Design parameters for dissolved air flotation in South Africa

Dissolved air flotation has been used in South Africa for more than 25 years in the field of water and waste-water treatment, with practically all the development and verification done locally. This substantial body of knowledge and experience was recently condensed into a document titled A South African Design Guide for Dissolved Air Flotation. A general literature survey was combined with a detailed survey of 26 dissolved air flotation plants operating in Southern Africa, to arrive at suggested design parameters. Two broad categories of applications were covered in the guidelines - those of water clarification, and of activated sludge thickening. A clear trend emerged from the data collected. Drinking water clarification plants were generally designed within a fairly narrow range of the most design parameters, and the perception of operators and managers was that these clarification plants performed very efficiently. Sludge thickening plants, on the other hand, showed considerable variability in terms of most design parameters, and the general perception of its efficiency consequently varied from highly positive to negative. The paper includes summaries of the ranges of the actually surveyed design parameters, the suggested design values and a comparison with typical design values available from other countries.

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Recent applications of dissolved air flotation pilot studies and full scale design

Water Science & Technology ◽

10.2166/wst.1995.0541 ◽

1995 ◽

Vol 31 (3-4) ◽

pp. 327-340

Author(s):

Steven R. Arnold ◽

Thomas P. Grubb ◽

Peter J. Harvey

Keyword(s):

Water Treatment ◽

Potable Water ◽

The United States ◽

Wastewater Sludge ◽

Design Parameters ◽

Dissolved Air Flotation ◽

Pilot Studies ◽

Air Flotation ◽

Potable Water Treatment ◽

Dissolved Air

The use of Dissolved Air Flotation (DAF) as a solids/liquid separation process in water treatment has been an effective alternative to sedimentation for 70 years. The process was initially applied for removal of materials which had a specific gravity less than water, such as fats, oils, fibers, and grease. DAF installations expanded in the late 1960s to wastewater and potable water treatment. Today, Dissolved Air Flotation is utilized for a wide variety of water and wastewater applications. DAF is applied extensively for wastewater sludge thickening and it is widely accepted in Scandinavia and the United Kingdom for potable water treatment. It has also gained a foothold in the United States with the start up of a 7.5 mgd (28.4 Ml/d) potable water flotation plant at New Castle, New York. The goal of this paper is to present recent applications of Dissolved Air Flotation technology on a variety of raw water sources. Descriptions and general design parameters of a typical flotation and a proprietary combined flotation and filtration process will be discussed.

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Empirical evaluation for design parameters and operating characteristics of the integrated sedimentation and dissolved air flotation (SeDAF) process at the pilot-scale plant

Journal of The Korean Society of Water and Wastewater ◽

10.11001/jksww.2021.35.1.001 ◽

2021 ◽

Vol 35 (1) ◽

pp. 1-14

Author(s):

Yeoju Jang ◽

◽

Jinhong Jung ◽

Hyunman Lim ◽

Weonjae Kim

Keyword(s):

Empirical Evaluation ◽

Pilot Scale ◽

Design Parameters ◽

Operating Characteristics ◽

Dissolved Air Flotation ◽

Air Flotation ◽

Dissolved Air

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Dissolved Air Flotation: A Review from the Perspective of System Parameters and Uses in Wastewater Treatment

TecnoLógicas ◽

10.22430/22565337.2111 ◽

2021 ◽

Vol 24 (52) ◽

pp. e2111

Author(s):

Jeimmy Adriana Muñoz-Alegría ◽

Elena Muñoz-España ◽

Juan Fernando Flórez-Marulanda

Keyword(s):

Climate Change ◽

Wastewater Treatment ◽

Biogas Production ◽

Clean Energy ◽

Design Parameters ◽

Wastewater Reclamation ◽

Dissolved Air Flotation ◽

Flotation Process ◽

Air Flotation ◽

Dissolved Air

The current issues of climate change and high freshwater demand worldwide have promoted the implementation of wastewater reclamation technologies. This study aims to review the efficiency of the dissolved air flotation (DAF) technique in a wide variety of applications in the agricultural, industrial, domestic, and municipal sectors, which have high freshwater consumption worldwide. We made a systematic review of the DAF technique in wastewater treatment in 2015-2021. We reviewed six indexed databases and governmental statistical reports; we used the keywords: dissolved air flotation, microbubbles, wastewater treatment, and the main operating and design parameters involved in the effectiveness of the flotation process. Additionally, we conducted a review of the most common synthetic coagulant studies used with DAF, as well as natural coagulants that promise to mitigate current climate change. Finally, we discussed advantages, disadvantages, and potential future studies. DAF to have considerable potential for wastewater treatment, as well as for waste utilization. The generation of large quantities of DAF sludge is a breakthrough for clean energy production, as it allows the use of this waste for biogas production.

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Treatment of spent filter backwash water using dissolved air flotation

Water Science & Technology ◽

10.2166/wst.2001.0465 ◽

2001 ◽

Vol 43 (8) ◽

pp. 59-66 ◽

Cited By ~ 3

Author(s):

A. Eades ◽

B. J. Bates ◽

M. J. MacPhee

Keyword(s):

Design Parameters ◽

Water Recovery ◽

Raw Water ◽

Dissolved Air Flotation ◽

Water Recycle ◽

The Usa ◽

Air Flotation ◽

Pathogenic Agents ◽

Dissolved Air ◽

Filter Backwash Water

There is increasing interest in treating recovered spent filter backwash water in the drinking water industry. In the USA the Filter Backwash Recycling Rule will come into effect in the near future. The purpose of the Rule is to prevent the concentrated pathogenic agents, potentially in the filter backwash water, from being returned to the head of the water treatment works without some form of treatment or dilution. By treating this flow both public health and financial liability can be better managed by the operating utility. Dissolved Air Flotation (DAF) was investigated as a possible technology alternative to simple or advanced sedimentation techniques. This application is not widespread but sits somewhere in between the two normal applications of DAF as a high solids sludge thickener and a low turbidity clarification system. Given this a pilot plant program, supported by jar testing, was undertaken to determine the process capability and the design parameters for this application. DAF proved to be very suitable for backwash water recovery. DAF effluent turbidities of <1.0 NTU could be easily obtained, when raw water turbidities were in excess of 50 NTU. Chemical requirements were low with only a single low dose of polymer required to bind the floc particles to form a solids matrix suitable for flotation. Flocculation contact times ranged from 0–10 minutes depending on the nature of the raw water. Recycle rates as low as 5% performed satisfactorily with no significant improvement when increased to 20%. Sludge solids of 3.5–9.6% dry solids were found and very low volumes of sludge, <0.1% of the incoming flow make the DAF solids handling system very compact.

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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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