Optimization Of Ozone Plants For Water Works In Switzerland

The disadvantage that chlorine as processing agent in the treatment of surface waters can lead to undesirable production of chlorinated hydrocarbon products, provided the impulse to involvement in alternate means of oxidation. This inevitably led the way to the means of oxidation used the most intensively in water treatment - ozone.

Extensive development work has been performed to optimize the dosage of ozone for water treatment. Potential users are kept informed on this technology through published data. Theory, however, is only one side of the problem, practical application quite another. Here technicians and engineers have been required to integrate oxidation and disinfection with ozone, into the technology for water treatment and to make this economic.

In Switzerland since the 1950s, more than 40 waterworks have been converted to ozone. The development and the experience that has been collected since the introduction of this technique is the subject of this paper, primarily in regard to cost development and cost economy through innovative engineering services for development, engineering and project execution.     

Ozone in the United States of America -- State-Of-The-Art

Applications for ozone in the United States have evolved through a lengthy maturation process, which began with drinking water treatment (taste/odor/color removal) in the early 1900s, and grew slowly until acceleration began in the mid-1980s. Although deodorization became a stable market in the 1960s-1970s, these applications were small, for the most part. One of the largest uses for ozone is oxidation of process chemicals in the chemical industry, which began in the USA about the 1940s, and subsequently has spread worldwide. Today, thanks primarily to environmental regulatory pressures which began to impact ozone in the mid-1980s, ozone now is used increasingly in the USA for drinking water treatment and for some municipal and industrial wastewater applications. The U.S. Environmental Protection Agency (EPA) has recognized the growing importance of ozone (> 200 drinking water plants use ozone today), and has appointed IOA representatives to two of its regulatory development committees as stakeholders. Several U.S. cities have installed or are installing wastewater treatment processes for potable reuse purposes, which include the use of ozone. Three full-scale U.S. pulp bleaching plants use tons/day quantities of ozone. Smaller applications for ozone include water treatment for cooling tower waters (biofouling control), swimming pools and spas, marine aquaria, bottled water disinfection and maintenance of high purity waters in the pharmaceuticals and electronics industries. A new application for ozone is in commercial laundries to reduce energy costs and replace chemicals. In mid-1997, a public declaration was made by an expert panel that ozone is Generally Recognized As Safe (GRAS) for contact with foods. This declaration opens the door for ozone to be used in U.S. food processing industries. U.S. research scientists and engineers are at the forefront in studies which define the technical aspects of ozone technologies in a variety of applications employing advanced oxidation, including the treatment of hazardous wastes, groundwater remediation, and process water recovery and reuse in the semi-conductor industry.     

Development Of An Ozone Disinfection Contactor Using A Physical Scale Model

This paper presents the design of a 1/5 scale model study of a five-stage counter-current ozone disinfection contactor. The selection of appropriate scaling laws is discussed and model test runs are presented and compared with the preliminary rule-of-thumb design. Simple modifications to the internal baffle design were tested leading to improved residence time characteristics.     

Effects Of Ozone On Biodegradable Dissolved Organic Carbon And Heterotrophic Plate Counts In The Distribution System

The impacts of ozone dose in the formation of biodegradable dissolved organic carbon (BDOC) were studied at the North Bay Regional Water Treatment Plant (NBR). Increasing the ozone to total organic carbon ratio to 0.45 (mg/mg) resulted in the formation of BDOC. Sedimentation and filtration/adsorption were effective in removing BDOC to non-measurable levels prior to the water entering the distribution system. Data from an on-going distribution system monitoring program indicate no discernible adverse impacts on microbiological parameters from using ozone during water treatment. Heterotrophic plate count (HPC) levels were similar before and after the use of ozone. Maintaining chlorine residual levels above 0.3 mg/L appears to be important for controlling HPC levels.     

The Price Of Ozonation In The Paris (France) Suburbs

The purely economic aspects of ozonation have, until now, given rise to surprisingly few publications. Yet they are of ever-growing importance in deciding on the choice of a system, if only because the number of competitive technical solutions available for ozone production has greatly increased.

First of all, an obvious fact must be remembered. Each installation is a special case. It is therefore out of the question to present general results with direct across-the-board applications. On the other hand, it is possible to engineer a general methodology for price calculation and apply it to a few specific examples. As operator of a large number of these facilities, Compagnie Générale des Eaux can present economic results in many, widely different technological economic conditions.

Generally speaking, it can be said that the cost of ozonation is increasingly optimized. This technique, considered a few years ago as a luxury, is now technically and economically ready for incorporation on an equal footing in most treatment trains.     

