The use of ozone for wastewater disinfection has been growing in popularity due to strict regulations on fecal coliform and other pathogens. As chemical costs rise, ozone becomes a more cost effective solution for wastewater disinfection. Ozone can be produced on site using oxygen from the ambient air. Only electrical power is required for operation.
When discharge limits on pathogens are lowered, the natural solution is to add additional chemicals to meet these new limits. Adding more chemicals to a wastewater stream effluent for disinfection may seem like an easy solution at first; however, in many cases these chemicals must then be removed from the effluent wastewater prior to discharge due to limits on these chemicals. For example, if chlorine is used for the reduction of E.coli the chlorine must be removed using de-chlorination prior to wastewater discharge. If 20% more chlorine is required to meet the new wastewater discharge limits, 20% de-chlorination must also be applied to this water. Over time, these costs can really add up.
Ozone’s reactive properties allow it to quickly kill bacteria. In fact, ozone is ten times stronger than chlorine as a disinfectant.
Ozone is a green solution
Ozone is a green solution to wastewater disinfection. Ozone is produced on site and is all natural, formed from only oxygen. No by-products or waste products are formed in the creation of ozone.
The use of ozone eliminates the need to transport chemicals to the site.
Ozone is produced on-site from air and electricity, all renewable resources.
Ozone is a completely renewable resource.
Potential hazardous storage of chemical is removed with ozone use.
After ozone is dissolved into water, ozone reverts to oxygen leaving no residual in the water.
The Ozone Advantage
Using ozone for wastewater disinfection offers many advantages in cost savings, space savings, labor savings, and cleaner water. More and more wastewater plants are making the switch to ozone use to capitalize on these advantages.
Ozone leaves no residual, so only ozone injection is necessary. No second chemical for quenching is necessary.
Ozone is produced on site from renewable resources and requires no chemical storage.
Ozone is clean, safe, and reliable, taking up less space, and less equipment than many chemical treatment/storage systems.
Using ozone saves money by eliminating on-going chemical costs.
Ozone will destroy all bacteria without a preference to one type of organism. Ozone will also remove some BOD, COD, and many other contaminates in the waste water stream. Many customers comment on the clarity of the water after switching to ozone.
Ozone is effective on wastewater with TDS and TSS levels that may not be acceptable with UV disinfection. Therefore, filtration will not be necessary for ozone use in many wastewater applications.
Fewer secondary by-products like tri-halomethones (THM’s) are formed with the use of ozone.
Secondary Benefits of Ozone Use
The use of ozone in wastewater disinfection has gained popularity in recent years due to the secondary effects that ozone may offer in some applications. These secondary benefits have helped make ozone a cost effective alternative, and a necessary alternative in some applications.
Color removal with ozone is a common use of ozone. While ozone is used primarily for disinfection a secondary effect is color removal of the effluent water stream. Using ozone for disinfection may offer the elimination of a second technology used for color removal.
Oxidation of odor causing compounds in the water may also be a secondary effect of ozone use in wastewater. By eliminating these compounds odor control may be completed during the disinfection process.
Micro-pollutant removal from water using ozone is gaining interest at a rapid rate. Using ozone for wastewater disinfection may offer the secondary benefit of micro-pollutant removal and eliminate the need to add processes in the treatment stream with future regulations.
Suspended solids may also be removed or reduced with the use of ozone. Ozone is commonly used for the removal of suspended solids in drinking water, these same effects are achievable in wastewater.
History of Ozone and Wastewater Disinfection
Ozone used for wastewater disinfection became popular early on when the widespread use of ozone gained popularity in the 1970′s and 1980′s. Due to lack of equipment reliability and rising costs, the use of ozone almost complete disappeared from this application. In recent years however, ozone is getting another chance in many locations across the USA and Europe. This is partly due to improvement in equipment reliability and lower cost; however, the main reason for this revival is the secondary benefits that ozone offers along with the increased costs of chemicals creating an economic advantage. See the timeline.
