Department of Civil and Environmental Engineering, University of Science and Technology, KICT school, 283, Goyang-daero, Ilsanseo-gu, Goyang-si, Gyeonggi-do, 10223, Republic of Korea.
Department of Land, Water, and Environment Research, Korea Institute of Civil Engineering and Building Technology, 283, Goyang-daero, Ilsanseo-gu, Goyang-si, Gyeonggi-do, 10223, Republic of Korea E-mail:
Water Sci Technol. 2020 Jun;81(12):2511-2521. doi: 10.2166/wst.2020.306.
The struvite crystallization process can recover struvite crystals as a valuable slow-release fertilizer from the side stream of wastewater treatment plants (WWTPs). The purpose of this study is to demonstrate the crystal growth characteristics and determine the appropriate recovery criteria for a struvite crystallization pilot plant. A pilot plant (8.6 m/d) was designed with a feeding system of MgO (magnesium oxide), a pH controller, and a hydrocyclone for recovering struvite; the plant was operated for 42 hours at a pH range of 8.25-8.5. The removal efficiencies for PO-P and NH-N were 82.5-90.7% and 13.4-22.9%, respectively. The struvite recovered from the hydrocyclone was sifted using standard sieves and analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The dry weight fraction of the precipitate in the 300-600 μm range increased gradually from 7% to 74% in 18 hours. The XRD analysis revealed that the crystalline structure of the precipitate in the 150-600 μm range indicates struvite without any peaks of MgO, Mg(OH), and MgCO. This indicates that the critical conditions for recovering struvite from the side-stream of WWTPs are an operation period of 18 hours and a crystal size greater than 300 μm.
鸟粪石结晶过程可从污水处理厂（WWTP）的侧流中回收鸟粪石晶体作为有价值的缓释肥料。本研究旨在展示结晶生长特性，并确定用于鸟粪石结晶中试工厂的适当回收标准。设计了一个 8.6 m/d 的中试工厂，配备氧化镁（MgO）进料系统、pH 控制器和用于回收鸟粪石的水力旋流器；该工厂在 pH 值为 8.25-8.5 的范围内运行了 42 小时。PO-P 和 NH-N 的去除效率分别为 82.5-90.7%和 13.4-22.9%。从水力旋流器回收的鸟粪石用标准筛进行筛选，并通过扫描电子显微镜（SEM）和 X 射线衍射（XRD）进行分析。沉淀在 300-600 μm 范围内的干重分数在 18 小时内从 7%逐渐增加到 74%。XRD 分析表明，沉淀在 150-600 μm 范围内的晶体结构表明是鸟粪石，没有 MgO、Mg(OH)和 MgCO 的任何峰。这表明从 WWTP 的侧流中回收鸟粪石的关键条件是 18 小时的操作时间和大于 300 μm 的晶体尺寸。
