| Summary: | 碩士 === 國立成功大學 === 環境工程學系 === 84 === THE FEASIBILITY OF WASTEWATER SLUDGE STABILIZATION WITH FLY ASH
AND WATER QUENCHED SLAGJuu-En Chang and Yi-Kuo ChangDepartment
of Environmental EngineeringNational Cheng Kung
UniversityABSTRACTWastewater sludges contain nutrients and
organic matters which make them suitable for reclaiming and
improving marginal soils. But when the quantities used are not
properly controlled, the sludge can be harmful to the lands and
plants both. Fly ash and slag contain a predominant fraction of
pozzolanic materials (Si, Ca, and Al oxides) which have the
pollutant stabilization ability and they benefit soil.
Therefore, the fly ash and slag can be useful for stabilization
of organic matters in the wastewater sludge, and the mixture can
be applied to land with a minimal environmental impact. In this
study, fly ash and slag were used as additives to stabilize the
organic matters, ammonia and phosphate in wastewater sludge. The
sludge was obtained from an industrial park wastewater treatment
plant, the fly ash was from a power plant, and the water
quenched slag was from a steel plant. To determine the optimal
operating conditions, parameters such as curing time, curing
temperature, additive dosages, water content and pH value were
varied. Leaching tests were performed to evaluate the
stabilization efficacy of the additives at designed dosages,
water content and curing conditions. Experimental results show
that both fly ash and slag could effectively reduce the
leaching-out rates of DOC and NH3-N of the wastewater sludge,
and the leached out DOC decreased with increased additive
dosages. The adsorption capacity for DOC and NH3-N of the fly
ash was higher than slag, because the fly ash had a larger
specific surface area. The optimal operating conditions for the
stabilization of wastewater sludge by fly ash and slag are :
leaching out ratio (Lr) of DOC was 0.43 with slag as additive
only for 7-day curing; Lr of NH3-N was 0.17 with slag as
additive only for 14-day curing; while Lr of PO43- was 0.50 with
slag or fly ash as additive for 3-hour curing. SEM-EDX and XRD
microanalysis show that the adsorption performance was better
than encapsulation at the beginning of curing, but the
stabilization mechanism turned into fixation/stabilization as a
result from Pozzolanic reaction when curing time increased.
Also, curing at low temperature could inhibit sludge
biodegradation and resulted in a decrease in leaching-out rates
of DOC, NH3-N and ortho-P.Key words : wastewater sludge,
stabilization, fly ash, slag
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