The SIROFLOC Sewage Treatment Process: A High Rate Process for Sewage Clarification
A process for rapid clarification of sewage has been developed, in Australia, by the CSIRO and extensively tested in pilot scale studies in Melbourne, Sydney and the UK. The results of the pilot studies were used to design a 5 Ml/day prototype of the SIROFLOC™ sewage treatment process (STP). This was constructed at the Malabar sewage treatment works (STW), in Sydney, and has been successfully operated since October 1992.
The process utilises finely divided particles of magnetite combined with an inorganic coagulant to aid the rapid separation of colloidal and suspended solids from sewage. The magnetite and inorganic coagulant are recovered and reused within the process, thus minimising the operating costs. The use of magnetite allows for the rapid coagulation and clarification of sewage; raw sewage can be treated to a high quality within 15 minutes.
Since the process is a coagulation process, it is ideally suited to the removal of insoluble matter from sewage. The 5 Ml/day prototype plant at Malabar has operated continuously to produce treated sewage containing 30 mg/l TSS and 6 mg/l oil and grease, equivalent to reductions of up to 90 %. Phosphate removal was better than 90%, consistent with the use of an inorganic coagulant and total coliforms were reduced by up to 3 logarithms. Significant reductions in heavy metals were achieved by the process, with removal efficiency dependent on the particular metal. Soluble contaminants present in the sewage, such as ammonia, were not significantly removed by the process. Biochemical and chemical oxygen demand (BOD and COD, respectively) were generally reduced by at least 50 %, consistent with the removal of their insoluble fraction from the sewage.
KeywordsMercury Sludge Cadmium Sedimentation Sewage
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