Exploring greywater hydroponic vegetable growing and phytoremediation capacity of coleus plants for urban farmers in Mbarara city Uganda

Urban Farm DB summary

This eight-week experiment, conducted from July to September 2023 in Mbarara city, Uganda, tested the capacity of greywater to serve as a hydroponic growing medium for vegetables (broccoli, spring onions, lettuce) and the greywater-cleansing capacity of Coleus ornamental plants. Greywater was collected from restaurant sculleries, and four treatments — greywater, greywater + NPK, tap water, and tap water + NPK — were each set up in triplicate, with pH, EC, TDS, temperature, turbidity, nitrates, phosphates, shoot length, leaf number, fecal coliforms, and heavy metals measured. All vegetables survived, but production levels differed significantly between treatments: lettuce had the highest production in three of the four treatments except greywater + NPK (ANOVA, F(3,56) = 2.970, p = 0.039), while spring onions grew best in greywater + NPK, differing significantly from other treatments (F(3,56) = 3.328, p = 0.026). Greywater treatments showed extreme EC and TDS values (1001.38 µS/cm and 502 ppm; 982.38 µS/cm and 490.75 ppm), significantly different from other treatments (p = 0.000), though no fecal coliforms were detected in vegetable tissue. Coleus progressively reduced TDS and EC and showed capacity to extract heavy metals from the greywater.