1st International Symposium in O3 Ozone Applications
O3 Ozone Water Treatments and Industrial Applications
October 31st to November 3rd 1990
________________________________________ |
The scope and organization of International O3 Ozone Association (IOA).
Naef H.R. - International Ozone Association, Switzerland.
System of water treatment with O3 ozone for hemodialysis.
The aim of this work is to determine the effectiveness of ozone in the sterilization of deionized water for the treatment of hemodialysis (artificial kidney) and its incidence in the infections of treated patients.
A closed system of water ozonization was designed and built to guarantee the pressure demanded of the hemodialyzers, by using a contact column which works as a balance tank under pressure, by means of a decompression valve, as well as a system of electrodes (magnetic) to control the water level. In the treatment, water receives an ozone dose, which guarantees a high microbiological quality, free from pathogenic germs, and suitable for the treatment of hemodialysis.
The ozone disinfection, together with deionization with exchange resins, avoid the acquisition of equipments of reverse osmosis for the treatment of water, which are very expensive in the international market and need a constant supply of membranes and other expensive parts.
________________________________________ |
Pilot plant pre-ozonation of a model surface water (II).
The use of ozone in the treatment of water for human consumption is very advantageous, mainly in waters which present a specific charge of organic compounds in which the addition of chlorine causes the formation of trihalomethanes (THM) and other organo-chlorinated compounds of high toxicity. In this work, some modifications in the pre-ozonation step of a model surface water were performed, with an aim of obtaining a more effective removal of THM precursors.
As a result of this work, the THM content in the drinking water was reduced below the established standards, and the elimination of manganese and iron were also achieved, which allowed the obtention of suitable values of color and turbidity, and in general, a water which fulfills all quality regulations.
Together with this, a comparison with the pre-clorination was performed, with evident advantages for pre-ozonation.
________________________________________ |
Application of pre- and post-ozonation in the treatment of surface water.
The oxidizing and disinfecting properties of ozone allow its increasing use in water potabilization. The superiority of this agent over chlorine has been demonstrated, because it does not form highly-toxic organo-chlorinated compounds.
In ozone water potabilization systems, a plan which includes pre-ozonation as a primary treatment, followed by coagulation, sedimentation and pouring off, and post-ozonization, placing it before and/or after sand filtration, was designed.
The development of this (O3 ozone) process at laboratory scale has the aim of obtaining results similar to those obtained by activated carbon filtration, which is very expensive. The comparison was done on the basis of the THM analyses in every step of the technological scheme.
________________________________________ |
The intensification methods for the processes of natural and waste water O3 ozonation.
Goncharuk V.V.
A.V. Dumansky Institute of Colloid and Water Chemistry of the Ukrainian SSR
Academy of Sciences, Kiev, USSR.
Ozone is most perspective reagent in both potable and waste water purification.
Even now it is quite evident that ozone application is effective method to render harmless to toxic admixtures in waste and potable water treatment.
We pay special attention to the use of ozone in potable water supply technology which recently became exclusively sharp due to the increased content of organic substances in water basins used for potable water supply.
Traditional chlorination of water leads to the formation of toxic chlororganic compounds.
Ozone application for deep water purification from hardly oxidized organic substances demands high consumption of ozone and even in this case, the products of partial oxidation may be not less toxic than initial compounds are formed. The intensification of the ozonation processes may be carried by the use of catalysts of ozone decomposition. In combination with photoradiation, i.e. by performing a photocatalytic reaction.
Here, we need special selection of photosensitive catalysts. The works concerning the photocatalytic water ozonation are in small number but it is the approach that leads to a considerable water purification rate and depth increase, specially when purifying water from hardly-oxidized compounds such as pesticides in agriculture all over the world go into ground water and open basins, causing the death of water inhabitants.
The kinetics of deep decomposition of nitrogen-bearing heterocyclic compounds (pesticide preparations) by ozone in combination with various physico-chemical actions has been investigated. On the basis of obtained data, photo-catalytic, liquid-phase technology for waste water purification from organic substances was developed.
The presence of a photocatalyst in the reaction zone permits to increase the degree of the ozone application and the depth of waste water purification.
________________________________________ |
Chemosorption of O3 ozone by wastewaters in co-current contact apparatus.
Preis S.
Tallinn Technical University, USSR.
This paper deals with ozonation of wastewaters containing organic compounds resistant to oxidation. Ozone is hard to dissolve, so the main resistance to mass transfer is concentrated on the liquid phase.
