Flushing is a common corrective action recommended by Legionella management guidelines to remove stagnant water and replenish disinfectant. Due to water age and different local regulations, buildings may receive water with low or no residual disinfectant. In such situations, the evidence for flushing efficacy is often anecdotal, and the benefits are poorly quantified. Using a pilot-scale premise plumbing system, flushed shower outlets were evaluated against non-flushed outlets during simulated periods of both active and low water demand. Water and biofilm concentrations of total bacteria, Legionella spp., and Vermamoeba vermiformis were quantified using real-time quantitative PCR. Even after all outlets returned to active water demand, flushed shower outlets continued to have lower quantities of Legionella compared to non-flushed outlets for several days, but the decrease was of little practical benefit (<0.5 log₁₀[copies/L]). During prolonged periods of low water demand, however, there was no apparent benefit to flushing. Total bacteria grew to stationary phase within 3 ± 1 days, while Legionella spp. took 12 ± 6 days, regardless of whether the pipes had recently been flushed or not. Flushing with hot or cold water had little to no effect on the concentrations of total bacteria and Legionella in pipe wall biofilms. Flushing with cold water (9.6 and 13.2°C) decreased total bacteria concentrations in the water by 0.96 and 1.00 log₁₀[copies/L], respectively and by 1.27 and 1.74 log₁₀[copies/L] with hot water (49 and 60°C, respectively) but the difference in Legionella spp. concentrations between flushing with cold (1.55 log₁₀[copies/L] for both) and hot water (1.32 to 1.88 log₁₀[copies/L], respectively) was negligible. This suggests that hot water flushing, even at 60°C, provides little or no added benefit for managing Legionella in non-chlorinated building plumbing systems versus cold water flushing. Finally, the immediate benefits of flushing in terms of reductions in total bacteria and Legionella in the water were comparable as well as the rates at which those populations recovered during post-flush or post-shower stagnation.

In Norway, placement of the water treatment plant intake within the lake hypolimnion is considered a hygienic barrier against pathogens of fecal origin. It is unclear, however, whether this practice provides a barrier against opportunistic pathogens such as Legionella. In this study, water samples were collected at 10 m depth intervals near the drinking water intakes of two lakes. Legionella and one of their common hosts, Acanthamoeba spp., were quantified using culture-based assays (Legionella pneumophila only) and real-time quantitative PCR (qPCR). L. pneumophila and Acanthamoeba spp. were never detected by qPCR; Legionella spp., however, were present in all samples at concentrations ranging from 2.33 to 4.14 log₁₀[copies/L] in lake A and from 2.69 to 4.27 log₁₀[copies/L] in lake B. For most sampling months in both lakes, there was no significant difference between total bacteria and Legionella spp. concentrations at the intake depth versus those on the lake surface. The results of this limited investigation of two Norwegian water supplies suggest that placement of water treatment plant intakes within the hypolimnion may not afford a sufficient hygienic barrier against Legionella.

Pilot-scale experiments were used to examine how hot-water temperature, chloramine disinfection, and pipe material (copper or PE-Xa) influence the effectiveness of two flow-based interventions─high-flow flushing vs showering─in controlling total bacteria, Legionella spp., and Vermamoeba vermiformis in premise plumbing. Flushing (ca. 16 L/min for 5 min) and showering (ca. 7 L/min for 8 min) both temporarily reduced bacterial concentrations by removing accumulated planktonic biomass. However, total bacteria rebounded within 1-4 days after a flush or shower, regardless of the presence of chloramines (1 mg/L Cl₂). In the absence of chloramines, Legionella spp. ssrA gene concentrations increased over 3-10 days following flushing or showering, whereas chloramines suppressed Legionella spp. for >10 days despite completely decaying within hours of water use. Without chloramines, hot-water flushing at 49 or 60 °C provided little additional control of Legionella spp. as compared to cold-water flushing. V. vermiformis concentrations decreased temporarily following water use, independent of disinfectant or temperature. Flushing was more effective than showering at removing Legionella spp. from biofilms, while pipe material had limited influence in this pilot-scale system. Overall, the results demonstrate organism-specific recovery dynamics and highlight the role of chloramines in prolonging the suppression of Legionella in premise plumbing.

Accurate and rapid determination of moisture content in waste sludge is essential for optimizing dewatering processes, reducing disposal costs, and minimizing environmental impact. This study investigates the use of Fourier Transform Near-Infrared (FT-NIR) spectroscopy combined with Partial Least Squares Regression (PLS-R) for predicting the moisture content of dewatered sludge. A total of 96 sludge samples, with dry matter contents ranging from 12.4% to 24.6%, were collected from two treatment plants. FT-NIR spectra were acquired over the 800–2500 nm range, and chemometric models were developed to correlate spectral information with gravimetrically determined moisture content. The optimized PLS-R model demonstrated strong predictive performance, achieving a cross-validated coefficient of determination (R²_CV) of 0.87, a root mean square error of cross-validation (RMSECV) of 0.92%, and a residual predictive deviation (RPD) of 2.73. Independent test set validation confirmed the robustness of the model (R²_Test = 0.88, RMSEP = 0.88%, RPD = 2.92), supported by strong calibration results (R²_CT = 0.95, RMSEE = 0.60%, RPD = 4.46). Principal component analysis indicated that spectral variability observed in sludge samples was primarily associated with wastewater treatment plant (WWTP)-specific characteristics, reflecting moisture–organic matter interactions. These results demonstrate that FT-NIR spectroscopy is a promising tool for sludge moisture prediction.

Accurate and rapid determination of moisture content in waste sludge is essential for optimizing dewatering processes, reducing disposal costs, and minimizing environmental impact. This study investigates the use of Fourier Transform Near-Infrared (FT-NIR) spectroscopy combined with Partial Least Squares Regression (PLS-R) for predicting the moisture content of dewatered sludge. A total of 96 sludge samples, with dry matter contents ranging from 12.4% to 24.6%, were collected from two treatment plants. FT-NIR spectra were acquired over the 800–2500 nm range, and chemometric models were developed to correlate spectral information with gravimetrically determined moisture content. The optimized PLS-R model demonstrated strong predictive performance, achieving a cross-validated coefficient of determination (R²CV) of 0.87, a root mean square error of cross-validation (RMSECV) of 0.92%, and a residual predictive deviation (RPD) of 2.73. Independent test set validation confirmed the robustness of the model (R²test = 0.88, RMSEP = 0.88%, RPD = 2.92), supported by strong calibration results (R² = 0.95, RMSEE = 0.60%, RPD = 4.46). Principal component analysis indicated that spectral variability observed in sludge samples was primarily associated with WWTP-specific characteristics, reflecting moisture–organic matter interactions. These results demonstrate that FT-NIR spectroscopy is a promising tool for sludge moisture prediction.