Phosphorus sorption characteristics of a light-weight aggregate

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Material Science

Background:

• Lightweight aggregate (LWA) from expanded clay is utilized as filter media in wastewater treatment.
• Phosphorus (P) removal is critical for preventing eutrophication.

Purpose of the Study:

• Investigate phosphorus sorption mechanisms using LWA.
• Determine the influence of grain size, time, temperature, and P concentration on P binding.
• Identify predominant P retention pools within the LWA filter media.

Main Methods:

• Laboratory batch experiments were conducted using three LWA grain sizes (0-2 mm, 2-4 mm, 0-4 mm).
• Phosphorus sorption isotherms were determined.
• Fractionation analysis was employed to identify P retention pools.
• Effect of temperature and P concentration on sorption was assessed.

Main Results:

• Fifty percent of P sorption occurred within the first 4-8 hours.
• Temperature showed minimal impact on P sorption for 0-2 mm LWA.
• No significant P desorption was observed even when P concentration in the solution decreased.
• Ca-bound P, loosely-bound P, and Al-bound P were the dominant retention pools.
• Fe-bound P was found to be negligible.

Conclusions:

• LWA demonstrates effective phosphorus sorption capacity in wastewater treatment.
• Phosphorus binding mechanisms are primarily governed by Ca-bound, loosely-bound, and Al-bound pools.
• Loosely-bound P is mainly influenced by the equilibrium P concentration.
• LWA shows potential as a sustainable filter media for phosphorus removal.