結合鹼化與超音波法降解污泥中鄰苯二甲酸酯類(PAE)之研究

Abstract

Phthalate acid esters (PAEs) are widely used in various industries where the usage of PAEs containing products leads to the entrance of PAEs into wastewater treatment plant. During wastewater treatment processes, higher molecular weight PAEs including dibutyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP) and butylbenzyl phthalate (BBP) could be easily attached to the surfaces of sewage sludge and transferred to sludge treatment units. Therefore, sludge pretreatment to remove PAEs before sludge treatment and disposal is necessary. In this study, alkalization combined with ultrasound was adopted for removing the PAEs from sewage sludge. The initial DBP, DEHP and BBP concentrations in sewage sludge were 718, 215 and 8 mg/kg-dw, respectively. Pretreatments were carried out by adding sodium hydroxide (NaOH) individually for designed concentrations to sewage sludge and mixing gently for 24 hours followed by sonication. The frequency of ultrasound was 20 kHz with the ultrasound power density and power intensity of 1 W/mL and 55 W/cm2. The total solids (TS) concentration of the sewage sludge was 3%. The central composite design (CCD) was used in this study to find out the better operation condition which the designed parameters were NaOH concentration (0 - 80 mM) and sonication time (0 - 15 min). NaOH alkalization of sewage sludge led to DBP removal only; removals of DEHP and BBP were almost zero. Increase of the soluble chemical oxygen demand (SCOD) in pretreated sewage sludge was 8.37 mg/L per 1 mM NaOH addition. Alkalization was responsible for more than 90% of DBP removal and more than 60% in SCOD increase in the alkalization-sonication pretreatment. The optimal NaOH concentration and sonication time were estimated as 68 mM and 10 min based on the CCD and response surface plots, respectively.