Going with the Flow - Analyzing the impact of failing septic systems on the storm-driven transport of sediment-associated fecal microbes
Abstract
In the Alabama Black Belt, shrink-swell clays (vertisols) result in continual failure of traditional septic systems, leaving residents with the options of continual septic pumping, installation of expensive alternative systems or the use of straight pipes, which discharge raw sewage onto nearby surfaces. Even though the latter is technically illegal, the impoverished residents simply cannot afford the other options. A recent study of this area showed that up to 60% of the homes in Wilcox County use straight pipes, resulting in millions of gallons of raw sewage discharged. The nature of the vertisols, which swell when wet, cause this fecal effluent to sit on the surface until rain events eventually flushed along with sediment into local waterways. The potential to transport large fluxes of fecal contaminants into surface water during rain events is concerning and yet has not been well characterized. The degree to which fecal microbes are associated with the suspended sediment load (SSL) has important implications for the sustained transport of these contaminants within the waterway, with ~60% of fecal microbes in surface water during storms associated with particles. Therefore, an accurate and efficient way to capture the SSL and determine the microbial association is critical in understanding the impact of storm influence on flushing fecal contaminants. This study tests the efficacy of a time integrated mass sediment sampler (TIMS), in capturing both the storm SSL flux and an efficient mass of sediment for the analysis of the particle associated microbial load. TIMS collectors were deployed in Big Prairie Creek, AL, a confluence for flushed surface water in these areas. Collectors were deployed both up- and downstream of the confluence. The TIMS were sampled with single time point samples on a weekly basis, before and after storm events. Upon collection, materials were centrifuged, split, and tested for microbial indicators of fecal contaminants, both in the water and sediment. Grainsize distribution on all sediment samples were analyzed to determine both size and shape components, for modeling the adherence expected for pathogens associated with sediment. This work will help to characterize how storms flush fecal contaminants into surface water, and the fate and transport of these fecal contaminants in waterways.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H35L1165E