Human fecal pollution can enter water bodies in a number of ways — from point sources and non-point sources (NPS). Point source water pollution refers to contamination from a single, identifiable source, such as a pipe or ditch, while non-point source pollution is simply the opposite in that it’s difficult to determine where the contamination comes from. In NPS, impurities are introduced through a non-direct route and from sources that are “diffuse” in nature.
Variations in DNA sequences between living organisms makes it possible to distinguish between these organisms through molecular biology techniques. In our microbial source tracking laboratory, Real-Time Polymerase Chain Reaction (real-time PCR) technology is used to identify the presence of microorganisms in water samples based on the unique genetic sequences. Water samples delivered to Source Molecular are first filtered to capture microorganisms. These organisms are then lysed (broken down) and the DNA (RNA in some virus) is extracted and purified in preparation for downstream PCR analysis.
Point Sources of Human Fecal Pollution
Point source pollution remains a major cause of water contamination. Examples of point sources of human fecal pollution include discharges from a municipal sewage treatment plant or storm sewer drains, and leaking sewage pipes. In 2000, the EPA disclosed that municipal point sources are major contributors of reported water-quality problems in the impaired portion of estuaries, ocean shorelines, river miles and lake acres.
Commercial Dumping of Fecal Pollution
Ideally, sewage or wastewater is treated to remove harmful fecal pathogen before it is discharged into a body of water. The EPA requires any facility that discharges wastewater directly to surface water to obtain a National Pollutant Discharge Elimination System (NPDES) permit. However, improperly treated sewage can be released as a result of upsets to the treatment process, as a result of infrastructure failure, or as a result of operator error. Furthermore, despite the regulation, there are still some cases of illegal sewer discharge happening around the country. Water from sewage treatment plants can contribute pollution in the form of pathogens that cause serious health hazards if it finds its way into drinking water and swimming areas. Previous studies have shown that there’s still a high probability of finding fecal indicator bacteria (FIB) and human pathogens in released wastewater as it comes from a large human population. Thus, developing the total maximum daily loads (TMDL) is essential to determine if the FIB levels are high enough to necessitate remedial action plans. Microbial source tracking (MST) plays a big part in TMDL development and implementation. Among the numerous MST methods used to detect human fecal contamination, specifically the presence of municipal sewage, is viral polymerase chain reaction (PCR). High concentrations of human polyomaviruses (HPyVs) (JC virus [JCV] and BK virus [BKV]) have been documented in municipal sewage. Source Molecular’s Human Urine Virus ID™ service uses a DNA analytical technology that quickly detects the presence of human polyomavirus.
Storm sewers are designed to drain untreated rain and ground water from paved streets, parking lots, sidewalks, and roofs into rivers or streams. In certain cases businesses or commercial establishments make illegal connections to the storm sewers, unknowingly or intentionally, through their floor drains. As a result, human fecal contamination enters the storm drains and then flow out directly into local waters without proper treatment. Billions of gallons of undisinfected sewage effluent continue to be discharged into river systems daily. Raw sewage is home to thousands of viruses. More than one hundred different enteric viruses may be excreted in human fecal material.
Non-Point Sources of Human Fecal Pollution
Fecal pollution from non-point sources can come from runoff, failing septic systems, leachate from dumps and landfills, illegal dumping, improper disposal of sewage from recreational practices such as boating or camping. NPS pollution is widespread because it can occur any time activities disturb the land or water. The U.S. EPA has identified NPS pollution as the largest source of water quality problems in the country, affecting 40 percent of its surveyed rivers, lakes, and estuaries.
Storm Water Runoff
Storm water runoff can be a significant source of fecal contamination. It consists of water from rain or snowmelt that has drained from roads, freeways, sidewalks, roofed structures, parking lots, airports and industrial sites among others. These impervious surfaces prevent storm water runoff from naturally soaking into the ground. Storm water can pick up pathogens released by leaking and poorly maintained septic systems and discharge them into a storm sewer system or directly to a lake, stream, river, wetland, or coastal water. Storm water systems are often combined with sanitary sewer systems in route to sewage treatment plants. Excessive storm water can cause this joint system to overflow, resulting in human fecal contamination of waterways. Numerous studies have found a link between storm water runoff and the elevated incidence of waterborne disease. One of the challenges presented by storm water runoff in MST analysis is the seasonality of its nature. Fecal sources and resulting bacteria concentrations might vary between base and storm flow conditions. Samples for MST analysis should be collected when bacteria concentrations are elevated and on numerous occasions at varying environmental conditions to verify the repeated presence or absence of a bacteria source.
