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.     

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.     

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.     

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.     

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.     

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     

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     

The Oxidation of Manganese and Disinfection By Ozonation in Water Purification Processing

The surface water of a river has been used as the raw water by the Waterworks Bureau of Osaka City. At present, the manganese contained in the raw water is oxidized by breakpoint chlorination and all oxides are removed by coagulation, sedimentation followed by rapid sand filtration, with chlorine being used as the final disinfectant.

Prechlorination was not conducted in the ongoing pilotplant experiment of an advanced water purification process with ozone and granular activated carbon. It is necessary, therefore, to oxidize manganese by the oxidative effect of ozone instead of prechlorination.

It is important for the treatment of manganese to adjust the ozone dosage because manganese is oxidized up to the soluble septavalent state by the surplus ozone. Since ozone does not continue to exist for very long in water, though its disinfecting power is high, final disinfection by chlorine is required.     

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.     

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.

     

Water Disinfection: A Relationship Between Ozone and Aldehyde Production

In the water potabilization plant of Turin city (Italy), the oxidation process is carried out with ozone. Due to its well-known insufficient performance, it is necessary to add alternative oxidants (hypochlorite ion and chlorine dioxide). In this paper, we discuss the formation of linear carbonyl groups during surface water treatment in Turin.

The results obtained in the field confirm the synthesis of some aliphatic carbonyl compounds of low molecular weight. This phenomenon happens preeminently during the ozone disinfection process and, secondarily, during the other disinfection processes.

Experimental results show that, in this last event, chlorine reacts with organic substances, and in a second moment, after organics consumption, if chlorine is still in a sufficient concentration, oxidizing them.     

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.     

Interactions Between Ozone,Halogens and Organic Compounds

During drinking-water treatment, ozone used as a preoxidant and chlorine required for final disinfection, lead to competing chemical reactions, in the case of raw water containing both organic compounds and inorganic salts (such as bromides and ammonia).

The study of the interactions between those reactants has been made according to the following main topics :

As for THM formation, experiments conducted on simple organic compounds or on natural fulvic acids show important decreases in THM or TCAA formation after ozonation. It may be noticed, however, that the ozonation of surface waters may induce the formation of haloform precursors, usually with a low level of reactivity.

In water supplies containing bromide ions, oxidation of the latter through hypobromous acid may take place during the ozonation stage. Failing preozonation treatment, hypobromous acid is generated very rapidly during chlorination, thus inducing the formation of chloro- brominated organic compounds.

During the ozonation of fulvic acid solutions, the presence of small amounts of bicarbonate was found to improve precursor removal significantly.

It can be concluded that the partial analogy of the action of ozone or chlorine on aromatic structures, whether simple or complex (such as humic and fulvic acids), seems to indicate that the consequence of preozonation is the destruction, at least in part, of the most reactive sites for THM production, thus leading to a decrease of the volatile organochlorinated compounds formed during the post-chlorination. However, some ozonation products of natural waters are THM precursors, though of low reactivity. Then, in the presence of bromide ions, the formation of volatile organobrominated compounds may be observed during ozonation.     

New Pilot Plant Studies at the Budapest Waterworks

The quality of water provided by the Budapest Waterworks should comply with the standards prescribed by the European Community. According to these provisions, on one of the major water-producing regions (Csepel Island), rows of wells of 60,000 m³/day yield have been closed recently, and in the immediate future further plants would have been closed because of the high iron and manganese content of the water.

The raw water obtained from 100 different wells will be purified by a water treatment plant of 150,000 m³/day capacity. Considering the high iron content (0.05–0.15 mg/L) and manganese content (0.05–0.2 mg/L), the raw water fails to comply with the requirements of the potable water standard.

Since 1990, over a period of three years, we conducted water purification experiments in several stages. In these, three methods of oxidizing as well as single and double layer open rapid filters were applied to oxidize the manganese (and, to a lesser extent, the water) present in dissolved form, resp., to destroy various living organisms.

In the course of the experiments, it became clear that the chlorine and chlorine + air methods are efficient in case of a small quantity of iron to be oxidized and only 20–25% of the dissolved manganese content could be oxidized.

Neither of the two methods could ensure firm management of microbiological and bacteriological characteristics. The best results were obtained by ozone oxidation, in which case the chemical oxidizing process was almost fully completed and even the chlorine-resistant living organisms could be destroyed.

On the basis of the experiments carried out, the investment program of the water treatment plant was worked out and the conditions of an international tender were compiled whose winner will be commissioned to build up the water works in the time period 1993–1996. One of the main steps of the proposed technology is the ozone treatment.     

Hydroxyl Radical Oxidation Processes For The Removal Of Triazine From Natural Water

The purpose of this study was to point out processes that can provide triazine oxidation via hydroxyl radical production in a water treatment line. We focus our attention on:

- oxido-flocculation, using Fe²⁺, H₂O₂

- inter-oxidation, using O₃, H₂O₂ and eventually an heterogeneous catalyst.

- disinfection, using UV, O₃ and H₂O₂ combinations.

Results show that triazines can be removed by all these processes with different efficiencies. At full scale, the O₃/H₂O₂ process presents the best performances from an economical and technical point of view.     

Ozone Treatment in Cooling Water Systems

Ozone treatment for preventing the biofouling in cooling water systems is investigated.

In the fresh water system, the separating effect of the ozonated water on the microorganisms such as the sphaerotilus and the zoogloea which adhere to the piping and form the slime is recognized. When the ozonated water is supplied intermittently to the piping without stopping the flow of the cooling water, a constant volume of cooling water can be maintained. At the velocity of 1 m/sec, the amount of metal corrosion produced by the ozonated water is reduced on the mild steel, increased on the copper and does not change on the cast iron, when compared with that produced by the water containing no ozone.

In the seawater system, since many substances are oxidized by the ozone, the same treatment as that in the fresh water system cannot be applied. However, if the seawater in the cooling system can be replaced with ozone-containing air intermittently once a week, the adhesion of organisms such as barnacles and mussels to the piping can be prevented without having a bad influence on the other living oceanic organisms.     

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.