Removal and fate of Cryptosporidium in dissolved air drinking water treatment plants

2001 ◽  
Vol 43 (8) ◽  
pp. 51-57 ◽  
Author(s):  
J. K. Edzwald ◽  
J. E. Tobiason ◽  
H. Dunn ◽  
G. Kaminski ◽  
P. Galant
Keyword(s):  
Natural Organic Matter ◽  
Drinking Water Treatment ◽  
Spring Water ◽  
Water Production ◽  
Dissolved Air Flotation ◽  
Model Predictions ◽  
Particle Counts ◽  
Recycle Rate ◽  
The Impact ◽  
Dissolved Air

In the first part of the paper, data from pilot plant studies are used to evaluate Cryptosporidium removal by dissolved air flotation (DAF) clarification and dual media filters under challenge conditions. Oocyst removals were investigated for design detention times and hydraulic loadings for winter and spring seasons. Coagulation was optimized for turbidity and removal of natural organic matter. DAF performance was better for spring water temperatures achieving 2.5 ± 0.3 log removal of oocysts compared to 1.7 ± 0.3 log removal in the winter. Cumulative log removal across DAF and filtration exceeded 5.4, and was not affected by water temperature. Low turbidities and particle counts are indicators of good treatment and good removals of Cryptosporidium. The second part of the paper uses a mathematical model to predict the fate of Cryptosporidium through a DAF plant and the impact of filter backwash recycle on oocyst build-up in the plant influent. Model predictions show that the fate of Cryptosporidium and the build-up of oocysts in the plant influent depend on: DAF performance, the percent of filtered water production used for backwashing, and the percent of filter backwash recycle flow. A DAF plant with 2.5% filtered water production for backwashing and that achieves 1.6 log removal or greater of oocysts by DAF clarification will not have a build-up of oocysts in the plant influent regardless of the recycle rate. This is because the oocysts are concentrated in the DAF floated sludge and not within granular filters.

Fate and removal of Cryptosporidium in a dissolved air flotation water plant with and without recycle of waste filter backwash water

2002 ◽  
Vol 2 (2) ◽  
pp. 85-90 ◽  
Author(s):  
J.K. Edzwald ◽  
J.E. Tobiason
Keyword(s):  
Water Production ◽  
Dissolved Air Flotation ◽  
Water Plant ◽  
Cryptosporidium Oocysts ◽  
Model Predictions ◽  
Particle Counts ◽  
Air Flotation ◽  
Recycle Rate ◽  
Dissolved Air ◽  
Filter Backwash Water

Pilot plant research focused on the removal of Cryptosporidium oocysts by dissolved air flotation (DAF) clarification and by dual media filtration and on the impacts of the recycle of waste filter backwash water containing oocysts. No impacts from recycle of filter backwash (10% rate) were found for turbidity, particle counts (2-15 μm), and UV254 on DAF and filtration performance. DAF achieved Cryptosporidium log removals of 1.6 to 2.2 without or with recycle of filter backwash. No impacts of recycle were found on filtration, and cumulative (DAF plus filtration) log oocyst removals exceeded 4 log. Model predictions show that the fate of Cryptosporidium and the build-up of oocysts in the plant influent depend on: DAF performance, the percent of filtered water production used for backwashing, and the percent of filter backwash recycle flow. A DAF plant using 2.5% of filtered water production for backwashing and achieving 1.6 log removal or greater of oocysts by DAF clarification will not have a build-up of oocysts in the plant influent regardless of the recycle rate.

Principles and applications of dissolved air flotation

1995 ◽  
Vol 31 (3-4) ◽  
pp. 1-23 ◽  
Author(s):  
James K. Edzwald
Keyword(s):  
Bubble Formation ◽  
Treatment Plant ◽  
Drinking Water Treatment ◽  
Plant Design ◽  
Dissolved Air Flotation ◽  
Floc Size ◽  
Hydrophobic Particles ◽  
Air Flotation ◽  
The Impact ◽  
Dissolved Air

