A mixotrophic algal wastewater treatment system capable of reducing biochemical oxygen demand (BOD), ammoniacal nitrogen (NH₄⁺-N), and phosphate (PO₄³⁻-P) in primary effluent in a single step has been demonstrated previously. Downstream processing of the resulting algal biomass by hydrothermal liquefaction (HTL) to recover its energy-content as biocrude oil has also been demonstrated. The current study evaluated the feasibility of recovering struvite from the two byproducts of HTL– a solid residue, rich in PO₄³–P; and an aqueous phase, rich in NH₄⁺–N, for use as fertilizer. Results of this feasibility study and a preliminary mass balance model show that the proposed pathway can potentially yield ~2.5 kg struvite per 100 m³ of wastewater treated, recovering nearly 73% of PO₄³–P and 6% of NH₄⁺–N in the primary effluent. Chemical and microscopic analysis of the wastewater-derived struvite revealed its composition to be close to that of pure struvite, with more than 12% P-content by weight. Scanning electron microscopy images depicted uniformly distributed sizes of irregular crystals in the wastewater-derived struvite. Low calcium content of this struvite indicated minimum amorphous calcium phosphate (ACP) impurities. Trace metal analysis showed that heavy metal levels in the recovered struvite were below current guidelines. This study confirmed the feasibility of recovering high-quality struvite from wastewaters, warranting further process optimization and characterization of the recovered struvite.

先前已经证明了一种混合营养型藻类废水处理系统，该系统能够一步一步降低初级污水中的生化需氧量（BOD），氨氮（NH ₄ ⁺ -N）和磷酸盐（PO ₄ ^3-- P）。还证明了通过水热液化（HTL）对所得藻类生物质进行下游加工以回收其能量含量（作为生物原油）。当前的研究评估了从HTL的两种副产物中回收鸟粪石的可行性。HTL是富含PO ₄ ³ -P的固体残渣。和富含NH ₄ ⁺的水相–N，用作肥料。该可行性研究的结果和初步的质量平衡模型表明，该拟议途径每处理100 m ³废水可潜在产生约2.5 kg鸟粪石，可回收近73％的PO ₄ ³ -P和6％的NH ₄ ⁺-N在主要废水中。对废水衍生的鸟粪石的化学和显微镜分析表明，其组成接近纯鸟粪石，其磷含量超过12％（重量）。扫描电子显微镜图像描绘了废水衍生的鸟粪石中不规则晶体的均匀分布尺寸。该鸟粪石的钙含量低表明无定形磷酸钙（ACP）杂质最少。痕量金属分析表明，回收的鸟粪石中的重金属含量低于当前标准。这项研究证实了从废水中回收高质量鸟粪石的可行性，保证了进一步的工艺优化和对回收的鸟粪石的表征。