Treated Air Systems, a manufacturer of ambient air ozone generation, in British Columbia, Canada has ceased operation as of May, 2011. Treated Air Systems has been involved in the design, fabrication, and sales of ozone generators since 1992. Treated Air Systems and Ozone Solutions, Inc of Hull, IA have made an agreement to sell and distribute all remaining inventory held by Treated Air Systems. Ozone Solutions will purchase 100% of the remaining inventory held at Treated Air Systems. All future production at Treated Air Systems has ceased, and the corporate offices will close. Ozone Solutions has also purchased the website, rights, and web contact from Treated Air Systems. While Treated Air Systems will shut down all day to day operations, Ozone Solutions will work to service the customers, and continue to offer parts, service, and sell the remaining inventory.
Ozone has many applications. One of these applications is a biocide in cooling towers. Cooling towers recirculate the same water over and over again within a mostly closed loop system. This water must have chemical treatment to maintain clean water with no bacteria or algae growth. Ozone can replace traditional chemicals and offer a green solution to this application.
We have recently completed an installation of a 300 g/hr ozone generation system into a large cooling tower at an ethanol plant. The use of ozone will replace chlorine and bi-sulfate chemical additions. Using ozone will eliminate the need to transport, store, and purchase bulk chemicals.
The ozone system produces ozone from a 300 g/hr water cooled ozone generator. This will produce 300 g/hr of ozone from 40 LPM of oxygen at 9% by weight from oxygen. Oxygen is provided by an Air-Sep AS-D oxygen concentrator using compressed air to provide 40 LPM of oxygen feed gas for the ozone generator. The AS-D is fed with compressed air supplied by the customers current compressed air systems.
Ozone is injected directly into a water recirculation line using a custom ozone injection point. The picture below shows the ozone gas plumbed into this injection point. This injection point will diffuse the ozone into the pipe via micro bubbles. This pipe recirculates ~300 gpm of water, this water travels 150 yards then discharges into the cooling tower basin. This pipe distance allows the ozone to achieve excellent mass transfer efficiency.
Currently this ozone system is rented by the customer with the option to purchase at any time. This offers great flexibility for the customer, and cost savings over the previous chemical additions. For information on our ozone solutions for your application contact us today.
A wet scrubber is used to remove pollutants or odors from process exhaust gases. The purpose of a wet scrubber is to remove pollutants from the air and dissolve them into water for discharge in a waste water stream.
In a wet scrubber, water is sprayed or misted into the air stream to mix with the polluted air. The soluble pollutants in the air will dissolve into the water and be discharged safely in a waste water stream where they can be safely removed or converted to safe compounds.
Water used in a wet scrubber may be mixed with Hydrogen Peroxide, Chlorine Dioxide, or a variety of other chemicals to both improve pollution removal efficiency, and to maintain a clean, efficient wet scrubber. These chemicals may bond to pollutants, or convert the pollutant to a safe alternative using chemical reactions.
Ozone can also be used in the wet scrubber to improve wet scrubber efficiency, and reduce chemical costs. Ozone can be used in any wet scrubber where the process of oxidation offers synergistic effects with water. Ozone may directly oxidize pollutants in the dirty gas stream, oxidize contamination on the scrubber walls, or help increase the efficiency of water to trap pollution. While the use of ozone in wet scrubbers is fairly new, the rising costs of chemicals ensures ozone use in wet scrubbers has a very bright future.
Ozone reduces costs and increases efficiency:
As chemical costs rise the costs to operate a wet scrubber go up. On going chemical costs can add up to very large operational costs. The use of ozone may reduce, or completely eliminate chemical usage drastically reducing the operational costs of a wets scrubber.
Many chemicals used in a wet scrubber remain in the waste water flowing from the wet scrubber basin. These chemicals may be undesirable, or costly to discharge. Ozone will maintain a clean, efficient wet scrubber and revert back to oxygen in the waste water stream.
Many wet scrubbers were designed to remove odor, however over time improved odor reduction is desired due to population growth, and increased odor complaints. Ozone use in a wet scrubber is a method to reduce a wide variety of odor emissions.