Principles of dissolved air flotation (DAF) discussed include: bubble formation and size, bubble-particle interactions, measures of supplied air, and modeling of the reaction and clarification zones of the flotation tank. Favorable flotation conditions for bubble attachment or adhesion to particles requires a reduction in the charge of particles and production of hydrophobic particles or hydrophobic spots on particle surfaces. A conceptual model for the bubble-particle reaction zone based on the single collector collision efficiency is summarized and discussed. An alternative modeling approach is considered. Clarification or separation zone modeling is based on particle-bubble agglomerate rise velocities. The application of DAF in drinking water treatment is addressed beginning with summaries of design and operating parameters for several countries. DAF should not be considered as a separate process, but integrated into the design and operation of the overall treatment plant. This concept shows that flocculation ahead of DAF has different requirements regarding floc size and strength compared to sedimentation. The efficiency of DAF in removing particles and reducing particle loads to filters needs to be integrated into DAF plant design. The impact on filtration performance is illustrated. Finally, fundamental and applied research needs are addressed.

Control of Cryptosporidium: from reservoirs to clarifiers to filters

1998 ◽  
Vol 37 (2) ◽  
pp. 1-8 ◽  
Author(s):  
James K. Edzwald ◽  
Michael B. Kelley
Keyword(s):  
Natural Organic Matter ◽  
Effective Control ◽  
Source Water ◽  
Water Protection ◽  
Treatment Technology ◽  
Dissolved Air Flotation ◽  
Mean Values ◽  
Source Water Protection ◽  
Particle Counts ◽  
Dissolved Air

Control of Cryptosporidium in potable waters requires an integrated multiple barrier approach of source water protection of water supply reservoirs and treatment technology through clarification, filtration, and disinfection. Pristine lakes and protected reservoirs have far lower concentrations of oocysts (mean values less than 10 oocysts/100 L) than unprotected supplies. Coagulation is critical to the effective control of Cryptosporidium by clarification and filtration. Coagulation conditions that produce filtered waters of low turbidities, particle counts, and effectively remove natural organic matter also produce high removals of Cryptosporidium. Dissolved air flotation (DAF) can achieve oocyst removals of 3 log compared to about 1 log by sedimentation. DAF and filtration provide two effective barriers to Cryptosporidium with cumulative log removals of 4 to 5 compared to log removals of 3 to 4 by sedimentation and filtration.

Dissolved air flotation in drinking water production

2001 ◽  
Vol 43 (8) ◽  
pp. 9-18 ◽  
Author(s):  
T. Schofield
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Potable Water ◽  
Water Production ◽  
Process Technology ◽  
Dissolved Air Flotation ◽  
Drinking Water Production ◽  
Air Flotation ◽  
Potable Water Treatment ◽  
Dissolved Air

Dissolved Air Flotation (DAF) has become increasingly important in the field of potable water treatment, as a preferred option for treating upland and stored lowland waters. This paper outlines the development of dissolved air flotation (DAF) in potable water treatment, the benefits and disadvantages and the recent advances that has taken the process technology from an art to a science.

Reducing the effect of cyanobacteria in the microfiltration of secondary effluent

2010 ◽  
Vol 62 (7) ◽  
pp. 1682-1688 ◽  
Author(s):  
Y. T. Goh ◽  
J. L. Harris ◽  
F. A. Roddick
Keyword(s):  
Organic Matter ◽  
Sewage Treatment ◽  
Cyanobacterial Blooms ◽  
Secondary Effluent ◽  
Dissolved Air Flotation ◽  
Algal Organic Matter ◽  
Alum Coagulation ◽  
Pre Treatment ◽  
The Impact ◽  
Dissolved Air

Cyanobacterial blooms in the lagoons of sewage treatment plants can severely impact the performance of membrane plants treating the effluent. This paper investigates the impact of Microcystis aeruginosa in a secondary effluent on the microfiltration filterability and cleaning of the membrane. Alum coagulation and dissolved air flotation (DAF) were investigated to remove the algae and so enhance the volume of effluent processed, and their influence on reversible and irreversible fouling. Degree of fouling due to the algal components was found to be in decreasing order of algal cells, algal organic matter and extracellular organic matter. Alum coagulation with 5 mg L−1 as Al3 +  led to a substantial increase in permeate volume, an increase in dissolved organic carbon removal, and a foulant layer which protected the membrane from internal fouling but which was hydraulically removable resulting in full flux recovery. Pre-treatment by DAF or 1.5 μm filtration following alum coagulation enhanced the flux rate and permeate volume but exposed the membrane to internal irreversible fouling.

