Characterization of aluminium-based water treatment residual for potential phosphorus removal in engineered wetlands

Aluminium-based water treatment residual (Al-WTR) is the most widely generated residual from water treatment facilities worldwide. It is regarded as a by-product of no reuse potential and landfilled. This study assessed Al-WTR as a potential phosphate-removing substrate in engineered wetlands for wastewater treatment. Results indicate the specific surface area ranged from 28.0 m2 g-1 to 41.4 m2 g-1 and this increased with increasing particle size. X-ray Diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and energy-dispersive X-ray spectroscopy all indicate that the Al-WTR is mainly composed of amorphous aluminium which influences its phosphorus (P) adsorption capacity. The pH and electrical conductivity ranged from 5.9 - 6.0 and 0.104 dS m-1 - 0.140 dS m-1 respectively, and both showed that it should suitably support plant growth. Batch tests showed a maximum P adsorption capacity of 31.9 mg-P g-1 and significant P removal was achieved in column tests. Overall, results showed that Al-WTR can be a low-cost, easily and locally available substrate for enhanced P removal in engineered wetlands and it carries the benefits of reuse of a by-product that promotes sustainability.