| Summary: | 碩士 === 國立高雄科技大學 === 化學工程與材料工程系 === 107 === Ammonium sulfate evaporation tank processes condensed wastewater (cw), and this wastewater consist high concentrations of ammonium nitrogen (NH4-N) and chemical oxygen demand (COD). Due to the limited water resources available, strict regulation of ammonium nitrogen in wastewater has been implemented. The use of condensation in wastewater treatment leads to a high removal efficiency of NH4-N and COD in the water thus, increasing the recovery rate and the possibility of the condensed wastewater to be reused. The techniques often used by the industry in eradicating NH4-N and COD are physicochemical treatment, biological treatment, and chemical dosing. However, there is still a lack of pretreatment process that can quickly and easily pretreat condensed wastewater. So, this study aims to investigate the different temperature and reaction times, pH value, as well as the effects of NH4-N, COD, and oxidation-reduction potential (ORP) upon the addition of chlorine dioxide. Once the optimal concentration of chlorine dioxide is determined, the use of membrane bioreactor (MBR) and reverse osmosis (RO) system can be disregarded, leading to a more efficient process.
The results showed that chlorine dioxide (900 mg/L) reacted rapidly to COD (600 mg/L) and NH4-N (190 mg/L), and it had obvious removal efficiency at 25 ℃ during 1-2 minutes of operation. However, exposing chlorine dioxide to a higher temperature (45°C) can cause the compound to self-decompose. It is found out that the removal efficiency is better at pH=3 rather than at pH =7. Furthermore, ORP can be used as an indicator in determining residues of chlorine dioxide. After conducting the experiment, it is determined that the preferred operating conditions are: 25 ℃, pH = 3, and dosing amount of 1:8 (condensed water / ClO2). At 5 minutes of operation, the laboratory results show that the COD removal rate is 50% and the removal rate of NH4-N is 85%. Nonetheless, in the actual test, the removal rate of COD can reach up to 87%, and the removal rate of NH4-N can surge up to 99%, which may be caused by the improved mixing efficiency.
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