Passive phosphorus capture in biofiltration context: nitrate impact on the performance.

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Biotechnology

Background:

• Passive phosphorus removal is crucial for preventing eutrophication.
• Wood-based biofilters offer a sustainable medium for phosphorus sorption.
• Nitrate's impact on phosphorus removal in these systems requires investigation.

Purpose of the Study:

• To evaluate the efficacy of iron hydroxide-impregnated wood biofilters for phosphorus removal.
• To determine the effect of varying nitrate concentrations on biofilter performance.
• To understand the mechanisms influencing phosphorus removal under nitrate influence.

Main Methods:

• Column tests using anaerobic activated wood-based media over 150 days.
• Application of synthetic phosphorus solution (5 mg P L⁻¹) followed by different nitrate concentrations (5, 10, 25 mg N-NO₃ L⁻¹).
• Monitoring of total phosphorus removal efficiencies and analysis of redox potential and bacterial communities.

Main Results:

• Total phosphorus removal efficiencies ranged from 70.6% to 96.9%.
• Increased nitrate concentrations led to decreased phosphorus removal efficiencies (C1: 96.9%, C2: 81.7%, C3: 70.6%, C4: 75.7%).
• Nitrate addition increased redox potential, inhibiting reductive dissolution and ferrous ion release, while promoting simultaneous denitrification.

Conclusions:

• Nitrate negatively impacts passive phosphorus removal in wood-based biofilters.
• The observed inhibition is linked to increased redox potential and altered iron dynamics.
• Biofilters host diverse microbial communities, including iron-related and denitrifying bacteria, influencing treatment processes.