Pf. Zhang et al., Extended tailing of bacteria following breakthrough at the Narrow Channel focus area, Oyster, Virginia, WATER RES R, 37(11), 2001, pp. 2687-2698
Extended tailing of low bacterial concentrations following breakthrough at
the Narrow Channel focus area was observed for 4 months. Bacterial attachme
nt and detachment kinetics associated with breakthrough and extended tailin
g were determined by fitting a one-dimensional transport model to the field
breakthrough-tailing data. Spatial variations in attachment rate coefficie
nt (k(f)) were observed under forced gradient conditions (i.e., k(f) decrea
sed as travel, distance increased), possibly because of decreased bacterial
adhesion with increased transport distance. When pore water velocity decre
ased by an order of magnitude at 9 days following injection, apparent bacte
rial attachment rate coefficients did not decrease with velocity as expecte
d from filtration theory, but, instead, increased greatly for most of the w
ells. The coincidence of the increase in apparent attachment rate coefficie
nt with the occurrence of protist blooms suggested-that the loss of bacteri
a from the aqueous phase during the protist blooms was not governed by filt
ration but rather was governed by predation. Simulations were performed to
examine the transport distances achieved with and without detachment, using
attachment and detachment rate coefficients similar to those obtained in t
his field study. Simulations that included detachment showed that transport
distances of bacteria may significantly increase because of detachment und
er the conditions examined.