Effect of Animal Waste Spills in the Cape Fear Watershed

4.1 Introduction

    During summer of 1995 at least six animal waste lagoons ruptured, releasing millions of gallons of liquid waste into receiving streams in Eastern North Carolina (J.C. Barker, NCSU, unpublished data). At least four spills occurred in the Cape Fear River watershed, and our laboratory compiled extensive data on two of these spills. A lagoon serving 75,000 chickens located just north of Beulaville in Duplin County breached on July 3rd and released 8.5 million gallons of poultry waste into Limestone Creek, which enters the Northeast Cape Fear River near Hallsville, N.C. The breach was caused by a combination of factors including an overloaded lagoon, rainy weather, and a leaking 12-inch drainpipe running along the lagoon wall which likely weakened the wall.
    On August 8th a Brunswick County lagoon serving 6400 head of swine leaked, releasing 2 million gallons of swine waste into a system of freshwater tidal creeks. The leak occurred through improperly plugged field tiles. The effluent entered Harris Creek, which feeds into Mills and Rices Creeks; these streams, in turn, enter Town Creek, a 4th order tributary of the Cape Fear Estuary. The Duplin County spill occurred during a period of high precipitation, but the Brunswick county spill occurred during hot, dry weather. The spills were the result of various combinations of adverse weather conditions, human mismanagement, and improper lagoon construction and/or maintenance.

4.2 Physical Effects

    Stream areas affected by the spills displayed a notable odor, and the water suffered discoloration. This was a deep reddish tinge in areas affected by both the poultry waste lagoon breach and the Brunswick County swine waste lagoon leak. Turbidity levels were high in areas affected by the plumes from the spills (Table 4.1). As a reference, the North Carolina state turbidity standard for acceptable water quality is 25 NTU (NCDEHNR 1994). Microscopic examination of affected waters in Harris Creek showed the presence of large quantities of bacteria, phytoplankton, and unidentified material.

Table 4.1. Maximum turbidity levels (NTU) in plume areas of streams affected by waste lagoon spills.

    The spills also introduced large BOD loads into the receiving waters. In and near plume areas, dissolved oxygen (DO) levels were nearly anoxic following the spills (Table 4.2). This indicates that there was a considerable amount of organic matter in the waste plumes, which led to greatly increased bacterial respiration in the receiving waters.

Table 4.2. Minimum surface water dissolved oxygen levels (mg/L) in stream areas affected by animal waste plumes, measured 1-3 days after the spills.

    The North Carolina state dissolved oxygen standard is 5.0 mg/L for surface waters, and 4.0 mg/L for swamp waters (NCDEHNR 1994). State biologists reported a fish kill in Limestone Creek during the Duplin County spill, and we suspect that low DO concentrations were a major contributing factor. The length of time that DO was depressed varied from a few days in Limestone Creek to more than two weeks following the Brunswick County swine lagoon breach. Recovery in the streams depended on subsequent rainfall and flushing events.
    Ten days after the chicken waste lagoon breach we sampled DO from a series of bridges beginning upstream of the input of Limestone Creek (NCF-24) all the way downstream to the upper estuary of the Northeast Cape Fear River at NCF-6 (Fig. 4.1). Our results indicated that the Duplin County lagoon breach introduced a heavy BOD load which were carried at least 90 km downstream in the Northeast Cape Fear River to Station NCF117. This load decreased bottom-water DO levels to 1.0 mg/L or less at the downriver location from 10 days to 2 weeks following the spills (Fig. 4.1).

4.3 Chemical Effects

    The waste lagoon ruptures introduced excessive loads of nutrients into the receiving waters. It is typical for waste lagoon liquid to have a high percentage of its nitrogen content in the form of ammonia, and a high percentage of its total phosphorus content in the form of orthophosphate (Westerman et al. 1990). Our data show that both ammonia and orthophosphate were introduced in large quantities into Limestone Creek and Harris Creek (Table 4.3).
    Nitrate contributes only a small percentage of the waste nitrogen content. Due to the anoxic or hypoxic conditions caused by the high BOD load in the waste, the reduced inorganic ammonia form prevails. The nutrient load was not confined to the immediate spill areas; there was long-distance transport documented in one of the cases. Ten days after the chicken waste lagoon rupture, ammonia concentrations in the Northeast Cape Fear River were elevated 9-fold over the previous month at a station (NCF117) 90 km downstream from the input from Limestone Creek. Ammonia concentrations similar to those found in the spill sites are known to have sublethal to lethal effects on fish (Boyd, 1979).

Table 4.3. Maximum surface water inorganic nutrient concentrations (mg/L) measured in stream areas affected by animal waste lagoon spill plumes.

