豬糞廢水中含有氨氮(約幾百到幾千mg/L)、正磷酸鹽(約幾十到幾百mg/L)以及少量的鎂，在臺灣，大部分豬糞廢水在經過廢水處理後即被排放。近年來，已有部分豬糞廢水以厭氧消化進行能源回收，本研究的主要目標為回收豬糞廢水中的氮、磷，利用從海水淡化鹵水中回收的Mg(OH)2作為Mg2+來源，將豬糞廢水中正磷酸鹽和氨氮沉澱為鳥糞石，以處理豬糞廢水。本研究將探討鳥糞石的生成反應動力學，了解反應速率常數(k)和過飽和度率(SSR)之間的關係，並評估影響鳥糞石的結晶大小的因子，包含混和方式、攪拌速度、分段加藥、導電度及有機質含量(TOC)。
本研究使用磁力攪拌進行合成廢水和豬糞廢水的反應動力學探討。此外，在合成廢水的反應動力學實驗中，本研究藉由控制N：P：Mg的莫爾比模擬反應為假一階。來了解在低磷鎂濃度的反應速率以及反應階數。根據結果，鳥糞石的生成動力學為假一階反應，但k卻隨不同的SSR而變化。而SSR會受到氨氮、正磷酸鹽、鎂的濃度和pH值的影響，進一步發現SSR與鳥糞石反應的k有正相關。為了讓k和SSR的相關性，能做為處理豬糞廢水設計參數的提供，本研究將比較豬糞廢水和合成廢水的相關性結果。根據回歸分析後，得到合成廢水中k和SSR的趨勢線與豬糞廢水相似。因此，證實可以藉由調整SSR來控制反應速率，未來可以應用在鳥糞石生成反應中。
除此之外，鳥糞石的大小對於作為肥料再利用也很重要。因此，本研究將嘗試使用混凝攪拌器和分次加入Mg2+來增加鳥糞石的大小。本研究的結果將被用來優化鳥糞石生成的大小。

為了提高合成廢水中鳥糞石的大小，其過程會受到很多因素的影響。藉由不同的攪拌器發現，混凝攪拌器使比磁力攪拌器能產生更大的鳥糞石從小於100 μm到大於100 μm。在分8次加入Mg2+的實驗，鳥糞石的平均大小可以大於100 μm，最大粒徑為519 μm。在不同濃度的TOC的實驗中，無論濃度從5000 ppm到20000 ppm，鳥糞石的大小都小於35 μm。在多種金屬離子(Mg2+、Na+、K+、Ca2+)作為背景溶液改變電導度與豬糞廢水相同的實驗，鳥糞石的大小也沒有增加到70 μm以上。本研究發現在豬糞廢水中，即使使用混凝攪拌器並分次加入Mg2+，其粒徑皆小於50 μm。根據研究結果推測可能的原因為TOC的濃度超過5000 ppm以及豬糞廢水中的其他離子(如Na+、K+、Ca2+)抑制了鳥糞石的生長。

There is rich nitrogen (from several hundred to several thousand mg/L), phosphorus (from several tens to several hundred mg/L), and slight magnesium in swine wastewater. Most swine wastewaters were discharged after treating wastewater treatment facilities in Taiwan. In recent years, swine wastewater was recycled by anaerobic digestion.
The research objectives of this study are recycling the phosphate and ammonia from swine wastewater by using the Mg(OH)2 recovered from the brine as an Mg2+ source to precipitate phosphate and ammonia into struvite to treat the swine wastewater. This study has discussed the kinetics of struvite formation to find the best way of struvite precipitation, figure out what kind of reaction it is, and the correlation between rate constants (k) and supersaturation ratio (SSR). In the end, assessing the factors that affect the struvite size, including the different stirrer, stirrer speed, adding Mg2+ in several separate times, conductivity, and the concentration of total organic carbons (TOC).
The experiment was divided into using a magnetic stir bar and jar test stirring. It was discussed the reaction kinetic of synthetic wastewater and swine wastewater was applied by the magnetic stir bar. Furthermore, in the synthetic wastewater kinetic experiment, this study tested the reaction rate by controlling the molar ratio of N:P: Mg to model that the reaction was pseudo-first-order then figure out the order of the reaction. The results showed that the kinetic of struvite formation was a pseudo-first-order reaction. Besides, the results indicated that the rate constant varied with different SSR. SSR was affected by the concentration of ammonia nitrogen, orthophosphate, magnesium, and pH, which is further found to have a positive correlation with k of struvite formation. To apply the correlation between k and SSR to design the treatment tank for swine wastewater, this study compared the correlation results from swine wastewater and synthetic wastewater. The trend line of k and SSR in the synthetic wastewater obtained from the regression analysis was similar to the swine wastewater. Therefore, it could be used as a future application to control the struvite formation reaction rate by adjusting SSR.
In addition, struvite size was also important to reuse as fertilizer. Therefore, this study was tried to increase the struvite size by using the jar test stirring and adding Mg2+ in several times. All the results were utilized to optimize the formation size of struvite.
For the enhancement of struvite size in synthetic wastewater, struvite size was affected by many factors. By different stirrers, jar test stirring makes the struvite larger than the magnetic stir bar from smaller than 100 μm to larger than 100 μm. By adding Mg2+ in eight times, the average size of struvite could be larger than 100 μm and the largest size is 519 μm. By different concentrations of total organic carbon, no matter the concentration was changed from 5000 ppm to 20000 ppm, the struvite size was smaller than 35 μm. By changing conductivity with multiple metal ions (Mg2+, Na+, K+, Ca2+) to the same conductivity as swine wastewater, the struvite size didn’t increase to over 70 μm as well. In this study, it was found that the struvite size was smaller than 50 μm even when using the jar test stirring and adding Mg2+ in several times in swine wastewater. The possible reason is that the organic matter and other metal ions (e.g., Na+, K+, Ca2+) in the swine wastewater inhibited the growth of struvite.

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