Wastewater Irrigation: Some Bacterial and Helminthological Effects


The survival of faecal coliforms, faecal streptococci and of helminths in soil and crops irrigated with wastewater was studied between March and June in 1988. The results showed a more than 90% reduction in the counts of faecal streptococci by the 4th day and of faecal coliforms by the 6th day. Helminths, Stronqyloides stercoralis larvae and Mite were not recovered from the soil after 14 and 4 days respectively. Ascaris lumbricoides, Toxocara canis, Ancylostoma duodenale, Trichuris Spp and Stronqyloides stercoralis eggs were recovered occasionally during the period. Rainy season studies yielded unreliable results because of the flooding of the experimental plot where survival studies were carried out. The wastewater used for the irrigation did not satisfy the WHO (1973) standard of 1,000 faecal coliform per 100 ml, for unrestricted irrigation. The average 4 faecal coliform count in the wastewater was 2.0 x 10 per 100 ml. Results obtained from the experimental farm showed significant differences at 0.5 confidence level for indicator organisms and helminths isolated from tap-water and wastewater-irrigated crops (Maize, Tomatoes and Amaranthus).

The finding reinforces the view that the use of wastewater for irrigation without further treatment may not only constitute a health hazard to the consumers but may expose the farmers to infections like ascariasis etc.