R. Armon et al., RESIDUAL CONTAMINATION OF CROPS IRRIGATED WITH EFFLUENT OF DIFFERENT QUALITIES - A FIELD-STUDY, Water science and technology, 30(9), 1994, pp. 239-248
Citations number
13
Categorie Soggetti
Water Resources","Environmental Sciences","Engineering, Civil
Unrestricted crop irrigation with wastewater effluents is a major conc
ern for public health. The aim of this investigation was to compare tw
o wastewater effluent reservoirs used for irrigation of a variety of v
egetables. The study covers the period from January to the end of July
, with sprinkle irrigation starting in mid-April. Lettuce, parsley, ca
bbage, onion, carrots, fennel, radish and tomato irrigated with highly
polluted effluents, displayed elevated numbers of indicator microorga
nisms. In contrast, vegetables irrigated with slightly polluted efflue
nts, showed significantly lower numbers of indicator microorganisms. A
lthough a low background of microbial indicators was detected in both
cases before irrigation started, a significant increase of residual co
ntamination was observed on vegetables irrigated with the polluted eff
luents, following the irrigation onset in mid-April. Independently of
the need to correlate quality standards for unrestricted crop irrigati
on with epidemiological data, irrigation with poorly managed wastewate
r, based on microbiological and chemical parameters, results in highly
contaminated vegetables. Vegetables often eaten raw or with rich dres
sings (which may result in regrowth of some pathogenic bacteria) may t
hreaten the public health, without clear outbreaks. It must be borne i
n mind that drinking water that does not differ much from these vegeta
bles in the way of consumption, has very restrictive quality standards
. Similar restrictive standards should be applied for vegetables irrig
ated with reused water. The results of this study strongly suggest the
necessity to treat wastewater effluents to an extent in which no resi
dual contaminants will be detected on irrigated crops.