Extended tailing of bacteria following breakthrough at the Narrow Channel focus area, Oyster, Virginia

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.