Bacteria, Protozoans, and Viruses: What’s in Your Stormwater?
With over 126 different constituents to test for in stormwater flows, and the media sensationalizing about male fish growing eggs, what should a stormwater manager really be concerned about? In a nutshell–all of it. Yet while chemical compounds with names such as butyl benzyl phthalate or 1,2,4-trichlorobenzene conjure up visions of the Swamp Thing, pathogens have an immediate impact on human health through the transmission of diseases.
According to the EPA, of the 54,363 top 100 impairments reported through 2002 under the Clean Water Act Section 303(d) list, pathogens made up the largest number, accounting for 7,742 reports. The EPA’s report, “Protocol for Developing Pathogen TMDLs” (EPA 841-R-00-002, pub. 2001), states, “Pathogens are a serious concern for managers of water resources. Because of pathogens’ small size, they are easily carried by storm runoff or other discharges into natural waterbodies. Once in a stream, lake, or estuary, they can infect humans through contaminated fish and shellfish, skin contact, or ingestion of water. Of the designated uses listed in section 303(c) of the Clean Water Act, protection from pathogenic contamination is most important for waters designated for recreation (primary and secondary contact); public water supplies; aquifer protection; and protection and propagation of fish, shellfish, and wildlife.”
What’s Wiggling in the Water
Pathogens are any agents that can cause disease. Three general categories of pathogens are most commonly identified and associated with waterborne diseases: bacteria, protozoans, and viruses.
Bacteria are unicellular organisms found throughout the environment that are responsible for a variety of processes and functions, from the manufacture of various food products to nitrogen uptake by plants. Only a small percentage of all bacteria present in the world cause diseases. Wastes from warm-blooded animals are a primary source for bacteria found in waterways. Some of the pathogenic bacteria of concern to water quality include Escherichia coli, which can cause gastroenteritis whose symptoms include vomiting and diarrhea; Salmonella typhi, which causes typhoid fever; and Vibrio cholerae, which causes cholera.
Anyone who studied high school biology has probably observed protozoans under a microscope, sampled from a pool of stagnant water. There are approximately 35,000 known species of protozoans occurring primarily in aquatic environments, with nearly 10,000 known to cause disease. They exist in the environment as cysts that hatch, grow, and multiply after ingestion. The cysts help the protozoans survive harsh conditions such as high temperatures or salinity. According to the EPA, two waterborne protozoans of concern include Giardia lamblia, which causes giardiasis with symptoms that include mild to severe diarrhea, nausea, or indigestion; and cryptosporidium, which causes cryptosporidiosis, whose symptoms include diarrhea and which can cause death in susceptible populations such as those with weakened immune systems.
Viruses are technically not living things; they cannot survive without a host organism. These infectious agents are particularly difficult to manage due to their ability to mutate readily, which is of major concern to world health managers each year at flu season. The most significant virus group affecting water quality and human health originates in the gastrointestinal tract of infected individuals and is excreted in feces. Viruses include hepatitis A, which can cause jaundice and fever, and enteroviruses, including those that cause polio, encephalitis, and conjunctivitis.
Tracking the various groups and subgroups of pathogens that might appear in a waterway can be a challenge to even the most comprehensive stormwater management program. Adding to the challenge is the fact that the density of organisms may be low in the water system and may be varied in characteristics or type. Although it would be preferable to be able to track precisely the specific pathogens that are present, water-monitoring programs generally use indicator organisms that are more easily sampled and measured. These indicator organisms are assumed to indicate the presence of human pathogenic organisms, with larger organism populations indicating the greater likelihood of correspondingly larger populations of pathogens.
Selection of the right fecal indicator organism is a difficult and controversial process. According to “Protocol for Developing Pathogen TMDLs,” in order for an indicator to function, the organism should “(1) be easily detected using simple laboratory tests, (2) generally not be present in unpolluted waters, (3) appear in concentrations that can be correlated with the extent of contamination…, and (4) have a die-off rate that is not faster than the die-off rate for the pathogens of concern. …
“Many issues surround the use of fecal indicators in determining the quality of waterbodies relative to pathogens. Major issues of concern are the correlation between the measured indicator and the presence of pathogens and the correlation between those pathogens and the incidence of disease.”
