ETS-UV for Drinking Water DisinfectionSource: Engineered Treatment Systems / ETS-UV
ETS has developed a range of drinking water UV systems that comply with the requirements of the US EPA Design Guidance Manual and have been independently validated to demonstrate performance under a variety of operating conditions. The systems are modeled using CFD and FEA emulation tools, which are continuously and iteratively improved following bioassay, routinely undertaken with a variety of surrogate organisms such as B. Subtilis, T1, and MS2 phage.
The Long Term 2 Extended Surface Water Treatment Rule (LT2) is aimed at water supplies originating from lakes, reservoirs, ground water aquifers, and rivers. The purpose of the legislation is to ensure that populations are kept safe from emerging pathogens such as Giardia and Cryptosporidium which demonstrate enhanced resistance to conventional disinfectants such as chlorine.
The Stage 2 Disinfectants & Disinfection Byproducts Rule (DBP) is designed to limit the formation of several byproducts of conventional disinfection, such as Total-trihalomethane (TTHM), Haloacetic Acid (HAA5), Chlorite, and Bromate. Several of these byproducts are either known to be or are suspected to be a carcinogenic.
The EPA uses the mandate of the Safe Drinking Water Act to monitor emerging contaminants, under the Unregulated Contaminant Monitoring Regulation (UMCR2). UV light is used successfully to remove Methyl-t-butyl ether (MTBE), a fuel oxygenate that causes unpleasant taste in water. Likewise N-Nitrosodimethylamine (NDMA) is removed using UV light. NDMA is toxic and is suspected to be a carcinogen.
UV is used as a primary disinfectant for all water-borne organisms. UV is used to photolyze contaminants. As the number of emerging pathogens increases, and as more contaminants need to be controlled, the demand for UV will grow.
Systems are installed in line either vertically or horizontally. The footprint is normally a key factor, as pipe galleries are usually very tight and cramped.
Emerging contaminants are all targets for AOP application; these Advanced Oxidation Processes use the combination of H202 and UV, or occasionally Ozone and UV. AOP processes are also used successfully to remove taste and odor contaminants from surface water, such as Geosmin and MIB.
The degree of redundancy is determined by ETS engineers working with consulting engineers, typical number of reactors plus one for redundancy (n+1). The delivered dose is controlled by continuously measuring the inputs of flow, water transmittance, and lamp intensity. The ETS systems all use power switching to vary the lamp power to optimize both power consumption and lamp life. ETS has designed wipers to keep the optical paths free from contamination and a third party monitor can be inserted to verify the performance of the ETS system.