At the same time, the ozonation kinetics of many types of organic compounds in water are first order with respect to ozone. Therefore, the choice of the contact apparatus has to be based on the following conditions allowing the process to be carried out with a high efficiency: intensive turbulization of the liquid phase to achieve a fast saturation of water with ozone, and keeping the inter-phase conditions close to equilibrium during the whole process time.
A contact apparatus consisting of two coaxial tubes is proposed. In the inner tube, down-flow takes place, in the annulus up-flow. In the head of the inner tube the wire-net-plates are transversally installed for purpose of turbulization of the gas-liquid flow. The hydrodynamics and mass transfer characteristics of the apparatus have been determined. Mathematic description of the process has set up on the basis of a cell-model with a reverse stirring flow.
The examination of model adequancy has been conducted in the experiment plant with nitrobenzene and oxalic acid solutions, and with original wastewater of aniline-dye production. The computer aided calculation results are at variance with experimental ones within the range of 30 - 40 %.
The application of the proposed apparatus will make it possible to reach 90 - 98 % absorption of ozone.
________________________________________ |
By products from the combination of O3 ozone and chlorine or chloramines for the treatment of drinking water.
Glaze W.H., Weinberg H. and Cavanagh J.
Department of Enviromental Sciences and Engineering
University of North Carolina, USA.
The combination of pre-ozonation followed by conventional treatment with post-chlorination or post-chloramination is gaining credibility for the treatment of drinking water in the United States of America. This project, sponsored by the American Water Works Association Research Foundation and a consumption of six US and Canadian utilities, seeks to investigate the nature of by-products formed by the reaction of ozone and chlorine, or ozone and chloramines, with organic and inorganic substances in natural waters.
The research includes two major phases. One is a laboratory-scale study of selected natural waters in which ozone by-products are being searched for, and new analytical methods are being developed and optimized.
The research is currently focusing on the formation of aldehydes, brominated organics and inorganics and epoxides, which are by-products of potential health concern. The second phase of the project is a survey of water utilities. In the US and other analytical methods to determine the levels of ozone and chlorine (or chloramine) by-products actually produced under treatment conditions.
________________________________________ |
Advanced Oxidation processes for the treatment of drinking water, ground water and industrial waste water.
Glaze W.H., and J.W. Kang
Department of Enviromental Sciences and Engineering
University of North Carolina, USA.
Advanced oxidation processes (AOPS) have been defined as ambient temperature processes which involve the generation of highly reactive oxyradicals.
Specially these processes show promise for the destruction of hazardous organic substances in ground water, industrial waste waters, and in drinking water.
Several types of AOPS are being evaluated: ozone with hydrogen peroxide (03-H202) ozone with ultraviolet radiation (O3-UV) hydrogen peroxide with ultraviolet radiation (H202 -UV), and semiconductor assisted photocatalysis. Kinetic models for these processes are being developed based on known chemical and photochemical principles.
The models take into account, measured effects of radical scavengers such as bicarbonate dose, ratios of the oxidants or UV intensity and pH. Also of interest are the products formed by AOP oxidation of organics. TCE, PCE and DBCP appear to be decomposed to inorganic chloride (and bromide) and only trace inorganic by-products are detected.
The structures of some of these by-products suggest interesting chemical pathways for organic halogen radical intermediates. Oxidation of aromatic compounds such as nitrobenzene yields more stable by-products such as organic acids.
________________________________________ |
Mutagenic activity of water samples submitted to different disinfection treatments.
Some samples of surface water were taken and submitted to ozonation and chlorination processes. Each sample was divided into two fractions, whose pH was ajusted to 2 and 7 respectively. Each fraction was concentrated using XAD resin columns; the samples were dissolved with dietilether and cyclohexane, dried in a vacuum stove to 50 oC and stored in cold, during less than 7 days until they were used.
The Salmonella typhimurium strains used were TA 98 and TA 100 with and without metabolic activation; 2 concentrations were tested (100 and 200 L/PL). The results obtained are discussed.
________________________________________ |
An assay of mutagenicity in products of chlorination and ozonolysis of humic substances and other patterns of reference.
A sample of terrestrial fulvic acid, as well as, several model compounds (aminoacids, carbohydrates, phenols, etc), were submitted to treatments with chlorine and/or ozone. The reaction products were evaluated using the Anies test. The strains of Salmonella typhimurium employed were TA 98 and TA 100, with and without metabolic activation; three concentrations of products (100, 50 and 10 L/PL) were tested.
