Assessment of agrochemical residues in wastewater from selected horticultural farms in Arusha, Tanzania

Arusha region in Tanzania has been involved for quite some time on commercial horticulture. The use of agrochemicals results to increased crop productivity and consequently offers farmers major economic returns. However, the use of agrochemicals and the adjacency of horticultural farms to streams and rivers have the potential to contribute to water pollution if control measures are not effective. We analysed the physical and chemical parameters of wastewater discharged from selected horticultural farms in Arusha and detected nitrates (NO₃⁻), phosphates (PO₄^3-), sulphates (SO₄^2-) and permethrins insecticide in the effluents discharged into the environment. The mean concentration levels ranged from (4.5 ppm 64.08 ppm) for NO₃⁻, (3.22 ppm-47.64 ppm) for PO₄^3-, (91.42 ppm-139 ppm) for SO₄^2- and permethrin was 0.63 ppm. Of all the farms monitored, eighty percent (80%) had high levels of PO₄^3-, sixty percent (60%) had high levels of NO₃⁻ and twenty percent (20%) had high levels of permethrin above the allowable limits for discharge into receiving water resources. It may be concluded that the continued agrochemical use may lead to contamination of adjacent water resources which may in the long run cause adverse health effects to the downstream water users. Continual monitoring of agrochemical residues is recommended to inform and ensure compliance with the stipulated standards and regulations for wastewater discharge.