ALBERT

Notes: Increasing restrictions on sewage sludge disposal routes and the tightening of treatment requirements have led to an escalation of sludge-disposal costs which are out of proportion to other sewage-treatment costs: consequently reducing sludge volume is becoming increasingly cost-effective. Consolidation of anaerobically digested sludge has traditionally been difficult and takes many weeks in secondary digesters or deep storage tanks. Pre-aeration of the sludge using the Aercon process can enable consolidation to take place in days instead of weeks.This paper reports the results of a pilot-scale plant designed to investigate further the mechanism by which aeration speeds up consolidation. It was concluded that the rate of consolidation depended on aeration intensity and cooling of the sludge. Inhibition of anaerobiosis was more important than gas stripping in enhancing consolidation.

Notes: This paper examines the relationship between the Chief Executive of a CO-operative retail society and his Board of Directors. It takes for its starting point three critical activities of the Chief Executive, i.e. the achievement of society objectives; the maintenance of the internal stability of the society and the adaptation of the society to the external environment.Two factors which influence the performance of these activities are the Chief Executive's orientation to society performance and his relationship with his Board.The Chief Executive will tend to be inward-outward in orientation. Factors affecting this will be his previous task experience and organisational experience of which two aspects are important (a) time—the length of service a t lower and middle management level and (b) structure—the degree of delegation. These will affect the Chief Executive Officer's ability to deal with uncertainty in the environment, A third influential factor will be the attitudes and expectations of his Board which will be structured by their perception of democratic control. Finally the nature of the environment will affect the Chief Executive's orientation and his flexibility.In dealing with the problems which face him the Chief Executive is influenced by his reference points, i.e. by the degree of internalisation of co-operative values, and by his beliefs about the rightness of previous decisions.His decision-making is influenced by the interaction of his beliefs and those of his Board and by the depth to which they are held. These beliefs may be seen in two parts, first, relating to the nature of co-operative enterprise and secondly, to the method by which the co-operative enterprise is controlled.Contributing to the depth of internalisation of co-operative beliefs would appear to be their social and political backgrounds. Additional factors for the Chief Executive Officer include length of service in the co-operative movement, non-co-operative experience and his commitment to :managerial values'.On the basis of the differing orientations of the persons concerned, it is possible to hypothesise the development of certain decision-making situations.

Notes: The Removal of heavy metals and aluminium residuals during upflow sludge-blanket clarification was investigated using a pilot-plant system. Pilot units treating predosed raw water on site were assessed for sludge-blanket formation and stabilization, and were found to produce clarified water of a comparable quality to the main works units after the start-up and stabilization periods were complete. The heavy metals Cr, Fe, Mn, and Ni were the only heavy metals detectable at the investigation site and these occurred at concentrations well below guidelines values for potable abstraction and supply.Mean removals of Fe, Mn, Cr, and Ni were about 98, 89, 51, and 30 per cent respectively, during steady-state operation, and Fe, Mn, and Cr all displayed reduced removals during transient changes in surface load, whereas Ni removal appeared to be relatively independent. Aluminium residuals derived from the dosed alum coagulant also showed decreases in removal from about 83 per cent during steady-state operation to between 40 and 50 per cent during transient experiments.

Notes: An organism diversity index for use with mixed liquor or wastewater samples was developed to assess the species richness and diversity of activated sludge. The index was used in several studies and was found to be fast and simple to perform using basic laboratory equipment. Two bench-scale and two pilot-scale studies found that the resulting ‘organism diversity index’value was a good indicator of process performance and was not influenced by the total concentration of the mixed-liquor suspended solids but by their nature alone. The technique rapidly yielded pertinent information about the health of the sludge and could be used instead of genetic investigations to obtain population information quickly enough for wastewater-treatment plant process control.