Comparative Evaluation of three Water Hyacinth, Water Lettuce, and Duckweed in a Hydroponic Reactor Treating High-Load Abattoir Wastewater

Abstract

Abattoir wastewater is a high-strength effluent rich in organic matter, nutrients, pathogens, and trace metals, requiring efficient and low-cost treatment solutions. This study evaluated a hydroponic phytoremediation system using Eichhornia crassipes, Pistia stratiotes, and Lemna minor for the treatment of abattoir wastewater collected from Zango Tudun Wada Abattoir, Nigeria. The influent exhibited BOD₅ of 630 ± 100 mg L⁻¹, COD of 980 ± 150 mg L⁻¹, TSS of 2700 ± 200 mg L⁻¹, NH₃–N of 325 ± 10 mg L⁻¹, and total coliforms of 1.05 × 10⁶ CFU 100 mL⁻¹. A modular hydroponic reactor (0.023 m³) was operated at hydraulic retention times of 7–21 days and organic loading rates of 0.5–2.0 kg COD m⁻³ day⁻¹ under a Taguchi design framework. Plant growth was assessed using morphometric parameters and a biomass–thickness index, with E. crassipes exhibiting the highest biomass development. Maximum treatment performance was achieved at 21 days HRT and 0.5 kg COD m⁻³ day⁻¹, particularly in polyculture systems. The tri-species configuration achieved up to 85% BOD₅ removal, 83% COD removal, 85–88% nutrient removal, 90–93% heavy metal removal, and 95% coliform reduction. The results highlight hydroponic macrophyte systems as an efficient and sustainable treatment option for high-strength abattoir wastewater, with strong potential for decentralized wastewater management