4.4 Biological Effects

    Being warm-blooded animals, domesticated animals carry fecal coliforms and pathogenic microbes (Dewi et al. 1994; Sobsey 1996). These organisms are not deactivated in waste holding ponds; rather, the conditions there (carbon source, nutrients, UV protection) support their survival. During the lagoon breaches large quantities of these potential human pathogens entered the environment (Table 4.4). The high turbidity levels in the waste plumes formed a UV-protective environment for enteric pathogens entering the open water (Pommepuy et al. 1992).
   Clostridium perfringens is a pathogenic bacterium which is specific to fecal wastes and has extensive survival capabilities through spore-forming abilities (Bisson and Cabelli 1980; Sorensen et al. 1989). It is believed to be a reliable indicator of the presence of many pathogens because its properties are analagous to those of human enteric viruses (Fujioka and Shizumura 1985; Sorensen et al. 1989). Samples were collected for this pathogen at several sites near the chicken waste lagoon spill the day following the incident. Results indicated high concentrations at several locations, with the highest near the juncture between Limestone Creek and the Northeast Cape Fear River (Table 4.4). The North Carolina state fecal coliform standard to protect human health for these receiving waters is less than or equal to 200 CFU/100 mL (NCDEHNR 1994).
    Surface water fecal coliform concentrations declined considerably after a few days; however, many of these organisms evidently found refuge in the sediments. A rain event two weeks after the Brunswick County lagoon leak caused resuspension of high concentrations (>800 CFU/100 mL) of fecal coliforms in Harris Creek surface waters. Water-column resuspension of sedimented fecal coliforms has been documented from polluted areas in other studies (Grimes 1975; Goyal et al. 1977).

Table 4.4. Maximum fecal coliform and Clostridium perfringens concentrations (CFU/100 mL) found in surface waters of streams affected by animal waste plumes, sampled 1-3 days after the spills.

    The nutrient loads stimulated phytoplankton blooms in the Brunswick County swine lagoon leak. Chlorophyll a levels exceeded 100 ug/L in areas affected by the swine lagoon waste (Table 4.5). In this fresh, but tidally-influenced area, the algal blooms lasted for several weeks and moved around possibly in accordance with the tides and sluggish streamflow. Since the North Carolina state chlorophyll a standard for acceptable water quality is 40 ug/L (NCDEHNR 1994), it is clear that waste lagoon breaches have a high potential for causing eutrophication symptoms, particularly in nutrient-sensitive waters. These blooms can lead to further low dissolved oxygen problems, food chain alterations, and possible toxic species. Microscopic observation of phytoplankton samples near the spill site showed high concentrations of the pollution-tolerant euglenoids (Euglena, Trachelomonas, and Phacus), flagellated chrysophytes, large dinoflagellates, and numerous small green non-flagellated unicells.

4.5 Conclusions

    The animal waste spills produced a variety of undesirable environmental effecrts on both near and distant receiving waters. Physical effects included high turbidity levels and low dissolved oxygen levels, creating unfavorable habitat for many organisms. Turbidity, however, provides a protective environment for fecal coliforms and other undesirable human pathogens. Chemical effects were most evident by loading of high concentrations of organic and inorganic nutrients. These nutrients can cause algal blooms and, in the case of ammonia, toxicity to fish and other organisms. Organic and inorganic nutrient loads also provide an environment conducive to the survival and propagation of fecal coliform bacteria and other pathogenic microbes. Biological effects include algal bloom formation and the release of quantities of untreated pathogenic microorganisms into the environment. Our results also demonstrate that waste lagoon constituents can be carried far downstream following spill events.
    The previous discussion focused on data gathered by Cape Fear River Program researchers for only two waste lagoon spills. A third even large spill on the New River in Onslow County was investigated as part of a cooperative effort with Dr. J. M. Burkholder of the North Carolina State University Botany Department and the results are presented elsewhere (Burkholder 1996; Mallin et al. 1996b). Other more remote spills were not sampled or even detected until several days after the incidents. The Cape Fear watershed hosts the highest concentration of swine and poultry operations in the state, many of which are situated in formerly pristine blackwater areas. With continually increasing construction of waste lagoons concurrent with swine industry expansion, the potential for water quality problems increases.
    Animal waste lagoons are reservoirs of multiple ingredients for water quality problems. We emphasize that the abundance of enteric pathogens in swine waste also poses risks to human health. Lagoon leaks and breaches can occur because of human error, deliberate mismanagement, faulty construction, or adverse weather conditions. The ultimate solution for these current and future problems is to apply improved technology to animal waste treatment and reduce dependence on lagoon systems.

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