Evaluation of irrigation suitability potential of brewery effluent post treated in a pilot horizontal subsurface flow constructed wetland system: implications for sustainable urban agriculture

The use of untreated or partially treated wastewater reuse for urban and peri-urban agricultural irrigation is a common practice in developing countries like Ethiopia. Such practices, however, pose significant environmental and public health risks. The objective of this study was to evaluate the irrigation suitability of anaerobic digestion brewery effluent (ADBE) and two-stage horizontal subsurface constructed wetland post-treated ADBE (CWPBE). A series of pot experiments were conducted in a plastic - greenhouse system arranged in three sets of irrigation schemes: Treatment Group1 (TG1): municipal pipe tap water (MPTW) irrigated pots; Treatment Group2 (TG2): ADBE irrigated pots, and Treatment Group3 (TG3): CWPBE irrigated pots. Pots packed with the same amount of sandy clay loam soil and local tomato seeds sown were irrigated following an updated tomato irrigation schedule derived from the FAO CROPWAT stimulation model for 120 days. The findings from key irrigation water quality parameters showed that the CWPBE achieved the prescribed irrigation water standards with values of pH (7.4 ± 0.15), electrical conductivity (1.9 ± 0.11 dS.m(−1)), total suspended solids (25 ± 4.17 mgL(-1)), chemical oxygen demand (185.1 ± 1.66 mgL(-1)), total nitrogen (17.4 ± 0.7 mgL(-1)), total phosphorous (8.8 ± 0.26 mgkg(-1)), calcium (10.5 ± 3.6 mgkg(-1)), magnesium (4.9 ± 0.98 mgkg(-1)), sodium (4.4 ± 1.51 mgkg(-1)), potassium (2.3 ± 1.15 mgkg(-1)), sodium adsorption ratio (1.6 ± 0.34), and total coliform (8 ± 0.16×10(−5) CFU/100 mL). Moreover, tomato plants grown in TG3 attained higher growth such as number of leaves (85.6 ± 4.68), plant height (92.2 ± 1.29 cm), stem diameter (13.1 ± 2.35 cm) and leaf area (35.5 ± 1.03 cm(2)) as well as higher biomass (61.2 ± 1.33 kgm(−2)) and fruit (46.4 ± 3.51 kgm(−2)) yields over other treatment groups. The results revealed that irrigation waters significantly improved both growth and yield parameters of tomato plants with the ascending order of TG1 < TG2 < TG3. Moreover, CWPBE showed minima short-term residual effect on soil physicochemical properties as compared to ADBE, and thus, it has potential suitability for agricultural irrigation reuse.