The study of enhancing volatile acids production from waste activated sludge

• Main Authors: Huang, shwu-jiuan, 黃淑娟
• Other Authors: Chang Cheng-Nan
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/51351298844969209970

碩士 === 東海大學 === 環境科學系 === 84 === ABSTRACTThe disposal of waste activated sludge (WAS) from secondary treatment process is getting close attention due to its high cost and land total sludge volume and transforming organic substance into a stable condition, which either require long process time or add excess chemical dosage to it. It is believed that hydrolysis is the main rate-limiting step during biological digestion of WAS. This study utilized alkaline and ultrasound vibration to enhance hydrolysis step and obtain high solubility of SCOD, DOC, and amino acids within limit time of reaction. The WAS was collected from a pseudo-steady bath reactor which was incubated using synthetic mixture of glucose and peptone. In this study we applied: (1) add alkaline only, (2) add alkaline for 1 day, then vibrated with ultrasound (24.08 sec/ml), and (3) add alkaline and vibrated with ultrasound simultaneously (14.4 sec/ml). The dosage of alkaline was controlled at 40 meq/L NaOH. The output energy of ultrasound generator was 120 W and at 20 KHz frequency.For 1% total solid (TS) of WAS treated with process (1) (I. E. add alkaline only), a 36.3% (SCOD/DCOD) and 42.1% (org. N/TN) dissolved organic substance was found. While WAS treated with process (2) an 89.3 % dissolved (SCOD/ DCOD) and 52.5% (org. N/TN) substance was obtained, i.e. 2.22 times more COD dissolved after hyper- hydrolysis process. In order to reduce overall treatment time, process (3) was proposed and obtained a similar output of process (2). As for the ratio of SCOD/DOC, process (1), (2) and (3) had the result of 3.57, 1.97 and 1.72 respectively. The low SCOD/ DOC ration of hydrolyzed initial WAS implied the hyper- treated soluble substance, which generated by ultrasound vibration, contained not only carbonaceous matter but also nitrogen contented matter, which lower the SCOD/DOC ratio. The amino acids released by hydrolysis process revealed that process either (2) or (3) generated as high as 8 times more than that of process (1) and was 110 time more than that of raw sludge solution. The major amino acids release form biomass after hydrolysis were: Lysine, Glutamic acid, Glycine, Histidine, Leucine and iso-leucine.According to the molecular weight distribution (MWD) study, the alkaline may generate as high as 14,000 amu substances, while after vibrated by ultrasound, it was distroyed into as small as 142 amu. The hyper-hydrolysis process utilizing ultrasound vibration to enhance hydrolysis of WAS, which can not only improve the speed limited step of traditional WAS digestion process but also provide more soluble substances (e.g. SCOD, DOC and amino acids) into system. The excess dissolved organic matter could be soon acidified into acetic acid and recycle back to denitrification step as carbon source.Keyword : Waste Activated Sludge (WAS) , Ultrasound treatment, Alkaline treatment, Acidification, Amino acid II