The treatment of algae-laden raw water with compact flofilter of dissolved air flotation and GAC deep bed filtration

2004 ◽  
Vol 4 (5-6) ◽  
pp. 35-41
Author(s):  
X. Zhang ◽  
S. Zhang ◽  
Y. Liu
Keyword(s):  
Conventional Treatment ◽  
Good Alternative ◽  
Raw Water ◽  
Deep Bed Filtration ◽  
Dissolved Air Flotation ◽  
Chl A ◽  
Air Flotation ◽  
Filtration Unit ◽  
Advanced Treatments ◽  
Dissolved Air

Compact flofilter of dissolved air flotation and GAC deep bed filtration is a good integrated procedure, having the following characteristics: flotation and filtration are integrated in one tank, the flotation unit is above the filtration unit, filtration is GAC deep bed, and conventional and advanced treatments are integrated in one tank. During the treatment of algae-laden raw water with compact flofilter of dissolved air flotation and GAC deep bed filtration, the general performance was good: the outlet algae-count was 1.21×105–1.26×106 cell/l, the average removal of algae was 95.4%, the outlet chl-a was 0.68 μg/l, the removal of chl-a was 92.2%, the outlet turbidity was 0.16–0.20 NTU, the outlet had no odor, the outlet color was 3, the removal of color was 86.4%, the outlet Al-residual was 0.011 mg/l. Good removal of organics can be achieved: the average removal of UV254 was 54.3%, the outlet UV254 was 0.016–0.018 cm−1, the removal of DOC was 29.6%, the outlet DOC was 1.608 mg/l, the removal of BDOC was 42.6%, the outlet BDOC was 0.120 mg/l, the removal of AOC was 72.2%, the outlet AOC was 52 μg/l. Filter run period and UFRV were 36 h and 504 m3/m2. The results show that flofilter is a good alternative process for conventional treatment plus GAC adsorption.

High-rate dissolved air flotation for water treatment

2001 ◽  
Vol 43 (8) ◽  
pp. 43-49 ◽  
Author(s):  
M. A. P. Raeli ◽  
M. Marchetto
Keyword(s):  
Reynolds Numbers ◽  
Pilot Scale ◽  
Water Velocity ◽  
High Rate ◽  
Raw Water ◽  
Parallel Plates ◽  
Dissolved Air Flotation ◽  
Removal Efficiencies ◽  
Air Flotation ◽  
Dissolved Air

This paper presents the results of an experimental investigation about the performance of a horizontal flow high-rate pilot scale Dissolved Air Flotation (HRDAF) unit containing inclined parallel plates for treating a coloured and low turbidity raw water. Experiments were performed with the DAF unit in order to verify the influence on flotation of : (i) the water velocity (Vh) between the plates, in the range 18 to 96.5 cm.min−1 with corresponding Reynolds numbers between 240 and 1060; (ii) the supplied air (S*) value ranging from 2.2 to 8.5 g of air/m3 of water ; (iii) the angle of the plates (60° or 70°). The best pilot plant operational condition was obtained applying only 4.0 g/m3 (S*) with Vh around 18 cm.min−1 for treatment of water coagulated with a Al2(SO4)3 dosage of 40 mg.l−1. In these conditions, the unit presented very good removal efficiencies of colour (90%, residual of 10 uC), turbidity (88%, residual of 0.8 NTU ) and TSS (94%, residual of 1.8 mg.l−1). Furthermore, the unit could operate at higher Vh values up to 76 cm.min−1 and still present good results. The DAF unit thus behaved as a high rate unit presenting good performance with low air requirement.

