A novel Fe(II)-Ca synergistic phosphorus removal process: process optimization and phosphorus recovery

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies
• Inorganic Chemistry

Background:

• Eutrophication control necessitates efficient phosphorus removal from wastewater.
• Phosphorus recovery from wastewater is crucial for resource management.
• Traditional phosphorus removal methods can be costly and less efficient.

Purpose of the Study:

• To develop a novel synergistic phosphorus removal process using a ferrous and calcium salt complex.
• To investigate the effects of Fe(II)/Ca molar ratios on phosphorus removal efficiency.
• To optimize process parameters and evaluate cost-effectiveness and phosphorus recovery.

Main Methods:

• Development of a novel Fe(II)-Ca synergistic phosphorus removal process.
• Experimental determination of optimal Fe(II)/Ca molar ratios (synergistic effect observed at >1:4, strongest at 7:3).
• Optimization of process parameters: Fe(II)/Ca ratio (3:1), M/P ratio (≥1.5:1), pH (7.0-8.0), and fast mixing speed (100-150 rpm).

Main Results:

• A synergistic effect was observed at Fe(II)/Ca molar ratios higher than 1:4.
• Optimal parameters identified for efficient phosphorus removal.
• Cost of phosphorus removal agents reduced by 30.39% (US$1.024 (kg P)⁻¹).
• Precipitate contained 32.70% phosphorus (as P₂O₅), indicating high recycling value.

Conclusions:

• The novel Fe(II)-Ca synergistic process offers an effective and cost-efficient solution for phosphorus removal from wastewater.
• The process significantly reduces operational costs compared to traditional methods.
• The high phosphorus content in the precipitate facilitates valuable resource recovery, contributing to a circular economy.