#oxidizing agents

Rank these species by their ability to act as an oxidizing agent.

Mg2+

Zn2+

Cu+

F2

How Do Ozonators Keep Your Food Fresh for a Prolonged Stretch of Time?

Introduction

Ozone has become one of the most popular choices of disinfectant for treating water systems, removing odors, preserving the freshness of food, and purifying the air. Its use in preserving food can be traced back to the 1900s when it was used as a food preservative of meat and fruits in cold storage. Studies found that the use of ozone inhibits the growth of molds and yeast. The food industry is always faced with the challenge of keeping food fresh for extended periods of time, while retaining its nutritional value is not lost.

Preserving the freshness of food using ozone

Ozone is a triatomic form of gas, comprising three molecules of oxygen. It is available on site for very short lengths of time and hence the use of ozonators, and ozone generators were manufactured. Its this highly effective oxidation capabilities that makes ozone an attractive choice in a wide variety of treatments. Bacteria, viruses, and other harmful pathogens do not stand a chance against ozone’s powerful oxidation process that breaks down the cell walls and completely destroys it.

In today’s world, the need for hygiene and ensuring sanitation is greater than ever. With the increased awareness of chemical additives used in food today, the need to protect consumers is a top priority. Chlorine is traditionally used as a disinfectant; however, it was found that against high Ph levels, chlorine is not as effective and to make it more alarming, chlorine is also known to react to trihalomethanes, which are a group of chemicals formed when the disinfectants react to organic or inorganic matter. These are environmentally hazardous and have adverse effects on humans.

Hence the hunt is always to find the perfect answer to an economical solution that can be adapted to different food processes, while retaining long lasting freshness, kills pathogens and keeps disease at bay! Hence a good food rinsing and sanitizing system is important. This is a tall order and sounds impossible to deliver, but it has been found that ozone is a great choice because of its high oxidization capabilities, its short contact time with the pathogens found on fresh fruits or vegetables, does not leave behind any residue unlike its other alternatives in the market, and what’s more, ozone is found to be versatile and can be applied to heat sensitive foods. Further ozone is also considered economical to use and does not require any heavy maintenance.

In the food industry, ozone is used to treat both the food plant waste as well as in killing pathogens, thereby extending the shelf life. Using ozone generators or ozonators are a great way to keep your fridge interiors sanitized and fresh, which leads to a reduction of waste and also saves money. It has been found that companies that use an ozone injection system, which automatically turns off when the level is high, has brought a volume of savings through less spoilage of food and greater payback.

Development of ozone technology Food Processing improvement in Chennai

When people in general hear the word ozone, it is usually associated as a harmful air pollutant that is typically caused by the reaction of impurities with other chemicals in the presence of sunlight. These pollutants are emitted by vehicles, chemical plants, refineries, industrial boilers and chemical plants to name a few.

Inhaling ozone can lead to health issues. However, these are not the only things that ozone is famous for. Will you be amazed to hear that ozone has a lot of beneficial effects? Ozone consultancy has also been playing a positive role in the environment because of its oxidation process.

Some of the healthy uses of ozone includes its use as a food preservative in cold storage of meats, a water disinfectant in drinking water, and prevents molds in fruits that are in storage. Its oxidation process is known to effectively destroy viruses, bacteria and fungi and also because the latter have not been able to effectively resist the oxidation.

Today, this potently beneficial effect of ozone is now being considered as yet another effective disinfecting agent in the food and beverage industry. In order to better appreciate the oxidation process, let us briefly understand how ozone oxidizes in water. Ozone is typically created on location through from a generator using an electrical charge or through the use of oxygen.

This gas is then pumped into the water, which is used for spray, mist, or rinse. However, the ozone in the water does not remain there for a long period of time. On the contrary, it breaks down into regular oxygen within a matter of minutes.

Given its popularity as a disinfectant and diverse benefits, it is not surprising to know that ozone is also being considered as an alternative to chlorine sanitizers in the food industry as well as a food surface hygiene, reuse of waste water, food plant sanitation including a host of other solutions.

