Disinfection of Rainwater for Economic Purposes

Abstract

Rainwater storage systems are one of the elements of the implementation of sustainable water management. The use of rainwater in households or public buildings reduces the consumption of water supply water for purposes that do not require very good quality water. In crisis situations, rainwater could also be a source of water for drinking and hygiene. In order to use rainwater, it must comply with sanitary quality standards. This paper presents the results of research on the disinfection of rainwater and the possibility of its safe use in the economy as an alternative to tap water. The elements of the proposed pretreatment and disinfection system were selected adequately for the quality of the collected rainwater and its intended use. The aim was to obtain water safe for drinking and hygienic purposes. Rainwater was collected from a roof covered with ceramic tiles, and then subjected to prefiltration, ultrafiltration and disinfection with UV rays. Water before and after treatment was characterized on the basis of a number of microbiological parameters (total number of bacteria at 37 °C and 22 °C; number of coliform bacteria, Escherichia coli, Enterococci, Pseudomonas aeruginosa) and the content of nutrients (TOC, ammonium nitrogen, nitrates, nitrites, phosphates). The use of ultraviolet radiation allowed for the complete removal of indicator bacteria and a significant reduction in the total number of bacteria, from nearly 2500 CFU/mL to 25 CFU/mL for bacteria at 22 °C and from 2010 CFU/mL to 18 CFU/mL for bacteria at 37 °C. The effectiveness of rainwater disinfection, its microbiological stability after disinfection and the time after which the bacterial microflora regenerates, as well as the possibility of using rainwater for drinking and hygienic purposes after disinfection, was determined.