Dissolved Air Flotation System Research Articles

PROCESSING BY-PRODUCTS FROM DAF SYSTEMS IN THE FOOD INDUSTRY

PROCESSING BY-PRODUCTS FROM DAF SYSTEMS IN THE FOOD INDUSTRYThe use of Dissolved Air Flotation (DAF) systems is well established in the meatpacking and food processing industry. If, however, the systems necessary to concentrate and process the recovered contaminants are not provided along with the DAF unit, the disposal problems are merely transmitted from the biological regime to the solid waste regime, and the second solution can be as onerous as the...Author(s)Jimmie A. ChittendenDale M. WesterholdSourceProceedings of the Water Environment FederationSubjectSession 4: Sludge ManagementDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2000ISSN1938-6478SICI1938-6478(20000101)2000:5L.187;1-DOI10.2175/193864700785155911Volume / Issue2000 / 5Content sourceIndustrial Wastes (IW) ConferenceFirst / last page(s)187 - 195Copyright2000Word count90

RETHINKING DISSOLVED AIR FLOTATION (DAF) DESIGN FOR INDUSTRIAL PRETREATMENT

RETHINKING DISSOLVED AIR FLOTATION (DAF) DESIGN FOR INDUSTRIAL PRETREATMENTDissolved air flotation (DAF) has been used with increasing frequency in recent decades for the treatment of industrial wastewater. Advances in the technology have expanded the range of applications for DAF; however, engineers and designers frequently use outdated and insufficient design data to design and specify DAF systems for industrial pretreatment. Discussions of advances in DAF design are...Author(s)Charles C. RossBrandon M. SmithG.E. ValentineSourceProceedings of the Water Environment FederationSubjectSession 1: Enhancing Physical-Chemical Treatment TechnologiesDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2000ISSN1938-6478SICI1938-6478(20000101)2000:5L.43;1-DOI10.2175/193864700785155795Volume / Issue2000 / 5Content sourceIndustrial Wastes (IW) ConferenceFirst / last page(s)43 - 56Copyright2000Word count113

A demonstration scaling-up of the dissolved air flotation

Dissolved air flotation (DAF) is currently being received in much attention as an effective process for solid–liquid separation in water technology. In this study, we scaled-up the DAF plant from a pilot-scale (72 m 3/day) to a full-scale (6000 m 3/day) plant and the sand-float type DAF was used. The concept of maintaining equal surface loading rate into scaling-up of DAF was a proper practice and strategy. In order to optimize the DAF plant, it was needed to determine the surface loading rate and air dissolving tube pressure. The optimum conditions of surface loading rate and air dissolving tube pressure were indicated in 7.5 m 3/m 2 day and 440 kPa from the pilot plant, respectively. The removal efficiency for TOC and UV 254 from the full-scale plant was as satisfactory as those from the pilot plant for the same surface loading rates. However, especially in flotation zone, the full-scale plant performed a little bit poorer than the pilot-scale plant in turbidity and chlorophyll- a reduction: because full-scale plant had long retention time and turbulent mixing condition during backwashing time which might be brought about the breakage of fragile flocs. Performance comparisons between the full-scale DAF plant and the conventional plant located at the city of Nam-Yang Ju in Korea are presented. DAF process showed higher efficiency than the conventional settling system improving the water quality in general, namely, turbidity, TOC, UV 254, Fe and Mn. We, therefore, conclude that DAF system should have substantial advantages over the conventional settling process in drinking water treatment.

Microbubble generation for environmental and industrial separations

Small gas bubbles are used in many environmental and industrial processes for solid-liquid separations or to facilitate heat and mass transfer between phases. Typically, smaller bubbles are preferred in treatment techniques due to both their high surface area-to-volume ratio and their increased bubble density at a fixed flow rate. This study examines some of the factors that affect the size of bubbles produced in the processes of electroflotation, dissolved air flotation, and a relatively new method known as electrostatic spraying. The effect of voltage, current and ionic strength was studied in electroflotation, the effect of pressure was studied in dissolved air flotation and the effect of voltage, capillary dimensions and flow rate was studied in electrostatic spraying. In electroflotation, the flow rate of gas produced increased as a function of voltage and current. Flow rate also increased as the ionic strength of the aqueous medium was increased. However, no clear trends in bubble size as a function of these parameters were evident. The bubbles produced in dissolved air flotation showed a decrease in size as saturation pressure was increased; however, the differences were insignificant at high pressures. Bubble size in electrostatic spraying decreased as voltage was increased. Finally, this study compares the three methods of bubble production in terms of average bubble diameter, bubble size distribution and power consumed during production. Dissolved air flotation produced the largest average bubble diameters, while electroflotation produced the smallest average bubble diameters. In terms of bubble size distribution, dissolved air flotation produced the most narrow distribution, electrostatic spraying produced the widest distribution, and electroflotation produced an intermediate distribution. In terms of power consumption, the pilot-scale dissolved air flotation system maximized surface area production, electroflotation produced an intermediate value, and electrostatic spraying of air produced the least surface area as a function of power consumed.

Mussel protein recovery using dissolved air flotation

A protein recovery process has been developed to recover protein from sea mussels. Chitosan and κ-carrageenan are shown to be good flocculating agents for the recovery of mussel protein, efficiencies of up to 90% being reported. Design data are given to enable other dissolved air flotation systems to be designed.