Read More: Food Safety Technology: A Potential Role for Ozone

Now that its potent effect in killing microbes is well known, it does away with the need for human resources to handle harsh chemicals for sanitation. When ozone converts to oxygen, it does not leave behind any residue on the contact surfaces.

As a result, water enriched with ozone can be directly sprayed on floors, walls, internal and external surfaces including tanks and pipes. It has been observed that by using ozone enriched water in food plants prevents the formation of biofilm. When used on fruits and vegetables, it is believed to increase the shelf life of the produce.

Ozone In Cooling Tower Water Management

The Use of ozone in Cooling Tower water management is becoming popular nowadays .Ozone has been in use in water treatment and has been very well established. This is because the use of ozone in water treatment is quite simple and non –complicated. Use of ozone In cooling Tower requires adequate knowledge especially with respect to ozone Chemistry viz a viz cooling Tower water Chemistry.

Ozone systems are designed to control scale formation, corrosion and organic growths. Simultaneously the system produces safe and non-toxic conditions within the Cooling Tower and the aerosol water passing from the system.

Description Of Operation.:

There are many manufacturing plants, power generating systems and air conditioning installations, which require efficient cooling. Frequently, this cooling is achieved by using re- circulating water systems.

The typical system consists of a basin or sump from which the pump circulates the water through pipes to the other components, which are normally one or more heat exchangers, and a cooling tower, in which the warmed water is sprayed into an air stream. Cooling is achieved by the evaporation of the circulating water.

The cooled water falls into the basin to complete the circuit and to obtain the most efficient utilization of water. Any make up water needed to replace water evaporated or bled from the system is added into the basin. The water evaporates as pure water, leaving behind – in the remainder of the water – any natural salts and impurities scrubbed from the cooling air stream.

Typical Cooling Tower & Operating Problems Within The Water Circuit:

Scale formation and or silt accumulation reduces the efficiency and performance of the cooling system, by restricting heat transfer and interfering with water flow. The evaporation of pure water at the cooling tower increases the natural salts in the circulating water.

As this process continues, the natural Calcium alkaline hardness in the water will pass its solubility limit and scale formation will take place. The higher temperature at the heat transfer surfaces increases the rate of scale formation on these surfaces, there by reducing the efficiency and operating capacity of the unit.

Often scale formation is accompanied by the trapping of airborne debris, removed from the cooling air by the scrubbing action of the water as it is spraying through the tower. Such inclusion of corrosion product debris or a combination of these materials, is often held more tightly together by organic growths. The accumulation of debris in the absence of scaling results in silt creation.

Existing Methods Of Treatment.:

It is necessary to bleed off in a controlled manner, some of the concentrated water, to limit scale forming and silting problems. In many cases the volume of bleed off needed to prevent scaling is excessive, and very precise control is required to achieve satisfactory results. This method is normally impractical. An extension of this method is the addition of acids to the circulating water.

Very precise application, missing and controls are needed to prevent severe damage to the system. There are also problems of safety arising from the need to store, handle and apply these acids. Target concentrations for either or a combination of the above may be calculated using the Langeliar Index approach.

But, as stated this technique is far from satisfactory because of the wide margins for error. These margins are further increased if there are variations in water composition. The above methods also impose uneconomic control requirements, especially in the higher output, smaller water capacity systems, which have come into use in recent times. Safer, less hazardous and more practical techniques are required.

Corrosion:

Corrosive attack on the metal surfaces reduces the life of the plant and requires repairs or complete replacement of the plant. Most waters are corrosive. These problems may be aggravated by absorption of acidic gases and other impurities from the cooling air. Many of the salts in solution in the water enhance corrosion, particularly Chlorides. Corrosion conditions may occur under scale, silt and / or organic growths. Corrosive product build up also interferes with heat transfer and water distribution. This may be amplified by inclusion of scale, silt, airborne material and or organic matter.

Read also:Air Treatment – COLD ROOM OZONATION A BOON TO THE INDUSTRY

Existing Methods Of Treatment.:

The control of Calcium Bicarbonate concentrations in the circulating water using the Langelier Index, as described by Dr. Wilfred L. Langelier, is an excellent method in theory. However, in practice it requires very precise controls to give the desired protection without causing scale formation. Attempts to widen are only partially successful and generally such methods have been superseded.