The Ozone Solutions:
Ozone can be dissolved into the makeup water flowing into the wet scrubber. This water should be plumbed directly into, or close to the recirculation water flow in the wet scrubber. This will allow the ozone to be sprayed into the wet scrubber contact area quickly. Make up water flowing to the wet scrubber can be plumbed through an ozone injection system for simple installation. If chemical usage is still necessary, chemicals can be delivered directly into the basin of the wet scrubber to ensure ozone does not negatively react with the chemicals.
Ozone Use in Odor Control Wet Scrubbers
Odor control wet scrubbers are commonly used for H2S removal, and other odorous compounds from rendering plants, fertilizer manufacturers, or other odor causing processes. Ozone is commonly used as a method to remove odor in other applications. Ozone is a great method of removing odor in a wet scrubber as ozone is a great method to remove odor, and ozone with water provides great synergistic effects. Odor control wet scrubbers commonly have bio fouling and slime forming inside the scrubber tower. Ozone slows this growth and removes this biological growth increasing the efficiency of the wet scrubber.
Ozone Use in VOC Wet Scrubbers
VOC wet scrubbers are used to remove Volatile Organic Compounds (VOC’s) or convert VOC’s to CO2. Sometimes VOC scrubbers are refereed to as CO2 scrubbers. A common use of VOC scrubbers is Ethanol plants. Ozone is very effective at converting VOC’s into CO2 by bonding with the carbon atom in the complex VOC molecules. When ozone is used within a wet scrubber ozone and water are used together with great efficiency to oxidize VOC’s and other hazardous gases.
Ozone Advantages
Lower operating costs due to lower chemical usage
Improved efficiency of wet scrubber by increasing oxidation
Lower maintenance due to lower scaling and biological growth
No chemical storage or transportation
Ozone offers a safe alternative to chemicals
Lower waste water discharge costs
The Use of Ozone in a Wet Scrubber
Ozone gas is generated on-site by an ozone generator. Compressed air is supplied to an oxygen concentrator that will provide concentrated oxygen for ozone generation. This oxygen will be passed through an ozone generator cell to convert this oxygen (O2) into ozone (O3). This ozone gas will then be dissolved into water using an ozone injection system. Typically all make-up water will flow through the ozone injection system into the wet scrubber. The goal is to achieve very high dissolved ozone levels into the water flowing to the wet scrubber.
(click to enlarge)
All excess ozone that is off-gassed in the ozone injection process can be plumbed to the wet scrubber sump and be bubbled into the sump using a bubble diffuser. This ozone gas can help treat the sump water, while off-gassing into the air stream to directly react with the polluted gas flow.
It is corn planting season here in Iowa. In honor of this, I though I would share the following. A paper was written recently on the effect of corn seed germination after exposure to ozone.
Effect of Oxidative Treatment on Corn Seed Germination Kinetics Authors: Freacutedeacuteric Violleaua; Kheira Hadjebaa; Joël Albetbc; Roland Cazalisa; Olivier Surela
Abstract:
Corn seeds were treated with high purity oxygen ([O3] = 0 g/m3) and oxygen mixed with ozone ([O3] = 20 g/m3) during 6.8 or 20.5 minutes. Germination tests started immediately or 48 h after treatment. Effects of oxidative treatments on germination were determined by measuring seedlings and roots (>3 and >20 mm) rate at 3, 4 and 5 days of germination test. Results obtained for treated seed samples were higher than for untreated ones. A faster start of germination was observed for treated samples. This early germination start led to a larger number of germinated seeds with longer roots at 4 and 5 days. Nevertheless, too long an ozone treatment seemed to be unfavorable for seed growth, whereas a short one seemed to be most beneficial.
Link to paper from the Journal of the International Ozone Association
See image below from the paper:
This testing did show faster germination of the corn seed, and larger roots on the germinated seed after 4-5 days. This is fun research, and could be a new use for ozone in agriculture?
