Alum sludge-based constructed wetland system for enhanced removal of P and OM from wastewater: Concept, design and performance analysis

The concept, design and performance analysis of a four-stage novel constructed wetland system (CWs) capable of enhanced and simultaneous removal of phosphorus (P) and organic matter (OM) from wastewaters is described. Alum sludge, a largely available by-product of drinking water facilities using aluminium salts as coagulant was used as the media. Under a hydraulic loading rate of 1.27 m3/m2 d and a range of organic loading rate of 279.4–774.7 g-BOD5/m2 d and 361.1–1028.7 g-COD/m2 d, average removal efficiencies (mean ± SD) of 90.6 ± 7.5% for BOD5 and 71.8 ± 10.2% for COD were achieved, respectively. P removal was exceptional with average removal efficiency of 97.6 ± 1.9% achieved for soluble reactive P at a mean influent concentration of 21.0 ± 2.9 mg/l. Overall, the system holds great promise as a novel CWs for simultaneous removal of P and OM, and at the same time, it transforms alum sludge from a waste into a useful material.