Bacterial Removal Within the Marshland Upwelling System: A Coastal Dwelling Wastewater Treatment System
Abstract:The marshland upwelling system (MUS) was installed in a f loating marsh along the banks of the Bayou Segnette Waterway in the Barataria-Terebonne Estuary, Louisiana. The site is characterized by native groundwater with low salinity regimes. The system was evaluated for its effectiveness in removing fecal coliforms from settled, raw wastewater. A suite of studies typified by injection flowrates of 0.9 and 1.9 L/min were performed to determine fecal coliform removal efficacy. In addition, a worse case study was performed to investigate the impacts of excessive loading rates on bacterial removal.
The worst-case study proved most effective in removing fecal coliforms. The depth of injection and biofilm development processes may be responsible for the observed removal trend. Mean influent concentrations of 92,510±489,614 were reduced to effluent concentrations of 4.0±7.6 (observed in the 2.7 m wells). Four-log reductions in influent concentrations were observed within a one-meter radial distance from the injection point. Overall removal followed a first-order decay relationship with respect to vector distance. Removal rate constants for fecal coliforms ranged from 1.5-2.0 m−1 for fecal coliforms, while that for E. coli ranged from 1.6-3.6 m−1.
Continuous injection experiments performed in one-dimensional columns packed with clayey soils from the field recorded bacterial retardation factors of between 7.3 and 14.5 with respect to the conservative wastewater tracer. Higher limitations to bacterial transport would be expected under field-scale conditions.
Laboratory simulated conditions under varying salinity concentrations and differing temperatures were used to determine inactivation rates for fecal coliforms. Rapid inactivation rates were recorded for each temperature studied (up to day 3), after which the die-off process slowed down. The higher temperature (25°C) was more detrimental to fecal coliform survival than the 20°C study. Variability in salinity concentrations appeared to be detrimental to fecal coliform survival in instances where there was synergism with temperature variations.
Document Type: Research Article
Publication date: January 1, 2004
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