First Year Operation Report of the Corona Discharge Ozone Swimming Pool Water Treatment Systems at the Peck Aquatic Facility,Milwaukee, Wisconsin

The two corona discharge ozone swimming pool water treatment systems installed in the Peck Aquatic Center in Milwaukee, WI now have been in continuous operation since September, 1987. The two pools are part of the Karl Jewish Campus Facility of the Harold and Judy Sampson Campus of the Milwaukee Jewish Community Center.

The operation of these water treatment systems has shown that safe and high quality pool water is obtained reliably and economically. One pool (Main Pool) is of Olympic size, the other (Learner pool) is designed especially for use by children. Both pools utilize a full corona discharge ozone water treatment system. They were the first ozone systems in the U.S. to be built for public pools using the process of ozonation, flocculation, filtration, ozone removal and residual chlorination.

An extensive testing program was initiated in cooperation with the Wisconsin Department of Health. The bacteriological water quality from these swimming pools was in compliance with Wisconsin State Health Regulations and the German DIN Standard 19,643.

The first year of operation of the Peck Aquatic Center has shown that the corona discharge ozone pool water treatment process can:

1) Operate reliably in a public swimming pool environment without the need for highly or special operator qualifications.

2) Produce continuously bacteria- and virus-free pool water without the harmful and unpleasant effects of chlorine.

3) Creates a user constituency group praising and promoting the use of “minimal chlorine swimming” in the community.     

Removal of Aromatic Nitro Compounds from Water by Ozonation

Experimental studies were carried out on the removal of five species of aromatic nitro hydrocarbons by ozonation. Ultraviolet spectrograms with distinct absorption peaks were plotted for each of them. It has been found that the absorbances of aqueous solutions containing the single compounds mentioned above increase to different extents at the wave lengths ranging from 200 to 230 nanometers with increase of ozone dosages. This is ascribed to the nitrite ions splitting out of the benzene rings and being further oxidized to nitrate ions by ozonation.

It has been indicated that the removal of the five species of aromatic nitro compounds by ozonation can well be expressed mathematically by first order reaction equations. Besides, the reaction constants and half-life periods for various species of the tested nitro compounds were calculated at different temperatures and pH.

An ozonation effect index (OI) was developed in the study to express the degree of degradation of substrates by ozonation, by means of which the five aromatic nitro hydrocarbons were compared with each other and finally ranked in the following order from greatest to smallest degrees of degradation:

p-nitroaniline > nitrobenzene > p-dinitrobenzene > p-nitrotoluene > m-dinitrobenzene

It has also found that the CODm/M ratio increases with ozone doses. This means that some easily degradable intermediates are produced, and increase in concentration with increase of ozone dose in the ozonation process.

The mechanisms of removing the five aromatic nitro hydrocarbons are discussed from the viewpoint of orienting effects of substituent groups on the aromatic rings.     

Use Of Static Mixer For Oxidation And Disinfection By Ozone

Ozone is used in drinking water treatment as a biocide, as an oxidant and as a pretreatment in order to improve the performance of subsequent processes. Increasing concern over the quality of drinking water has led to a number of new stringent regulations in the control of chemical and microbiological contaminants. Disinfection deals with the concept of “CT”, which is the need to maintain a certain minimum concentration for a given time. Under ideal laboratory conditions, it is 0.4 mg O₃/L for 4 min. In practice, since the method for the CT determination has not been finalized by the EPA, “T” can be the minimum detention time of 90% of total flow, and “C” can be a measured ozone residual at the outlet of cells of the contactor. New standards for micropollutants in drinking water imply an optimization of the ozonation step, by improving the ozone transfer from gas to water, and the control of the detention time as well as ozone residual within the contactor.

All these considerations have led us to use static mixers to transfer ozone into water. This process enables us to control the ozone concentration in water and detention time. It is a very simple system, with very low maintenance requirements due to the lack of moving parts. Civil engineering is minimized. A pilot scale study is presented here. It took place at the Méry-sur-Oise water treatment plant, on a pilot plant working at 8-12 m³/h. It is composed of a static mixer for the transfer of ozone from gas to liquid, linked to an air lift to separate gas from liquid, providing ozonated water.

The optimization of transfer was achieved by studying the impact of water flow, gas flow and ozone concentration in the gas. It is possible to reach 90% of transfer in less than 15 s. Headloss (ΔP) across the mixer is a function of gas and water flows and remains economically very acceptable as 0.15 bar for 12 m³/h.

