Keywords
UASB reactor
hospital effluents
heavy metals
How to Cite
Abstract
Introduction
Hospital effluents often contain heavy metals that pose significant environmental and public health risks, particularly in settings with limited access to advanced wastewater treatment technologies. Upflow Anaerobic Sludge Blanket (UASB) reactors represent a low-cost alternative; however, pilot-scale data on heavy metal removal remain scarce.
Purpose
This study evaluated the performance of a pilot-scale UASB reactor for heavy metal removal under optimised and non-optimised operational conditions and identified key factors influencing treatment efficiency.
Methods
A Plackett–Burman experimental design was used to screen critical operational parameters. The UASB reactor was operated for 12 weeks using real hospital effluent collected from the University Clinics of Kinshasa, with 36 samples analysed per monitoring point. The optimised reactor (P14) incorporated natural additives, including clay, eggshells, maize, and lime. Heavy metal concentrations were determined using atomic absorption spectrophotometry (AAS), with quality assurance and quality control procedures, calibration standards, and analytical blanks applied throughout.
Results
Under optimised conditions, substantial reductions were observed in chemical oxygen demand (COD; 620 → 150 mg/L) and heavy metal concentrations: iron (1.20 → 0.45 mg/L), copper (0.85 → 0.30 mg/L), and zinc (0.60 → 0.22 mg/L), corresponding to removal efficiencies of approximately 60–70%. Nickel and manganese concentrations also decreased but remained above World Health Organization guideline limits. Reactor performance remained stable throughout the 12-week operational period.
Conclusion
Pilot-scale UASB reactors supplemented with natural additives can significantly enhance heavy metal removal from hospital effluents. Further research is required to assess long-term operational stability, heavy metal fate, sludge management, and scalability prior to full-scale implementation.
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