Assessment of Fecal Contamination in Oklahoma Water Systems through the Use of Sterol Fingerprints
Fecal contamination is a major concern for water quality management, since the fecal materials are associated with pathogens that can cause illness wherever water is used for recreational, drinking and aquaculture purposes. In order to monitor source(s) of fecal contamination in Oklahoma water systems, sterol profiles were previously examined in rural and urban samples collected from the Illinois River Basin and the Norman Wastewater Treatment Plant (WWTP), respectively. Two distinctive,
... distinctive, qualitatively and quantitatively, sterol fingerprints were recognized. Despite the effective removal of organic material by the Norman WWTP, human-derived sterol fingerprints, characterized by a predominance of fecal stanols such as coprostanol, were still significant in the output from the plant. The source of fecal material in the Illinois River samples (rural) was defined as being characteristic of corn-feed chicken manure originating from surrounding feedlots through the principal component analysis (PCA) of the sterol distributions and carbon compound specific isotope analysis of selected sterols (CSIA, δ 13 C). Thiosteranes, formed during sludge treatments, were also shown to be useful tracers for monitoring sludge application in agriculture fields. The results obtained were used to provide water management authorities with qualitative insights into the source of fecal material inputs into the environment. Environments 2016, 3, 28 2 of 16 with feces, whenever water is used for recreational, drinking and aquaculture purposes    . Fecal contamination also promotes algal proliferation  that leads to eutrophication that destabilizes the equilibrium of aquatic systems  . In order to assess the fecal contamination, fecal indicator bacteria (FIB), which link the observed illness and level of the bacterial indicator (e.g., Escherichia coli and enterococci), were developed and applied globally for water quality monitoring  . FIB sources are multiple and widespread in the environment. Wildlife, domestic pets, defective septic tanks and sewage from human wastewater are the major potential sources of fecal contamination  . Moreover, human-sourced fecal contamination was estimated to be more related to health risk than non-human sources  . The concept of microbial source tracking (MST) was recently introduced for monitoring fecal contamination [5, 10] . It offers the possibility of identifying, and in some cases, of quantifying nonpoint or multiple sources of pollution. MST combines multiple approaches for source identification. They were developed based on identification of numerous feces-related microbiological (e.g., Bifidobacterium spp.), molecular (e.g., DNA fingerprints) and biochemical (e.g., sterols) markers found in drinking, recreational, groundwater and aquatic wildlife habitat [5, 10] . Specific MST markers for human, different livestock and wildlife are well defined and have been confirmed  . MST has been successfully applied for source identification in some fecal contamination case studies     . In order to help choose the most appropriate method for source tracking, several authors have reviewed and described the performance of existing MST approaches [3, 5, 10, 11] . According to these authors, the microbiological method is easy to perform but some specific markers are not very abundant in the environment, and microbial survival rates are also variable, altering the reliability of results. The molecular approach is rapid and easy to perform, and markers also show high specificity. Human, pig and ruminants specific markers were well investigated and widely applied in some case studies  . However, due to the geographical and/or environmental dependence of some specific markers and an incomplete molecular database, the effectiveness of the molecular approach could be then limited [3, 10] . Nevertheless, the biochemical markers, in particular sterols, bearing a degree of specificity are also valuable for source discrimination. Sterols are a group of organic compounds that are synthesized by a large range of living organisms like plants, animals, bacteria and fungi    and are found in various environmental matrices such as water, soil and sediments. A significant number of recent studies has shown that sterol distributions are capable of distinguishing human and non-human sources of fecal contamination    . Sterol distributions within these fingerprints may also be affected by climatic and geographic factors    . Leeming, et al.  pointed out that fecal sterol profiles could be specific for some warm-blooded animals based on diet and the presence of anaerobic bacteria in the gut. Sterol profiles will vary according to diet, and the major ingested sterols will vary for herbivores and carnivores as well. During the digestion process, through the help of intestinal microflora (if present), the ingested sterols are transformed into stanols with different isomeric structures and then released into the environment. However, in some warm-blooded animals, such as several avian herbivores, the intestinal microflora are not very abundant, or even absent in the gut, the ingested sterols are not significantly altered during digestion before being released. In the case of two or more organisms having similar qualitative fecal sterol distributions, the sterol concentrations may provide an additional tool to distinguish the different organisms. The quantity of produced fecal sterols can vary considerably depending on the animal sources. For instance, humans and pigs have similar fecal sterol fingerprints, but the sterol concentration is much higher in human feces than in pig feces. Nevertheless, in some receiving water, use of sterol concentration could be limited to distinguish human and pig feces due to the dilution effect. In this case, the molecular MST analysis would be more appropriate. In addition, some endogenous sterols, which are biosynthesized and discharged to the digestive tract, could also be specific to a particular host [21, 26] . The combination of all the above factors is responsible for the specificity of the fecal "sterol fingerprints", qualitatively and quantitatively, for most warm-blooded animals. Environments 2016, 3, 28 3 of 16 This paper aims to provide an overview on the application of sterol fingerprints as a source tracer for fecal contamination in water quality monitoring in different environmental backgrounds, such as urban and rural, within the state of Oklahoma (U.S.). In addition, it will provide water management authorities with a qualitative insight into the impact of human and non-human input of fecal material into the Oklahoma water systems. Materials and Methods Samples Sterol fingerprints from urban and rural water samples from Oklahoma have been characterized over the past four years. Samples were collected from the Norman wastewater treatment plant (WWTP) and the Illinois River Basin (Figure 1 ). Samples collected included water, sediment and sludge. Environments 2016, 3, 28 3 of 16 such as urban and rural, within the state of Oklahoma (U.S.). In addition, it will provide water management authorities with a qualitative insight into the impact of human and non-human input of fecal material into the Oklahoma water systems. Materials and Methods Samples Sterol fingerprints from urban and rural water samples from Oklahoma have been characterized over the past four years. Samples were collected from the Norman wastewater treatment plant (WWTP) and the Illinois River Basin (Figure 1 ). Samples collected included water, sediment and sludge.