AWWA WQTC62478

The Long Term 2 Enhanced Surface Water Treatment Rule (LT2) is intended to improve controlof Cryptosporidium through watershed control programs, improved removal processes or the useof alternative disinfectants (U.S. Environmental Protection Agency, 2003). Large systems may satisfy LT2 requirements byswitching to ultraviolet (UV) disinfection; however, small treatment systems may not have the capabilities toimplement this technology. Adenovirus, which is on the Contaminant Candidate List, is highlyUV resistant (Gerba et al., 2002). Also, certain bacteria can photoreactivate after treatment withUV (Harris et al., 1987) contributing to the challenge of properly applying UV disinfection.Utilities using chlorine alone may not be able to simultaneously meet LT2 and disinfectionbyproduct regulations because C. parvum is highly resistant to chlorination (Driedger et al.,2000). An alternative is the use of multiple disinfectants which can enhance inactivation(Corona-Vasquez et al., 2002). Sonication is an innovative chemical free disinfectant that shouldbe considered.Ultrasonic waves create pressure variations in time and space that ultimately lead to cavitation.Collapsing bubbles cause dramatic increases in fluid velocity and temperature on a microscopicscale, increasing velocity to near the speed of sound and temperatures to 3,000 K or more (Rieszet al., 1985). When used in combination with a second disinfectant, the stresses on cellmembranes can cause an increase in microorganism sensitivity such that inactivation is greaterthan would be predicted based on additive effects (Phull et al., 1997; Jyoti and Pandit, 2003). Inaddition, sonication can reduce the required dose or contact time of a second disinfectant whilestill achieving the same inactivation (Burleson et al., 1975). The objective of this study was toquantify the synergistic impact of ultrasound treatment on chlorination for the disinfection ofdrinking waters. This technology was studied for potential application at small utilities thatcurrently use chlorine for primary disinfection and need to enhance levels of inactivation in orderto meet the LT2 requirements.Laboratory experiments were performed to quantify the inactivation of E. coli and MS2coliphage (as representative bacterial and viral indicator organisms, respectively) throughcombined disinfection with chlorine and sonication. Three separate sets of experiments wereconducted. The first two, which tested sonication alone and chlorination alone, were used todetermine benchmark inactivation levels. In the third set of experiments, the two disinfectantswere applied simultaneously. Includes 10 references, tables.

Product Details

Edition:

Vol. - No.

Published:

11/01/2005

Number of Pages:

4

File Size:

1 file , 150 KB