Assessment of irrigation water quality for vegetable farming in peri-urban Kumasi

Polluted water contains a variety of toxic compounds that tend to affect human health. Farmers have recently looked at runoff wastewater as a source of irrigation water because it comes at no cost and is a more efficient alternative to potable water due to the high demand but limited supply. This present study assesses the quality and suitability of water sources used for irrigation at the Kwame Nkrumah University of Science and Technology vegetable farmlands. The study specifically investigated the quality of water used for irrigation with the following parameters: pH, turbidity, total dissolved solids, total suspended solids, chloride, chemical oxygen demand, biological oxygen demand, oil and grease, fluoride, nitrate, nitrite, sulphate, sodium, calcium, magnesium, sodium adsorption potential, alkalinity, conductivity, phosphate, Escherichia coli, fecal and total coliforms. The results revealed that the water contained moderate levels of chloride and could be good for plant growth. The total coliform counts range from 2.1 × 10⁶ to 4.15 × 10⁷ MPN/100 mL, suggesting a relatively high microbial load in the irrigation water. The results also suggested that the sodium absorption ratio was very low and may not affect the quality of water for irrigation purposes. Fe levels far exceed the 5 mg/L maximum acceptable limits recommended by the WHO and FAO for the irrigation of vegetables. The high Fe concentration could discolor the leaves of some plants, especially foliage leaves. However, the levels of Cd were within the WHO maximum permissible limit of 0.01 mg/L.