Atrazine removal was studied using a static mixer, an air lift and a contact pipe 80-m long, providing an optimum contact time phase, working as a plug flow reactor. Ozone and H₂O₂/O₃ treatments were compared. The maximum reduction of atrazine concentrations (e.g., for an infinite contact time) is a function of the amount of transferred ozone, but H₂O₂ influences the kinetics of the reaction. In the presence of H₂O₂ with a ratio of H₂O₂ to O₃ of 0.4 w/w, maximum elimination is reached in 2 min 30 s.

The effect of such treatments on environmental bacteria also was followed. A counting of total germs at 20°C showed a decrease of 1- to 3-logs 10 after 1 min 30 s of contact time for about 2 mg/L of transferred ozone. No significant difference between treatments with or without H₂O₂ was shown. The same conclusions were obtained from heterotrophic plate counts (37°C) and epifluorescence countings.     

Controlling Blown Polyethylene Film Optical Properties

The conventional blown process imparts an inherent haze to the product. The percentage of haze varies with certain process variables:

1. Surface irregularities caused by melt flow phenomena

2. Crystallization behavior

3. Melt drawing phenomena in certain types of polyethylene     

Research Note: O3 or O2 and Ag: A New Catalyst Technology for Aqueous Phase Sanitation

Silver deposited on an inert surface with a very large area exhibits a strong catalytic interaction with oxygen which results in strong bactericidal activity. This catalytic process is fundamentally different from other known silver-based approaches which deliver low levels of silver ions into water.

Two factors appear to control the rate of this catalytic reaction process: (1) the size and dispersion of the silver crystals and surface area of the supporting bed; and (2) the volume of oxygen in solution. The source of the oxygen can be atmospheric oxygen dissolved in the water or, for a greatly enhanced reaction rate, dissolved ozone produced by an ozone generator. In this process, oxygen molecules absorbed onto the catalyst surface are subsequently transferred to other oxidizable substrates including bacteria and viruses.

These catalytic oxidizing reactions exhibit two properties of significance in the sanitation of water. First, because oxygen on the catalyst surface reacts with both living and nonliving substrates, bacteria or viruses which are in the water flowing over the catalyst-containing medium are killed or inactivated on contact by the oxidizing reactions (i.e., without requiring the release of metals into water). Second, oxygen also is transferred to oxidizable inorganics (such as bromide ion) to generate readily measurable and relatively stable “residual” oxidizers/disinfectants that continue to sanitize water downstream.

Results of this Author's experiments have been independently replicated by sources from the University of Arizona, and at Herbert V. Shuster, Inc. Laboratories in Massachusetts.     

Recent Advances in Flame Retardancy of Polymeric Materials (Materials,Applications, Industry Developments,Markets)

The Fifth Annual Conference on Flame Retardancy was held May 24–26, 1994, at the Ramada Plaza Hotel, Stamford, Connecticut, USA. The conference was organized by Business Communications Company, Inc., Norwalk, Connecticut (Company President, Mr. Louis Naturman; Conference Coordinator, Mrs. Sharon D. Faust). New materials (polymers, blends, composites), their applications, industry developments, and markets were considered. Specifically, the most important topics were:

Introduction of new technological achievements and development in the field of flame retardancy (FR)

Review of the current state of science and technology in FR

Review of applications and markets for FR products

Presentation of recent developments in local and global standardization and in testing technology

Discussion of toxicity and environmental issues

Provision of a unique opportunity for newcomers to FR research technology and marketing to become acquainted with the FR field in all its aspects

Discussion of halogen-based and non-halogen-based flame retardant chemicals, syngergism, intumescence, FR mechanisms, modeling, flame parameters, inherently FR polymers, and polymer blends     

The Photochemical Generation of Ozone : Present State–of–the–Art

This paper reflects an investigation of the feasibility of photochemical generation of ozone by irradiating gases containing oxygen with Hg lamps of the highest performance emitting the 185 nm line. Besides the expected photostationary equilibrium, determining factors for practical yields in ozone generation by the 185 nm wavelength are : the reactor and gas temperature, the reactor geometry, and the gas composition, as well as the pressure.

Further developments are expected in the field of lamp construction and also improvement of reactor geometry. A better knowledge of the aging of the lamps is required, as well as of the photochemical reactions of oxygen in the technologies applied.

