D. R. Shelton

FECAL COLIFORM TRANSPORT AS AFFECTED BY SURFACE CONDITION

Land application of manure is recommended to recycle organic matter and nutrients, thus enhancing the soil quality and crop productivity. However, pathogens in manure may pose a human health risk if they reach potable or recreational water resources. The objective of this study was to observe and quantify the effects of vegetated filter strips (VFS) on surface and vertical transport of fecal coliform (FC) bacteria, surrogates for bacterial pathogens, released from surface-applied bovine manure. A two-sided lysimeter with 20% slope on both sides was constructed with a sandy loam soil on one side and a clay loam soil on the other. Each side of the lysimeter was divided into two subplots (6.0 × 6.4 m), one with grass and the other with bare soil. Plots were instrumented to collect runoff samples along a 6.0 m slope at three equidistant transects. Samples of runoff were also collected in a gutter at the edge of each plot. All plots were equipped with multi-sensor capacitance moisture probes to monitor water content through the soil profile. Bovine manure was applied at the top of each plot in a 30 cm strip. Rainfall was simulated at a 61 mm h-1 intensity using a portable rainfall simulator. Surface runoff rate was measured and water quality sampled periodically throughout the simulation. Soil samples were taken at incremental depths (0-60 cm) after each simulation. Runoff (as % of total rainfall) decreased from 93% to 12% in the bare vs. vegetated clay loam plots and from 61% to 2% in the bare vs. vegetated sandy loam plots. The reduced runoff from vegetated plots decreased the surface transport of FC while increasing its vertical transport. The amount of FC in runoff (as % of applied) decreased from 68% to 1% in the bare vs. vegetated clay loam plots and from 23% to non-detectable levels in the bare vs. vegetated sandy loam plots. These data indicate that VFS can reduce surface transport of FC, even for slopes as high as 20%, especially in soils with high infiltration (e.g., sandy loam).

Response of coliform populations in streambed sediment and water column to changes in nutrient concentrations in water

As sediments increasingly become recognized as reservoirs of indicator and pathogen microorganisms, an understanding of the persistence of indicator organisms becomes important for assessment and predictions of microbial water quality. The objective of this work was to observe the response of water column and sediment coliform populations to the change in nutrient concentrations in the water column. Survival experiments were conducted in flow-through chambers containing sandy sediments. Bovine feces were collected fresh and introduced into sediment. Sixteen days later, the same fecal material was autoclaved and diluted to provide three levels - 1×, 0.5×, and 0.1× of nutrient concentrations - spike in water column. Total coliforms, Escherichia coli, and total aerobic heterotrophic bacterial concentrations were monitored in water and sediment. Bacteria responded to the nutrient spike with initial growth both in the water column and in sediment. The response of bacterial concentrations in water column was nonlinear, with no significant changes at 0.1 and .5× spikes, but a substantial change at 1× spike. Bacteria in sediment responded to the spikes at all added nutrient levels. Coliform inactivation rates both in sediment and in water after the initial growth occurred, were not significantly different from the inactivation rates before spike. These results indicate that introduction of nutrients into the water column results in nonlinear response of E. coli concentrations both in water and in sediments, followed by the inactivation with the same rate as before introduction of nutrients.

Storm water pollutant removal performance of compost filter socks.

In 2005, the U.S. Environmental Protection Agency (USEPA) National Menu of Best Management Practices (BMPs) listed compost filter socks (FS) as an approved BMP for controlling sediment in storm runoff on construction sites. The objectives of this study were to determine if FS with or without the addition of a flocculation agent to the FS system can significantly remove (i) suspended clay and silt particulates, (ii) ammonium nitrogen (NH(4)-N) and nitrate-nitrite nitrogen (NO(3)-N), (iii) fecal bacteria, (iv) heavy metals, and (v) petroleum hydrocarbons from storm water runoff. Five separate (I-V) 30-min simulated rainfall-runoff events were applied to soil chambers packed with Hartboro silt loam (fine-loamy, mixed, active, nonacid, mesic fluvaquentic Endoaquepts) or a 6-mm concrete veneer on a 10% slope, and all runoff was collected and analyzed for hydraulic flow rate, volume, pollutant concentrations, pollutant loads, and removal efficiencies. In corresponding experiments, runoff was analyzed for (i) size of sediment particles, (ii) NH(4)-N and NO(3)-N, (iii) total coliforms (TC) and Escherichia coli, (iv) Cd, Cr, Cu, Ni, Pb and Zn, and (v) gasoline, diesel, and motor oil, respectively. Results showed that: (i) FS removed 65% and 66% of clay (<0.002 mm) and silt (0.002-0.05 mm), respectively; (ii) FS removed 17%, and 11% of NH(4)-N and NO(3)-N, respectively and when NitroLoxx was added to the FS, removal of NH(4)-N load increased to 27%; (iii) total coliform and E. coli removal efficiencies were 74 and 75%, respectively, however, when BactoLoxx was added, removal efficiency increased to 87 and 99% for TC and 89 and 99% for E. coli, respectively; (iv) FS removal efficiency for Cd, Cr, Cu, Ni, Pb, and Zn ranged from 37 to 72%, and, when MetalLoxx was added, removal efficiency ranged from 47 to 74%; and (v) FS removal efficiency for the three petroleum hydrocarbons ranged from 43 to 99% and the addition of PetroLoxx increased motor oil and gasoline removal efficiency in the FS system.

Depth-Dependent Survival of Escherichia coli and Enterococci in Soil after Manure Application and Simulated Rainfall

ABSTRACT Once released, manure-borne bacteria can enter runoff via interaction with the thin mixing layer near the soil surface. The objectives of this work were to document temporal changes in profile distributions of manure-borne Escherichia coli and enterococci in the near-surface soil layers after simulated rainfalls and to examine differences in survival of the two fecal indicator bacteria. Rainfall simulations were performed in triplicate on soil-filled boxes with grass cover and solid manure application for 1 h with rainfall depths of 30, 60, and 90 mm. Soil samples were collected weekly from depth ranges of 0 to 1, 1 to 2, 2 to 5, and 5 to 10 cm for 1 month. Rainfall intensity was found to have a significant impact on the initial concentrations of fecal indicator bacteria in the soil. While total numbers of enterococci rapidly declined over time, E. coli populations experienced initial growth with concentration increases of 4, 10, and 25 times the initial levels at rainfall treatment depths of 30, 60, and 90 mm, respectively. E. coli populations grew to the approximately the same level in all treatments. The 0- to 1-cm layer contained more indicator bacteria than the layers beneath it, and survival of indicator bacteria was better in this layer, with decimation times between 12 and 18 days after the first week of growth. The proportion of bacteria in the 0- to 1-cm layer grew with time as the total number of bacteria in the 0- to 10-cm layer declined. The results of this work indicate the need to revisit the bacterial survival patterns that are assumed in water quality models.

Survival of E. coli O157:H12 in creek sediments after inoculation and re-inoculation

This work tested the hypothesis that E. coli survival after streambed sediment inoculation does not differ significantly from survival in the same sediment after re-inoculation. The E. coli O157:H12 survived in two sediments with markedly different particle size distributions and organic matter contents in one-month-long experiments in flow-through chambers at 14°C and 23°C. The inactivation rates after re-inoculation were smaller than after inoculation; the differences were significant (P < 0.1) in two of four experiments. This study suggests that E. coli O157:H12 was able to adapt to the sediment environment so that its survival after re-inoculation improved.