Conditioning of Wastewater Sludge from Science-Based Industrial Park Using Freezing and Thawing

The Hsinchu Science-based Industrial Park (HSIP) is the main manufacturing base of “high-tech” commodities of Taiwan. The treatment of wastewater of HSIP produces hard-to-dewater sludge, at a rate of 80 Mg/day, which is resistant to chemical conditioning, whose disposal is costly. The use of chemical flocculation and physical conditioning, including heating and freezing and thawing, on the dewaterability of HSIP sludge was examined in this Note. The dewaterability of the original sludge was poor, and neither chemical flocculation nor thermal heating enhanced its dewatering. However, the freezing and thawing could release up to 83% of moisture from the sludge body; in line with this occurrence, the settleability and filterability of the sludge were considerably enhanced. The ice front developed during freezing, which could destroy the floc network, release the interstitial water, and might correspond to the successful conditioning using freezing and thawing.