The Ozone Hole

The Earth’s atmosphere is made up of many layers and ozone is a part of that atmosphere that protects the Earth from the effects of UV rays. Ozone is in the stratosphere layer of the atmosphere. The ozone in the stratosphere absorbs UV rays and other solar radiations. Strong UV rays and other radiations can cause skin cancer, cataracts, and even a suppressed immune system. The stratosphere, where the ozone molecules are located, is about 10-40kms (6-25miles) above the surface of the Earth.

Discovered by British scientists in 1985 Joesph Farman, Brian Gardiner, and Jonathan Shanklin of the British Antarctic Survey, the ozone hole is actually a reduction in concentrations of ozone high above the earth in the stratosphere. Over the past couple of decades, the ozone hole has steadily grown both in size and in the length of existence. Chloroflourobcarbons (CFCs), which are man-made chlorines, are responsible for the thinning of the ozone layer. The ozone layer thinning means there are larger quantities of harmful ultraviolet rays reaching the Earth’s surface. People around the world are starting to make a conscious effort to not use anything that will produce compounds that deplete the ozone layer.

Early Morning Ozone

Ground-level formation of ozone starts early in the morning, and as the day goes on the ozone generation increases, causing pollution. Performing everyday tasks from driving a car to mowing the lawn generates ozone. Volatile organic compounds and nitrogen oxides are the most significant contributors.

Traffic is the biggest contributor to pollution in the air. Continued traffic pollutions added to the earlier ones begins to form ozone as the UV rays intensify. During warm summer months, an inversion may develop and traps the pollutants close to the ground (400-500ft above sea level). Any wind will restrict the pollution dispersion. The UV rays from the sun cause a chemical reaction between the volatile organic compounds and nitrogen oxides to form ozone in the atmosphere. For maximum ozone concentration, temperatures in the 90s are required. The intensity of the UV rays impacts the levels of ozone. The more intense the UV rays, the higher the levels of ozone and the lower the intensity of the UV rays, the lower the levels of ozone. By the evening, most of the ozone that was formed during the day breaks down into other different compounds, and soon enough all of the ground-level ozone is essentially destroyed.

Ozone During Thunder Storms

Everyone has experienced the refreshing feeling after a thunderstorm. This freshness is associated with the formation of ozone. During thunderstorms, the lightning that is produced can conduct more than 25,000 volts. This high voltage causes oxygen in the air to break and recombine to form ozone. The ozone spreads and purifies the air. The rain in the thunderstorm takes away some of the pollutants in the air, as well as contains small amounts of ozone dissolved within the water. This is why we feel very refreshed after and during thunderstorms.

Ozone Formed in Photo Copying Machines, Televisions, X-rays Machines

Anywhere there is high voltage, there is also small amounts of ozone being formed. This is why you can smell ozone behind televisions, in X-ray machines, and in photocopy shops. Ozone is okay to breathe in when it is in small amounts, but doing so continuously can be dangerous. Because of this, it is important to take care of ambient ozone levels. Anyone who works with high voltage producing equipment needs to be aware of the danger of ozone.

Ozone in Refrigerators and Cars

Ozone is used in both refrigerators and cars to purify the ambient air. By doing this, it can ensure longer life for vegetables and other foods inside the refrigerator. High value cars such as Mercedes have small ozone generators systems (in some models) that produces controlled ozone inside the car. This keeps the car fresh from contamination and odor, as odor is the most common problem in air-conditioned cars.

Ozone Uses in Odor Control

The Problem Today

Awareness is growing for a variety of hazardous airborne microbes such as mold, fungi, bacteria and viruses found within the indoor environment. Exposure to these microbes can occur in a variety of indoor settings such as residences, office buildings, hospitals, airplanes, and medical and dental offices. High levels of microbes can also be found in most enclosed locations where people gather such as schools, theatres, restaurants, etc.

The average person spends approximately 90% of their time indoors. This can increase their risk of health more than the outdoors.

