RESUMEN
Introduction: Microbial contamination of drinking water, particularly by pathogens such as Escherichia coli O157: H7, is a significant public health concern worldwide, especially in regions with limited access to clean water like the Gaza Strip. However, few studies have quantified the disease burden associated with E. coli O157: H7 contamination in such challenging water management contexts. Objective: This study aimed to conduct a comprehensive Quantitative Microbial Risk Assessment to estimate the annual infection risk and disease burden attributed to E. coli O157: H7 in Gaza's drinking water. Methods: Applying the typical four steps of the Quantitative Microbial Risk Assessment technique-hazard identification, exposure assessment, dose-response analysis, and risk characterization-the study assessed the microbial risk associated with E. coli O157: H7 contamination in Gaza's drinking water supply. A total of 1317 water samples from various sources across Gaza were collected and analyzed for the presence of E. coli O157: H7. Using Microsoft ExcelTM and @RISKTM software, a Quantitative Microbial Risk Assessment model was constructed to quantify the risk of infection associated with E. coli O157: H7 contamination. Monte Carlo simulation techniques were employed to assess uncertainty surrounding input variables and generate probabilistic estimates of infection risk and disease burden. Results: Analysis of the water samples revealed the presence of E. coli O157: H7 in 6.9% of samples, with mean, standard deviation, and maximum values of 1.97, 9.74, and 112 MPN/100 ml, respectively. The risk model estimated a median infection risk of 3.21 × 10-01 per person per year and a median disease burden of 3.21 × 10-01 Disability-Adjusted Life Years per person per year, significantly exceeding acceptable thresholds set by the WHO. Conclusion: These findings emphasize the urgent need for proactive strategies to mitigate public health risks associated with waterborne pathogens in Gaza.
RESUMEN
Biofilm systems are efficient in the removal of organic matter and ammonium from wastewaters. In this study, loofa sponge, a natural product, was used as a supporting medium in an aerated submerged fixed-film reactor to evaluate its performance in removing organic matter and nitrogen from wastewater. Four pilot runs were performed with chemical oxygen demand (COD) concentrations of 100, 200, 300 and 400 mg l-1 to provide an organic loading rate of 0.6, 1.2, 1.8, and 2.4 kg m-3d-1 respectively. In these pilot runs, the influent ammonium nitrogen concentrations were justified to 5, 10, 15 and 20 mg l-1 as N to provide an influent nitrogen loading of 30, 60, 90 and 120 g m-3.d-1 respectively. Although soluble COD removal efficiency greater than 80 percent was achieved up to a loading rate of 2.4 kg m-3d-1, loofa deformation and clogging after 72 days of application might be considered a serious shortcoming during use in full-scale applications. Nitrogen removal efficiency decreased from 85.6 percent at an organic loading rate of 0.6 kg m-3d-1 to 56.1 percent at an organic loading rate of 2.4 kg m-3d-1.