Ultrasonic Pretreatment to Enhance the SDS-sodium Hypochlorite Method for Extracting Polyhydroxyalkanoate from Waste Sludge

• Main Authors: Yi Lin-Chen, 陳翊驎
• Other Authors: Yung-Pin Tsai
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/6v998w

碩士 === 國立暨南國際大學 === 土木工程學系 === 106 === Taiwan produces nearly 4 million tons of sludge each year, the cost of sludge treatment has constituted approximately 50% of the budget of wastewater treatment plants. From the viewpoint of waste recovery, this study used a two-stage extraction method to extract polyhydroxyalkanoates (PHAs) from waste sludge from a domestic wastewater treatment plant; the extraction results were evaluated. The optimal procedures and parameters were determined in the first stage and then used in the second stage to improve sodium dodecyl sulfate (SDS)–sodium hypochlorite (NaOCl) extraction. The extraction method was expected to meet objectives of reducing the use of chemicals, minimizing wastewater discharge, shortening operating time, reducing waste, and enhancing waste circulation. For SDS–NaOCl extraction, the optimal operating conditions were a SDS concentration of 1%, sludge liquid-to-solid ratio of 1.00 mL/mg, and chemical retention time of 15 min. After the extraction, the observed PHA content was 43.08 ± 1.73 mg PHAs/g VSS. Ultrasonic pretreatment was added to the extraction method, and the SDS concentration was reduced to 0.7%, liquid-to-solid ratio of the sludge was reduced to 0.83 mL/mg, and retention time of the chemicals was shortened to 10 min. Therefore, the addition of a physical pretreatment process before chemical extraction can effectively reduce the amount of chemical use and the retention time of chemicals; it can also increase the per unit volume of treated sludge. The optimal operating parameter for the ultrasonic pretreatment process was an output power of 20 W for 0.5 min. The chemical extraction of 1 kg of PHAs after the physical pretreatment cost US$202. After the amount of chemical use was reduced, extracting the same amount of PHAs was estimated to cost US$154; the extraction cost decreased by 24%. A comparison of domesticated sludge and raw materials produced by pure cultures indicated that waste sludge contained an excessively low amount of PHAs. However, this study focused on reducing the amount of chemicals; therefore, cost reduction was the primary assessment indicator in this study. Keywords: West sludge, Ultrasonic pretreatment, SDS–sodium hypochlorite extraction, Polyhydroxyalkanoates