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Floating media flocculation as pre-treatment for capillary ultrafiltration in drinking water treatment
Expanded Title:To develop a floating media water treatment process, this project addressed the following aims: 1) Develop floating media separation (FMS) media of uniform size and fixed charge, with specific gravities in the 0.94-0.98 range and enhanced adsorption capacity; 2) Develop protocol to maximise bed-shear during short-interval backwash to increase the net water production of FMS; 3) Develop operating protocol and evaluate the efficacy of FMS in the treatment of surface water for potable use with and without the addition of chemicals; 4) Compare the operability and efficacy of FMS with that of conventional coagulation, sedimentation and sand filtration; and 5) Evaluate FMS as a pretreatment technology for low-pressure UF for drinking water production. The initial approach taken was to consider various means to alter the chemistry of the buoyant media, determine whether size and shape of media had an effect on floating media flocculation (FMF)performance and develop and evaluate an adequate back-wash protocol to minimize water consumption. The final section of the work was the development and evaluation of the efficacy of FMF as a pretreatment operation for ultrafiltration (UF). The effects of altering media geometry and chemical properties were investigated and it was found that alteration of geometric properties was the more successful of the two approaches. Factorial experiments in which the factors included granule geometry, filter bed depth, rising velocity and coagulant concentration were conducted. It was concluded that 1-2 mm diameter, lace-cut granules were best suited for FMS. The FMF process can treat highly turbid feed, so it was possible to blend all process rinse and backwash effluents with the feed for re-treatment and thus increase the overall recovery of water achieved and minimise wastewater production. When each unit process was operated as stand-alone the FMF operated at 98% recovery and the UF process typically at 92%; however, operating the FMF-UF tandem process allowed a recovery of 98.5% to be achieved. The researchers concluded that FMF is eminently suitable as a technology by which the feed water to UF can be treated. A very effective and ‘water-wise’ backwash and bed-rinse method was developed and tested. The 7 m2 UF module, which is manufactured under license of a WRC patent, was improved and the water recovery of the combined FMF-UF tandem process can be increased from 92% to >98% by collecting the rinse and backwash water for retreatment by FMF.
Date Published:01/12/2012
Document Type:Research Report
Document Subjects:Drinking water - Water supply
Document Keywords:Water Quality
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:1527/1/12
ISBN No:978-1-4312-0110-5
Authors:Jacobs EP; Bradshaw SM; Brika B; Verster IH; Pillay VL
Project No:K5/1527
Document Size:2 018 KB
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