DISSOLVED-AIR FLOTATION IN ACTIVATED SLUDGE

Wastewaters from separate chemical factories are treated together in an extended aeration activated sludge plant. The factories produce chemicals for paper industry (e.g. starch), latexes and animal feed. The components of the wastewaters include styrene, tertiary butanol and vinyl acetate. Activated sludge is clarified by sedimentation. During winter time, when the water temperature was 3-12°C, the clarification deteriorated causing carry over of suspended solids containing COD. Enhancement of suspended solids and COD removals was studied in a dissolved air flotation jar test unit. Flotation trials were conducted for activated sludge, sedimentation treated final effluent (tertiary treatment) and separate wastewater fractions. The need for chemicals, flocculation and amount of recycle water were judged according to the achieved removals. Dissolved air flotation was found well suited for the clarification of activated sludge, but not technically and economically feasible for the clarification of the wastewater streams before the activated sludge treatment.

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High-rate activated sludge systems combined with dissolved air flotation enable effective organics removal and recovery

Bioresource Technology ◽

10.1016/j.biortech.2019.121833 ◽

2019 ◽

Vol 291 ◽

pp. 121833 ◽

Cited By ~ 4

Author(s):

Cristina Cagnetta ◽

Bart Saerens ◽

Francis A. Meerburg ◽

Stijn O. Decru ◽

Eddie Broeders ◽

...

Keyword(s):

Activated Sludge ◽

High Rate ◽

Dissolved Air Flotation ◽

Organics Removal ◽

Air Flotation ◽

Removal And Recovery ◽

Activated Sludge Systems ◽

Dissolved Air

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Water clarification with natural coagulants and dissolved air flotation

Waterlines ◽

10.3362/0262-8104.1986.044 ◽

1986 ◽

Vol 5 (2) ◽

pp. 23-26 ◽

Cited By ~ 2

Author(s):

Folkard ◽

Sutherland ◽

Jahn

Keyword(s):

Dissolved Air Flotation ◽

Natural Coagulants ◽

Air Flotation ◽

Dissolved Air

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Behaviour of air injection nozzles in dissolved air flotation

Water Science & Technology ◽

10.2166/wst.1995.0513 ◽

1995 ◽

Vol 31 (3-4) ◽

pp. 25-35 ◽

Cited By ~ 12

Author(s):

E. M. Rykaart ◽

J. Haarhoff

Keyword(s):

Bubble Coalescence ◽

Second Phase ◽

Initial Growth ◽

Two Phase ◽

Dissolved Air Flotation ◽

Nozzle Orifice ◽

Pressure Release ◽

Air Volume ◽

Air Flotation ◽

Dissolved Air

A simple two-phase conceptual model is postulated to explain the initial growth of microbubbles after pressure release in dissolved air flotation. During the first phase bubbles merely expand from existing nucleation centres as air precipitates from solution, without bubble coalescence. This phase ends when all excess air is transferred to the gas phase. During the second phase, the total air volume remains the same, but bubbles continue to grow due to bubble coalescence. This model is used to explain the results from experiments where three different nozzle variations were tested, namely a nozzle with an impinging surface immediately outside the nozzle orifice, a nozzle with a bend in the nozzle channel, and a nozzle with a tapering outlet immediately outside the nozzle orifice. From these experiments, it is inferred that the first phase of bubble growth is completed at approximately 1.7 ms after the start of pressure release.

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Enhanced rapid gravity filtration and dissolved air flotation for pre-treatment of river thames reservoir water

Water Science & Technology ◽

10.2166/wst.1998.0098 ◽

1998 ◽

Vol 37 (2) ◽

pp. 35-42 ◽

Cited By ~ 5

Author(s):

M. J. Bauer ◽

R. Bayley ◽

M. J. Chipps ◽

A. Eades ◽

R. J. Scriven ◽

...

Keyword(s):

Water Treatment ◽

Water Supply ◽

21St Century ◽

Reservoir Water ◽

Dissolved Air Flotation ◽

Lowland Rivers ◽

Air Flotation ◽

Pre Treatment ◽

Counter Current ◽

Dissolved Air

Thames Water treats approximately 2800Ml/d of water originating mainly from the lowland rivers Thames and Lee for supply to over 7.3million customers, principally in the cities of London and Oxford. This paper reviews aspects of Thames Water's research, design and operating experiences of treating algal rich reservoir stored lowland water. Areas covered include experiences of optimising reservoir management, uprating and upgrading of rapid gravity filtration (RGF), standard co-current dissolved air flotation (DAF) and counter-current dissolved air flotation/filtration (COCO-DAFF®) to counter operational problems caused by seasonal blooms of filter blocking algae such as Melosira spp., Aphanizomenon spp. and Anabaena spp. A major programme of uprating and modernisation (inclusion of Advanced Water Treatment: GAC and ozone) of the major works is in progress which, together with the Thames Tunnel Ring Main, will meet London's water supply needs into the 21st Century.

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