Cyanide is a rapidly acting, potentially deadly chemical that can exist in various forms. Breathing cyanide gas causes the most harm, but swallowing cyanide can be toxic as well. Cyanide prevents the cells of the body from using oxygen. When this happens, the cells die .
Cyanide in waste water is mostly observed in gold mining waste water. Cyanide is produced in large amounts (about 1.4 million tons each year) and gold recovery accounts for approximately 18% of total world cyanide production. Several methods, including chemical oxidation, are applied to destroy and reduce cyanide in several industries . The methods leave by products and sometimes they need time to complete the reaction. Ozone is an extremely powerful chemical agent which its oxidation reaction by cyanide is very rapid. Ozone provides complete decomposition and retains no harmful residue.
If you have more questions regarding the removal of cyanide from waste water, contact us via email at email@example.com.
Conventional flotation relies on floating of suspended solids on the top of liquid by air bubbles. A better separation effect is obtained when air bubbles are very small (micro-bubbles and nano- bubbles). In traditional dissolved air flotation (DAF) systems suspended solids and oily compounds are removed by coagulation, flocculation and removing the formed sludge by flotation by applying small air bubbles to increase buoyancy. Dissolved COD remains unaffected in DAF systems. By employing DOF, high concentration of ozone is available, which means a high potential of ozone oxidation and a high volume of micro-bubbles.
Schematic of a DOF system .
Dissolved COD remains unaffected and leaves a DAF with the effluent. When ozone is added to the air bubbles, it partially decomposes to highly reactive OH radicals, which in their turn oxidize the remaining dissolved COD. DOF removes non-biodegradable COD in a high level. As it is obvious in DOF systems, water quality parameters are removed by the two mechanisms of flotation and ozone oxidation. For this the reason, DOF systems have better efficiencies compared to DAF systems. It is estimated that DAF systems will be replaced by DOF systems especially in very polluted water systems to provide a one-step reduction of water quality parameters.
Recently we ran successful pilot tests to evaluate phenol reduction with ozone in industrial wastewater. Our customer was a waste management company that offers wastewater treatment services to it’s customers. They will take wastewater from customers and process this water to safely discharge to the municipal wastewater system.
Limits on Phenol were lowered from 50 ppm to 1 ppm for an acceptable discharge limit to the municipal wastewater system. This presented a problem to our customer as phenol levels from various locations could range from very low, to well over 50 ppm. All of this water is mixed together in equalization tanks and processed with chemical processes, and ultra-filtration. None of these processes were able to lower the phenol level below 8-12 ppm on average.
What is Phenol?
Phenol is an organic compound – C6H5OH. Phenol is also known as carbolic acid. Phenol is found in petroleum products, detergents, herbicides, and pharmaceutical drugs. High levels of phenol are toxic and can cause permanent health issues.
Initial pilot test:
The first ozone pilot test consisted of a 300 g/hr ozone injection system recirculating water in the 5,000 gallon over a period of 12 hours of time. This did successfully lower phenol levels and prove that ozone was a viable solution. See chart below for data:
This data did confirm that ozone was a viable option. However, lower phenol levels were required, and a better process was required for process flow situations.
Final Pilot Test:
After initial processing the wastewater is stored in 5,000 gallon holding tanks prior to discharge. Overall water flow rate for the processing plant is an average of 10 GPM when averaged over a 24 hour time-frame. We decided to pull water from one holding tank treat that water with ozone at 10 GPM and pump that water to a second holding tank.
This new setup allowed for a 100 gallon contact tank to be used that could be operated under pressure up to 35 PSI to improve mass transfer of ozone into water. Also, the smaller 100 gallon tank allowed for very high dissolved ozone levels to be maintained for about 10 minute of contact time. See diagram below for details on this set-up:
Using the same 300 g/hr ozone injection system 300 g/hr of ozone was introduced into the water flow rate of 10 GPM for an effective ozone dosage rate of 132 mg/l. Despite this lower ozone dosage rate improved phenol reduction was achieved. This did achieve an acceptable phenol level of less than 1 ppm. Phenol levels up to 12 ppm were consistently reduced to less than 1 ppm at water flow rates up to even 12 GPM, an ozone dosage rate of 110 ppm.
