Fate of coliphage during wastewater treatment by water hyacinth ( Eichhornia crassipes)

Abstract

This study examined the survival of indigenous coliphages (serving as indicators of viral pollution) during operation of a field-scale (1140 m 3 day −1) water hyacinth ( Eichhornia crassipes) treatment system in San Diego, CA. At a hydraulic residence time of 4.4 days, about 20% of the indigenous coliphages could be recovered after flow through the water hyacinth pond. The decay rates of coliphages in stagnant mesocosms with the water hyacinth plant ( k = −0.015 h −1) and in wastewater incubated in dialysis bags suspended in the pond ( k = −0.019 h −) were both greater than the value for coliphage decay in the operational water hyacinth system ( k = −0.014 h −1), indicating that filtration/adsorption of coliphage by the root matrix is not a major contributor to coliphage reduction. Coliphage decay in mesocosms without plants was more rapid ( k = −0.024 h −1) than in planted mesocosms ( k = −0.015 h −1) and covered mesocosms ( k = −0.011 h −1). These results suggest the important role of sunlight in coliphage inactivation, and reflect the fact that coliphage decay in the presence of the plant is slower than the natural decay rate in wastewater without plants.