Solar Water Disinfection (SODIS)

This bulletin provides general information about biocides that may be used with Hydranautics membrane elements for disinfection and/or storage. Before storage or disinfection of Hydranautics elements, one should become familiar with Technical Service Bulletins 108 and 118 which describe the general storage and flushing procedures for all Composite Polyamide, and PVD membrane elements. Also, one should confirm which type of membrane elements are actually in the system. Since elements may be composed of either composite polyamide membrane or polyvinyl derivative, it is imperative to be certain of the type to be disinfected.

. Explain the general purpose and regulatory requirements of the disinfection process. . List bacteria, viruses and intestinal parasites that contaminate drinking water. . List factors that influence disinfection and explain how they influence it. . List five types of chemical disinfectants and explain the advantages and disadvantages of each. . Explain how irradiation is used as a disinfection process.

. Chemical and physical relationships govern all disinfection chemistry . Knowledge of these relationships increases operator skills and troubleshooting abilities . Allows operators to control conditions that optimize disinfection practices . Treatment processes are managed to disinfect water for consumption and to meet regulatory objectives . Minimum disinfectant residuals . CT compliance - demonstration of efficient disinfection

Drinking water supplies in Ireland are predominantly sourced from surface waters or groundwaters influenced by surface water. In recent reports on “The Provision and Quality of Drinking Water in Ireland” the Environmental Protection Agency (EPA) found that 81.6% originates from surface water (i.e. rivers and lakes) with the remainder originating from groundwater (10.3%) and springs (8%). Source waters, susceptible to surface contamination, particularly surface waters and groundwater and spring sources contain micro-organisms such as bacteria, viruses and protozoan parasites (e.g. Cryptosporidium) which can present a risk to human health if not effectively treated and disinfected. Since 2008 the EPA has set out as its policy that the most effective means of consistently ensuring the safety of a drinking water supply is through the use of a comprehensive risk assessment and risk management approach that encompasses all steps in water supply from catchment to consumer. The EPA has advised Water Service Authorities to implement the World Health Organisation (WHO) Water Safety Plan approach to risk assessment and risk management.

1. Characters of chlorine dioxide • ClO2 is a yellowish‐green gas with acrid odor under room temperature. • Extremely unstable, both gas and liquid chlorine dioxide are explosive. Thus it should be prepared on site and used as aqueous solution. • Soluble in water with a solubility 5 times of the chlorine’s; and It exists in water as dissolved gas, without any hydrolysis.