The use of various inhibitors such as Chromate, Zinc, Phosphates etc., have been successful, but the increasingly tighter controls on the discharge of toxic wastes into natural or piped disposal systems are limiting the use of these chemicals. The toxic water droplets or aerosols in the air exhausts from the tower have caused concern to health authorities. Pollution control regulations are increasingly preventing the use of these inhibitors. An improved and non-toxic corrosion protection method is clearly required.

Organic Growths.:

Organic contamination present in the water supply, and / or brought into the system by the flow of cooling air, provides the basis for very rapid growth of various forms of organic materials, such as slimes, algae etc. The conditions of temperature, aeration and sometimes, exposure to sunlight promote very vigorous growth.

Algae and slimes reduce heat transfer, interfere with water distribution and help bind more layers of scale and silt to adhere firmly to internal surfaces of the cooling system. This further aggravate heat transfer problems. Corrosion is frequently accelerated by the presence of organic matter.

Bacteria are another form of organic contamination. They rapidly multiply in the ideal growing conditions within the cooling water system. The presence of other organic materials within the system supplies the nutrient for the growth and multiplication of bacteria.

Many forms of bacteria are dangerous and in recent years, special attention has been drawn to the virulent power of some strains of Legionella bacteria, especially on the elderly and those not enjoying the best of health. It is widely recognized that many deaths caused by Legionella have been attributed to other causes, such as pneumonia – due to diagnostic limitations.

Bacteria passes into the exhaust air from the tower in the fine water droplets, known as aerosols. These drift and are sucked in by air conditioning fresh air intakes or are directly inhaled by people, thus providing a source for the infection. Bacteria also escape from the system in the bleed off water and in the aerosols created when the system is washed out or maintenance is taking place.

Existing Methods of Treatment.:

A wide range of chemicals, such as Chlorine, Chlorine Dioxide as well as a multitude of organic chemicals have on algae and slimes, but with dangerously haphazard results on bacteria. The dosage and control is often in the hands of plant staff and usually is far from satisfactory. There are problems in the storing and handling of toxic Chlorine containing compounds. Also the discharge, either directly or as aerosols, of water containing some of these chemicals, is prohibited.

There is an urgent need for a vastly improved control method, which is not only effective, particularly against Legionella, but also safe, non-toxic and non-polluting.

Ozone Method Of Corrosion Control.:

The OZONE system is a process for the control of scale formation, corrosion and organic growths of all types in re-circulating water systems, such as condenser cooling water systems, industrial cooling systems etc. The equipment to control the process is also specified.

Ozone has a further deposition inhibiting property, which is well documented. In part this relies on the destruction of organic binding matter such as slimes, algae etc., which in many systems hold together precipitated Calcium Carbonate with airborne dust etc., to form heat transfer reducing scales and deposits. Ozone breaks down all these organic impurities to harmless by- products. Thus, Ozone eliminates all organic binder, which would otherwise aggregate insoluble matter.

De-scaling of fouled systems.: The same properties generally result in the de-scaling of fouled systems, by destroying the binding matter, and thereby, releasing the inorganic deposits from the surfaces.

Corrosion Prevention.:

The properties of Ozone to passivate metal surfaces by means of a stabilized oxide layer on the metal surface is well documented. This effectively prevents corrosion and thus corrosion protection is far superior than using corrosion in controlling Calcium Carbonate.

This results in corrosion protection superior to that of the arithmetic addition of both methods.

The Ozone System Of Biocidal Treatment.:

Ozone destroys organic growths by breaking them down into simple by-products such as water and carbon dioxide with the release of oxygen. The removal of algae, slimes etc., is complete in the presence the specified level of ozone in the water system. Further, Ozone breaks down almost every organic contamination which could be expected to be found in a cooling system, removing the major source of sustenance for the growth, thereby having a twofold effect in growth control.

Control of organisms such as Legionella is significantly increased when ozone is supplied in correct quantities, so that only very low levels (if any) of infestation occur. The risks of exposure to Legionares disease in aerosol emissions from the cooling tower and the waste water from the cooling water system is considerably reduced.

