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 m(3)/m(2) d and a range of organic loading rate of 279.4-774.7 g-BOD(5)/m(2)d and 361.1-1028.7 g-COD/m(2)d, average removal efficiencies (mean+/-SD) of 90.6+/-7.5% for BOD(5) 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.