Ozone is produced from oxygen. The oxygen source for ozone generation can be found either in the air we breathe every day, or from concentrated oxygen produced by an oxygen concentrator or other device. While most ozone generators produce ozone from concentrated oxygen, the oxygen found in ambient air can also be used. The oxygen level in ambient air is about 20%. While this is a less efficient method to produce ozone, it may be useful depending upon your application. The following information is helpful when producing ozone from dry air.
Importance of Dry Air for Ozone Generation
The moisture level of feedgas to a corona-discharge-based ozone generator is directly related to the ozone output. More moisture equals lower ozone output. See the chart below:
Critical to all corona discharge ozone systems is proper air preparation. Because the presence of moisture affects ozone production and leads to the formation of nitric acid, the gas feeding the ozone generator must be very dry (minimum -60 degrees F). Nitric acid is very corrosive to critical internal parts of a corona-discharge-based ozone generator, can cause premature failure, and will increase the frequency of required maintenance. Make sure you have reliable air drying equipment.
The following paper can now be found on our website.
Antimicrobial Effects of Ozonated Water Against Generic E.coli on Swine Intestines Varying Ozone Concentrations and Exposure Times
Abstract:
Swine intestines harvested then turned inside-out and washed with cold water to remove all visible contaminants were tested to have a generic E.coli load of 6 to 7.5 logs per gram of tissue. Samples of these tissues were treated with ozonated water at various concentrations for various lengths of time up to a total of 30 seconds. It was determined that concentrations below 1 ppm had no significant anti-E.coli effects at any of the exposure times tested. At 1 ppm and above significant kills were achieved with a 1 second exposure time. At 1 ppm and up to 2.5 ppm a 15 second exposure time was needed to achieve the greatest E.coli kill, and at 3 ppm and above a 1 second exposure time was all that was needed to achieve the greatest E-coli kill.
This paper is very exciting as it shows the concentration of ozone in water and the contact time necessary to achieve E.coli reduction. This papers shows that 2.0 ppm of dissolved ozone for only 1 second of contact time achieves a 3 log reduction of E.coli bacteria. This new data is extremely useful in understanding the effectiveness of ozone use in spray applications where contact time is very short.
The system Ozone Solutions designed for Glendale Warehouse is a perfect example of an ozone system achieving success in odor abatement and improving a customer’s bottom line.
The Problem
Spice Warehouse stores, packages, and distributes spices and other products
The spice products emanate an extremely offensive odor to the residential and industrial development located up to one block from the facility.
Warehouse is 230,000 square feet.
Ventilation of the facility is necessary to keep the indoor air quality acceptable.
All vented air carries an offensive odor to the local area outside the warehouse.
The local area is filled with other industries, housing developments, and busy roadways.
Complaints were coming from the local community about the odor problem.
The county health department was levying large fines against the warehouse for the odor.
Inside the Warehouse
Ozone Solutions Used
Ozone gas was used within the building at low levels to maintain an odor free environment.
Low ozone levels (0.05 – 0.1 PPM) were maintained in the building at all times.
The building was made up of five individual rooms.
Ozone was applied to the four main areas. The last area was a sealed cooler and was not a contributor to the odor issues
The ozonated areas were as follows:
33,000 ft2
45,000 ft2
60,000 ft2
80,000 ft2
Four regulated ozone outputs were used to control the ozone level in each room.
Four additional ozone outputs were used to inject unregulated ozone flow into the exhaust stacks.
Any unused ozone flow for the rooms was diverted into the exhaust stacks. The ozone system operated at 100% capacity at all times.
All ozone equipment, including the air compressor, was placed on one skid for simple operation and installation.
Ozone System Inside the Warehouse
Results
After the ozone system was implemented the odor directly next to the building was almost completely eliminated.
The county health department praised the spice warehouse for the amazing difference in odor emissions.
Due to the improved air quality inside the warehouse, the vent fans could be slowed down to recirculate less air.
Air quality inside the warehouse improved creating a better work environment for the employees.
Fines and odor complaints were completely eliminated after installation of the ozone system.
Ozone Gas distribution piping placed along the ceiling of the warehouse
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