Hazardous, scale preventing chemicals, corrosion inhibitors and organic growth retardant are not used in this process. Chemicals currently used in cooling systems such as Chromate, Zinc, Pentachlorophenols etc. are all highly toxic and their disposal into water courses or via public waste services is either forbidden or strictly limited. The presence of these materials in the aerosol form the tower is of considerable concern. The Ozone system produces no such dangerous toxic wastes.

Monitoring And Control Equipment.:

Adequate ozone treatment results in the creation of a residual oxidation capacity in the water, which can be sensed by an appropriate electrode and measured by a Redox monitor in millivolts (mV). It has been amply documented that the required level of Redox potential to achieve control of scale formation, corrosion and organic growths is between 700 and 900 mV.

The Redox meter gives a continues reading of the oxidation potential. It is fitted with an alarm in case of system malfunction or heavy external infestation.

Recognition Of Superior Treatment And Control.:

In countries like Australia where the controls on quality of cooling tower water are as strict as that of drinking water , local Government authorities have agreed to waive certain regulations in towers with ozone treatment. Some of these regulations are :

The cooling water system be completely chemically cleaned out every three months.

The placing of fresh air intakes at least 20 meters away from the cooling tower. (in the case of existing installations where the air intakes are less than 20 meters from the cooling tower, the necessary work must be undertaken to achieve this separation. This would normally be an extremely costly alteration).

They have recognized that the use of ozone could be a solution to many of the perpetual problems often faced by a cooling Tower operator. NASA has been one of the earliest organization to recognize this fact and have conducted lots of trials and published lot of papers on this Technology.

Today NASA have many of their cooling towers Ozonated. Prevention of scale, silt and corrosion deposits of the system, allows the efficiency of the Ozone sterilization process to be enhanced, by virtue of the more complete access that Ozone has to all the surfaces and contents of the water system on a continuing basis.

The measurement of conductivity is achieved using a modified ohmmeter with an adjustable set point. When the conductivity reaches the set point, the control system operates a purpose built solenoid valve to bleed off a determined volume of water from the cooling system. The water is automatically replaced with make up water, containing only the natural level of Calcium Bicarbonate.

On mixing with the concentrated water in the system, this results in the lowering of the calcium bicarbonate value in the circulating water. The bleed off water also removes suspended solids along with the circulating water .A dead band in the control action prevents overshoot and waste of water.

SUMMARY

The passivation of the metal surfaces by Ozone, plus the threshold raising effect of Ozone through micro flocculation and scale inhibition, results in a remarkably effective scale prevention, corrosion inhibition and organic contamination control. This treatment does not require any toxic chemicals or harmful products in the aerosol or waste water from the cooling water system.

Disinfection is a common disease management tool for aquaculture sector. It can be both a routine bio-security practice to prevent specific diseases or a routine sanitation process to reduce overall occurrence of diseases that may lower farm productivity. The nature and mode of disinfection greatly varies with the specific reason that leads to disinfection practices. The most commonly practiced approach is chemical treatment in specified doses and for sufficient retention periods to destroy pathogenic organisms that would otherwise access the water systems repetitively.

In aquaculture systems, the threat of cross contamination is prevalent between fauna in the same tank as well as between water holdings, both in fish and crustacean farming. In addition, use of disinfectants is not possible in open systems owing to environmental impacts of chemicals in natural waters and in case of seawater; there is risk of residual oxidant by-products due to chemical reactions with salts in water. Thus disinfectants can be applied safely and most conveniently only to hatcheries and incubation tanks.

Since most aquatic species are highly sensitive to toxic chemicals and the disposal of such waters threatens to contaminate natural water bodies, it is highly needed that a “safe” product be used for disinfection. The term “safe” implies to toxicity tolerance by farm as well as wild aquatic organisms. Thus only a few chemicals can truly adhere to the properties of ideal aquaculture disinfectants in real practice. Some disinfectants are effective against a large range of microorganisms: bacteria, viruses, fungi and parasites. In addition some chemicals are selective biocides to certain strains of exotic eutrophic microalgae. While some disinfectants can work on a short term before the microbes grow resistant to them. Thus the choice of disinfectant and methods of disinfection should be based on the spectrum and ease of application as well.

