Irrigation with tertiary effluent, secondary effluent, and raw wastewater (sewage) were studied with tap water irrigation as the control. The effects of the irrigations on the qualities of three testing crops: cucumber, celery cabbage and maize were investigated. The contents of residual chloride ion, phosphate, nitrate, nitrite, and residual heavy metals in these irrigated crops were also examined. The results showed that the secondary and tertiary effluent had no significant effects on the crop qualities. However, irrigation with the sewage could lead to increase parts of nutrient components in the crops. Irrigation with the sewage caused accumulation of nitrate and heavy metals in the crops, indicating that sewage was not suitable for irrigation. The risk assessment results suggested that the health risk of the irrigations using sewage and secondary effluent exceeded the maximum acceptable risk level. Comparatively, the risk in the tertiary effluent irrigation was much lower than the acceptable level.

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