PARTICLE SIZE CHARACTERIZATION OF CONTAMINANTS IN WASTEWATER (TREATMENT, BIOLOGICAL RESPIROMETRY)

Wastewater treatment objectives and design specifications are typically defined in terms of nonspecific parameters such as biochemical oxygen demand (BOD) and suspended solids (SS). However, the contaminants that must be removed from wastewater are complex mixtures of particulate and soluble constituents. To develop a more fundamental understanding of the complex interactions that occur in wastewater treatment operations and processes, it is important to characterize the size distributions of the contaminants in wastewater. The use of particle size measurement as an adjunct to the use of nonspecific parameters is developed in this thesis.;The influence of particle size on the performance of selected unit operations and processes used for the treatment of wastewater is examined. Particle size distributions are used to evaluate the effectiveness of treatment processes and to develop a data base that can be used to predict process performance and to develop a more fundamental understanding of the complex processes used for the treatment of wastewater.;Particle size distributions in wastewaters were altered using a pulsed-bed filter to remove particles larger than about 5 micrometers and a laboratory blender to reduce the effective particle sizes of the particulate contaminants. The influence of the altered wastewater on the performance of biological treatment processes is evaluated using respirometric studies.;The removal of contaminants from wastewater can be enhanced through the selection of appropriate treatment technologies based on the use of data on particle sizes in conjunction with BOD and SS measurements. A systematic approach for incorporating particle size into the design process is developed. Ultimately, more efficient operation of treatment processes and reduced treatment costs can result from improved waste characterization techniques.;Wastewater contaminants are separated into two major size categories using a membrane filter with a pore size of 0.1 micrometer. The distribution of filtrable solids larger than 0.1 micrometer is evaluated by fractionating wastewater contaminants using a series of membrane filters or by steric field flow fractionation. Organic contaminants smaller than 0.1 micrometer are fractionated using gel filtration chromatography. The organic content of the individual size fractions in both sizes is quantified using organic carbon analyses.