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.

scholarly journals The evaluation of polymeric organic coagulants for potable water treatment by dissolved air flotation

2001 ◽  
Author(s):  
◽  
Rachigan Rajagopaul
Keyword(s):  
Water Treatment ◽  
Ferric Chloride ◽  
Potable Water ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Potable Water Treatment ◽  
Dissolved Air

Historically inorganic coagulants were the coagulants of choice for OAF treatment of potable water. Water treatment practitioners using OAF technology preferred ferric chloride, an inorganic coagulant. Ferric chloride formed light, floatable floes at relatively low flocculation intensities and detention times. The inorganic coagulant was also more forgiving during incidents of overdosing and raw water and pH variability

Pretreatment considerations for dissolved air flotation: water type, coagulants and flocculation

1995 ◽  
Vol 31 (3-4) ◽  
pp. 63-71 ◽  
Author(s):  
Donald Q. Bunker ◽  
James K. Edzwald ◽  
Jan Dahlquist ◽  
Lars Gillberg
Keyword(s):  
Chemical Properties ◽  
Water Type ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
Mixing Intensity ◽  
Flotation Performance ◽  
Air Flotation ◽  
Favorable Conditions ◽  
Flocculation Time ◽  
Dissolved Air

Pretreatment considerations of coagulant selection, flocculation time and flocculation mixing intensity were studied for two different water supply types, aquatic humic and non-aquatic humic waters of low turbidity. Alum, ferric salts, and various polyaluminium chlorides (PACs) with different chemical properties were all effective in dissolved air flotation (DAF) when used under favorable conditions of dosage, pH, and flocculation time. A stoichiometry was found for the aluminium coagulants between coagulant dose and raw water DOC. Si and sulfate PACs were effective in treating cold waters with short flocculation times of 2.5 to 5 minutes. Flotation performance improved slightly with increasing flocculation mixing intensity. The results suggest that flocculation tanks be designed to produce strong, “pinpoint” size floc particles.

A decade of large scale experience in dissolved air flotation

2001 ◽  
Vol 43 (8) ◽  
pp. 27-34 ◽  
Author(s):  
S. Kempeneers ◽  
F. Van Menxel ◽  
L. Gille
Keyword(s):  
Water Quality ◽  
Large Scale ◽  
Mechanical Design ◽  
Operational Experience ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
The Past ◽  
Air Flotation ◽  
Entire Treatment ◽  
Dissolved Air

In April 1990 Antwerpse Waterwerken brought a new DAF-plant into operation at the production centre Notmeir-Walem. The flotation unit, which has a capacity of 200,000 m3/d, was integrated in one of the two existing treatment lines. Its main objective was to eliminate the important raw water quality fluctuations caused by increasing algal growths. During the past ten years several optimisation studies were carried out which resulted in a further simplification of operation and mechanical design. This paper will focus mainly on the integration of dissolved air flotation in the entire treatment line, the consequences on the dual layer filtration and the operational experience and information gathered during the past decade.

A case study of dissolved air flotation for seasonal high turbidity water in Korea

2004 ◽  
Vol 50 (12) ◽  
pp. 245-253 ◽  
Author(s):  
S.B. Kwon ◽  
H.W. Ahn ◽  
C.J. Ahn ◽  
C.K. Wang
Keyword(s):  
Operation Mode ◽  
Raw Water ◽  
Freshwater Algae ◽  
Water Turbidity ◽  
Dissolved Air Flotation ◽  
Flotation Process ◽  
Direct Filtration ◽  
Air Flotation ◽  
Full Scale Tests ◽  
Dissolved Air

A DAF (Dissolved-Air-Flotation) process has been designed considering raw water quality characteristics in Korea. Although direct filtration is usually operated, DAF is operated when freshwater algae blooms occur or raw water turbidity becomes high. Pre-sedimentation is operated in case when the raw water turbidity is very high due to rainstorms. A main feature of this plant is that the operation mode can be changed (controlled) based on the characteristics of the raw water to optimize the effluent quality and the operation costs. Treatment capacity (surface loading rate) and efficiency of DAF was found to be better than the conventional sedimentation process. Moreover, low-density particles (algae and alum flocs) are easily separated while the removal of them by sedimentation is more difficult. One of the main concerns for DAF operation is a high raw water turbidity. DAF is not adequate for raw water, which is more turbid than 100 NTU. In order to avoid this problem, pre-sedimentation basins are installed in the DAF plant to decrease the turbidity of the DAF inflow. For simulation of the actual operation, bench and full-scale tests were performed for highly turbid water conditions. Consequently, it is suggested that pre-sedimentation with optimum coagulation prior to DAF is the appropriate treatment scheme.

