BACKGROUNDThe efficiency of extracting extracellular polymeric substances (EPS) in activated sludge depends on the extraction method, which provides an important foundation for studying the composition and characteristics of EPS. Because a single chemical extraction method is affected by many factors such as the source of the sludge, a variety of chemical methods can be combined to extract many different types of EPS. RESULTFour methods, including cation exchange resin (CER), sodium sulfide (Na2S) extraction, NaOH extraction and sodium tripolyphosphate (STPP) extraction, were used separately to extract different metal-bound EPS. After the optimization of each method, a new sequential extraction method was obtained, the sequential extraction received an adequate extraction amount of EPS (nearly 500 mg g(-1) MLSS). CONCLUSIONA sequential extraction method was formed using a sequence of CER 2 h - Na2S + NaOH (C-S/C-Fe = 3, pH = 10.5) - STPP 100 mmol L-1, which is more effective than the single extraction method and provides a new method for extracting EPS in activated sludge. (c) 2014 Society of Chemical Industry