Microfiltration and Coagulation of Particle Suspensions

To simulate a real surface water the previously described systems, containing organics and either stabilised or aggregated inorganic colloids, were now coagulated. 

Iron rejection is initially very low at the high dosage but increases rapidly to near 100%. Such low initial rejections would lead to contaminanon of the product water, especially if a backwash is carried out frequently. 

Organic T pe Colloids FeCb ImgL l Fe Rejection T [%] Fe Rejection 2 [%] TOC Rejection 1 (%] TOC Rejection 2 [%j 

In some cases, flux decline was observed to be detrimental when coagulant was added to the solution prior to MF. The difference between the various solutions was significant - at 25 mgL , with or with out aggregates, a stable flux was reached. At this lower dosage, the solid load on the membrane is smaller and the floes are larger. 

MF with ferric chloride pretreatment increased NOM removal substantially. However, the process efficiency (towards organic removal) is very dependent on the nature of the organic matter. In a surface water the composition of organics changes constantly, and thus the treatment efficiency cannot be readily predicted. Careful monitoring and control would be required to maximise organics removal. 

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