Quantitative detection of human adenoviruses in wastewater and combined sewer overflows influencing a Michigan river

Abstract

Enteric viruses are important pathogens found in contaminated surface waters and have previously been detected in waters of the Great Lakes. Human adenoviruses were monitored because of their high prevalence and persistence in aquatic environments. In this study, we quantified adenoviruses in wastewater, surface water, and combined sewer overflows (CSOs) by real-time PCR. Between August 2005 and August 2006, adenovirus concentrations in raw sewage, primary-treated effluent, secondary-treated effluent, and chlorinated effluent from a wastewater treatment plant in Michigan were examined. CSO samples (n = 6) were collected from a CSO retention basin in Grand Rapids, MI. Adenoviruses were detected in 100% of wastewater and CSO discharge samples. Average adenovirus DNA concentrations in sewage and CSOs were 1.15 x 10(6) viruses/liter and 5.35 x 10(5) viruses/liter, respectively. Adenovirus removal was <2 log(10) (99%) at the wastewater treatment plant. Adenovirus type 41 (60% of clones), type 12 (29%), type 40 (3%), type 2 (3%), and type 3 (3%) were isolated from raw sewage and primary effluents (n = 28). Six of 20 surface water samples from recreational parks at the lower Grand River showed virus concentrations above the real-time PCR detection limit (average, 7.8 x 10(3) viruses/liter). This research demonstrates that wastewater effluents and wastewater-impacted surface waters in the lower Grand River in Michigan contain high levels of viruses and may not be suitable for full-body recreational activities. High concentrations of adenovirus in these waters may be due to inefficient removal during wastewater treatment and to the high persistence of these viruses in the environment.

FIG. 1.

Sampling sites along the lower Grand River during the intensive study in June 2005. The map shows sites that were positive for adenoviruses (•), sites that were negative for adenoviruses (○), and sites selected for continued monitoring between 2005 and 2007 (▴).

FIG. 2.

Concentrations of HAdV (log₁₀ viruses/liter) in wastewater collected from an advanced WWTP in East Lansing, MI, between August 2005 and August 2006.

FIG. 3.

Neighbor-joining tree of adenovirus hexon amplicons detected in wastewater. The scale indicates the number of nucleotide substitutions per position. Numbers above the branches indicate bootstrap percentages (those above 50%) based on 1,000 replicates. Reference strains of human adenovirus were selected from GenBank, using the accession numbers indicated in the text.

FIG. 4.

Human adenovirus concentrations (log₁₀ viruses/liter) in CSO discharge samples collected from Market Avenue retention basin in Grand Rapids, MI.