Fifteen Years Experience In Ozonation For Drinking Water In Montreal

Since 1978, the City of Montreal has been operating an ozonation facility at one of its two water filtration plants. Various studies have been conducted which have resulted in improvements to the process. Among these projects, evaluation of THMs and haloacetic acids, optimization of the dryers' regeneration cycle, evaluation of the ozone recirculation system, revision of the ozone generators' cleaning program and implementation of ozonation process control loops have been undertaken. The reliability of the ozone plant has now been proved with downtimes less than 1% for the past six years.     

The Installation of GAC and Ozone Surface Water Treatment Plants In Anglian Water,UK

The surface water treatment plants in Anglian Water are being upgraded in order to more reliably meet the requirements of the EEC Drinking Water Directive. Ozone and additional GAC filtration capacity are being installed at 11 waterworks treating river and reservoir water, with capacities ranging from 11 to 360 ML/d. The installations and reasons for the plant designs are discussed.     

Use Of Ozone And Flotation For The Treatment Of A Reservoir Water: The Dinan Case History

The plant of Dinan supplies water to the urban district of Dinan (Brittany-France). The raw water is a dam water, soft, containing iron and manganese, highly colored with a high content of organic carbon. The area providing water to the dam is rural country, so water also contains residues of agricultural practices such as pesticides and nitrates.

During summer, algae blooms may occur. The old plant (including prechlorination, coagulation, flocculation, settling and sand filtration) has been replaced with a treatment line including: remineralization, preozonation, flotation, ozonation and granular activated carbon. Nitrate removal will be considered in the future. The paper presents the results obtained in the plant, the optimization of the preozonation dose as well as comparison with laboratory tests. A special reference concerns algae removal.     

The Application of Ozone for Water Treatment In The United Kingdom — Current Practive and Recent Research

Only two water works in the UK apply ozone at present as part of their treatment, onefor taste and odor control and theother forcolor removal. Forthetwo applicationus ozone was the most economical option at thetime theplants were installed andozone has been successful for the purpose for which it was designed.     

The Development Of Ozone For Potable Water Treatment Within The United Kingdom

The historical development of the application of ozone to potable water treatment within the United Kingdom is reviewed up to 1990. The impact of privatization of the water utilities on the use of ozone is discussed and the process applications currently being considered are described. The paper concludes with a survey of water treatment plants which are using ozone in 1993, and those planned for completion by the year 2000.     

The Role of Mixing in Ozone Dissolution Systems

The mixing efficiency of four alternative ozone dissolution systems, including conventional bubble diffusion and pipeline injection/diffusion reactors, were compared by measuring the variability of ozone residual measurements at the outlet of each reactor. The standard deviation and coefficient of variation of a time series of residual measurements were used to provide a quantitative measure of the level of mixing in the reactor. The results indicate that properly designed pipeline dissolution systems provide significantly improved mixing over oxygen-fed or air-fed bubble diffusion systems. Minimum mixing criteria for bubble diffusion systems cited in the literature may underestimate the level of mixing required to achieve stable ozone residuals downstream of the dissolution chamber of conventional bubble diffusion chambers.     

Operating Strategy To Meet SWTR Disinfection Regulations At The Los Angeles Aqueduct Filtration Plant

Preozonation facilities were installed at the Los Angeles Aqueduct Filtration Plant originally to enhance coagulation assistance (microflocculation). The Surface Water Treatment Rule will amend this primary purpose to meeting disinfection standards. Additional ozone generation equipment and a revised ozone system operating strategy will be required to accomplish these changed objectives. The topics discussed in this paper are the considerations surrounding the development of a successful, cost-effective operating strategy. The strategy proposed herein was based on data collected between January and July 1991. On-line process monitoring plans and automated system control logic are described.     

A Comprehensive Investigation On The Application Of Ozone In Cooling Water Systems –– Correlation of Bench–Top,Pilot Scale and Field Application Data

The first comprehensive study – bench–top laboratory investigations, pilot scale testing, and critical monitoring and evaluation of field applications – addressing the effects of ozone as a stand–alone cooling water treatment program is presented. The study also represents the first critical comparison of ozone–treated systems with non–treated systems. Excellent corrosion control can be attained in ozone–treated cooling water systems. However, the corrosion rates are completely dominated by the water chemistry of the system and have no dependence on the presence of ozone at typical use levels. Good control of fouling can also be attained. However, as was the case with corrosion control, deposition on the heatexchange surfaces is not determined by the presence of ozone, but by several factors that traditionally influence fouling in a system. The strong biocidal properties of ozone resulted in excellent microbiological control in all Pilot Cooling Tower (PCT) investigations and in both case studies. Excellent agreement was observed among all stages of testing.