Skip to main content


The full text article is not available for purchase.

The publisher only permits individual articles to be downloaded by subscribers.

or click here to sign up for a free trial


Recent laboratory observations from research groups in California provide new insight into the shielding of pathogens from ultraviolet (UV) radiation in wastewater disinfection systems. These observations are of two types: particle size distributions, obtained with a commercial particle counter at the Hyperion Treatment Plant (HTP) in Los Angeles; and direct determinations of UV light attenuation in wastewater solids from several plants, obtained by a novel fiber optic microprobe. They show that particles small enough to pass through a typical microfiltration unit with a pore size of a few hundred nanometers are much too small to be detected by a turbidimeter or a particle counter, and the particles of sludge from most types of secondary treatment are also too small to provide a high degree of shielding to viruses, the only pathogens small enough to be present in the filtrate of intact microporous membranes. Hence, this is another step toward quantitatively understanding why UV doses much lower than those mandated in, for example, California water reclamation standards, are sufficient to disinfect water that has been microfiltered. Hence, combined microfiltration-UV disinfection systems can be designed to consume less electricity for the lamps than UV disinfection systems that operate alone. Since the cost of microfiltration is also going down, and since the bacterial pathogens removed by microfiltration eventually go into primary or secondary sludge, to be killed by heat at a much lower cost if the sludge receives pasteurization or thermophilic digestion, these results appear to be a potentially significant contribution to the rapidly improving overall economics of pathogen reduction in reclaimed wastewater.

Document Type: Research Article


Publication date: January 1, 2000

More about this publication?
  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

    WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access.
  • Subscribe to this Title
  • Membership Information
  • About WEF Proceedings
  • WEFTEC Conference Information
  • Ingenta Connect is not responsible for the content or availability of external websites

Access Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more