MIAMI DADE’S WASTEWATER HIGH-RATE DISINFECTION PILOT STUDY: PATHOGEN TESTING – LESSONS LEARNED AND SUGGESTIONS FOR THE FUTURE

Authors: Boutros, Susan; Boutros, Edward; Moffa, Peter; Paterniti, Joe; Chorlog, John; Di Giovanni, George; Bowman, Dwight
Source: Proceedings of the Water Environment Federation, Disinfection 2007 , pp. 85-94(10)
Publisher: Water Environment Federation

Abstract:
The Miami Dade High-Rate Disinfection Pilot Study at the South District Wastewater Treatment Facility compared high-level disinfection with chlorine to high-rate disinfection using chlorine dioxide and to disinfection with ultraviolet light. This presentation discusses some of the analytical challenges presented by the Florida Department of Environmental Protection (FDEP) pathogen guidelines, how those challenges were met and suggests innovative method changes to meet the guidelines in the future.
FDEP’ rigorous pathogen guidelines define protozoan and virus limits for reuse water and set the standards for the pilot plant testing. For the protozoans, Cryptosporidium and Giardia, limits are defined in terms of “viable” oocysts and cysts. The standard EPA test, Method 1623 for Cryptosporidium and Giardia, gives total counts and information about protozoan morphology but does not measure viability. The results of Method 1623 counts were used to calculate physical removal and destruction with pilot scale tests, but those counts could not be used to calculate reduction in viability. Viability measurements were made by the focal detection cell culture method for Cryptosporidium and by live animal studies for Giardia with bench scale tests.
For viruses the FDEP guidelines recommend acceptable average limits as 0.044 plaque forming units (PFU)/100 liters or less than one 1PFU/ 2273 liters. The most probable number (MPN) assay used for the pilot study is considerably more sensitive than the plaque assay implied by the guidelines. The large volume and high solids used to simulate “worst case” conditions increased the analytical challenges. Method modifications were developed and validated at Environmental Associates Ltd. to accommodate each of the analytical challenges.
Surrogate assays were included to attempt to validate process control tools that would be cheaper and faster to run than pathogen assays. These assays included spores, coliphages and enterococci. Surrogate assays yielded mixed results with only some surrogates providing good predictive value. Pathogen levels varied by season, rainfall, time of day, day of week and year-to-year. The variability indicates that risk evaluation and treatment decisions need to be based upon large enough data sets to encompass these variations.
For new disinfection studies, method modifications are presented that will reduce cost and improve the accuracy and usefulness of the data.

General Microbiology Services

EAL is approved for protozoan and virus testing through NELAP and holds approval for Methods 1622/1623 for Giardia and Cryptosporidium for the LT2 through EPA.    We can assist with microbial services including:

   1. Analyses for Giardia and Cryptosporidium with water and wastewater
   2. Analyses for total culturable viruses
   3. Microscopic Particulate Analysis (MPA) for ground water and filtration evaluation
   4. On-Site pilot plant studies and sampling services
   5. Many more specialty microbiology analysis and consultation

Non-Potable & Reuse Water Microbiology

  •    Cryptosporidium EPA 1623
  •    Giardia EPA 1623
  •    Helminth ova EPA 600/1-87-014
  •    Coliform, Fecal SM 18-20 9222D (97)
  •    Coliform, Total SM 18-20 9222B (97)
  •    E. coli (Enumeration) Colilert
  •    Enterococci Enterolert
  •    Standard Plate Count SM 18-21 9215B

How do I find an approved laboratory?

 

 

 

Environmental Associates Ltd. is EPA approved for the LT2.  With more than 22 years experience in protozoan analyses Environmental Associates Ltd. can offer the highest quality work for the LT2. and a unique LT2 data package designed to eliminate false positives as far as scientifically possible.  Please contact the laboratory for more details at (607) 272-8902.

What can I do to prepare my utility for the LT2 in the most cost effective manner?

 

 

 

Become informed about the rule and about EPA Methods 1622/1623. Review historical data. Discuss the rule with your consulting engineer.  Secure the services of Environmental Associates Ltd.  Phone 607-272-8902

 

 

 

 

 

 

 

Environmental Associates Ltd.

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Environmental Associates Ltd. offers a variety of microbiological laboratory, research and consulting
services, and EAL is NELAP certified.