A Study of the Ecological Factors Influencing the Efficiency of the Activated Sludge System for Treating Organic Wastes

A study of the activated sludge process of wastewater treatment was carried out to determine the effect of specific ecological factors on the efficiency of the system. Laboratory and pilot plant tests were employed to determine the effect of changes in plant layout, biomass loading, characteristics of the sewage feed, and degree of discontinuity of oxygen input. Methods were developed for the quantitative extraction and study of bacterial exocellular polymers from activated sludge, and these polymers were shown to be directly concerned in the flocculation of bacteria and in the destabilisation and adsorption of colloidal and particulate material from sewage. At high biomass loadings, the activated sludge settlement deteriorated, with a corresponding increase in quantity and water retention capacity of the extracted exocellular polymer. The addition of carbohydrate to replace a proportion of the organic load resulted in poor bio-flocculation with an increase in the carbohydrate content of the exocellular polymer and an increase in the water retention capacity. Rebalancing of the feed C:N ratio by the addition of urea resulted in a reduction of the polymer carbohydrate level and an improvement in supernatant turbidity, indicating the influence of nutrient balance. The comparison of aeration tank layouts under closely controlled conditions showed that the sludge settlement characteristics from interseries and four-pocket series flow systems were significantly better than those from completely-mixed and two-pocket series flow systems. Adsorption tests showed the surface characteristics of the sludges to be different; the discontinuity of feed is considered to be the important factor in this instance. Simulation of plug-flow systems indicated that the settlement characteristics of the activated sludge biomass change during the treatment process, with no corresponding change in exocellular polymer. This phenomenon is thought to be due to the surface effect of adsorbed colloidal and particulate matter of sewage origin

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

Aston University

Year dc:date.issued

1975

Author dc:creator

• Kiff, Robert J.

DOI dc:identifier.doi

https://doi.org/10.48780/publications.aston.ac.uk.00010504

OAI identifier oai:identifier

oai:publications.aston.ac.uk:10504