Analyses of nutrient and E. coli contamination within the Otter Creek watershed, Madison County, Kentucky

The Otter Creek watershed exhibits dissolved nutrient (ammonium, NH4+; nitrate, NO3-; phosphate, PO43-) and Escherichia coli contamination that compromises its water quality. The watershed covers a substantial portion of Madison County (~168 km2) and consists of Lake Reba, Dreaming Creek, and east and west forks, all of which enter the trunk of Otter Creek before flowing into the Kentucky River. Suspected contaminate sources include leaky sewage system pipes, runoff from pasture land, and septic system leachate. We collected 330 water samples on three occasions during summer 2014 to determine the extent and sources of contamination, in hopes to mitigate contamination and improve water quality. Nutrients were measured using colorimetric methods, whereas E. coli counts were determined by using IDEXX materials. We found highest nutrient concentrations immediately below discharge from the Otter Creek sewage treatment plant (STP), which is a point source for nitrate (3.5 – 4.4 mg/L N-NO3) and phosphate (0.8 - 1.0 mg/L P-PO3). Background levels were ~0.4 mg/L N-NO3 and ~0.09 mg/L P-PO4. Nitrate and phosphate values progressively decrease at stations downstream from the STP. Ammonium averages ~0.4 mg/L N-NH4, ranging from 0 to 1.4 mg/L in May, but measurable ammonium occurs only sporadically in June and July. The highest observed value is 1.8 mg/L N-NH4 (station CC, June) with the majority of stations having no measurable ammonium. 53% of samples exceeded EPA E.coli concentration standards for human contact (\u3e575 cfu/100 mL) and are distributed throughout the watershed, displaying classic non-point-source pollution. Phosphate and fecal microbes are the principal contaminants within the watershed. Compared to a national data set, phosphate contamination is most severe, often exceeding the 90th percentile value. Nitrate is generally below the 25th percentile level. Ammonium concentration is not related to STP discharge but exceeds the 90th percentile value in May; concentrations approach those of pristine streams in June and July. Non-point sources for nitrate, phosphate, and E. coli are likely due to leaky sewage pipes within the town of Richmond, and to pasture runoff in rural areas. Ammonium sources are more enigmatic, but seem associated with pasture land and septic systems. Sampling in June and July after rain events saw higher nitrate, phosphate, and E. coli concentrations, but lower ammonium levels relative to measurements in May

Preliminary results of a nutrient source study in Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake (Madison County, Kentucky) is an eutrophic lake formed by damming Taylor Fork, part of the Silver Creek watershed. Two principal tributaries drain urban areas of the city of Richmond, agricultural land typified by cattle grazing, and a high-density residential area using septic systems. The lake is “nutrient impaired,” so it is likely that anthropogenic nutrient loading is affecting water quality. Our study aims to first characterize the physical characteristics and water quality of the lake (2006), and then determine the specific proportion of nutrient inputs (2007) to the lake with the aim of remediating any possible degradation of water quality. We anticipate using nitrogen isotopes and microbial DNA templates to identify specific nutrient sources. Research started in May 2006 with work occurring throughout the 2006 field season with the intent of establishing a baseline for key lake parameters. We used an YSI probe to measure temperature, conductivity, oxygen concentration, and pH and assayed for total ammonia nitrogen using the sodium hypochlorite, colorimetric method. The lake was already strongly stratified in May with disoxic and anoxic water below about 4 meters. Stratification strengthened in the summer with the disoxic-oxic boundary moving upward to about 3 meters, and showing a sharper gradient between oxic and disoxic waters. Ammonium concentrations are typically zero in the oxic zone, and increase in concentration with increasing water depth in anoxic waters to about 6 ppm. We anticipate that phosphate and nitrate concentrations will mirror ammonium concentration profiles in character

Dynamics of a eutrophic lake (Wilgreen Lake, Madison County, Kentucky): A first step in cleansing a lake system impaired by nutrient loading