Performance of Presedimentation and Dissolved Air Flotation to Overcome Highly Turbid Raw Water

2010 ◽  
Vol 27 (2) ◽  
pp. 127-136 ◽  
Author(s):  
Dong-Heui Kwak ◽  
Seung-Joon Yoo ◽  
Byeong-Yong Sohn
Keyword(s):  
Raw Water ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Dissolved Air

Pre-treatment with dissolved air flotation considering an integrated process design

2001 ◽  
Vol 1 (2) ◽  
pp. 115-122
Author(s):  
J. Dahlquist ◽  
M. Kulesza
Keyword(s):  
Organic Matter ◽  
Process Design ◽  
Treatment Plant ◽  
Integrated Process ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Pre Treatment ◽  
Treatment Step ◽  
Dissolved Air

The raw water from Lake Zegrzynski is difficult to treat and requires a high chemical dosing rate of coagulant for the reduction of organic matter in order to comply with EU standards. The high degree of reduction calls for an efficient coagulant, but also an optimal chemistry such as correct dosing amount and an optimal flocculation-pH. The paper describes different removal efficiencies of organic matter, particularly with respect to pH in flocculation. During the warm season, the raw water can also suffer from large amounts of plankton that are difficult to remove to a satisfactory degree. In a two-step chemical treatment concept, with Dissolved Air Flotation (DAF) and the pulsator process, the plankton content in the final outlet water is reduced to very low levels. It follows that eventual peaks of plankton in the raw water cannot be detected in the final outlet water. Ozone is added for removal of taste and odour originating from the presence of plankton. In the pre-treatment step prior to the ozonation, a great deal of the organic matter is removed, which reduces the necessary ozone dosage. The Municipal Water Company of Warsaw City has decided to consider an additional pre-treatment step to the existing water treatment plant at Wieliszew. For that purpose, and bearing in mind an integrated process design, the company has performed pilot-scale experiments with DAF installed prior to a process line identical with the existing full-scale plant. The experimental flow is about 10 m3/h.

Treatment of spent filter backwash water using dissolved air flotation

2001 ◽  
Vol 43 (8) ◽  
pp. 59-66 ◽  
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.

Characterization of Nova Scotia surface waters and treatment options for removal of colour and trihalomethane precursors

1996 ◽  
Vol 23 (6) ◽  
pp. 1316-1325 ◽  
Author(s):  
D. H. Waller ◽  
M. J. MacPhee ◽  
P. W. Prendiville ◽  
R. F. McCurdy ◽  
A. W. Gates ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Surface Waters ◽  
Carbon Surface ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
Direct Filtration ◽  
Air Flotation ◽  
Dissolved Air

This paper provides an overview of the results of a study undertaken to provide a basis for predesign evaluation of the effectiveness of options for treatment of municipal surface waters in the province of Nova Scotia. Seasonal samples of raw water were obtained from the fall of 1992 through the fall of 1993 from five sites. Results were compared with a Nova Scotia Department of Health data base of randomly collected samples. For project samples, strong relationships were evident between raw water total organic carbon (TOC) and both colour and trihalomethane formation potential. Laboratory batch tests, supported by plant results, indicated that percentage removals of TOC increase with raw water TOC, and that settling-filtration was more effective than direct filtration for waters with higher raw TOC concentrations. Results of solids settling tests were consistent with TOC results. A treatment optimized for TOC removal also ensured removal of colour. TOC removals by dissolved air flotation followed by filtration exceeded removals by direct filtration or settling-filtration, based on laboratory bench tests, particularly at sites with higher values of raw TOC. Colour removal by dissolved air flotation was consistently higher at all sites. Key words: enhanced coagulation, trihalomethane precursors, total organic carbon, surface water treatment, dissolved air flotation.

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