Medical research linked Indoor Air Quality (IAQ) to numerous allergies, asthma, bronchitis, emphysema, heart disease and cancer. In addition to this, there are many less severe symptoms and diseases such as congestion, coughing, dermatitis, dry throat, headaches, eye irritation and viral infections that also reduce your well-being and health.

A reduction in fresh air supply in most buildings have a negative side effect of withholding pollutants inside the building. Reductions may be used to conserve air conditioning cooling costs. This affects the health in both short and long term for the occupants of the buildings.

Odor

Most odoriferous (aromatic) substances are all organic compounds conjugated linkages which are easily attacked by ozone.

Ozone is particularly useful in odor control in the following areas:

  • Smoke Odor Removal: Hotel rooms after heavy smoking or parties, cleaners, painting and decorating operations, new carpets.
  • Buildings: Air recirculation systems, effectively stops algae, fungus and bacteria formation, saves maintenance expenses, cuts down the amount of air needed. It also saves fuel expense.
  • Apartments: Destroys smelly food and other odors from various apartments, kills odors of garbage rooms and deodorizes party rooms. Most effective in removing odors in all types of ventilated office and buildings.
  • Beauty Parlors: Destroys odors of hair sprays, nail polish, perms, etc. Keeps air fresh.
  • Super Market Stores: To keep air fresh all the time. Ideal for meat preparation areas, meat and vegetable coolers, fresh fish areas, etc.
  • Department Stores: Store smells nice and fresh when opened in the morning.
  • Banks: Vault areas, storage areas, central ventilating areas, etc.
  • Hospitals: Chronic care rooms ICU & ICCU, cancer rooms, laundries, food preparation area, garbage rooms, operation theatres, and wards, etc.
  • Forensic Centers: Morgue rooms, autopsy rooms, laboratory exhaust systems, etc.
  • Pet Hospitals: Removal of stench of animal excreta and odors.
  • Process Areas: Removes odor from process areas especially in the sea food industry chemical factory, and to maintain sterile areas in pharmaceutical process areas, electronic industries, etc.

Advantages of Ozone in Air Treatment

  • Cleans and disinfects air.
  • Biological air contaminants are destroyed.
  • Effective against microbes, endo toxins, VOCs and organic odors.
  • No toxic chemicals need be employed.

To see Oxidation Technologies wide variety of ozone generators, please click here!

Listeria Reduction with Ozone

Listeria is a common name for a specific strain of seven different bacteria species. Listeriosis is a serious infection that is caused by the specific species of Listeria called L. monocytogenes. This infection is caused by eating food contaminated with the strain of bacteria. This disease poses a great risk for those who have weakened immune systems or are immune deficient, and at times can even be deadly. Both L. monocytogenes, and Listeriosis are commonly known as Listeria, and Listeria illness.

Fruit and vegetable contamination can be caused because Listeria can be found in soils. Listeria is also found to be in all types of meat products, milk and eggs. The foods that are at high risk to have Listeria include uncooked or undercooked foods, unpasteurized milk, raw vegetables, and some ready-to-eat foods.

Click HERE to learn more about Listeria from CDC (Center for Disease Control and Prevention)

The use of ozone on foods has increase significantly since 2001 when it was GRAS approved for direct contact with foods. Ozone has proven to help reduce or eliminate any strains of L. monocytogenes on food products.

The correct implementation of ozone is necessary for it to be effective at eliminating any bacteria. Each application may be different, but there are a few fundamentals that apply with most application processes.

Implementation of Ozone

Aqueous Ozone

Dissolving ozone into water is the most common method of using ozone to get rid of pathogens. Ozone is dissolved into water using an ozone injection system and then sprayed onto the surface that needs disinfection. Surfaces that use this method can include hard equipment surfaces or the surface of a food product.

In 2000, a paper written by Kim and Yousef was published by the Journal of Food Science that showed the effect of dissolved ozone in a batch reactor on Listeria monocytogenes. Dissolved ozone at 0.4 and 0.8 ppm inactivated 4.6 and 5.7 log CFU /ml within 30 seconds. More tests were also run at higher levels of dissolved ozone, and it showed a faster inactivation of Listeria monocytogenes.