WilgreenLake (Madison County, Kentucky) is a eutrophic lake formed by damming Taylor Fork, part of the Silver Creek watershed. The lake is listed “nutrient impaired” by the Commonwealth and the EPA, and it is likely that nutrient input from human activities is affecting water quality. Our study aims first to characterize the physical characteristics and water quality of the lake (2006), and then to determine the specific proportion of nutrient inputs (2007) to the lake with the ultimate aim of improving its water quality. Research started in May 2006 with work occurring throughout the 2006 field season with the intent of establishing a baseline for key lake parameters. We used a YSI probe to measure temperature, conductivity, oxygen concentration, and pH, and assayed for total ammonia nitrogen using the sodium hypochlorite, colorimetric method. The lake was already strongly stratified in May with disoxic and anoxic water below about 4 meters. Stratification strengthened in the summer with the disoxic-oxic boundary moving upward to about 3 meters, showing a sharper gradient oxygen gradient. Ammonium concentrations are typically zero in the oxic zone, and increase in concentration with increasing water depth in anoxic waters to about 5 ppm

Sources of nutrient and Escherichia coli contamination within the Otter Creek watershed, Madison County, Kentucky

The Otter Creek watershed exhibits dissolved nutrient (ammonium, NH4; nitrate, NO3; phosphate, PO4) and Escherichia coli contamination that compromises its water quality. The watershed covers a substantial portion of Madison County and consists of Lake Reba, Dreaming Creek, and east and west forks, all of which enter the trunk of Otter Creek before flowing into the Kentucky River. Suspected contaminate sources include leaky sewage system pipes, runoff from pasture land, and septic system leachate. We collected 330 water samples on three occasions during summer 2014 to determine the extent and sources of contamination. Nutrients were measured using colorimetric methods, whereas E. coli counts were determined by using IDEXX materials. We found highest nutrient concentrations immediately below discharge from the Otter Creek sewage treatment plant (STP), which is a point source for nitrate (3.5 – 4.4 mg/L N-NO3) and phosphate (0.8 - 1.0 mg/L P-PO3). Background levels were ~0.4 mg/L N-NO3 and ~0.09 mg/L P-PO4. Nitrate and phosphate values progressively decrease at stations downstream from the STP. Ammonium averages ~0.4 mg/L N-NH4, ranging from 0 to 1.4 mg/L in May, but measurable ammonium occurs only sporadically in June and July. The highest observed value is 1.8 mg/L N-NH4 (station CC, June) with the majority of stations having 0 mg/L. 53% of samples exceeded EPA E.coli concentration standards for human contact (\u3e575 cfu/100 mL) and are distributed throughout the watershed, displaying classic non-point-source pollution. Phosphate and fecal microbes are the principal contaminants. Compared to a national data set, phosphate contamination is most severe, often exceeding the 90th percentile value. Nitrate is generally below the 25th percentile level. Ammonium concentration is not related to STP discharge but exceeds the 90th percentile value in May; concentrations approach those of pristine streams in June and July. Non-point sources for nitrate, phosphate, and E. coli are likely due to leaky sewage pipes within the town of Richmond, and to pasture runoff in rural areas. Ammonium sources are enigmatic, but seem associated with pasture land and septic systems. Sampling in June and July after rain events saw higher nitrate, phosphate, and E. coli concentrations, but lower ammonium levels relative to measurements in May

Nuclear thermal propulsion transportation systems for lunar/Mars exploration

Nuclear thermal propulsion technology development is underway at NASA and DoE for Space Exploration Initiative (SEI) missions to Mars, with initial near-earth flights to validate flight readiness. Several reactor concepts are being considered for these missions, and important selection criteria will be evaluated before final selection of a system. These criteria include: safety and reliability, technical risk, cost, and performance, in that order. Of the concepts evaluated to date, the Nuclear Engine for Rocket Vehicle Applications (NERVA) derivative (NDR) is the only concept that has demonstrated full power, life, and performance in actual reactor tests. Other concepts will require significant design work and must demonstrate proof-of-concept. Technical risk, and hence, development cost should therefore be lowest for the concept, and the NDR concept is currently being considered for the initial SEI missions. As lighter weight, higher performance systems are developed and validated, including appropriate safety and astronaut-rating requirements, they will be considered to support future SEI application. A space transportation system using a modular nuclear thermal rocket (NTR) system for lunar and Mars missions is expected to result in significant life cycle cost savings. Finally, several key issues remain for NTR's, including public acceptance and operational issues. Nonetheless, NTR's are believed to be the 'next generation' of space propulsion systems - the key to space exploration

