Simultaneous removal of nutrients from simulated swine wastewater by adsorption of modified zeolite combined with struvite crystallization

• MgCl2-modified zeolite was used as adsorbent material and magnesium source.
• 82% TAN and 98% PT in synthetic swine wastewater were simultaneously removed.
• K+, Ca2+, Na+ and Mg2+ had a significant effect on the proposed process.
• The presence of citric acid had a significant effect on the proposed process.

This paper proposes a novel process for the simultaneous removal of ammonia–nitrogen and phosphate from simulated swine wastewater using modified zeolite. The natural zeolite was modified by magnesium salts as the adsorbent material for ammonia–nitrogen from wastewater. Mg2+ released from the adsorption process served as the magnesium source in struvite crystallization. The treatment of simulated swine wastewater using modified zeolite at pH 8–9.5 showed much better efficiencies of ammonia–nitrogen and phosphate removal than those by natural zeolite at the same pH. The high nutrient-removal efficiencies were mainly achieved because of cooperation between adsorption by modified zeolite and struvite crystallization. When the reaction condition was controlled at 110 g/L of modified zeolite and 40 min of reaction time, the ammonia–nitrogen and phosphate-removal efficiencies reached 82% and 98%, respectively. The individual presence of K+, Ca2+, Na+, and Mg2+ had a significantly negative effect on the removal of ammonia–nitrogen in the order of preference of Ca2+ > Mg2+ > K+ > Na+ at identical molar concentrations. Nevertheless, the presence of these ions, except for Na+, had a positive influence on the removal of phosphate. In addition, investigation of the effects of organic acids on the process showed that the removal of nutrients could be significantly reduced by inhibiting struvite crystallization by citric acid present in the simulated swine wastewater. However, the presence of acetic acid had no effect on the proposed process. An economic evaluation revealed that the treatment cost of the proposed process was 3.65 $/m3 of simulated swine wastewater.

Figure optionsDownload as PowerPoint slide