| Summary: | 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
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