Design and Performance Evaluation of a Laboratory-Scale Horizontal Subsurface-Flow Constructed Wetland for Brewery Effluent Treatment

Abstract

Brewery wastewater is characterised by high organic and nutrient loads that pose a significant risk of eutrophication when discharged untreated into receiving water bodies. This study presents the design, construction, and performance evaluation of a laboratory-scale horizontal subsurface-flow constructed wetland (HSSF-CW) for the treatment of effluent from a brewery in Kaduna, Nigeria. The raw effluent was characterised and found to be of moderate strength (pH 7.76, COD 609 mg/L, TSS 185 mg/L, total nitrogen 45 mg/L, total phosphorus 12 mg/L), with elevated turbidity (197 NTU) and iron content (8.5 mg/L). A wetland cell of dimensions 0.93 m × 0.43 m × 0.36 m, aspect ratio 2.16:1 and volume 144 L, was sized using first-order plug-flow kinetics with a reaction rate constant of 0.612 d⁻¹, yielding a theoretical hydraulic retention time (HRT) of 47.04 hours; an experimental HRT of 72 hours was adopted in operation. Effluent quality was monitored at 0, 24, 48 and 72 hours across thirteen physicochemical and heavy-metal parameters. After 72 hours of treatment, turbidity fell from 197 NTU to below 6 NTU (>97% removal), COD reduced by 77–87%, TSS by over 92%, and iron, lead, copper and zinc concentrations all declined below NESREA and FAO discharge and irrigation limits. The results demonstrate that a compact, low-cost HSSF-CW designed on basic hydraulic and kinetic sizing principles can reliably bring brewery effluent into regulatory compliance, offering an economical and low-maintenance alternative to conventional treatment for small and medium-scale breweries in developing regions.