As a result, a positive response was obtained in some samples, the chlorinated ones presented a great toxicity to the highest concentration and a greater mutagenic response to the minor concentration.
________________________________________ |
Automated system for the treatment of water with O3 ozone.
Disinfection of water with ozone is guaranteed when water acquires a certain concentration of dissolved ozone, capable of eliminating pathogenic microorganisms.
This may be achieved by countercurrent mixing of ozonized air with the water in a contact column, or by means of an ejector. In such a way that it allows a good transfer of ozone from the air to the liquid.
The use of ozone in water disinfection for breeding of animals free from pathogenic germs, has as main feature that the work of the system should be guaranteed.
Otherwise, the losses due to contamination of special animals are enormous. A system of automated control was designed to allow the inter-communication of two ozone generators, one with a contact column) and the other one with an ejector, which monitors the detection of ozone concentration in the water which enters the storage tank, as well as the time necessary for the decomposition of residual ozone in the stored water.
________________________________________ |
Swimming-pool water treatment with O3 ozone.
This work consists on the design, construction, assembling and evaluation of an ozonation system for pool water, for the first time in Cuba. It is made up by an ozone generator and a gas-liquid contact system.
A computing program in Pascal language was used to develop the design of the ejector, according to the necessary conditions for the installation (flow of water to be treated, diameter of the pipes). The pool has a volume of 60 m3 and the water receives the ozone treatment by recirculation.
The results show the advantages of the treatment and the convenience to spread it throughout the country.
________________________________________ |
________________________________________ |
Decoloration of cotton tissues with O3 ozone.
It has been demonstrated that ozone is a very effective decolorizing agent, due to its high oxidating power and the great selectivity in its reaction with double bonds of unsaturated compounds.
Cotton is a material mainly formed by cellulose and lignin, the latter in addition to giving a slight dark color to the fiber, also protects it again the attack of microorganisms.
That is why it was made a decoloration process which allows, taking into account the contact time, ozone concentration, reactor used and appropriate concentrations of the reagents to be used, the ozone reaction with the lignin compounds, without affecting the structure of cellulose or eliminating the natural protection of the fiber against the attack of microorganisms.
The tables show the bleaching degree obtained in each case, in relation to the extent of ozone reaction with the fiber.
________________________________________ |
The use of O3 ozone for the decolorization of paper mill effluents.
Boyden B.H.
New South Wales University, Australia.
Highly colored effluent (1,200 to 25,000 color units as per Standard Methods test 204 B) from the chlorine bleach plant of kraft mill pulping Southern pine was treated with ozone for removal of color.
Wash waters from the first chlorination (add) and caustic wash sequences, comprising 15 percent of total mill effluent flow, were responsible for 93 percent of total mill effluent color. Color in these types of effluents can be attributed to the presence of conjugated group in solubilized lignin fragments. These fragments are often so large as to be non-biodegradable in conventional oxidation ponds.
Dialysis of the acid wash revealed that 85 percent of this stream"s color was due to compounds less than 6,000 molecular weight. Moreover, in the caustic wash, 55 % of this stream's color was due to lignin fragments less than 6,000 molecular weight and 28 percent of the color from fragments greater than 25,000 molecular weight.
Ozonation of the acid extract was shown to be equally effective for removal of color at pH ranging from 2 through 9.
However, ozonation of the caustic wash was most effective at pH 2. Ozonation of these two effluents was also conducted in synergism with 10 mg/L of hydrogen peroxide and 6 W/L of UV (at 254 nm).
Little or no increase in ozone effectiveness (for color removal) was noted. Lower ozone gas concentrations of around 5 mg/L were shown to be more effective at removing color than concentrations exceeding 15 mg/L. CDOCs (D Color decrease per mg/L of ozone consumed) of between 90 and 40 were measured utilizing ozone gas concentration of 5 mg/L with an ozone gas concentration of 20 mg/L, CDOCs were between 40 and 5. Wash waters reduced in color via ozonation were shown to increase in color when exposed to a biological oxidative environment.
This was particulary acute in the case of the caustic wash, which increased in color in the biological reactor from 4,000 to 7,500 c.u. in a period of about 12 days. Post ozonation color levels were once again resumed after 20 days.
________________________________________ |
Source: Ozone Research Center
|