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Research Objectives: 1. Identify tank subgroups within the LM in which FC removal is most effective.
1. Identify tank subgroups within the LM in which FC removal is most effective.
2. Increase our understanding of the relationship between microbial metabolism and FC removal, focusing on the specific dynamics between FC removal and the two components of BOD: carbonaceous BOD (CBOD), and nitrogenous BOD (NBOD).
3. Determine the effect of water flow on FC concentration and microbial metabolism, as measured by BOD.
Hypothesis: Active microbial communities will compete with and predate upon FC, and therefore tanks with higher microbial respiration will have higher rates of FC removal. We expect the OA tanks to facilitate the most effective FC removal due to the complexity and high metabolism of the microbial communities they are designed to support. During period of increased flow we expect to see higher concentrations of FC and increased BOD as a function of increased loading.
y = 1317x -
FC v. CBOD
Thousands of CFU/100mL
Concentration of FC
Understanding Dynamics of Fecal Coliform Removal in a Biological Wastewater Treatment Facility at Oberlin College
Jeffrey Beem-Miller, Lenore Braford, Andrew de Coriolis
Systems Ecology (ENVS 316) Fall 2006
In the last ten years biological wastewater treatment facilities have emerged as increasingly promising systems for wastewater treatment that do not require high energy input or the addition of allogenic chemicals. It has been shown that these systems are effective at removing solid material, organic solids, nutrients and human-borne pathogens from wastewater (Todd, 1995), but the specific mechanisms of human-borne pathogens removal have not been well documented. The focus of this study was to better understand the dynamics of fecal coliform (FC) removal, a commonly used indicator species for the presence of harmful human-borne pathogens such as E. coli, in biological wastewater treatment facilities.
We studied the Oberlin College Living Machine (LM) as a model biological wastewater treatment system. The LM incorporates aspects of both natural wetland systems, and conventional wastewater treatment plants to process wastewater. The LM consists of a series of discrete microhabitats in sequentially arranged tanks, each of which is designed to perform a different function in the treatment process (Figure 1).
2. We found a strong positive correlation between BOD and concentration of FC in all of the sample locations, R² = 0.92, and that CBOD is more closely related to FC (Figure 3) than NBOD. Despite this correlation, we were unable to establish competition and/or predation as the causal mechanism.
Figure 3: Blue points represent outliers which were not included in the regression due to measurement error. AN values were not included extremely high value.
3. In the third run, approximately two weeks after a period of increased flow, FC concentrations rose dramatically and persisted father into the treatment processthan in the previous two runs (Figure 4). Though our methodology did not allow us to establish a direct link between these factors, the results are consistent with the mechanism of increased flow.
Figure 1: Conceptual diagram of the Living Machine. Samples were taken from all tanks labeled in bold except AN2 and OA2.
*FC concentrations for OA1 in run 3 were too high to count.
Water flow adjusted for 2 week delay.
The LM tanks we studied can be subdivided into four different groups according to shared environmental conditions (italics Figure 1):
The AN tanks are designed for primary treatment, which includes suspended solids settle, and anoxic conditions support anaerobic microbes that decompose organic matter. FC is most concentrated in AN as it is the first stage of treatment.
The CA tanks are actively aerated settling basins, designed to support a population of aerobic microbes, which may play a role in FC removal by predation or competition.
The OA tanks are open aerated tanks designed to host to a complex biotic community of macrophytes, protozoans, and microbes. The roots of emergent vegetation provide a substrate for microbial communities, which play an important role in the removal of suspended organic material, ammonia and perhaps FC.
The clarifier (CL) is a tertiary-stage anaerobic settling basin, designed to allow collection and removal of bio-solids from the water column. FC concentrations in the CL have been historically low.
Results & Discussion
Figure 2:Graph of median FC value per tank. Scale is logarithmic.
*FC value for AN1 is from Run 3 only, due to sampling inaccuracies.