Getting to the Source
For a stormwater manager, trying to determine the source of pathogens in a complex ecological water system can be as frustrating as trying to get at the meaning of life. With point-source pollutants, it’s easier to pinpoint: Simply go to the end of the discharge pipe and take a sample.
Tracking nonpoint-source pollutants, however, might require systematic survey and analysis of the entire watershed and its contributing factors. In urban areas, litter, contaminated refuse, domestic pet and wildlife excrement, failing sewer lines and septic systems, and illicit or illegal discharges all can contribute to pathogen-loading into a water system. The greater the density of development–including population density, housing concentration, and the number of pets–the greater the density of fecal bacteria found in the waterway.
Although rural areas don’t suffer the same human-generated waste issues, confined animal operations such as dairies or feedlots are significant generators of manure and therefore sources of bacteria, viruses, and protozoal cysts. Wildlife can also be a significant source of pathogens in many areas, with many species harboring microorganisms pathogenic to both animals and humans. For example, waterfowl such as geese, ducks, and heron can contaminate surface water bodies with excrement, rendering them literally microbial Edens. Pathogens can also be found in sediments, with exponential increases in population density occurring after stormwater has scoured the benthic area of the waterway.
A variety of factors can also impact the density of pathogen populations. Depending on conditions of light, nutrients, temperature, and chemical balances, pathogen populations can explode or decay. These factors include sunlight or ultraviolet radiation, temperature, moisture, salinity, soil and water-body conditions, settling, and encystation. Each of these factors can influence the activation or inactivity of pathogens, with sunlight, temperature, and moisture conditions seeming to play the largest role in whether an issue becomes a problem.
A study prepared in February 2001 by the Office of Water Resources of the Rhode Island Department of Environmental Management (RIDEM), titled “Fecal Coliform TMDL Development for Hunt River, Rhode Island,” illustrates some of the issues facing stormwater managers when it comes to developing the necessary strategies to deal with pathogens. The Hunt River Basin is a 25-square-mile watershed located on the west side of Narragansett Bay and includes the communities of Exeter, North Kingstown, East Greenwich, West Greenwich, Coventry, West Warwick, and Warwick. The watershed is primarily forest, medium-density residential, and wetlands. In 1998, the state placed the Hunt River on its 303(d) list of impaired water bodies as impacted by fecal coliform bacteria that occurred primarily during wet-weather conditions.
As part of the study, the state identified five major sources of fecal coliform bacteria in the Hunt River watershed. These included runoff from highways and residential/commercial areas; a dairy farm; pigeons roosting under a bridge over a state highway; a horse farm; and resident waterfowl, domestic pets, and wildlife. The largest sources during dry weather were the dairy farm, pigeons, and wild and domestic animals, and stormwater runoff provided the largest source during wet weather. The determination of the sources of the pollutants was made through site visits during wet and dry conditions, review of aerial photos, topographical and land-use maps, and other GIS resources.
Water-quality monitoring performed by RIDEM had determined that fecal coliform concentrations were highest during the summer months in most rivers and streams, and it was extrapolated that this condition would apply to the Hunt River as well. A numeric water-quality target, consistent with the state’s standards for Class A (public drinking water/recreational activities/habitat) and Class B (habitat/secondary recreational activities) waters was established for the Hunt River.
A series of 14 best management practices (BMPs) was established, including eight structural stormwater BMPs and two that discouraged the presence of resident waterfowl. A public outreach program was recommended to educate the public about the impacts that resident waterfowl can have, and about the potential health risks associated with encouraging these waterfowl in local ponds, impounds, and lawns. Additional education included proper drainage maintenance and pet-waste cleanup. The dairy farm owner was contacted and BMPs were being implemented in conjunction with the Natural Resources Conservation Service (NRCS) and the RIDEM Division of Agriculture. These BMPs focused on fencing of riparian and wetland areas and addressing the heavy-use areas of the farm.
The horse farm located in the watershed was also targeted for BMPs, including a waste storage area and roof runoff management system. Funding for these BMPs was being obtained through RIDEM Nonpoint Source Program grants to supplement the NRCS and other sources. Finally, the pigeons under the bridge at the state route were targeted for a deterrent system designed to eliminate the roosting location.
