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Ozone

Pacific Water Technology supplies a range of ozone generators for dissolution in water or gaseous applications for various sectors of industry. This also includes portable sanitation systems and also monitoring systems for detection of ozone in the atmosphere and also dissolved ozone in aqueous solutions. For larger systems we supply complete packages including oxygen concentrators to increase the efficiency of ozone generation. Below follows a list of applications in the Food Industry.

How Ozone Disinfects?

Ozone functions as both an oxidant and disinfectant in the treatment of drinking (potable) water and wastewater.  This is similar to chlorine.   Chlorine and Ozone, however, operate by different mechanisms when disinfecting water.  As a result, ozone and chlorine can act synergistically.

Ozone’s germicidal properties are associated with its high oxidation potential.  Disinfection by ozone is a direct result of bacterial cell wall disintegration, also known as lysis.  This mechanism is different than that by chlorine.  Although the exact chemical action of chlorine is not clear, it is believed that the chlorine residual in aqueous solution diffuses through the cell wall of the microorganisms and attacks the enzyme group which results in the destruction of the microorganism.

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Food and Beverage Industry Applications:

  • Ozone use in CIP
  • Ozone for surface sanitation
  • Ozone for seafood processing
  • Ozonated Ice
  • Ozone in fruit and vegetable processing
  • Listeria inactivation with ozone
  • reduction with ozone
  • Food Storage with ozone
  • Portable sanitation systems for wine barrel- , tank- and other POU sanitation applications.

The portable ozone cart systems incorporate a high concentration ozone/oxygen generation systems with on-board pump, compressor, and mass transfer system in a rugged, all-stainless steel package. Simply connect plant water in and get high concentration of ozonated water out with no loss of flow or pressure.

  • Bottling filling plants and ozone sanitation

OZONE IN WATER TREATMENT

Applications:

  • Ozone water treatment for drinking water
  • Ozone for reduction of iron and manganese

Ozone and waste water disinfection


OZONE IN COOLING WATER

The key to an effective cooling water treatment programme includes management of the interrelationship between corrosion, scale/deposit and biological activity (micro and macro). For this reason treatment programmes normally include Orthophosphates, polymers and free halogens. Ozone can complement an existing water treatment programme reducing chemical costs and inventory, and reacts synergistically with other halogen based oxidisers.

Ozone Advantages

  • A factor 10 to 100 times more germicidal than chlorine10
  • Reduces the use of chemicals
  • May reduce discharge liabilities
  • Destroys all types of microorganisms instantly
  • Less risk of microbes building resistance to ozone treatment.
  • Minimises condenser fouling
  • Decomposes organic waste by oxidation
  • Removes existing calcium carbonate scale by destroying the biomass glue bonding agent
  • Low maintenance costs
  • The most environmentally friendly oxidant
  • No persistent chemicals or disinfectants in bleed – ozone breaks down to oxygen
  • Reduces the corrosion rate of metals, including copper heat exchangers
  • Saves on energy costs by increasing the heat transfer efficiency of the chiller

 Ozone Reduces Costs in the Following Ways:

  • Reducing makeup water to the cooling tower by permitting more cycles between blowdowns
  • Reducing the cost of regular chemicals and less issues with waste water disposal.
  • Reducing power consumption by keeping the chiller heat transfer efficiency high through cleaner condenser tubes

 OZONE IN GROUND WATER REMEDIATION

Chemical oxidation uses chemicals called “oxidants” to help change harmful contaminants into less toxic ones. It is commonly described as “in situ” because it is conducted in place, without having to excavate soil or pump out groundwater for above ground clean-up.

In situ chemical oxidation, or “ISCO,” can be used to treat many types of contaminants like fuels, solvents and pesticides. ISCO is usually used to treat soil and groundwater contamination in the source area where contaminants were originally released. The source area may contain contaminants that have not yet dissolved into groundwater. Following ISCO, other clean-up methods, such as pump and treat or monitored natural attenuation, are often used to clean up the smaller amounts of contaminants left behind. There are a number of oxidising agents that can be used including ozone and hydrogen peroxide (or a mixture of both, or in the presence of a catalyst).

Ozone Advantages

  • Twelve times more soluble than oxygen in water
  • Moves easily through the soil
  • Produced on-site, no need for hazardous chemical transportation or storage
  • Most powerful oxidiser available
  • Complex organics break down to carbon dioxide or less toxic molecules
  • Breaks down to oxygen which increases DO levels

Contaminants Destroyed by Ozone

  • MTBE (methyl tertiary butyl ether)
  • BTEX (benzene, toluene, ethyl benzene, & xylenes)
  • Hydrocarbons
  • Diesel Fuel
  • TCE (trichloroethylene)
  • Pesticides
  • Chlorinated Solvents
  • VOCs (volatile organic compounds)
  • Aliphatic & Poly-aromatic Hydrocarbons

 OZONE & AQUACULTURE

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Ozone is increasingly used in aquaculture due to its numerous advantages over traditional water treatment methods. Supplementing or replacing an existing system, ozone implementation has the potential to boost the competitive advantage of your aquaculture application. Ozone oxidation can kill microorganisms, but requires maintaining a certain dissolved ozone concentration in the water for a given contact time.  Disinfecting efficiency depends upon the product of the ozone residual concentration and its contact time.  An ozone contact vessel provides the time necessary for the ozone residual to react with and inactivate pathogenic microorganisms.