Systems presently available are most promising for application on small scale or in areas of public water distribution which have no developed structure.

     

Comparison of Ozone and Hydroxyl Radical-Induced Oxidation of Chlorinated Hydrocarbons in Water

The efficiency of ozonation and advanced oxidation processes such as ozone/UV, ozone/H₂O₂ and H₂O₂/UV was assessed for chlorinated hydrocarbons using a closed batch-type system. 1,1-Dichloropropene (DCPE), trichloroethylene (TCE), 1-chloropentane (CPA), and 1,2-dichloroethane (DCA) were used as model compounds.

The direct reaction between substrates and ozone predominated at lower pH, which resulted in the efficient oxidation of the olefin, DCPE. At higher pH, ozonation resulted in more efficient oxidation of the chlorinated alkanes, with a corresponding decrease in the efficiency of DCPE oxidation. Consistent results were observed for ozone/H₂O₂ and ozone/UV treatment. Due to slow UV-induced decomposition of H₂O₂, the process using H₂O₂/UV (254 nm) resulted in very slow oxidation of all four compounds.

The total ozone requirement to achieve a given degree of elimination (to 37% of the original concentration), δ0.37, was used to assess the combined effects of the direct and indirect reactions for different types of waters.     

Reactivity Studies In The Ozonolysis Of Pollutants Using A Perforated Spinning Disc Reactor To Enhance Mass Transfer

A perforated spinning disc ozone contactor is described with reference to its use as an absorber with simultaneous chemical reaction.

Greatly enhanced mass transfer coefficients k_L are measured whilst simultaneously maintaining low ozone loss. Comparisons of k_L and volumetric coefficient, k_L a values, are made with more conventional packed or bubble columns.

Acetic acid, 2-propanol and 4-nitrophenol, representing a wide reactivity range, are used to elucidate the applicability of rotating contactors in effluent treatment. It has been possible to study the effects of surface activity on mass transfer with subsequent reaction and to generate design data for the next generation of rotating contactors.     

Biological Filtration for Ozone and Chlorine DBP Removal

This paper presents results from a water treatment pilot testing program in Winnipeg, Canada (pop. 650,000) which evaluated a DAF/ozone/deep bed filtration process. As part of the testing program, biological filtration using GAC and anthracite media was assessed for the removal of ozone DBPs and background chlorine DBPs (due to upstream chlorination of the source water). The results were used to evaluate the effectiveness of biological filtration for DBP removal.

High filtration rates were tested in this study. The 2.1m deep filters were run at a hydraulic loading rate (HLR) of 35 m/h with an empty bed contact time (EBCT) of only 3.6 minutes.

The important findings of this work are

?The high-rate biologically active carbon (BAC) filters met the objective of controlling ozone DBPs. These results confirm that high rate, low EBCT filters can provide significant biodegradation. Anthracite biofilters provided significantly less removal of ozone DBPs.

?The high rate BAC filters showed significant reduction of background HAAs. BAC reduced the background HAAs to below the long-term target of 30 μg/L. Anthracite biofilters did not exhibit HAA removal.

?Biological filtration with either media was ineffective for background THM removal. The long-term target of 40 μg/L could not be achieved without GAC adsorption.     

Comparative Efficiency Of Three Systems (O3, O3/H2O2, and O3/TiO2) For The Oxidation Of Natural Organic Matter In Water

CATAZONE is a new process of heterogeneous catalytic ozonation in which water is ozonated in the presence of a solid catalyst composed of titanium dioxide. The efficiency of this O₃/TiO₂ system has been compared to the two well-known oxidant systems: ozone alone and ozone combined with hydrogen peroxide.

This comparison was undertaken on three models of natural organic compounds : an aquatic fulvic acid, a protein and a disaccharide. The first results showed the following order of relative efficiency: O₃/TiO₂ > O₃/H₂O₂ > O₃ as far as Total Organic Carbon (TOC) removal was concerned.     

CHLORINATION KINETICS OF Nb2O5

The reaction of single sintered pellets of α-Nb₂O₅ with chlorine and carbon monoxide was studied in the temperature range from 773 K to 1073 K using a thermogravimetric apparatus. The rate controlling step of the reaction was determined from experiments carried out at variable gas flow rates, gas composition, surface geometry, pellet porosity and temperature. The vapor phase transport reaction can be written as:

Nb₂O₅(s) + 3Cl₂ (g) + 3CO(g) = 2NbOCl₃ (g) + 3CO₂(g).

