Phosphorus retention capacity in red ferralitic soil

Area of Science:

• Environmental Science
• Soil Science
• Water Treatment

Background:

• Subsurface wetlands are crucial for wastewater treatment.
• Red ferralitic soil's potential as a phosphorus removal substrate requires investigation.
• Understanding soil characteristics is key to optimizing phosphorus removal efficiency.

Purpose of the Study:

• To determine the physical-chemical properties of red ferralitic soil for use in subsurface wetlands.
• To evaluate the phosphorus (P) removal capacity of this soil.
• To investigate the influence of temperature and flow rate on P sorption.

Main Methods:

• Isotherm batch experiments and column percolation tests were conducted.
• Sorption isotherms were analyzed using Langmuir and Freundlich models at 25°C and 35°C.
• Sequential extraction was used to identify phosphorus binding mechanisms.

Main Results:

• Red ferralitic soil exhibits acidic properties and high iron content, facilitating phosphorus removal.
• Phosphorus sorption capacity increased with temperature, with better fit to Freundlich isotherms.
• Maximum P-sorption capacities were 0.96 g/kg at 25°C and 1.13 g/kg at 35°C.
• Phosphorus was primarily bound to iron and aluminum minerals in saturated soil.

Conclusions:

• Red ferralitic soil demonstrates significant potential for phosphorus removal from urban wastewater.
• Its characteristics make it a suitable substrate for subsurface constructed wetlands.
• Temperature and soil mineralogy are key factors influencing phosphorus sorption efficacy.