Treatment Spent Filter Backwash Water using Dissolved Air Flotation (DAF) in Isfahan WTP

2008 ◽  
Vol 3 (3) ◽  
Author(s):  
Mohammad Hassan Mahmoodian ◽  
Mohammad Mehdi Amin ◽  
Mohammad Reza Shahmansouri ◽  
Mohammad Ghasemian
Keyword(s):  
Low Dose ◽  
Saturation Pressure ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Recycle Rate ◽  
Polyaluminium Chloride ◽  
Significant Concentration ◽  
Dissolved Air ◽  
Filter Backwash Water

Recovering spent filter backwash water is currently receiving a great deal of attention. EPA published the Filter Backwash-Recycling Rule (FBRR) in 2001. Recycle stream may contain significant concentration of pathogens, such as, cryptosporidium and Giardia. Dissolved Air Flotation (DAF) was investigated as a possible technology alternative to simple or advanced sedimentation technology. In this study with using a pilot of DAF effluent turbidities of >20NTU could be easily obtained, when raw water turbidities were in excess of 800 NTU. Chemical requirements were low with only a single low dose of polyaluminium chloride (PACl) required binding the floc particles to form a solids matrix suitable for flotation. The results showed that the efficiency of continuous flow DAF with using PACl as coagulant for removal of Turbidity, COD, HPC, SS and MPN were 97, 72, 75, 95 and 100 percent, respectively. The statistical analyses indicated that the optimum saturation pressure is 4-5 atm, during recycle rate of 20-25 percent. The removal efficiencies of turbidity and bacteria in coagulation with sedimentation were reported up to 70 and 65 percent, while in this study using DAF with coagulant PACl could remove turbidity, COD, SS and bacterial up to 97,72, 95 and, 72 percent respectively.

The use of selective and direct DAF for removal of particulate contaminants in drinking water treatment

1995 ◽  
Vol 31 (3-4) ◽  
pp. 49-57 ◽  
Author(s):  
James P. Malley
Keyword(s):  
Drinking Water ◽  
Drinking Water Treatment ◽  
Cationic Polymers ◽  
Ionic Polymers ◽  
Charge Reversal ◽  
Dissolved Air Flotation ◽  
Polymer Addition ◽  
Anionic Polymers ◽  
Particulate Contaminants ◽  
Dissolved Air

Cationic polymers were found to coat bubbles resulting in charge reversal and increasingly positive EPM. Batch bench-scale dissolved air flotation (DAF) studies show promising benefits from the addition of cationic or non-ionic polymers to the saturated recycle line of conventional DAF. In cases where low turbidity, low color waters are being treated, direct DAF compared well with conventional DAF. Polymer addition improved the percentage solids of the float. Anionic polymers were not found to be effective. Further research at the pilot and full-scale is needed to verify these findings.

scholarly journals Water footprint analysis as an indicator of sustainability in nonconventional drinking water treatment systems

DYNA ◽  
2020 ◽  
Vol 87 (213) ◽  
pp. 140-147
Author(s):  
Víctor Alfonso Cerón Hernández ◽  
Isabel Cristina Hurtado ◽  
Isabel Cristina Bolaños ◽  
Apolinar Figueroa Casas ◽  
Inés Restrepo Tarquino
Keyword(s):  
Drinking Water ◽  
Cultural Context ◽  
Water Footprint ◽  
Drinking Water Treatment ◽  
Climatic Conditions ◽  
Water Production ◽  
Drinking Water Production ◽  
Footprint Analysis ◽  
Cultural Component ◽  
The Impact

The impact of multiple-stage filtration (MSF) was determined in two study systems. Water footprint (WF) was estimated with all its components and their results allowed the identification of those responsible for the environmental impact associated with drinking water production. Climatic conditions of high and low precipitation and socio-cultural context were considered. Results showed technicalshortcomings, such as the presence of fissures that generate losses and the contribution of polluting substances in the effluent from filter washing. Socio-economic limitations increase the WF. Water management can be improved by studying the WF components and their relationships with the socio-cultural component.

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