Adsorption and partitioning behaviour of selected trace polycyclic synthetic musks in a suspended growth aerobic activated sludge system

This thesis investigated the influence of sludge retention time (SRT) and temperature (T) on selected activated sludge properties and their influence on partitioning and sorption behaviour of selected trace polycyclic synthetic musks (PSMs) of environmental concern. Suspended growth aerobic activated sludge systems under controlled temperature (10 and 20°C) and SRTs (3.5 and 10.5 days) conditions fed by municipal sewage were investigated. The selected PSMs monitored included Cashmeran, Celestolide, Phantolide, Traseolide, Galaxolide and Tonalide. Activated sludge floc properties including relative hydrophobicity (RH) and extracellular polymeric substances (EPS) showed significant differences which correlated well (r [subscript p] of ± 0.4 to ± 0.7) to the removal and partitioning of PSMs removed from the aqueous phase and associated with activated sludege. Galaxolide and Tonalide were found to represent over 95% of the total PSMs in both the aqueous and solid phases. PSMs aqueous reduction from 62 to 80% was observed. The total PSMs associated with sludge ranged from 15 to 27 [micro]g/g d.m. and the lowest concentration was observed under 10.5 days SRT and 20°C which also resulted in nitrifying conditions. SRT was the dominant operational factor, followed by SRT and TxSRT in influencing the partitioning of the PSMs and floc properties. The Freundlich equilibrium PSMs sorption and desorption isotherms, for sludges were generated and showed significant differences in sorption behaviour.

Adsorption and partitioning behaviour of selected trace polycyclic synthetic musks in a suspended growth aerobic activated sludge system

This thesis investigated the influence of sludge retention time (SRT) and temperature (T) on selected activated sludge properties and their influence on partitioning and sorption behaviour of selected trace polycyclic synthetic musks (PSMs) of environmental concern. Suspended growth aerobic activated sludge systems under controlled temperature (10 and 20°C) and SRTs (3.5 and 10.5 days) conditions fed by municipal sewage were investigated. The selected PSMs monitored included Cashmeran, Celestolide, Phantolide, Traseolide, Galaxolide and Tonalide. Activated sludge floc properties including relative hydrophobicity (RH) and extracellular polymeric substances (EPS) showed significant differences which correlated well (r [subscript p] of ± 0.4 to ± 0.7) to the removal and partitioning of PSMs removed from the aqueous phase and associated with activated sludege. Galaxolide and Tonalide were found to represent over 95% of the total PSMs in both the aqueous and solid phases. PSMs aqueous reduction from 62 to 80% was observed. The total PSMs associated with sludge ranged from 15 to 27 [micro]g/g d.m. and the lowest concentration was observed under 10.5 days SRT and 20°C which also resulted in nitrifying conditions. SRT was the dominant operational factor, followed by SRT and TxSRT in influencing the partitioning of the PSMs and floc properties. The Freundlich equilibrium PSMs sorption and desorption isotherms, for sludges were generated and showed significant differences in sorption behaviour.

Understanding the coagulation mechanism and floc properties induced by Fe(VI) and FeCl3: population balance modeling

Coagulation kinetics and floc properties are of great fundamental and practical importance in the field of water treatment. To investigate the performance of Fe(VI) and Fe(III) salt on particle coagulation, Malvern Mastersizer 2000 was employed to continuously and simultaneously monitor the kaolin floc size and structure change, and population balance modeling was used to investigate the coagulation mechanism. The results show dosage increase had positive effect on collision efficiency and floc strength and negative effect on restructure rate. Low shear rate resulted in higher collision efficiency and stronger floc. Low water temperature had a pronounced detrimental effect on coagulation kinetics. Temperature increase showed the most significant positive effect on collision efficiency, floc strength and restructure rate. The optimum pH zone for the coagulation was found to be between 6 and 8. Further pH increase lowered the collision efficiency and floc strength and increased the restructure rate. FeCl3 resulted in a larger ratio of the mass to volume of kaolin flocs (compactness) than those induced by ferrate.

On the importance of mixing characterization and application in the water treatment process

Floc properties can be controlled only by selecting a coagulant type and adjusting mixing parameters. However, optimization of mixing is widely overlooked. Well-chosen mixing conditions increase floc separation efficiency, which decreases the operating costs of drinking water treatment plants (DWTPs). This paper presents guidelines for designing mixing parameters in water treatment. Special attention is paid to the determination of mixing intensity and the purpose of different mixing intensities with respect to the subsequent separation. For instance, single-stage separation by filtration must be preceded by homogenization and rapid flocculation mixing. Double-stage separation by sedimentation and filtration should be preceded by homogenization, rapid flocculation mixing and slow flocculation mixing.

Coagulation/flocculation prior to low pressure membranes in drinking water treatment: a review

Coagulation/flocculation has been grouped into three typical configurations and the impact of each examined in terms of floc properties and membrane fouling.