FAECAL CONTAMINATION AND HEALTH ASPECTS OF PROCESSING TOMATOES (SOLANUM LYCOPERSICUM) IRRIGATED WITH WASTEWATER TREATED BY DECENTRALISED WASTEWATER TREATMENT TECHNOLOGIES

Abstract

Direct or indirect water reuse involves several aspects including faecal microbial contamination. The challenge is to apply new strategies and technologies which allow using the lowest irrigation water quality without jeopardising food safety and health of farmers. The EU project SAFIR aims to develop flexible water treatment technologies to solve problems with low quality water and decreased access to water resources. Wastewater produced by small communities (≤2000 EI) was treated by Membrane Bio Reactor (MBR) technology and gravel filter during three cropping seasons in Italy. Treated wastewater, soil and processing tomatoes were analysed for the faecal indicator bacterium E. coli and helminth eggs. The study found processing tomatoes free of E. coli and low levels of E. coli in soil (95 cfu g -1 ) even though elevated concentrations were detected in irrigation water (1677 cfu per 100 ml). A quantitative microbial risk assessment model adopted by the World Health Organisation (WHO) deemed the consumption of tomatoes to be safe. The accidental ingestion of wastewater irrigated soil by farmers was associated with risk that exceeded permissible risk as proposed by the WHO (1×10 -3 disease risk per person per year) even for soils irrigated with tap water free of E. coli. This result in conjunction with no identical DNA fingerprint of E. coli isolated from water and soil by Pulse Field Gel Electrophoresis (PFGE) highlights limitation of the WHO QMRA and indicates other sources of faecal contamination, ex. wildlife.