Simultaneous recovery of microalgae, ammonium and phosphate from simulated wastewater by MgO modified diatomite

In this study, MgO modified diatomite (MgO-D) was used for recovery of microalgae (Chlorella pyrenoidosa FACHB-9), NH4+-N and phosphate from wastewater. The effects of adsorbent dosage, solution pH, contact time, and coexisting substances were investigated. The results showed that MgO-D exhibited excellent recovery efficiency for microalgae, NH4+-N and phosphate in a wide pH range of 3.0-9.0. With initial pH= 8.0, MgO-D= 0.5 g/L and reaction time= 2 h, the recovery efficiencies of microalgae, NH4+-N and phosphate were 182.04 mg/g, 63.3 mg/g, 121.07 mg/g, respectively. Coexisting organic matters inhibited the recovery of microalgae, NH4+-N and phosphate in the order of alginate > humic acid > acetic acid. When in proper concentration range, NH4+-N and phosphate were preferentially recovered by MgO-D through struvite precipitation, and then the charge neutralization of hydroxylated Mg(OH)(2) and sweeping of struvite precipitation played an important role in harvesting of microalgal cells. This study shows new guidelines and useful methods for the simultaneous recovery of microalgae, NH4+-N and phosphate from wastewater.