Reducing False Alarms of Intensive Care Online-Monitoring Systems: An Evaluation of Two Signal Extraction Algorithms

Online-monitoring systems in intensive care are affected by a high rate of false threshold alarms. These are caused by irrelevant noise and outliers in the measured time series data. The high false alarm rates can be lowered by separating relevant signals from noise and outliers online, in such a way that signal estimations, instead of raw measurements, are compared to the alarm limits. This paper presents a clinical validation study for two recently developed online signal filters. The filters are based on robust repeated median regression in moving windows of varying width. Validation is done offline using a large annotated reference database. The performance criteria are sensitivity and the proportion of false alarms suppressed by the signal filters

Using E. coli and Bacteroides distribution and abundance in a eutrophic lake as a tracer for nutrient inputs, Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake is a eutrophic lake that has been listed on the EPA’s 303d list as nutrient impaired. Potential sources of this impairment are likely from humans, cattle manure, and fertilizers. We suspect that the majority of nutrients originate from human sources, namely from septic tank effluent emanating from key housing developments ringing the lakeshore. We test our hypothesis with conventional microbial assays (Escherichia coli) and RT-PCR techniques (Bacteroides). We took water samples at 19 sampling locations on 4 occasions, and measured the abundance of Escherichia coli using IDEXX methods. Corresponding sub-samples slated for potential PCR analysis were stored at -40oC. We chose PCR assay candidates on the basis of elevated E. coli levels, and the probability of differing source contributions. There is a systematic decline in E. coli microbial abundance distal to developments with closely-spaced septic units. This suggests that the principal source of microbial input is from septic systems; however, we cannot eliminate the possibility that fecal microbes are introduced into the lake via inflows. We used quantitative PCR analysis to measure Bacteroides abundance, and to distinguish between human and cattle sources. We measured 14 samples and found total fecal microbe concentrations in all samples targeting all Bacteroides species ranged from 45 mg/L to 142 mg/L. Unlike other studies, there was no apparent relationship between the concentration of all Bacteroides species and that of E. coli. We also attempted to quantitatively determine the proportion of Bacteroides contributions from specific sources, namely human and bovine fecal matter. Although fecal contamination was measured in all 14 samples, only 1 sample had significant amounts of human fecal contamination (21%) as measured by the human-associated Bacteroides assay. None of the samples had significant amounts bovine fecal concentration as measured by the bovine-associated Bacteroides assay. These inconclusive results suggest that either there are other unidentified sources of fecal contamination by Bacteroides and/or E. coli, or that the prevailing drought conditions skewed our results by not capturing fecal transport effects due to lack of surface and/or groundwater flow

Nutrient and fecal microbe sources for a eutrophic lake and recommended remediation steps, Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake is a man-made lake, classified as nutrient-impaired (303d list) by the EPA and State of Kentucky. The lake drains a watershed with residential developments, cattle pasture, modified woodlands, and some industrial/urban usage in the city of Richmond. The principal tributaries are Taylor Fork and Old Town Branch that meet to form the trunk of the lake approximately one mile in length. The upper reaches of Taylor Fork are adjacent to a densely-packed (quarter-acre lots) housing development with septic systems, and its watershed drains some portions of southern Richmond. Old Town Branch drains cattle pasture and residential areas of moderate to large lot size. An intermittent tributary flowing into Pond Cove drains cattle pasture and one small housing development. Fecal material contributes both nutrients and microbes to Wilgreen Lake. Both cattle and human fecal material enter the lake as documented by high fecal microbes counts and DNA tracing techniques. DNA tracing methods are limited by our sampling frequency but show that bovine Bacteroides microbes dominate water samples even at loci where suspected septic effluent enters the lake. The nitrogen isotopic composition (d15N) of lake plankton and algae are broadly consistent with nitrogen input from human fecal material, but results are equivocal. We suspect that large amounts of nutrients do enter the lake through septic groundwater input, however, the strong bovine signal clearly suggests deployment of remediation methods that would limit runoff from pastures adjacent to Wilgreen Lake and within its watershed. Such methods include fencing cattle off from drainages and the lake, and planting vegetative buffers around stream and lake margins. Our data alone cannot justify elimination of septic systems by costly implementation of a sewage treatment system