| dc.description.abstract | The objectives of this study were to evaluate the characteristics of sludge production and the reuse potential of sludge cake from various water treatment plants in Taiwan. The statistical analysis of water source, raw water turbidity and coagulant dosage related to sludge quantities from 19 different plants was carried out. In addition, the physical and chemical properties of coagulation sludge and dewatering sludge cake from Ping-Jan Water Treatment Plant were analyzed.
According to the statistical data, the average unit sludge production of the 19 water treatment plants was 96 g/m3. It also found that the average unit sludge production from the plants with river as water source was 10 g/m3 higher than those plants took water from reservoir. When the plants had raw water turbidity less than 30 NTU, the sludge quantity generated in these plants was equally contributed by turbidity in raw water and coagulant added. However, when raw water turbidity was high (in the range of 30 to 3000 NTU), the major sludge quantity was contributed by the turbidity in raw water.
For coagulation sludge, the average SS concentration of settled sludge from sludge blanket clarifiers in Ping-Jan Water Treatment Plant was 3,781 mg/L. However, due to the settled sludge in tube settling clarifiers was artificial withdraw without on-schedule, the average SS concentration of the settled sludge was 23,682 mg/L and the SS concentration was generally increased with the storage time in tube settling clarifiers. Besides, the coagulation sludge from tube settling clarifiers indicated a better settling and thickening properties. In addition, the samples of thickening sludge took from gravity thickener had an average SS concentration of 11,371 mg/L, SRF of 1.51×1013 m/kg, and CST of 65.3 sec.
The properties of dewatering sludge cake showed that the water content and VS were 76.4% and 12.4%, respectively, and the major chemical composition were 51.08% of SiO2 and 34.62% of Al2O3. The cumulative particle size of sludge cake was 96% less than 75 μm.
The results of this study also indicated that the sludge cake from various water treatment plants in Taiwan were mostly reused as cement material, brick manufacture and cultivate soil. The potential and distribution of these reuse technology depended on sludge generated quantities, reuse organization location, specification and regulation. Based on the analysis results of sludge properties and composition, reuses of sludge cake from Ping-Jan Water Treatment Plant is better for cement material and cultivate soil. However, due to the limitations of the physical and engineering properties of the sludge cake, direct reuse of the sludge cake as backfill soil or aggregate without any modification is unfavorable.
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