Magnetiteand Microwaves in Sewage Effluent Treatment

ReportNo WSAA 37

September 1991




Thepurpose of this investigation was to examine the effectiveness and feasibilityof a non-chemical means of regenerating magnetite laden with contaminants previouslyremoved from sewage effluents. In the conventional SiroflocTM  process for treatment of sewage effluents,the magnetite particles are regenerated by the addition of alkali therebygenerating an effluent of small volume but high concentration. In this work,the concept of utilising microwave radiation to strip organics from themagnetite, was explored.


Thusthe primary objectives were


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

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

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

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


Thekey findings of the research are summarised below:


Microwaveirradiation is an effective way of removing organics from loaded magnetitesamples. The extent of regeneration can be varied by careful selection ofirradiation time and conditions (atmosphere).


Thehandling advantages of the magnetic adsorbent particles can be retained bylimiting the maximum temperature whilst still removing a satisfactory amount ofadsorbed organics. This can be achieved by pulse heating of the samples in apredetermined manner, which also improves the efficiency of regeneration.


Theorganics released from the magnetite surface under irradiation vary with thesource of the sewage, but are such that scrubbing of these exhaust gases wouldbe required. There is some evidence that catalytic conversion, involvingdehydrogenation, is occurring at the surface, and


Aneconomic comparison of chemical versus non-chemical regeneration clearlyfavours the former, at the present time. However, with the current rate ofdevelopment of microwave technology, and an increasing dislike of chemicaladditives in large amounts, the calculation will bear repeating at frequentintervals.


TMSiroflocisa registered trademark of the Commonwealth Scientific and Industrial ResearchOrganisation.


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