title: Enzyme disintegration with spatial resolution reveals different distributions of sludge extracellular polymer substances.
abstract: BACKGROUND
  To understand the intrinsic role of hydrolytic enzymes in sludge treatment, particularly their effect on the digestibility and dewaterability of sludge, activated sludge flocs were disintegrated using various techniques that included different enzymes (amylase, cellulase, proteinase, DNase, and polygalacturonase), pH adjustment, and temperature adjustment. The effectiveness of each enzyme treatment was pinpointed by quantifying the spatial distribution of each type of organic matters (protein, polysaccharide, DNA, fluorescent organics) in outer layer extracellular polymeric substances (EPS), inner layer EPS, and cells.
  
  
  RESULTS
  Most hydrolytic enzymes functioned only owing to a temperature or pH effect. The release of organic matter from the interior fraction of EPS to the exterior fraction was prompted under high pH and temperature even without enzyme addition. The effectiveness of enzyme addition was only significant for cellulase and polygalacturonase treatments. Polygalacturonase unexpectedly increased the total EPS polysaccharides up to seven times, accompanied with improved dewaterability, while the amount of EPS proteins was almost unchanged. Combining chemical and morphological evidence, a new conceptual model considering the spatial distribution of polygalacturonic acid-like matter, proteins, cellulose, and other organics in EPS was proposed.
  
  
  CONCLUSIONS
  Polygalacturonic acid-like matter hydrolysis caused significant release of polysaccharides. Polygalacturonase released polysaccharides while keeping proteins unreleased. Temperature and pH adjustment were as effective as enzyme at sludge disintegration. Cellulose hydrolysis led to massive release of all kinds of organic matters. A new conceptual sludge structure model regarding organic components is proposed.
authors: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai, 200092 People's Republic of China.
authors: Fan
authors: F
authors: Lü
authors: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai, 200092 People's Republic of China.
authors: Jingwen
authors: J
authors: Wang
authors: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai, 200092 People's Republic of China ; Institute of Waste Treatment and Reclamation, Tongji University, Shanghai, 200092 People's Republic of China ; Centre for the Technology Research and Training on Household Waste in Small Towns and Rural Area, Ministry of Housing and Urban-Rural Development (MOHURD) of China, Shanghai, People's Republic of China.
authors: Liming
authors: L
authors: Shao
authors: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai, 200092 People's Republic of China ; Institute of Waste Treatment and Reclamation, Tongji University, Shanghai, 200092 People's Republic of China ; Centre for the Technology Research and Training on Household Waste in Small Towns and Rural Area, Ministry of Housing and Urban-Rural Development (MOHURD) of China, Shanghai, People's Republic of China.
authors: Pinjing
authors: P
authors: He
keywords: Environmental scanning electron microscope; Excitation and emission matrix; Micro assembly; Parallel factor analysis; Polygalacturonase; Polygalacturonic acid; Sludge flocs