Understanding Microbial Biofilms in Receiving Waters Impacted by Airport Deicing Activities (2014) / Chapter Skim
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33 C H a P T E R 5 This chapter describes the results and conclusions of hypothesis testing. The reader should note that these findings reflect the specific conditions under which the monitoring and testing were conducted.
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34 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities availability increased, decreased, or stayed the same (Figure 51)
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Hypothesis Testing Results and Conclusions 35 (a)
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36 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities (a)
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Hypothesis Testing Results and Conclusions 37 Figure 5-3. Reactor appearance after 4 days of operation.
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38 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities (a)
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Hypothesis Testing Results and Conclusions 39 The levels of HPC observed, approximately 108 CFU/cm2, are typical for relatively high nutri ent conditions. This level of biomass accumulation represents a biofilm approximately 50 to 100 µm in average thickness, a condition that would likely lead to the development of discrete anaerobic zones near the biofilmsubstratum interface.
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40 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities 5.1.3 Modeling Evaluations The amount of phototrophic organisms (i.e., algae) comprising the active biofilm biomass (i.e., the sum of heterotrophic [XH]
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Hypothesis Testing Results and Conclusions 41 Under low concentrations of COD (i.e., COD = 1 mg/L) , phototrophic organisms compose approximately 5 percent of the projected active biofilm mass for the dark condition and approxi mately 25 percent of the active biofilm mass for the sunlight condition.
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42 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities Hypothesis 1 is not supported by the results. The amount of biofilm growth that occurs under given conditions of readily biodegradable dissolved organic matter does not appear to be directly proportional to the availability (or intensity)
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44 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities increasing in the Nvaried reactor and remaining apparently absent from the Pvaried reactor (Figure 515)
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Hypothesis Testing Results and Conclusions 45 This is an important point to the extent that some biofilm morphologies may be considered less objectionable in the context of water quality in streams receiving airport runoff. Fungal Organisms.
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46 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities Figure 5-17. Fungal plate counts from biofilm accumulated on coupons.
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Hypothesis Testing Results and Conclusions 47 from the upstream and downstreammost monitoring locations on Wilson Park Creek and the unnamed tributary were analyzed for available N (as dissolved total N) and P (as orthophosphorus)
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48 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities ranged from less than 0.002 to 0.05 mg/L as P (median of < 0.002 mg/L as P)
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Hypothesis Testing Results and Conclusions 49 decreases with increasing C:N (i.e., decreasing relative availability of N)
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50 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities of concentrations in the ambient water and N that has accumulated in the biofilm structure over the duration of the experiments. 5.2.4 Discussion and Conclusions Hypothesis 2/4(a)
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Hypothesis Testing Results and Conclusions 51 5.3 Hypothesis 3 -- Impact of Physical Stream Characteristics on Biofilm Growth Hypothesis Statement The physical characteristics of receiving streams influence the extent of biofilm accumulation for a given water chemistry condition as follows: • Category 1: Shallow, turbulent, wellmixed channels promote biofilm growth and require ambient BOD5 concentrations less than 50 mg/L to avoid prolific biofilm growth. – streambed surface area (ABED)
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52 Understanding Microbial Biofilms in Receiving Waters Impacted by Airport Deicing Activities (a)
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Hypothesis Testing Results and Conclusions 53 Although the streams investigated in this study did not cover the full range of physical condi tions described in the hypothesis statement, they were representative of conditions reported for typical airport receiving streams; according to a U.S. EPA survey of airports, the majority of ini tial receiving waters draining airports have flows less than 20 cfs (U.S.
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54 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities that depth may influence biofilm growth with increasing stream size and increasing depth beyond that examined. Transects from the same reach were used in this comparison to control for substantial differ ences in water quality.
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Hypothesis Testing Results and Conclusions 55 at these transects (Figure 522) and at all biofilm sites on Wilson Park Creek and the unnamed tributary (Figure 51)
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56 understanding microbial Biofilms in Receiving Waters Impacted by airport Deicing activities consistently lower. COD concentrations at KK ranged from less than 8 to 65, with a median concentration of 19.1 mg/L (Figure 525)
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Hypothesis Testing Results and Conclusions 57 concentrations at downstream monitoring locations decreased from upstream to downstream from 175.0 to 109.2 to 35.4 mg/L at Howelldark, 13th, and KK, respectively. Results of the flow composite samples at the Outfall 7 site and estimated concentrations at the downstream sites indicate much larger fluctuations in concentration than the monthly samples collected during biofilm sampling.
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