Septic tank systems are a type of plumbing primarily used in areas that do not have a connection to main sewage pipes. About 25 percent of U.S. homes use septic tanks to rid the home of waste that is deposited through the plumbing. Septic tanks will leak at various points and for various reasons. Modern septic tanks may include a rubber gasket to help seal at the tank entry and exit openings. The septic tank could spring a leak if there is rust on a metal tank or if a plastic or fiberglass tank ruptures. A leak can spring in a sewer line that is connected to the tank if the sewer line is not properly sealed; many older tanks lack sealant. As a result, excess water can get into the pipes, drainage field and tank of the septic system. The cover of a septic tank can also get a leak, especially if it is below ground and becomes loose. Cracks can occur in a concrete septic tank, which can let waste leak out or let water leak in. The EPA had reported that septic tanks contaminate 1% of the nation’s usable aquifers.
When dumps and landfills aren’t properly sealed, rain can percolate through the waste and then this contaminated water or leachate enters fresh water streams, lakes and ground water sources. While leachate is already a toxic brew of paper waste and construction debris, human feces is also present in the mix. Even though it is illegal to do, disposable diapers are thrown in the trash still containing feces. As a result, not only does this hazardous practice put the sanitation workers’ health at risk, it also increases the amount of dangerous bacteria that already exists in landfills. Quantitative PCR is an MST method that is primarily being used to detect human fecal contamination. qPCR is a technique that measures the amount of DNA present in a water sample rather than simply detecting a presence or absence of microbial DNA. Another microorganism recognized to indicate fecal contamination is Bacteroidetes, which is found primarily in the intestinal tracts and mucous membranes of warm-blooded animals and is sometimes considered pathogenic. Furthermore, certain categories of Bacteroidetes have been shown to be predominately found in humans. Within these Bacteroidetes, certain strains of the Bacteroides and Prevotella genus have been found to be specific to humans. Source Molecular’s Human Bacteroidetes ID™ service filters the entire portion of water sampled for Bacteroidetes. This method avoids the randomness effect of culturing and selecting bacterial isolates. It is an advantage for highly contaminated water systems with potential multiple sources of fecal contamination.
Some people try to avoid paying disposal fees or expend time and effort necessary to properly dispose garbage and thus resort to throwing trash in unpermitted places. Illegal dumping in a back area of a yard, along stream bank, at some other off-road area, or even storm drains can impair water quality. Like landfills, illegally thrown trash may also include used diapers still containing human feces. Some campers, hikers and even RVs toss their waste in non-designated areas. Runoff from these illegal dumpsites may contain human bacteria that can contaminate wells and surface water used as sources of drinking water. In MST analysis, fecal Bacteroidetes are considered interesting alternative fecal indicator bacteria to the more traditional FIBs such as E. coli and Enterococci. Bacteroidetes are indicative of recent fecal contamination when found in water systems and are more abundant in feces of warm-blooded animals than E. coli and Enterococci. The Human Bacteroidetes ID™ service provided by Source Molecular releases results in as little as three working days, which fast turnaround is important to clients who might be trying to determine recent outbreaks in fecal pollution. It is recommended that Source Molecular’s Human Bacteroidetes ID™ service should be combined with other DNA analytical services to strengthen the validity of the results.
Recreational boaters, who raw or poorly treated sewage into the waterways, are also big contributors to the overall pollution problem. When sewage is dumped by recreation boaters in shallow water and in areas that don’t have significant flushing action like in harbors, marinas, coves, inlets and sloughs, it poses a serious health risk to swimmers, waterskiers and others who swallow or come in contact with the contaminated water. Moreover, people can still be affected if they eat raw or poorly cooked clams, mussels or oysters from contaminated shellfish beds. High levels of coliform bacteria have been found in areas with heavy concentrations of recreational boats. Studies have shown that the untreated discharge from one weekend boater puts the same amount of bacterial pollution into the water as does the treated sewage of 10,000 people.