Advances in Recycling & Waste Management

Agro-industrial sectors in Ethiopia are highly expanding and offering environmental problems. Some brewery factories in Ethiopia had installed advanced wastewater treatment technologies. Sludge generated from waste treatment plants are recognized as good alternative options for agricultural reuse. However, the difference in sludge properties due to the wastewater action process variation and the inconstant nature of contaminant inputs to the original wastewater, the fertilizer prospective and contaminant risks should be evaluated. Hence, the goal of this study was to illustrate the physical, chemical and biological properties of Kombolcha brewery wastewater treatment plant bio-solid in relative to agricultural reuse. The physicochemical and biological characteristics of the brewery sludge were 7.85, 2.35 mScm^-1, 54%, 92.9%, 49.1%, 84.6%, 3.84%, 5.92%, 12.78:1, 5.46 x 10⁶ MPN/ml and 3.06 x 10⁴ MPN/ml for pH, EC, WHC, TS, OC, OM, TKN, P₂O₅, C/N ratio and TFC (as fresh and dry weight) respectively. The secondary and other plant nutrient contents of the BS were 0.24%, 1.61 mg/Kg for K₂O and K, 4.74%, 3.19 mg/ Kg for CaO and Ca, 0.76%, 1.19 mg/Kg for MgO and Mg, 0.86%, 0.37 mg/Kg for Na₂O and Na, 2.94% for Al₂O₃, 27.98% for SiO₂ and 0.18% for TiO₂ with the detected heavy metals concentration of 0.07, 0.05, 10211.5 and 0.77 mg/Kg for Zn, Pb, Fe and Cu respectively. Overall, the result revealed that the sludge has high OM and P₂O₅ content that fulfills the suggested standards for the fertilizer value of sludge, optimum pH and EC values, substantial qualities of nitrogen and high WHC and deficient secondary plant nutrients (calcium, magnesium, potassium and sodium), all able to contribute beneficial improvement of soil properties. In line with this, the very lower heavy metals concentration, existed below both the EPA and Canadian class A limits and ideal C/N ratio, meets the fertilizer value of sludge and make it to serve as a valuable organic fertilizer. However, the higher pathogen contents are stabilized to the required standard (<10³ MPN/g) for unrestricted reuse of the sludge for agricultural application.