Some environmental problems associated with the use of treated wastewater for irrigation in Jordan

Treated effluent was used for eggplant (aubergine) irrigation through a trickle system at As-Samra experimental site. The soil characteristics were determined prior to irrigation. Physical, chemical and biological characteristics of the effluent were determined during the growing season. Suitability of the effluent for irrigation was studied. The crop and soil were tested for pathogenic pollution. The accumulation of salts and heavy metals in the soil as well as concentration of the nutrients and heavy metal accumulation in the plant tissues were determined. Clogging of the irrigation system was evaluated and treated. Yield was determined. Results of the study showed that the effluent has a low heavy metal content. It showed moderate restriction for surface trickle irrigation. Regarding the microbiological quality of the treated wastewater, it was found that the faecal coliform ranged from 2.1 X 10(3) to 1.8 X 10 Most Probable Number (MPN) per 100 ml at the irrigated site, while it is free from nematode eggs. The soil surface under the effluent irrigation water was found to contain faecal coliform, but the count drastically decreased with depth. Except for a very low coliform count on fruit skins, no coliform count was found on the crop leaves, whether they were Free or in contact with the soil. The effluent showed a rather high concentration of chlorophyll a due to the presence of algae. Results of soil analysis after eggplant harvest showed a slight increase in heavy metals and salt accumulation at the periphery of the wet zone. Nutrients and heavy metal concentration in eggplant tissue under treated effluent irrigation was within the normal range in agricultural crops. Although filtration of the effluent was not practised, there was minimum clogging of the irrigation system. This clogging was successfully controlled with acid and chlorine. Eggplant yield under treated effluent was twice the average eggplant production under fresh water irrigation using conventional fertiliser application in Jordan. (C) 1997 Elsevier Science B.V.