Magnetite and Microwaves in Sewage Effluent Treatment

This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.

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Magnetite and Microwaves in Sewage Effluent Treatment

Report no. UWRAA 37

September 1991


The purpose of this investigation was to examine the effectiveness and feasibility of a non-chemical means of regenerating magnetite laden with contaminants previously removed from sewage effluents. In the conventional Sirofloc TM process for treatment of sewage effluents, the magnetite particles are regenerated by the addition of alkali thereby generating an effluent of small volume but high concentration. In this work, the concept of utilising microwave radiation to strip organics from the magnetite, was explored.

Thus the primary objectives were

(a) To identify the parameters which most influence the efficiency of regeneration,

(b) To examine the surface properties of the regenerated magnetite,

(c) To investigate the nature of the released organics, and

(d) To determine the feasibility of the process as an alternative to chemical regeneration.

The key findings of the research are summarised below:

Microwave irradiation is an effective way of removing organics from loaded magnetite samples. The extent of regeneration can be varied by careful selection of irradiation time and conditions (atmosphere).

The handling advantages of the magnetic adsorbent particles can be retained by limiting the maximum temperature whilst still removing a satisfactory amount of adsorbed organics. This can be achieved by pulse heating of the samples in a predetermined manner, which also improves the efficiency of regeneration.

The organics released from the magnetite surface under irradiation vary with the source of the sewage, but are such that scrubbing of these exhaust gases would be required. There is some evidence that catalytic conversion, involving dehydrogenation, is occurring at the surface, and

An economic comparison of chemical versus non-chemical regeneration clearly favours the former, at the present time. However, with the current rate of development of microwave technology, and an increasing dislike of chemical additives in large amounts, the calculation will bear repeating at frequent intervals.

TM Sirofloc is a registered trademark of the Commonwealth Scientific and Industrial Research Organisation.

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