Removal and inactivation of microbial pathogens and indicators in water

Enteric microorganisms are the major source of water contamination and the cause of innumerous emerging infectious diseases which have been threaten the public health. The main purpose of this research was to characterize microbial removal and inactivation in water in different settings and under different environmental conditions. The first setting was the examination of the treatability of two microbial pathogens included in the United States Environmental Protection Agency Candidate Contaminant List and microbial surrogates by bench and pilot studies. Jar test were performed using different concentration of ferric chloride as coagulant to assess an optimum coagulant dose for microbial removal. In addition, a pilot plant was used to measure microbial removal under optimized coagulant dose condition. The results demonstrated that ferric chloride dose of 40 mg/1 applied in a conventional water treatment pilot plant resulted in an overall of 3 logs of virus removal. In a second study, a set of pilot filters packed with treated Zeolite filter media were evaluated for antimicrobial removal and inactivation capabilities. A series of microbial challenge studies using bacteria, bacteriophages, algae and parasites were performed. The outcome from the studies shows that the pilot system inactivated and removed 2.3 logs of virus, 2.5 logs of bacteria, 2 logs of algae and 1.65 logs of Cryptosporidium parvum. The third study assessed the capability of microbial inactivation by sunlight during different seasons. The study was performed by exposing seeded water (with bacteria and bacteriophages) to sunlight during 90 minutes under different conditions. Three conditions were evaluated, an open reactor without mixing, a closed reactor and an open reactor with mixing. The results demonstrated that sunlight (UV) has great inactivation capabilities during summer where an average of 4 logs of viruses was inactivated in a closed and open reactor. The outcome of this study can be used as guideline for improving the microbial water quality in different settings using simple or advance technologies.