Characteristics of organic matter released from drinking water treatment sludge under different storage conditions: Evaluation based on activated carbon adsorbability.

Recycling water from drinking water treatment sludge (DWTS) as raw water raises several problems in the drinking water supply. In this study, the impact of storage temperatures and oxygen conditions for DWTS on the characteristics of dissolved organic matter (DOM) released from sludge was evaluated in terms of adsorbability by activated carbon. Results showed that the adsorbability of the released DOM varied greatly with storage temperatures and oxygen conditions. The modified Freundlich isotherm model revealed that the average adsorption strength (K) estimated based on dissolved organic carbon (DOC) and ultraviolet absorbance at 260 nm (UV) varied in the ranges of 4.01-12.1 (mg g) and 23.1-52.6 (L m g), respectively. DOM released under the condition without aeration possessed higher adsorbability compared to DOM released under the condition with aeration (1.41-3.01 times for DOC-based; 1.14-2.28 times for UV-based). Moreover, the K values of fluorescence excitation-emission matrix (EEM)-based fulvic acid-like and humic acid-like substances were higher than those of tyrosine-like and tryptophan-like substances, indicating humic-like substances released from DWTS were more adsorbable than protein-like ones. The methods or adsorption conditions that can enhance the removal of protein-like substances are essential for dealing with water quality problems associated with recycling water from drinking water treatment sludge.