Knowing What to Target
Knowing what to monitor and why as it relates to pathogens and other constituents is challenging to all parties. In the EPA document, “Protecting the Nation’s Waters Through Effective NPDES Permits: A Strategic Plan FY 2001 and Beyond,” (EPA-883-R-01-001, June 2001), the challenge of figuring out what to monitor is described: “Incorporating water quality standards into permits can be a complex process. The water quality standards being developed today are scientifically more complex and often require specialized implementation in different ecological regions. TMDLs [total maximum daily loads] add another layer of complexity in that a given facility must be considered within the context of the watershed and the other sources of pollution in that watershed. Further complicating this picture are several factors including: the need to consider varying hydrological conditions (wet and dry weather), some outdated water quality standards, inappropriate classification of waterbodies, inconsistent availability of water quality data, and lack of standardized water-quality-to-standards translation methodologies.”
A good example of the challenge of understanding what to sample is in the Las Vegas Wash and Lake Mead Watershed in southern Nevada. The cities of Las Vegas, North Las Vegas, and Henderson, as well as portions of Clark County, are experiencing a doubling of population approximately every 10 years. The Las Vegas Valley’s flows drain into Lake Mead and the Colorado River system. Elevations in the valley range from 11,918 feet at Charleston Peak in the Spring Mountains to about 1,500 feet at the eastern edge of the valley. The valley is drained to the southeast by the Las Vegas Wash and its 11 tributaries.
“What helps us decide what’s on the top our list is our permitting authority, and that’s the State of Nevada,” says Kevin Eubanks, assistant general manager for the Clark County Regional Flood Control District in Las Vegas. “We get 4 inches of rain per year, which is not a whole lot. One of our goals is to keep our resource allocation commensurate with a real problem. The other goal is to abide by the law. It’s an interesting balancing act there.”
Eubanks notes that one of the state’s primary concerns is construction runoff. “Being a very fast-growing community, there are a lot of construction sites. The pollutant of most concern is sediment leaving construction sites. We are in the process of developing a construction-site inspection program that compliments the state construction-site permitting program, in compliance with state and federal laws. Our local construction program focuses on compliance with local non-pollution ordinances.
“We’ve been sampling the major tributaries to the Las Vegas Wash since 1991 for a whole suite of constituents,” he continues. “Bacteria is one of those constituents. Our permit allows us to discharge to the Las Vegas Wash, so the Las Vegas Wash is our receiving water. We have had high hits for total coliform–not so much in dry-weather flows as in wet-weather flows–but not to the point that the state sees it as an impairment to the regulated use of the Las Vegas Wash.”
The Las Vegas Wash is not regulated for full-body contact. It is dominated by wastewater flow during dry weather and has additional flow only during wet weather. “We’re finding very great fluctuations in the bacteria,” says Eubanks. In spite of the significant growth in the Las Vegas metro area, this has not translated into an increase in the populations of pathogens within the water. “There have been some high numbers, but not consistently high on a daily basis, only associated with stormwater runoff. To this point, even given those numbers, we have determined so far that it’s not necessary to do anything to counter or improve those readings,” he says.
“We have taken the population data and plotted it against bacteria and other constituents and really shown no trends so far. Additionally, our sampling data for dry weather and wet weather has been so consistent since 1991 and has shown no real trends or change. We’re changing our sampling program starting this year to focus on the impacts of our detention basins and flood control system in improving stormwater quality. The original monitoring plan was intended to characterize stormwater in the Las Vegas Valley at the beginning of the permitting program. It has served that purpose in that it has shown no changes or no benefit of certain activities, so we’re going to focus on what our system and what our management plans might do to improve stormwater and monitor accordingly. As far as pathogens, the sampling thus far has shown no areas of significant concerns. We do get high levels when it rains. We’re not seeing a clear indication of whether it’s human or animal influence, and more of an indication that it might be occurring in nature more than human impacts.”
Much of what is regulated is decided by the states and, like water, flows down to the local agencies charged with water-quality monitoring. But local stakeholders and interests ultimately play a role in deciding what’s critical to monitor. In southern California, the Los Angeles County Flood Control District is the principal permittee for administering the NPDES program, with the LA County Department of Public Works handling the monitoring and sampling program. Each of the County’s 84 cities, excluding Long Beach, is included in six watershed management areas (WMAs) within the county. Several of the watersheds within the county are monitored for fecal coliform as an indicator.