There are many ways that dissolved ozone can be sprayed onto food and produce, one of the best ways is using spray bars along with conveyers to allow sufficient contact time and offers full coverage of the aqueous ozone. Having every part of the food or produce contacted by the aqueous ozone is very important for disinfection. Conveyer speeds, spray tip design, and the quantity of aqueous ozone all can alter the contact time to get it to where it is desired. It is very easy to add ozone to the application process if there is already a method of washing the produce or food with water. This allows for no interruption in the processes and still improves disinfection.

Gaseous Ozone

Gaseous Ozone is also used for the elimination of pathogens from food and produce but it is much less common than aqueous. There has been less research about the effects of gaseous ozone on bacteria. There are many factors that gaseous ozone is dependent on if it is going to be effective. Things such as temperature, humidity, contact time, and ozone levels all factor into whether or not the process is going to be successful. There has been research conducted to determine that gaseous ozone will reduce the strain of bacteria L. monocytogenes; however, there is more research necessary in to determine effectiveness based on all of the different variables.

Cargo containers, chambers, or rooms are all places that produce that is needed to be disinfected can be placed. Any area that is sealed and able to contain the produce and ozone gas while maintaining human safety works. Air movement is important in order to cover every angle of the produce. Ozone levels from 1.0 – 100 ppm are used in this application with contact times from 20 minutes to 10 hours.

Product Spotlight: Oxygen Concentrators

Oxygen Concentrator Types Compared

The purpose of this article is to explain the main types of oxygen generators available for ozone production and the advantages/disadvantages of each.

There are a few manufacturers of oxygen generators and a few differences between each. However, the fundamental operation of each manufactures version is very similar so that will not be reviewed here. We will focus on the three main styles of oxygen generators and how they could be implemented into your ozone generation system.

Turnkey oxygen concentrators OGSI, OG-15 and OG-20 AirSep, AS-12 and Onyx Sequal, Workhorse line
OEM oxygen concentrator modules Sequal, ATF modules OGSI, OG-OEM modulesSequal and OGSI OEM Oxygen Generator
Industrial oxygen concentrator systems AirSep, AS-A, AS-B, etc OGSI, OG-25, OG-50, etcIndustrial oxygen generator

Generally smaller ozone systems will use the turnkey oxygen generators, and larger ozone systems with higher ozone production rates will use the industrial oxygen generators, while small to medium integrated ozone systems will use the OEM modules. However, there are applications where the industrial style oxygen generator is required for higher pressures, or turnkey oxygen generators are required due to the lack of space or available compressed air.

Turnkey Oxygen concentrators

Packaged oxygen generators that include an oil-less compressor, PSA oxygen generator, and all components to concentrate oxygen from ambient air. These units only need electrical power for operation and will provide oxygen at 93% purity.

Examples:

  • OGSI, OG-15 and OG-20
  • AirSep, AS-12 and Onyx
  • Sequal (Chart), Workhorse line
Turnkey packaged oxygen generators from airsep, OGSI, Sequal

Advantages:

  • Compact size allows for install in relatively tight spaces
  • Turnkey design allows for quick and easy operation
  • Relatively low cost

Disadvantages:

  • Lower oxygen output delivery pressures due to limitation of internal oil-less compressors
  • Poor reliability due to the lack of ability to purge moisture from process air
  • High maintenance costs due to poor reliability

OEM Modules

OEM models are offered by both OGSI and Sequal (Chart). The OEM modules use the same PSA sieve beds and valving systems as the turnkey packaged oxygen generators provided by those companies. These modules are commonly used to build ozone generators with integrated oxygen generators, or smaller integrated ozone systems.

