THE BACTERIAL QUALITY OF SALAD CROPS DRIP AND FURROW-IRRIGATED WITH WASTE STABILIZATION POND EFFLUENT - AN EVALUATION OF THE WHO GUIDELINES

Field- and glasshouse-grown lettuces and radishes were drip- and furro w-irrigated with waste stabilization pond effluent and with trickling filter effluent diluted with clean water. Crop contamination levels va ried considerably. Under dry weather conditions they were at worst of the orders of 10(3) and 10(4) E. coli per 100 g (fresh weight) for rad ishes and lettuces, respectively; salmonellae were always absent The b acterial quality of experimental lettuces was similar to those of lett uces on sale in local markets. When rainfall occurred E. coli numbers increased and salmonellae were isolated From lettuce surfaces. These r esults are interpreted as partially substantiating the current World H ealth Organization bacteriological guideline for unrestricted wastewat er reuse, but suggest the need for further assessment on the variation in crop contamination caused by climatic conditions.