Effectiveness of Wastewater Treatment Plants in Reducing Pathogens in the Paso del Norte Region

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Effectiveness of Wastewater Treatment Plants in
Reducing Pathogens in the Paso del Norte Region

• Geoffrey B. Smith
• New Mexico State University, Las Cruces, NM
• Kevin H. Oshima
• Environmental Protection Agency, Cincinnati,OH

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Project Objectives

• Based on high incidence of pathogen occurrence in
  Rio Grande and irrigation canals (eg., Morales et
  al. 2006), effectiveness of local wastewater
  treatment plants was questioned.
• Recently developed methods (Morales et al. 2003)
  allow for quantification of protozoa, bacteria
  and virus.

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Paso del Norte Study Location
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Methods

• One liter sampled from Influent, Ten liters of
  Effluent sampled.
• Protozoa.
• Giardia and Cryptosporidium quantified by EPA
  Method 1623,
• with a Immunomagnetic Separation (IMS)
  purification step.
• Bacteria.
• Helicobacter pylori. Quantified by selective
  medium containing
• 5 antibiotics and 2 antifungal agents (Morales
  and Vidal).
• Fecal coliforms by Standard Method 9222 D.
• Virus. E. coli phage and Pseudomonas phage by
  EPA method 1602.

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Influent Protozoa El Paso del Norte
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Cryptosporidium - El Paso del Norte Sewage
Pathogens as Epidemiology Assay
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Sewage Pathogens as Indicators of Current
Disease? Cryptosporidium
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Cryptosporidium Occurrence is Correlated between
Las Cruces, NM and El Paso,TX
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Cryptosporidium Occurrence is Correlated between
El Paso,TX and Juarez, MX
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No Relationship between Fecal Coliforms and
Coliphage Virus in Wastewater
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Log ReductionsHow well does a treatment plant
reduce the levels of pathogens?
Eg. Influent Effluent Log Reduction Plant
A 10,000 10 log(10,000/10) 3
(one-thousand-fold lower) Eliminated 99.9
of influent Plant B 10,000 1000 log(10,000/100
0) 1 (ten-fold lower)
Eliminated only 90 of influent
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Protozoa Log Reductions El Paso, TX
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Protozoa Log Reductions - LasCruces,NM
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Protozoa Log Reduction - Juarez, MX
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Fecal Coliform Log Reductions
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Conclusions

• Las Cruces, NM and El Paso, TX wastewater
  treatment plants functioned properly over the
  2-year study.
• The Ciudad Juarez Planta Norte functioned in
  reducing putative Helicobacter pylori, but had
  little or no effect on fecal coliforms, and
  coliphages. On average, protozoa were reduced by
  1 log (90 reduction).

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Giardia - El Paso del Norte.
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Giardia (Influent)Similar trends in Las Cruces
and El Paso