摘要:

This case study evaluates the integration of ozone in a softening plant with emphasis on the feasibility of high pH ozonation. The softening plant in Jefferson City, Missouri, treats Missouri River water characterized by high hardness, TOC of up to 8.0 mg/L, and occurrences of atrazine at concentrations up to 20 μg/L. As part of the predesign effort for rehabilitation of the existing WTP, ozone was evaluated to achieve current and anticipated future disinfection requirements, as well as atrazine removal. Testing using a continuous flow bench scale unit was conducted to evaluate ozone for 2-logCryptosporidiuminactivation and to oxidize 10 to 14 μ/L of atrazine. Because of the high CT required for 2-logCryptosporidiuminactivation, it was found that practicing an AOP was not necessary to reduce the atrazine level to below the current maximum contaminant level (MCL) of 3 μg/L. In this case, the long term disinfection requirements forCryptosporidiumlikely will drive the ozone system design criteria despite the high levels of atrazine occurring in the raw water supply.

ISSN:0191-9512    

DOI:10.1080/01919519808547269

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Since the 1960s, the use of oxygen for generating ozone in operational potable water plants has increased significantly. However, at present, treatment of industrial process liquids and effluents require high dosages of ozone and have focused interest in higher ozone concentrations in the process gas. As a consequence, the use of oxygen to generate ozone has increased. Different options are possible: purchase liquid oxygen, producing liquid oxygen on-site by cryogenic processes, generating on-site gases rich in oxygen by pressure swing or vacuum swing adsorption-desorption, etc. The purpose of this contribution is to highlight the fundamental determinants of choice of the feed gas in ozone generation by electrical discharge.

ISSN:0191-9512    

DOI:10.1080/01919519808547271

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The bactericidal effects of high concentrations of airborne ozone were tested againstEscherichia coliandStaphylococcus aureus. Petri dishes containing the microorganisms were inserted in a chamber and exposed for 10 - 480 seconds to ozone concentrations between 300 and 1500 ppm. Death rates in excess of 99.99% were achieved for both species. The mechanism of inactivation accorded with the predictions of first- and second-order kinetics, suggesting that the disinfection action of ozone in air parallels the action of ozone in water.

ISSN:0191-9512    

DOI:10.1080/01919519808547272

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The potential for the oxidant ozone used in water treatment, to destroy the various classes of toxins produced by cyanobacteria (blue-green algae) was investigated. Toxin destruction was determined by chemical analyses or mouse bioassay. Ozone was more effective than chlorine, hydrogen peroxide and potassium permanganate in destroying the peptide hepatotoxin microcystin-LR. Ozone in combination with hydrogen peroxide was more effective than ozone alone. Ozone was capable of destroying the alkaloid neurotoxins anatoxin-a and paralytic shellfish poisons (PSPs), whereas chlorine has been previously reported to be ineffective (Rositano and Nicholson, 1994). Destruction of peptide hepatotoxins by ozone was pH-dependent. Ozone was less effective under alkaline conditions, consistent with its lower oxidation potential under these conditions (1.24V) compared with acidic conditions (2.07V).

ISSN:0191-9512    

DOI:10.1080/01919519808547273

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Salt brine electrolysis systems produce a solution that can contain up to 400 mg/L free available chlorine (FAC). These systems are very appealing to small utilities. The scientific literature contains numerous reports from utilities using electrolysis systems citing enhanced microbiological kill rates and lower THM levels than normally would be expected by disinfection with FAC alone. Researchers have speculated that the presence of minority oxidant species (ozone and/or chlorine dioxide) are responsible for the observed increased disinfection capability of salt brine electrolysis systems. If strong oxidants such as ozone and chlorine dioxide are present in electrolysis cell liquors, the chemical reactions that can occur are complicated both thermodynamically and kinetically. This paper describes analytical methods developed to identify reactive species and potential interferences in salt brine electrolysis cell anode liquors.

ISSN:0191-9512    

DOI:10.1080/01919519808547274

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Measurements of ozone concentrations in the air in dental treatment areas while using water ozonating equipment show no values in excess of the current limits and guideline values for ozone concentrations in places of work in Germany. Therefore, there are no objections from the toxicological viewpoint against using the excellent microbiological properties of ozonated water by employing it to disinfect dental units.

ISSN:0191-9512    

DOI:10.1080/01919519808547275

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0191-9512    

DOI:10.1080/01919519808547276

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor