Christine Cotton
UV Disinfection for Water and Wastewater Treatment Systems
ISSUE:
The Long-Term 2 Enhanced Surface Water Treatment Rule has been signed — Is your water system ready for the new requirements?
Background
The Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) was finalized on January 5, 2006, and aims to reduce disease incidence associated with Cryptosporidium and other pathogenic microorganisms in drinking water. The LT2ESWTR applies to all systems that use surface water or ground water under the direct influence of surface water, and USEPA estimates almost 3,000 public water systems will have to update their water treatment processes.
Based on the concentration of Cryptosporidium present in their source water, this rule requires up to 5.5 log total treatment (99.99968 percent removal and/or inactivation) for Cryptosporidium. Additional treatment may need to be in place as early as 2012, depending on the number of customers served by the system.
Almost 3,000 public water systems will have to update their water treatment processes
USEPA has identified several treatment alternatives that are effective in removing or inactivating Cryptosporidium. One of the most cost-effective treatment barriers is UV disinfection. Other significantly more expensive, but also effective, treatment technologies include membranes and ozone.
Benefits of UV Disinfection
The primary benefit of UV disinfection isits effectiveness against Cryptosporidium, which is resistant to chemicals typically used for disinfection such as chlorine and chloramines.
UV disinfection has other benefits:
- Because UV disinfection is a physical process, it does not involve transport, storage, handling or use of dangerous chemicals.
- Taste and odor of drinking water are not affected by use of UV light.
- UV disinfection has no known carcinogenic or toxic by-products.
- The required residence time, on the order of seconds as opposed to many minutes, allows for smaller reactors and thus lower costs.
UV disinfection can also be used to treat wastewater for reclaimed water applications and is especially effective for meeting stringent re-use standards and minimizing disinfectant residuals for discharge permits.
Evaluation Tools
As part of an AwwaRF research project, Malcolm Pirnie helped develop an interactive electronic tool available on the internet to help utilities during the early stages of UV disinfection planning and evaluation.
This AwwaRF tool addresses such issues as the feasible retrofit locations for UV disinfection, the implementation issues of UV disinfection at each retrofit location and how they can be addressed. It also estimates the cost of various retrofit options by evaluating existing infrastructure, hydraulic limitations, water quality variability, flow variability, power source limitations, and lamp breakage issues.
Another source of help is USEPA's UV Disinfection Guidance Manual, which supports the LT2ESWTR, and which Malcolm Pirnie played a leading role in developing. This document, due to be published in the Spring, includes background information on UV disinfection as well as specific information on the design, construction, validation, and operation of UV disinfection systems in drinking water.
Malcolm Pirnie - A Valuable Resource
To help you decide if UV disinfection is right for your water system, Malcolm Pirnie offers independent planning and design for facilities throughout the U.S.
We can provide assistance throughout the design process, from technology evaluation to construction and startup assistance. Our unique perspective reflects our long-time involvement with regulatory agencies, giving us particular expertise in research projects, regulatory compliance, and design of UV disinfection for drinking water and wastewater. And, because we recognize that resources are limited, Malcolm Pirnie has helped utilities find alternative sources of funding, the right equipment procurement strategy, and innovative approaches for retrofitting or upgrading existing facilities.
We invite you to contact our UV disinfection expert:
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