Enhanced phosphorus removal in intermittently aerated constructed wetlands filled with various construction wastes

Abstract

Phosphorus (P) loss by various pathways in constructed wetlands (CWs) is often variable. The effects of intermittent aeration and different construction waste substrates (gravel, red brick, fly-ash brick) on P processing using six batch-operated vertical flow constructed wetlands (VFCWs) were studied for decentralized domestic wastewater treatment. Average removal of total phosphorus (TP) in three aerated CWs was markedly higher (21.06, 24.83, and 27.02 mg m⁻² day⁻¹, respectively) than non-aerated CWs (10.64, 18.16, and 25.09 mg m⁻² day⁻¹, respectively). Fly-ash brick offered superior TP removal efficiency in both aerated and non-aerated batch-operated VFCWs, suggesting its promising application for P removal in CWs. Aeration greatly promoted plant growth and thusly increased plant uptake of P by 0.57–1.45 times. Substance storage was still the main P sink accounting for 23.92–59.47% of TP removal. Other process including microbial uptake was revealed to be a very important P removal pathway (accounting for 14.86–34.84%). The contribution of microbial uptake was also indicated by microbial analysis. Long-term results suggested that the contribution of microbial P uptake could be always ignored and underestimated in most CWs. A combination of intermittent aeration and suitable substrates is effective to intensify P transformation in CWs.

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