Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2013

Microbial contamination in lettuce irrigated with wastewater: The preliminary study to improve the estimation of health risks from wastewater irrigated salad crops consumption (#294)

PRASERT MAKKAEW 1 , Howard Fallowfield 1 , Megge Miller 2 , Nancy Cromar 1
  1. Health and Environment Group, School of the Environment, Flinders University, Adelaide, SA, AUSTRALIA
  2. OzFoodNet, Communicable Disease Control Branch, Department for Health and Ageing, Adelaide, SA, AUSTRALIA

Water scarcity is becoming a serious problem worldwide resulting in the increasing reuse of wastewater in agriculture. However, wastewater irrigation poses potential health risks due to the possible existing pathogens which could contaminate agricultural products, particularly salad crops which are consumed raw. This study was conducted to assess the contamination of two indicator organisms of faecal contamination, Escherichia coli and bacteriophage MS-2, in lettuce grown with partially treated domestic wastewater in four different irrigation system beds; open spray, spray under plastic sheet cover, open drip and drip under plastic sheet cover. Samples of lettuce for each irrigation system bed were collected during the growing season in week 4, 5, 6 and 7. Samples of the treated wastewater being used for irrigation were collected weekly over the same period. Results show that E. coli and MS-2 concentration in wastewater samples ranged from 488.4 – 2419.6 MPN/ 100 mL (863.33 + 520) and 0 – 30 PFU/ 100 mL (10 + 8.53), respectively. Greater E. coli contamination of lettuce occurred in spray beds than drip beds. All samples from spray beds were positive for E. coli, whereas 5 out of 24 samples from drip beds contain E. coli. No MS-2 was found in any lettuce samples. No statistical difference (p > 0.05) was detected in E. coli concentration between the open sprayed bed lettuce and plastic sheet covered bed lettuce; similarly, there no difference was found between E. coli concentration in open bed drip-irrigated lettuce and those covered with plastic sheeting. These preliminary study results could be used for improving the estimation of health risk related to wastewater irrigated salad crops consumption. Variations in lettuce morphology and the quality of wastewater are also currently being investigated.