Chapter 9 Pollution Removal by TiO2/UV Photocatalysis Coupled with Membrane Filtration

The City of Baltimore, Maryland is one of many US cities faced with challenges related to increasing potable water demands, diminishing fresh water supplies, and aging infrastructure. To address these challenges, the City recently undertook a $7M study to evaluate water supply and treatment alternatives and develop the conceptual design for a new 120 million gallon per day (MGD) water treatment plant. As part of this study, an innovative raw water management tool was constructed to help model source water availability and predicted water quality based on integration of a new and more challenging surface water supply. A rigorous decision-making approach was then used to screen and select appropriate treatment processes. Short-listed treatment strategies were demonstrated through a year-long pilot study, and process design criteria were collected in order to assess capital and operational costs for the full-scale plant. Ultimately the City chose a treatment scheme that includes low-pressure membrane filtration and post-filter GAC adsorption, allowing for consistent finished water quality irrespective of which raw water supply is being used. The conceptual design includes several progressive concepts, which will: 1) alleviate treatment limitations at the City's existing plants by providing additional pre-clarification facilities at the new plant; and 2) take advantage of site conditions to design and operate the submerged membrane system by gravity-induced siphon, saving the City significant capital and operations and maintenance (O&M) costs. Once completed, the new Fullerton Water Filtration Plant (WFP) will be the largest low-pressure membrane plant in North America, and the largest gravity-siphon design in the world.

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Membrane filtration retentate thickening efficiency using electrolytic ion products instead of chemical coagulants

Water Science & Technology Water Supply ◽

10.2166/ws.2003.0006 ◽

2003 ◽

Vol 3 (3) ◽

pp. 43-48

Author(s):

J.Y. Huang ◽

T. Uchiburi ◽

K. Fujita

Keyword(s):

Membrane Filtration ◽

Wash Water ◽

Aluminum Anode ◽

Alkaline Agent ◽

Iron Anode

Electrolytic coagulation has advantages compared with conventional chemicals coagulation treatment. First of all, the addition of alkaline agent is necessary in chemicals coagulation treatment as the addition of acid agents in coagulation of dense wash water makes pH decline. While not much change of pH is observed with electrolytic coagulation, where alkaline agent is not demanded. Secondly, it is easy to control the dose of additional coagulants. In this study, electrolytic coagulation sedimentation treatment is adopted for membrane retentate from membrane filtration treatment without using coagulants. As electricity can control the addition of coagulation, an automation method is applied in the experiment. The lower the iron as well as aluminum dissolved, the higher the sludge density becomes; especially aluminum has this tendency. It is possible to achieve 400 kg/m3 of condensed sludge density with artificial wash water and more than 80 kg/m3 for real retentate, in terms of electrolytic coagulation of iron anode. The sludge density of aluminum anode is higher, but its filtrate density is lower than iron anode.

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Low-pressure membrane filtration with unconventional coagulation regimes

Water Science & Technology Water Supply ◽

10.2166/ws.2005.0032 ◽

2005 ◽

Vol 5 (5) ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

K.Y. Choi ◽

B.A. Dempsey

Keyword(s):

Activated Carbon ◽

Membrane Filtration ◽

Membrane Surface ◽

Cross Flow ◽

Chemical Cleaning ◽

Sand Filters ◽

Charge Neutralization ◽

Floc Size ◽

Filtration System ◽

Pre Treatment

The objective of the research was to evaluate in-line coagulation to improve performance during ultrafiltration (UF). In-line coagulation means use of coagulants without removal of coagulated solids prior to UF. Performance was evaluated by removal of contaminants (water quality) and by resistance to filtration and recovery of flux after hydraulic or chemical cleaning (water production). We hypothesized that coagulation conditions inappropriate for conventional treatment, in particular under-dosing conditions that produce particles that neither settle nor are removed in rapid sand filters, would be effective for in-line coagulation prior to UF. A variety of pre-treatment processes for UF have been investigated including coagulation, powdered activated carbon (PAC) or granular activated carbon (GAC), adsorption on iron oxides or other pre-formed settleable solid phases, or ozonation. Coagulation pre-treatment is often used for removal of fouling substances prior to NF or RO. It has been reported that effective conventional coagulation conditions produced larger particles and this reduced fouling during membrane filtration by reducing adsorption in membrane pores, increasing cake porosity, and increasing transport of foulants away from the membrane surface. However, aggregates produced under sweep floc conditions were more compressible than for charge neutralization conditions, resulting in compaction when the membrane filtration system was pressurized. It was known that the coagulated suspension under either charge-neutralization or sweep floc condition showed similar steady-state flux under the cross-flow microfiltration mode. Another report on the concept of critical floc size suggested that flocs need to reach a certain critical size before MF, otherwise membranes can be irreversibly clogged by the coagulant solids. The authors were motivated to study the effect of various coagulation conditions on the performance of a membrane filtration system.

