Transcription levels (amoA mRNA-based) and population dominance (amoA gene-based) of ammonia-oxidizing bacteria.

A population shift of ammonia-oxidizing bacteria (AOB) was described within a bench-scale activated sludge process treating an industrial wastewater in a previous report (Kuo et al. in Environ Eng Sci 23:507-520, 2006). In this investigation, transcriptional levels (amoA mRNA-based) of the three AOB groups (i.e., RI-27, B2-3, and Nitrosomonas nitrosa) identified in the treatment process were determined by quantitative real-time reverse transcription (RT-PCR) assays to circuitously evaluate AOB ammonia-oxidizing activity and to assess the presumed correlation between cellular activity and the dominant (greatest number) AOB population. Results demonstrated that the AOB group with higher amoA mRNA levels dominated the overall AOB population in the wastewater treatment process. Although AOB population dominance did not correlate well with transcripts at a normalized cellular level (amoA mRNA/DNA ratio), overall amoA mRNA levels did reflect the activity of distinct AOB groups under different N-loading conditions. Thus, an additional molecular parameter (amoA mRNA) was successfully utilized to assess timely shifts in AOB population structure that may impact nitrification treatment performance.

Occurrence of human adenoviruses at two recreational beaches of the great lakes.

Human adenoviruses (HAdVs) have been related to several waterborne diseases such as acute gastroenteritis, conjunctivitis, and respiratory illness, and it has been shown that an important human exposure pathway is through recreational waters. However, HAdV occurrence at recreational freshwater beaches has not been previously investigated. In this study, a total of 58 water samples were collected from two recreational beaches on Lake Michigan (i.e., Silver Beach and Washington Park Beach) during the summer of 2004. Occurrences of HAdVs in these lake samples were determined using two hexon-based real-time PCR assays (one for monitoring all 51 serotypes of HAdVs and another for specifically detecting F species HAdVs, i.e., serotypes 40 and 41) and compared to an integrated cell culture (ICC) PCR method. The real-time PCR results showed that 8 of 30 Silver Beach samples and 6 of 28 Washington Park Beach samples contained HAdVs, and F species HAdVs were detected in three of these positive samples. The concentrations of HAdVs ranged from (1.7 +/- 0.7) x 10(1) to (3.4 +/- 0.8) x 10(2) and from (7 +/- 2) x 10(0) to (3.8 +/- 0.3) x 10(3) virus particles/liter for Silver Beach and Washington Park Beach, respectively. F species HAdVs were detected at levels ranging from (4.8 +/- 0.8) x 10(1) to (4.6 +/- 1.5) x 10(2) virus particles/liter. Approximately 60% of the ICC-PCR analyses agreed with the real-time PCR results. This study revealed the occurrence of HAdVs at Lake Michigan recreational beaches. Given the potential health risks, further assessment regarding sources, virus transport, and survival is needed to improve the safety of the region.

Removal of human enteric viruses by a full-scale membrane bioreactor during municipal wastewater processing.

In the US, human enteric viruses are the main etiologic agents of childhood gastroenteritis, resulting in several hospitalizations and deaths each year. These viruses have been linked to several waterborne diseases, such as acute gastroenteritis, conjunctivitis and respiratory illness. The removal of human enterovirus (EV) and norovirus genogroup II (NoV GGII) was studied in a full-scale membrane bioreactor (MBR) wastewater treatment plant (WWTP) and compared with the removal of human adenovirus (HAdV). In total, 32 samples were quantified using real-time reverse transcription-PCR (RT-PCR) from four separate locations throughout the treatment process; influent, primary settling effluent, membrane influent (which includes the MLSS) and membrane effluent. EV was detected in all 32 samples (100%) with an average concentration of 1.1 × 10(7) and 7.8 × 10(1) viruses/L for the membrane influent and membrane effluent, respectively. NoV GGII was detected in 20 of 32 samples (63%) with an average membrane influent and membrane effluent concentration of 2.8 × 10(5) and 1.2 × 10(1) viruses/L, respectively. HAdV was detected in all 32 samples with an average membrane influent concentration of 5.2 × 10(8) and 2.7 × 10(3) viruses/L in the membrane effluent. Our findings indicate that this particular full-scale MBR treatment was able to reduce the viral loads by approximately 5.1 and 3.9 log units for EV and NoV GGII as compared to 5.5 log units for HAdV. This full-scale MBR system outperformed the removal observed in previous pilot and bench scale studies by 1 to 2 log units. To the best of our knowledge, this is the first study focusing on the removal of EV in a full-scale MBR WWTP using real-time RT-PCR, and on the solid-liquid distribution of EV and NoV GII in secondary biological treatment.

Assessment of human adenovirus removal in a full-scale membrane bioreactor treating municipal wastewater.

Human adenoviruses (HAdVs) in wastewater samples taken from four different treatment stages of a full-scale municipal wastewater treatment plant (i.e., incoming raw sewage, primary sedimentation effluent, membrane bioreactor (MBR) influent, and MBR effluent) were quantified by real-time PCR assays to further estimate removal efficiency of the HAdVs. Based on hexon gene sequence comparisons, HAdV species A, C, and F were consistently found in the wastewater samples. In general, all three identified HAdV species were detected in most of the wastewater samples using the real-time PCR assays. Overall HAdV concentrations were rather stable over the entire 8-month study period (January-August, 2008) (approximately 10(6)-10(7)viral particles/L of wastewater for the raw sewage and primary effluent; 10(8)-10(9)viral particles/L for the MBR influent; and, 10(3)-10(4)viral particles/L for the MBR effluent). No significant seasonal differences were noticed for the HAdV abundances. Removal efficiencies of the viral particles in the full-scale MBR process were assessed and showed an average HAdV removal of 5.0+/-0.6logs over the study period. The removal efficiencies for F species (average log removal of 6.5+/-1.3logs) were typically higher (p-value <0.05) than those of the other two species (average of 4.1+/-0.9 and 4.6+/-0.5logs for species A and C, respectively). These results demonstrate that the full-scale MBR system efficiently removed most HAdV from the wastewater leaving about 10(3)viral particles/L in the MBR effluent.