Recycled Water Quality – Lettuce

This Poster describes the study conducted by Brooke Anderson in 2004 for North East Water in conjunction with The University of Melbourne.

The study investigated potential microbial contamination on lettuce grown hydroponically, comparing Class A & B reclaimed water and river water.

A green oak lettuce variety was grown over 6 weeks in a controlled greenhouse environment under uniform conditions.

Water quality was monitored throughout and random lettuce samples from all treatments were analysed for contamination.

Objectives :

  1. Determine if Class A and B Reclaimed water is safe & within recommended guidelines to use on hydroponically grown lettuce in comparison to River water.
  2. Determine differences in growth rate between reclaimed and river water treatments for the commercial sale of hydroponically grown lettuce.

Brooke Anderson – North East Water

Poster- Potential microbial contamination of hydroponic lettuce irrigated with recycled water - Brooke Anderson - North East Water
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Conclusions :

  • No E.coli, Salmonella or Listeria were detected on final lettuce produce.
  • Faecal coliforms were detected however the recommended guidelines for irrigation water based on crops for direct human consumption is <1000 faecal coliforms and no more than 20% samples should exceed 4,000 organisms/100ml.
  • Faecal coliforms (used as an indicator organism for the presence of pathogens) were detected and within recommended guidelines.
  • TAC were also detected however this is an overall measurement of aerobic colony contamination, and is not necessarily an indicator of harmful contaminants.
  • Further investigation is required to determine the strain of faecal coliforms and TAC present. The problem associated with reclaimed water is it contains human faeces in comparison to river water which is predominantly contaminated with animal faeces.
  • Concern exists if human pathogens can be transferred by consuming raw food produce in contact with reclaimed water, hence further investigation is necessary.
  • The high contamination results for Class A were due to two extreme outlying figures in comparison to Class B and river water. These results were unexpected and errors may have occurred during the sampling process.
  • Overall, none of the water treatments contaminated the final lettuce matter with E.coli, Salmonella or Listeria.
  • Faecal coliforms were detected however were still within the recommended guidelines.


Mark Samblebe & Ian Riemers, Wodogna TAFE

Geoff Brumley (Gnangara Premium Fresh®,

Robert Premier & Janet Tragenza (DPI-Victoria)

The Anglian Water Purification Plant

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