Phenol removal prior to ozone was performed with carbon vessels. These did work well and achieve the necessary phenol reductions. Carbon replacement was necessary every 2-weeks at a total cost of $15,000/month. An ozone system to replace this carbon was rented at a cost of $3,900/month. With electric and all maintenance costs total costs were still less than $5,000.month for a total savings of $10,000/month.
This pilot test did show good results and proved two things.
First: Phenol reduction with ozone, in heavy industrial wastewater is possible and can be cost effective.
Second: using proper ozone mass transfer methods the efficiency of phenol reduction, and likely many other contaminates with ozone is much more efficient and offers large cost savings.
We recently completed a pilot test using ozone for wastewater disinfection at a beef processing plant in Nebraska. This pilot test proved to be a great success and will now move into a full scale implementation. This is a recap on the pilot test that was performed.
Wastewater disinfection of E.coli was the main concern at this application. The limit on E.coli was 126 CFU/ml in the wastewater stream. Historically chlorine was used to meet these standards. However the limit on residual chlorine at this site was very low (0.001 ppm). To meet these standards additional chemicals are necessary. As limits on E.coli are tightened additional costs increase for both chlorination and chlorination. These increasing costs were the catalyst for ozone use at this location.
Total discharge wastewater flows range from 800 – 2000 GPM. This water is piped through a 10″ pipe for about 1/2 mile to a creek.
This customer had no method of ozone contacting, and no on-site compressed air. We decided to bring on-site a very high concentration ozone generator producing ozone from Liquid Oxygen Tanks (LOX).
Ozone was injected directly into the 10″ pipe in 2 separate locations using a proprietary ozone injection device. See image below.
Diagram below shows the entire system. LOX tanks provided oxygen at high pressures that were regulated to 40 PSI. This oxygen flowed at up to 80 LPM through the Semozon 250.3 Ozone Generator that was cooled with a recirculating water chiller. The ozone was split via flow meters to 2 locations for ozone injection.
Oxygen flows of 70 LPM produced 700 grams/hour of ozone at 11.6% by weight. This provided a 1.71 ppm ozone dosage rate into 1800 GPM of water. These parameters were used to collect data during the pilot test.
E.coli levels of 1700 cfu/ml were reduced to 30-40 cfu/ml consistently throughout the 1-week pilot test. This was well below the required discharge limit of 126 cfu/ml.
Ozone proved to be a success in this application and has the potential to eliminate the need for chlorination, and chlorination. Details on full scale implementation are in the works at this time.
Ozone Use in Wichita Aquifer Storage and Recovery Project
Mazzei released this great informative video on the use of Mazzei products to dissolve ozone into water for the Wichita aquifer storage and recovery project. This video shows the expertise that Mazzei has on large scale projects like this:
Mazzei Degas Separator was selected for the Wichita Aquifer Storage and Recovery Project. Mazzei’s GDT™ Degas Separator was chosen as the best method for entrained gas bubbles removal.
The expertise that Mazzei has on ozone mass transfer is also utilized on smaller applications with the commonly used ozone injectors and flash reactors.
Ozone Solutions for Endocrine Disrupting Chemicals in Wastewater.
Mazzei released this great video on the use of ozone to remove EDC’s from wastewater. While this is a promo video for Mazzei products, it is still interesting as a promo video for ozone use in general:
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.
This Ozone Journal is a blog managed by the employees of Ozone Solutions. The purpose of this blog is to inform and educate the readers about the world of Ozone, provide news about the ozone industry, and have an easy opportunity to inform about new ozone products.
Check back often, ask questions, and let us know if there is anything you would like to hear about.
What is ozone?
Ozone is an oxidant. Ozone (O3), sometimes called “activated oxygen", or "triatomic oxygen", contains three atoms of oxygen rather than the two atoms we normally breathe. Ozone is the second most powerful oxidant in the world and can be used to destroy bacteria, viruses, and odors.
Ozone is a gas at ambient temperatures and pressures with a strong odor. Ozone can be produced as a gas from oxygen in air, or concentrated oxygen. This ozone gas can be dissolved into water, or used in the gas phase for a variety of applications discussed in this Journal.