Up to 60% conversion, the amount of volatilized product was found to be directly proportional to the time of reaction. The external surface area of the pellets remains unchanged up to this stage while the intergranular morphology changes.

These results were compared with reaction rates of commercial pyrochlore concentrate in order to establish the fundamental reaction stages of the process of extraction of Nb₂O₅ from pyrochlore.     

A RELATIONSHIP BETWEEN CHEMICAL STRUCTURE AND THE CRITICAL TEMPERATURE

Six distillation column models have been used in studies of the usefulness of the Inverse Nyquist Array (INA) method for design of dual composition control for distillation. Five of the column models are experimental, one describing an industrial column, the others four pilot plants. One column model is obtained by modeling from first principles.

The control strategies investigated and compared are multiloop SISO, 2-way decoupling and l-way decoupling. The control variables are the standard ones, i.e. reflux flow and boilup.

In most of the cases INA has been found to be a useful tool for design of the loops and for comparison of the different control approaches. INA has also been found to be useful for simultaneous tuning of the decouplers and the feedback controllers.

For 2-way decoupling the criterion to minimize interaction at the critical frequency for each primary feedback loop has been found useful in most, but not all, cases. The scheme can be designed by pure gains in the decouplers and there is no reason to introduce dynamics into the decouplers—the systems studied are already sufficiently rich in dynamics.

INA has been found to be a suitable vehicle for the choice between the two possible l-way decoupling schemes.

With the design approach taken, l-way decoupling has been found to provide considerably better control quality than 2-way decoupling in two of the six systems, the differences in control quality being small in the other cases.

The effect of model mismatching on the results, caused e.g. by process nonlinearities, is discussed and simple rules to decrease the parameter sensitivity for 2-way decoupling schemes are given. When model mismatching is considered, the advantage of l-way decoupling over 2-way decoupling seems to increase.

One deficiency of the INA design as used in this paper is that it does not single out the design which is to be preferred on the grounds of robustness.     

Effects Of Ozone As A Biocide In An Experimental Cooling Water System

Experimental work on a laboratory recirculating apparatus, for the simulation of a cooling water system has yielded information on the effectiveness of ozone as a biocide for biofouling control. Biofilms were developed within glass tubes of the simulated cooling water system using filtered mainswater and Pseudomonas fluorescens as the test bacteria. A summary of the results obtained is presented and an interpretation of these results relating to the full-scale application of ozone is provided.

Ozonated water was produced using a contact system specifically designed for these tests by Ozotech Ltd. Ozone residual concentrations in the order of 0.1 mg/L were found to be capable of removing 80-99% of the biofilm in single applications. However, effectiveness of ozone was dependent on morphology, thickness and age of the biofilms. Intermittent application of ozone, using residual concentrations < 0.1 mg/L, was found to be capable of weakening the biofilm, but a minimum period of 3-h was required for effective control.

The fluid velocity was found to affect the rate and amount of biofilm removed. The effects of fluid velocities in the range 0.5-2.5 m/sec were examined. In general, the higher the velocity the greater the initial rate of removal and the percentage of the biofilm removed; this suggested that ozone action was mass transfer dependent.

The effect of ozone on bacterial cell structure was investigated using scanning electron microscopy techniques. Changes in cell structure were revealed after contact with ozone and residuals above 0.4 mg/L were required for 100% kill of bacterial suspensions.

In conclusion, the effectiveness of ozone for full-scale application will vary depending on the morphology of the biofilm, the velocity of the fluid and the ozone dose applied. An ozone dosing regime for commercial application is suggested.     

Effect of Preozonation on Flux and Water Quality in Ozonation-Ultrafiltration Hybrid System for Water Treatment

The effect of ozonation on membrane flux and water quality was investigated in an ozonation ultrafiltration (UF) hybrid system. Crossflow UF was performed in total recycle mode to study the effect of ozonation on membrane fouling and disinfection by-product formation potentials of organics. Total organic carbon (TOC), UV absorbance at 254 ran (UV254) and trihalomethane formation potential (THMFP) were measured as water quality parameters.