Requisites of an ideal Disinfectant are summarized herein:

-Should have a wide spectrum antimicrobial activity

-Should not be irritating to aquatic organisms or humans

-Should have minimal toxicity to non target organisms

-Should have high penetrability

-Should be active in presence of Pus and Necrotic Tissue

-Should be non-interfering with normal immunity of fishes

-Should be cost friendly

-Should be non corrosive and non staining

-Should be highly stable

-Should be biodegradable with nil/minimum bio-accumulation potential

Disinfectants can be classified based on their mode of activity as:

1.       Oxidizing Agents

2.       Reducing agents

3.       Detergents

Oxidizing Disinfectants can again be of two types:

a)      Those that oxidize without releasing oxygen, most common being Halogen bleachers and Potassium Permanganate and Peracetic Acid

b)      Those that oxidize by release of nascent oxygen i.e. Peroxides

They are mostly used to control phytoplankton, pathogens and bottom soil oxidants. Most oxidizing agents are irritant to skin and eyes in high concentrations and except for chlorine, most don’t have long bioaccumulation potential thus non contaminants to food.

Reducing agents consist of organic aldehydes like Formaldehyde and Glutaraldehyde that are popular general disinfectants used as germicide, fungicide or as preservatives in industries. Their main mode of action is by formation of covalent bonds and disruption of functional groups in cellular proteins. They are thus target specific and can be easily applied in selective removal of microbial contaminants. Aldehyde disinfectants are non-irritant, readily biodegradable and do not possess bioaccumulation risks.

Detergents or popularly referred to as Cationic detergents are Quaternary ammonium compounds (Benzalkonium Chloride) that are used I hatcheries to eradicate aquatic insect larvae and nematodes. They are active in disruption of cell membrane and destruction of cytoplasm and cell nuclear material. They are highly active against Gram negative bacteria. There are no known records of reactive products not degrading or chances of bioaccumulation in environment as of yet.

Irrespective of the mode of application and action most aquaculture disinfectants listed above seem to be highly effective in their respective treatment domain but choice of the same lies totally on the users end needs of disinfection and the type of pathogen to be controlled.

ChemEqual is a vast online chemical B2B marketplace and various grades and compositions of specific Aquaculture Disinfectants and Biocides can be searched here.

Oxidation: element that LOSES electrons and becomes more POSITIVE

Element being oxidized called reducing agent

Reduction: element that GAINS electrons and becomes more NEGATIVE

Element being reduced called oxidizing agent

Ox and Red happen at the same time.

*If you have common sense, then this shouldn't be confusing-- at all.

Example:

Cd(s) + NiO2(s) + 2H2O(l) -> Cd(OH)2(s) + Ni(OH)2(s)

What is being reduced and what is being oxidized?

1. H's and O's, compared to other elements, usually don't oxidize or reduce.

2. Single elements always have a 0 ox #.

Cd = 0

3. Try to find all of the compound/ element's charges.

NiO2 = +4

For this one, I use algebra. 

Since, in the original problem, it doesn't give you a charge and you have to find it yourself, (i.e NiO2-) you have to treat the TOTAL charge of THE WHOLE compound to be 0. Remember that O2 doesn't usually reduce/oxidize, which is why Ni = x.

O has charge of -2 and there are 2 O's in the compound, so -2*2=-4. 

Solve for x.

(Total charge of the whole compound) = charge of other elements + x

0 = -4 + x

x = +4

NiO2's charge is +4.

4. Disregard H2Os. Usually.

5. Repeat # 3 with ALL of the compounds.

Cd(OH)2 = +2

0 = +2 + -4 + x

Ni(OH)2 = +2

0 = +2 + -4 + x

6. Find the change in charges.

Cd started with 0 and ended with +2. Ni started with +4 and ended with +2.

Cd gained. Ni lost.

Cd= oxidized, reducing agent

Ni= reduced, oxidizing agent