The heterogeneous complexity of sludges and wastewaters has created gross uncertainty and deviations in predictions of suitable models for their measurement. At the same time, it is becoming increasingly obvious that the current paradigms and ideologies are wrought with problems and limitations suggesting the need to move to a more consolidated analytical objective evaluation. Rapid developments in understanding activated sludge processes and wastewater remediation warrants exploitation of different strategies for studying their degradation. It is time to replace subjective terms like sludge volume index (SVI), zone settling velocity (ZSV), filament index (F-I), fractal dimension (D), flocculating ability, surface charge (zeta), degree of hydrophobicity, chemical oxygen demand (COD) with a mathematical one that can provide an absolute quantitative relationship for the properties of wastewater and/or a sludge floc. There are no current objective values that can be introduced to represent the plethora of biological remediation terminologies such as bioleaching, biosorption, bioaugmentation, biostimulation, biopulping, biodeterioration, biobleaching, bioaccumulation, biotransformation and bioattenuation. Enzyme technology has been receiving increased attention and this review focuses on the latest developments on the enzymology of biological remediation. It discusses the present pitfalls with current strategies and suggests that sludge-floc parameters, such as internal structure and composition, sludge retention time, microbial ecology, nutrient concentration, dissolved oxygen and type of industrial wastewater, whether from an aerobic or anaerobic system, are replaced by quantitative kinetic terms (K-m, V-max, K-cat) associated with the enzymology of the sludge floc and/or wastewater. (c) 2005 Elsevier Inc. All rights reserved.