Phosphorus Dynamics in Coastal Sediments: Implications for the Marshland Upwelling System

Nitrogen and phosphorus from domestic wastewaters can cause eutrophication in natural waters. Unlike nitrogen, the only permanent phosphorus removal mechanism from water is sediment accretion. The marshland upwelling system (MUS) is an alternative onsite wastewater system developed to treat domestic wastewater derived from coastal communities where saturated soils render septic systems ineffective. Previous research has assessed the ability of MUS to remove phosphorus and identified a zone of phosphorus (P) saturation. A laboratory column study was performed to determine the fate and fractionation of phosphorus in the soil matrix and their relation to cations, redox and microbial population in the soils commonly used in the MUS as a means to provide better overall design and operational guidelines for MUS operation. Anaerobic, low redox conditions dominant in the MUS soil indicate that sorption of inorganic P, mainly retained by calcium and iron ions dominates over organic P.