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Coagulation/flocculation/ultrafiltration for natural organic matter removal in drinking water production

Water Science & Technology Water Supply ◽

10.2166/ws.2004.0111 ◽

2004 ◽

Vol 4 (5-6) ◽

pp. 215-222 ◽

Cited By ~ 2

Author(s):

A.R. Costa ◽

M.N. de Pinho

Keyword(s):

Drinking Water ◽

Organic Matter ◽

Natural Organic Matter ◽

Membrane Fouling ◽

Membrane Filtration ◽

Membrane Surface ◽

Water Production ◽

Cellulose Acetate Membranes ◽

Wide Range ◽

Drinking Water Production

Membrane fouling by natural organic matter (NOM), namely by humic substances (HS), is a major problem in water treatment for drinking water production using membrane processes. Membrane fouling is dependent on membrane morphology like pore size and on water characteristics namely NOM nature. This work addresses the evaluation of the efficiency of ultrafiltration (UF) and Coagulation/Flocculation/UF performance in terms of permeation fluxes and HS removal, of the water from Tagus River (Valada). The operation of coagulation with chitosan was evaluated as a pretreatment for minimization of membrane fouling. UF experiments were carried out in flat cells of 13.2×10−4 m2 of membrane surface area and at transmembrane pressures from 1 to 4 bar. Five cellulose acetate membranes were laboratory made to cover a wide range of molecular weight cut-off (MWCO): 2,300, 11,000, 28,000, 60,000 and 75,000 Da. Severe fouling is observed for the membranes with the highest cut-off. In the permeation experiments of raw water, coagulation prior to membrane filtration led to a significant improvement of the permeation performance of the membranes with the highest MWCO due to the particles and colloidal matter removal.

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Monitoring and maintaining the integrity of immersed ultrafiltration membranes used for pathogen protection

Water Science & Technology Water Supply ◽

10.2166/ws.2002.0184 ◽

2002 ◽

Vol 2 (5-6) ◽

pp. 307-311

Author(s):

P. Côté ◽

J. Cadera ◽

N. Adams ◽

G. Best

Keyword(s):

Drinking Water ◽

Membrane Filtration ◽

Ultrafiltration Membranes ◽

Vacuum Decay ◽

Integrity Monitoring ◽

Pressure Decay ◽

Decay Test ◽

Conventional Technology ◽

Water Borne

Membrane filtration has become the preferred alternative to conventional technology to remove water-borne pathogens in the preparation of drinking water. This paper presents the integrity monitoring and maintenance options for the ZeeWeed® immersed membrane. Results from two versions of air-based tests, a pressure decay test and a vacuum decay test are presented and shown to be conservative when compared to challenge results from independent studies.

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A Most Probable Number Method for the Enumeration of Legionella Bacteria in Water

Water Science & Technology ◽

10.2166/wst.1991.0046 ◽

1991 ◽

Vol 24 (2) ◽

pp. 143-147 ◽

Cited By ~ 6

Author(s):

N. A. Grabow ◽

R. Kfir ◽

W. O. K. Grabow

Keyword(s):

Water Samples ◽

Membrane Filtration ◽

Quantitative Method ◽

Fluorescent Antibody ◽

Most Probable Number ◽

Probable Number ◽

Comparative Tests ◽

Antibody Staining ◽

Direct Fluorescent Antibody ◽

Yeast Extract Agar

A new quantitative method for the enumeration of Legionella bacteria in water is described. Appropriate tenfold serial dilutions of water samples concentrated by membrane filtration are plated in triplicate on buffered charcoal yeast extract agar. After incubation for 3 days representative smears from individual plates are tested for the presence of Legionella by direct fluorescent antibody staining. The number of positive plates in each dilution is used to calculate the Legionella count by means of conventional most probable number statistics. In comparative tests on a variety of water samples this method yielded significantly higher counts than previously used procedures.

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Detection of Hepatitis a Virus in Drinking Water by Enzyme -Immunoassay Using Ultracentrifugation for Virus Concentration

Water Science & Technology ◽

10.2166/wst.1985.0093 ◽

1985 ◽

Vol 17 (10) ◽

pp. 39-41 ◽

Cited By ~ 1

Author(s):

A. Schnattinger

Keyword(s):

Membrane Filtration ◽

Hepatitis A ◽

Hepatitis A Virus ◽

Solid Phase ◽

Phosphate Buffer Solution ◽

Enzyme Linked Immunosorbent Assay ◽

Virus Concentration ◽

Buffer Solution ◽

Solution Ph ◽

Two Stage

Ten litres of tapwater were seeded with 200 µl (8×108 HAV particles) of a commercial (Organon Teknika) suspension of hepatitis A virus. Following WALTER and RÜDIGER (1981), the contaminated tapwater was treated with a two-stage technique for concentration of viruses from solutions with low virus titers. The two-stage technique consists of aluminium hydroxideflocculation (200 mg/l Al2(SO4)3. 18 H2O, pH 5,4-5,6) as first stage, the second stage of a lysis of aluminium hydroxidegel with citric acid/sodium citrate-buffer (pH 4,7; 1 ml/l sample), separation of viruses from the lysate by ultracentrifugation and suspension in 1 ml phosphate buffer solution (pH 7,2). A commercial solid phase enzyme-linked immunosorbent assay (ELISA) was used for the detection of HAV. HAV was detecterl in the 10.000:1 concentrates, but not in the seeded 101 samples. Approximately 4×108 of the inoculated 8×108 HAV particles were found in the 1 ml concentrates. The efficiency of detection is about 50%, the virus concentration 5000-fold. Although the percentage loss of HAV in comparison with concentration by means of membrane filtration is similar, the ultracentrifugation method yields a larger sample/concentrate ratio, so that smaller amounts of HAV can be detected more efficiently because of the smaller end-volume.

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