[Evaluation of pathogen disinfection efficacy by chlorine and monochloramine disinfection based on quantitative PCR combined with propidium monoazide (PMA-qPCR)].

A novel detection method of quantitative PCR combined with a DNA intercalating dye propidium monoazide (PMA-qPCR) was developed and then applied to analyze inactivation efficacy of chlorine and monochloramine on E. coli as a representative organism. The results shows that PMA removed 99.94% and 99.99% DNA from non-viable E. coli and Salmonella cells respectively and PMA-qPCR could effectively differentiate viable bacteria from non-viable bacteria; According to the first-order kinetic model, the inactivation coefficients on E. coli obtained by PMA-qPCR were 2.24 L x (mg x min)-1 and 0.0175 L x (mg x min)-1 for chlorine and monochloramine respectively, both of which were lower than those obtained by traditional plating counting method. In order to inactivate 99% of E. coli, the ct values by PMA-qPCR were 0.9 mg L(-1) min and more than 100 mg x L(-1) x min for chlorine and monochloramine while those by plating counting method were only 0.6 mg x L(-1) x min and 20 mg x L(-1) min, respectively; E. coli concentration detected by conventional qPCR kept almost the same when ct value increased, indicating that conventional qPCR was unable to evaluate inactivation efficacy of both chlorine and monochloramine disinfection. In summary, PMA-qPCR shows to be a promising method for evaluating disinfection efficacy by chlorine and monochloramine more accurately.

[Control of microbial communities achieved by pH adjustment and its influences on batch treatment of antibiotic wastewater].

Scanning electron microscope (SEM), Fluorescent in-situ hybridization (FISH)-Flow Cytometry (FCM) as well as Biolog method were used to discuss the effect of pH control during the batch treatment on the composition and catabolic diversity of the microbial communities obtained from antibiotic wastewater. The following results were obtained: 1) At the end of batch treatment, the percentages of yeast cells in three cultures amount to 88.20%, 54.43% and 1.75%, respectively, when pH levels are individually maintained at 4-5, 5-6 and 6.5-7.5 throughout three batch experiments. Correspondingly, the percentages of bacterial cells in three cultures increase with the increase of pH levels. 2) No significant differences are found among the catabolic diversity of three cultures while the yeast-predominant culture has slightly less catabolic activities in Biolog FF microplate. 3) When bacteria gradually develop to be the dominant species in the culture, gradually enhanced COD removals of 34.8%, 44.8% and 61.2%, respectively, are achieved.