 Disinfecting waters may require maintaining a residual ozone concentration of 0.1–2.0 mg/L in a plug-flow type contact vessel for periods of 1–30 min, depending upon the target microorganism (Wedemeyer,1996).

Ozone Advantages

  • Reduced Water Usage
  • Faster Growth Rates
  • Reduction of Waterborne Diseases
  • Higher Standard of Environmental Control
  • Supplements other Treatment Processes

Why Ozone Use is growing in Aquaculture?

  • It effectively removes organics, pesticides, discolouration, and nitrates.
  • Typically unconsumed ozone reverts back to oxygen, leaving no harmful residuals behind.
  • Ozone oxidizes long chain molecules, which are unaffected by bio filtration.
  • Ozone involves far lower risk of accidental pollution in comparison to other water treatment methods.
  • O3improves the effectiveness of biological and particulate filtration.

 


OZONE DISINFECTION

Ozone Disinfection / Ozone Contact Time Kinetics

Water is disinfected but never completely sterilized in the water treatment process. This disinfection is a two part process that includes:

Figure 1:
Simplified Diagram of a Pathogen Encapsulated by a Particulate

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Courtesy of Eric Karch and David Loftis

  • Removal of particulate matter by filtration. A rule of thumb is that high turbidity in the effluent is a potential health risk, because viruses and bacteria can hide within the rough texture of particulates. Therefore, removal of the particulates reduces the chance of pathogenic microorganisms in the effluent. (Refer to Figure 1)
  • Inactivation of pathogenic microorganisms by chlorine, chlorine dioxide, ozone, or other disinfectants: Contact time and kinetics are simply a measure of the inactivation due to time and concentration of the disinfectant. The USEPA has developed regulations for the minimum kill percentages (inactivation) necessary for public water to be considered potable. These regulations include a minimum disinfection of:
  • Three log (99.9%) for Giardia Lamblia cysts
  • Four log (99.99%) for enteric viruses

In “water treatment terms” 1 log inactivation is referred to as 1 credit inactivation. Different types of filtration are assigned certain removal credits. For example, conventional filtration is worth 2.5 credits for Giardia cysts. Since the EPA requires 3 log (credit) removal, an additional 0.5 credit inactivation from disinfection must be attained.

Varying degrees of disinfection can be attained by altering the type and concentration of disinfectant, as well as the time water is in contact with the disinfectant. The decision to use one type of disinfectant versus another will set the precedence for the remainder of the values needed to attain the proper disinfection. The time untreated water is exposed to the disinfectant and the concentration of that disinfectant are the main factors in the equation that will be discussed in the next section. [Notice that the units of contact time are (mg/l)(min).]


Relationship between Kill Efficiency and Contact Time

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Figure 2: Graphical Representation of Chick’s Law Edit Heading Taken from R.C. Hoen’s CE 4104 Spring Notes.

A relationship between kill efficiency and contact time, was developed by Harriet Chick while she was a Fellow in the Pasteur institute in Paris, France. The research yielded data supporting her relationship that is shown in Figure 2. (No) represents the initial number of organisms and N is the number of organisms at time t. As contact time between water and disinfectant increases, the ratio of No/N decreases as Chick’s Law predicts.

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Factors Affecting C*t Values

  • As pH increases the value of C*t also needs to be increased. This can be explained by examining the effects of pH on free chlorine. As the pH increases, more of the weak disinfectant (OCl-) exists than the strong disinfectant (HOCl-), thus increasing the C*t value. Refer to Table 1 below.
  • The greater log removal needed, the greater the C*t needs to be, as can be seen in Table 1.

Table 1: C*t for Removal of Giardia Cysts in Relation to Log Removal and pH

Log Removal

pHpH 6.5pH 7.0pH 7.5

1.0

46

54

65

79

1.5

69

82

98

119

2.0

91

109

130

158

2.5

114

136

163

198

Information from the Virginia Department of Health Waterworks Regulations

  • The strength of a disinfectant directly affects the C*t. For a weak disinfectant, the C*t will have to be higher than for a strong disinfectant. As Table 2 below shows, ozone is the strongest disinfectant, thus the C*t value required is less when compared to chlorine and chlorine dioxide.
  • Different organisms have different resistances to disinfectants. If an organism has a strong resistance to a certain disinfectant, the C*t will be higher than for an organism with a weaker resistance. Refer to Table 2 below.

Table 2: C*t Values for the 99% Inactivation at 5 Degrees Celsius of Organisms Using Various Disinfectants

Organism

Free Chlorine (pH 6-7)

Chlorine Dioxide (pH 6-7)

Ozone (pH 6-7)

Rotavirus

0.01-0.05

0.2-2.1

0.006-0.06

E.Coli

0.034-0.05

0.4-0.75

0.02

Giardia lamblia cysts

47-150

0.5-0.6

Crytosporidium parvum

7200*

79*

5-10*

 

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