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Effect of adsorbent addition on floc formation and clarification
Jessica M Younker1, Margaret E Walsh1
1Department of Civil and Resource Engineering, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia, B3H 4R2, Canada.
Water Research
|April 12, 2016
Summary
Adding adsorbents like powdered activated carbon (PAC) and organoclay (OC) to ferric chloride (FeCl3) coagulation effectively removes dissolved organic compounds from water. These hybrid flocs are efficiently clarified using dissolved air flotation (DAF) or sedimentation (SED).
Area of Science:
- Water treatment technologies
- Environmental engineering
- Adsorption science
Background:
- Dissolved organic compounds (DOCs) are challenging to remove using conventional water treatment.
- Adsorbent-enhanced coagulation is an emerging solution for difficult-to-remove DOCs.
- Powdered activated carbon (PAC) and organoclay (OC) are effective adsorbents.
Purpose of the Study:
- To investigate the impact of PAC and OC addition on ferric chloride (FeCl3) coagulation flocs.
- To evaluate the removal efficiency of hybrid flocs using dissolved air flotation (DAF) and sedimentation (SED).
- To assess the removal of dissolved aromatic compounds (phenol and naphthalene) from synthetic freshwater and oily wastewater.
Main Methods:
- Bench-scale jar tests were conducted using synthetic freshwater and oily wastewater.
- FeCl3 coagulation was performed with and without PAC or OC adsorbents.
- Floc characteristics (size, structure, breakage, regrowth) were analyzed.
- Clarified water quality was assessed after DAF and sedimentation treatment.
Main Results:
- Adsorbent addition reduced median floc size by up to 50% without affecting floc strength or regrowth.
- Sedimentation was more effective than DAF for freshwater clarification.
- Both DAF and SED effectively removed hybrid flocs from oily wastewater, achieving lower turbidity than coagulation alone.
- PAC and OC achieved over 50% or nearly complete removal of dissolved aromatics, respectively.
Conclusions:
- Adsorbent-enhanced coagulation improves the removal of dissolved organic compounds.
- Hybrid flocs formed with PAC or OC are effectively removed by DAF and SED.
- This combined approach offers a promising solution for treating challenging industrial and drinking water sources.
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