaller farms no longer able to produce pigs profitably. Thus, the situation now is more pigs now but fewer farms. The EPA has identified North Carolina and the Midwestern and plains states, including Nebraska, Iowa, Minnesota, Missouri, Indiana and Illinois, as the top swine producers. A study by Dr. Mark Sobsey, a professor at the University of North Carolina's School of Public Health, reported that a hog produces 10 times the fecal waste of a human. To illustrate, the study notes the swine in eastern North Carolina are producing the same amount of feces each and every day as would be produced by 100 million people. With such high amount of waste, disposal is not always clean as a whistle.
Point Sources of Swine Fecal Pollution
Waste products from swine are discharged from a single, identifiable source.
Historically, swine manure was handled as a solid, either deposited directly by grazing animals, or collected in bedding placed on solid shelter floors to absorb the urine. Nowadays, most swine manure is handled as a liquid. Manure typically falls through a slotted floor into either a gutter or a concrete storage pit. Storage pits provides from 3-12 months storage of the manure. However, reports of farms dumping hog waste directly into surrounding streams, rivers, and lakes continue to make headlines. Whether intentional or unintentional, such practice is illegal and has resulted in the death of millions of fishes and other aquatic life as well as closure of rivers and lakes from swimming and water sports. Waste water from pig farms are supposed to be treated to reduce the level of pollutants before it is discharged into any body of water. In fact, the National Pollutant Discharge Elimination System under the Clean Water Act requires CAFOs to get a permit from the state and the U.S. Environmental Protection Agency before they can discharge wastewater. In remediation efforts, it is important to determine the source of fecal pollution. Microbial source tracking (MST) analysis is used to determine whether the fecal indicator bacteria (FIB) come from humans or animals. Bacteroidetes
is a family of gram-negative bacteria found primarily in the intestinal tracts and mucous membranes of warm-blooded animals, which makes it a good FIB. Within the phylum Bacteroidetes
are certain strains of the Bacteroides
genus that have been found in swine. Source Molecular's Pig Bacteroidetes ID
™ service samples and filters the entire water sample submitted to the laboratory for these bacterial strains as indicators of swine fecal contamination. This method of testing is a particular advantage to clients who provide samples from highly contaminated water systems with potential multiple sources of fecal contamination.
Manure Lagoon Leakage, Spills and Overflows
Typical of concentrated animal feeding operations (CAFO), fecal matter from pigs are flushed from the confinement buildings and stored outside in huge earthen sewage pits called lagoons. Lagoons are different from liquid manure storage because they are operated to encourage anaerobic digestion of organic material while it is being stored. This reduces odor when the treated manure is land applied. Lagoons are supposed to be protected with an impermeable liner, but some do not work properly causing disastrous spills into water bodies or leaks into the ground water. In 1996, a news report revealed that over 30 percent of water wells near hog farms were contaminated by hog waste. Heavy rains could also result in overflow of lagoons. When monitoring recent outbreaks of swine fecal pollution, Source Molecular recommends its Pig Bacteroidetes ID
™ service. Bacteroidetes
are strict anaerobes, which mean they do not need oxygen for growth and may even react negatively if oxygen is present. They are also more abundant in feces of warm-blooded animals than traditional FIBs such as E. coli and Enterococci. Since E. coli and Enterococci are facultative anaerobes, they can be problematic for monitoring purposes since it has been shown that they are able to proliferate in soil, sand and sediments.
Non-Point Source of Swine Fecal Pollution
Fecal matter from swine winds up in water bodies in a diffuse manner.
Spray Field Run-off
As manure lagoons fill up, the hog waste is sprayed onto heavily ditched fields. Large tanker wagons or trucks haul liquid manure from storage to the fields for application. In remote areas, liquid manure may be pumped to the land application site and then irrigated onto cropland. The EPA pointed out manure can enter surface waters via runoff if it is over-applied or misapplied to land. For example, manure application to saturated or frozen soils may result in a discharge to surface waters. Factors that promote runoff to surface waters are steep land slope, high rainfall, low soil porosity, and proximity to surface waters. To decrease runoff, manure is incorporated into the soil. One incorporation method is injecting the liquid manure directly into the soil to a depth of 6 to 9 inches. While efforts are made to control runoff, it still remains a major non-point source pollution to surface waters.