The effect of ozonation on membrane flux was found to be largely dependent on raw water quality as well as ozone dose. In case of upstream water (A), preozonation achieved significant flux enhancement regardless of ozone dose. Whereas, for the downstream water (B), the steady state flux was increased or decreased depending on ozone dose.

The analysis based on the resistance-in-series model provided the mechanistic interpretation on the membrane flux variation. Ozonation in an ozone-ultrafiltration system always brought about a decrease in cake resistance (R_c) and an increase in fouling resistance (Rf). Based on the measurement of particle size distribution and zeta potential, the reduction in cake resistance through ozonation was attributed to an increase in particle size due to “ozone-induced particle destabilization”. However, the increase in the fouling resistance seems to be caused partly by the microbial characteristics of raw water.

Although there was little effect on TOC, ozone-UF treatment could get much higher removal of UV 254, THMFP (lday) and THMPF/TOC ratio than UF treatment alone.     

Economics of Treating Waste Gases from an Air Stripping Tower Using Photochemically Generated Ozone

Air stripping towers have been recommended for the removal of volatile organic compounds (VOCs) in drinking water supply and industrial waste treatment systems. This technique removes VOCs economically in the liquid phase. It can, however, create adverse secondary environmental impacts by removing VOCs from the water and discharging them to the air.

A commonly proposed method for controlling .VOC emissions is filtration of the off-gas through adsorption of the stripped organics in the off-gas by granular activated carbon. The high incremental cost of this alternative has produced an interest in alternative control technologies.

One alternative currently available is based on short wavelength ultraviolet (UV) radiation. This technique combines the effects of ozone generation, free radical formation and photolysis of the contaminants to effectively control the VOC emissions. This technique is known as Advanced Photo Oxidation (APO)^R.

The cost for APO is $0.27/m³ for a 3.8 m³/hr contaminated water system. A system of this size is adequate for a groundwater decontamination project where a moderate length of time is available for restoration of the site. The cost of a conventional air stripping tower with Granular Activated Carbon (GAC) adsorption emissions control in this size range would be $0.40 to $0.45/m³ (J.M. Montgomery, 1986).

Additional testing will be required to fully develop design guidelines for different contaminants and larger systems. Another area for additional technical documentation is the application of this technique to the liquid phase oxidation of VOCs.     

The Basic Clinical Applications of Ozone Therapy

Medical ozone is a mixture of ozone and oxygen, prepared via silent electrical discharge, within a concentration range of 0.05 volume % O₃ to max. 5.0 volume % O₃.

In order to exclude its toxic effect on the pulmonary epithelium, the medical ozone/oxygen mixture is administered so that exposure of the respiratory tract is avoided at all times, i.e., without the disturbing effects of its odor.     

Bromate Surveys in French Drinking Waterworks

Two bromate surveys were made recently in order to evaluate the frequency of bromate appearance in drinking waters issued from waterworks including one or two ozonation steps. The First survey was carried out on 47 waterworks. Two sampling campaigns were analyzed in cool and warm seasons. The objective of the second survey was to follow, during 4 to 10 months, at 12 selected waterworks.

The aim of this paper is to present the data obtained and to try to model for some waterworks the bromate formation by means of some important parameters (Br, O₃/DOC, T° and pH) of water to ozonate.

The main conclusion is that the bromate presence in distributed drinking waters is a reality for waterworks using ozonation steps, especially in warm period of the year. In the case of some waterworks, disinfection by sodium hypochlorite increased bromate levels in distributed water.

As shown by others on a laboratory-scale level, a multi-linear regression allows us the prediction of the bromate formation from some determining parameters, for some waterworks. However, the poor values of the linear regression lead us to have some doubts about its universal application in the real situation of an operating waterworks. A better evaluation of “C.t” will be required in the future in order to get a better prediction by the use of multi linear regression.     

Review of Operating Experience Of Ozone Systems In Municipal Plants In The United States

The treatment chemical ozone has now been successfully used in the United States in municipal water and wastewater plants for many years. To insure continuous, successful operations of these applications, operating obstacles had to be dealt with and overcome.

In this paper, examples of field operating problems and their solutions are described. The experiences at specific municipal water and wastewater installations are reviewed in detail. Discussed for each example are : the background and effects of the problem, the problem-solving process, and the eventual resolution of the problem. The examples include simple unit operations to entire processes.

By observing the ozone installation's operation several years after start-up, the design of future ozone systems can be improved and operating problems minimized.