“We can’t just keep expanding the pot to look for more and more exotic pollutants, usually costing more and more money,” states Gerald E. Greene, senior civil engineer with the City of Downey Department of Public Works. Downey is part of the San Gabriel River WMA. According to reports prepared by the Los Angeles County Department of Public Works, the total coliform criteria set forth in the Basin Plan was exceeded in 100% of the dry-weather samples in the San Gabriel River WMA during the 2002–2003 storm season. “We are focusing on finding what we think is the most appropriate attack point and going after those first,” says Greene. “As an example, there has been a significant shift through this new monitoring plan that has just been proposed to look at a variety of issues. It has been actually a very satisfying experience. The group that has worked together on this project has said, “˜Let’s work this or that problem out. This looks like a higher priority to us than the next item was, so let’s concentrate on this higher priority.'”
In LA County, the regulators have worked together with the local stakeholders in addressing the issues, states Greene. “We’ve had some difficulty with some groups at some times so in this case there seems to be a discussion to highlight the biggest problem, the most significant problems, or the ones that can be defined relatively easily and concentrate on them first. I really have actually been surprised and we’ve been trying to make some efforts with the cities to help fund some of the parts of it that were not being funded or were not going to have funding, because they’re worthwhile endeavors. The cities are generally feeling like this has been our process that we can work with. We don’t necessarily have to agree with everything, but it’s worthwhile and I think we’re heading in the right direction.”
In the Rogue Valley of southern Oregon, a 1992 TMDL addressed phosphorus, ammonia, and biological oxygen demand in the Bear Creek Watershed. A second TMDL is currently under development that will address temperature and bacteria and is expected to be completed in 2005. “We found bacteria throughout the system in terms of storm drain monitoring,” reports Greg Stabach, project manager for the Rogue Valley Council of Governments in Central Point, OR. “Generally you get more bacteria in the summer than in the winter. That has to do with the nutrients in the lower flow, because there’s a lot of irrigation and a lot of potential sources in the valley including leaking septic systems, agricultural, and feral animals. In terms of pinpointing sources, we’re looking at experimenting with different technologies. We have a pilot project looking at DNA fingerprinting, which is trying to get at the underlying source of the bacteria in the water. You get a lot here in the summer and it’s not really any consistent source. We’re not really sure exactly where it’s coming from.”
While the Bear Creek Watershed continues to maintain a rural lifestyle, housing development is increasing in the Grant’s Pass area. Orchards and livestock are the predominant agricultural land use, and both have the potential to affect the watershed. Another former land use was mining, so determining what is a concern becomes difficult. “Looking at bacteria, there’s a lot of contact recreation, so trying to keep the streams safe so that people can use them and enjoy them is very important,” says Stabach. Other parameters of concern may be examined more closely. “There are concerns of a number of different things in terms of orchards and the possibility of having pesticides in the stormwater.” From the mining that was historically done in the valley, he says, “There’s the possibility of metals and other toxics.”
Data drive the decision of whether a particular constituent becomes a concern, comments Stabach. “There’s a general lack of data, so it would really be evidence that something is a problem.” He notes that in the streams being monitored as a condition of the 1992 TMDL “there have been some parameters that we’ve expanded because of the data we’ve collected. There needs to be some sort of a trigger that would make it a concern. Usually finding something, depending on how it’s collected, is enough to go a step further. It all depends on what it is, how much, and whether somebody gets excited about it.”
Constituents such as antibiotics or hormones from feedlots don’t appear to be an issue yet, and regulation of agricultural operations is handled by the Oregon Department of Agriculture. “It could potentially be on the radar screen,” Stabach observes. “In Oregon, the Oregon Department of Agriculture is responsible for handling water-quality issues with the agricultural community, so they’re sometimes separately regulated from the communities in the valley. The one thing that I think is a little more relevant is the potential impact of feedlots and manure on bacteria levels in terms of having a pile too close to the stream. I know if that’s a concern–it’s kind of a complaint-driven system–that the Department of Agriculture will take care of it.”