Examples:

  • OGSI, OG-15-OEM and OG-20-OEM
  • Sequal (Chart), ATF Modules, ATF-8, ATF-12, ATF-15, ATF-23, ATF-25, and ATF-32
OEM oxygen generator from OGSI and Sequal

Advantages:

  • Compact size allows for install in relatively tight spaces
  • OEM configuration allows for installation into the same enclosure as an ozone generator if desired
  • Use of compressed air from plant air compressor may allow for very clean, dry air to be used increasing reliability dramatically when compared to the turnkey packaged oxygen generators.
  • Can provide slightly higher oxygen delivery pressure than turnkey packaged oxygen generators due to the higher compressed air inlet pressures that can be used
  • Lowest potential operational costs if plant compressed air is used

Disadvantages:

  • Installation equipment is required and must be done properly for reliable operation
  • Lower oxygen output delivery pressures than industrial oxygen generators
  • Potentially high replacement costs (applies to Sequal/Chart ATF-modules)

Industrial Oxygen concentrators

Industrial oxygen concentrators are used for medium to large scale ozone generation systems. These systems require compressed air for operation along with proper plumbing and set-up. Large steel cylinders are used to hold the molecular sieve material, and quality rebuildable solenoid valves are used to perform all purging and oxygen recovery actions.

Examples:

  • OGSI, OG-25, OG-50, OG-100, etc
  • AirSep, AS-A, AS-B, AS-D, AS-E, etc
Industrial oxygen generators from Airsetp and OGSI

Advantages:

  • Long term reliability of the system – only periodic maintenance is required
  • Lower overall long-term operational costs than other options due to low cost for rebuilding the unit
  • Higher oxygen delivery pressures (45 – 65 PSI)
  • Higher oxygen flow-rates available

Disadvantages:

  • Higher up-front capital costs for oxygen generator, tanks, and potentially the air compressor
  • May require more physical space for installation
  • Greater installation work required

To See Our Complete Oxygen Concentrator Lineup, Please Click HERE

Energy Efficient Ozone System Design

Conservation is a big topic in todays era, and the water industrial solutions should address this and ensure power savings are part of the solutions provided. The solutions provided should have a balance between CAPEX and OPEX costs.

Ozone generation is impossible without power and power consumption. High voltage power is used to split oxygen, producing ozone. During the ozone production, power is also used to produce chilled water to cool the ozone electrodes as well as injecting ozone during the process. Power is also used to destroy any unused ozone. Therefore, because the production and implementation of ozone take so much power, it is important to consider this when looking for a design where power required is minimized. How do we do it?

Ozone Generators

Today the prime consideration of selecting an ozone generator is its energy efficiency.

Ozone production consumes in power two ways:

1. Production of ozone

2. Requirement of chilled water to cool ozone electrodes

The normal power requirements for ozone production is around 10 W per grams of ozone for ozone produce from oxygen, and around 18 W per grams of ozone for ozone produced from air. The most energy efficient ozone system today, produces ozone from oxygen at less than 8 W per gram of ozone.

Most ozone generators require chilled water between 12-20 degrees because the electrodes need to be chilled during the process in order to keep the generator from damage. The production of ozone generates heat, which damages the electrodes as well as destroys some ozone produced. Producing chilled water requires power and energy for the closed loop chiller. The most energy efficient ozone generators can now produce ozone with cooling water temperature as high as 35 degrees Celsius, requiring just a closed loop heat exchanger instead of a chiller.

The choice of air or oxygen depends on the application and the correct air-liquid ratio when diffusers are used for ozone contacting. Both air and oxygen preparation can be costly in different terms. Air preparation is costly in terms of OPEX, whereas oxygen preparation is costly in terms of CAPEX. The application will determine whether it should be air feed or oxygen feed. The wrong choice will compromise the efficacy of the system.

Diffusers or Injectors

Using an air feed and injection system requires a lot of energy because large injection systems are needed for handling large volumes of gas. Diffusers are typically preferred if the volumes of water are large because no energy is required and efficacy depends on the air liquid ratio in the ozone contactor. In injection systems choices of the correct injectors and energy efficient pumps can reduce OPEX costs.