These are some of the applications of pure oxygen in water treatment including both drinking water and wastewater.
Aeration is by far the biggest consumer of energy in water treatment consuming > 60% of all energy in the plant. The standard for many years has been air diffusion with fine bubble becoming the predominate method by which oxygen is injected into wastewater.
Pure oxygen in waste water is not new. It’s been used in many plants for over 40 years starting with the UNOX and OASES processes. These were innovative uses of pure oxygen at the time, but as with everything, technology advances and new applications are emerging that exploit pure oxygen’s unique properties. One thing to note: many of these emerging technologies are coming from companies that are not aligned with the major industrial gas companies so they are open to various sources of oxygen such as onsite generation. One inhibition to market adoption may be that in the past many pure oxygen water treatment processes were captive technologies that are tied to the molecules delivered from industrial gas companies.
Under standard conditions (25 C or 77 F and atmospheric pressure) the maximum DO level that can be achieved with standard aeration is 8 mg/l. Under these same conditions, if you substitute pure oxygen, a maximum DO level that can be achieved is 5 times greater at 40 mg/l. The chart on the left also indicates that as temperature increases, it will be more difficult to achieve higher DO levels, but it also shows that if you increase the pressure of the system you can increase the DO levels significantly. This is unrealistic in a standard aeration system because the power to compress air is significant. When working with pure oxygen however, you’re dealing with 1/5 the volume of gas with a much greater driving force (higher concentration) to significantly increase DO levels which leads to shorter retention times and smaller reactor volumes. The chart on the left is an example of a company that is taking advantage of the unique properties of pure oxygen. At atmosperic pressure you can see that pure oxygen starts at about 40 mg/ whereas air is starting at around 8. Using a pressurized bioreactor, this company, Grundfos, is taking advantage of the fact that oxygen concentration increases faster with pure oxygen as opposed to air. The take away from this slide is that pure oxygen may be the answer to DO limited water treatment process, however pure oxygen presents an opportunity to couple it with application equipment that can exploit it’s unique features to achieve a synergistic benefit. There are many companies that are exploiting these features such as Aqua Aerobics, Grundfos, Eco2, Blue in Green, etc.
The advantages of pure oxygen have been well documented and have been implemented in many WWT processes including activated sludge and more recently MBBR, and IFAS. Again, it is important to note that pure oxygen alone is not the answer but coupling it with application equipment that can achieve high transfer efficiencies can save a substantial amount of power and maintenance costs.
To meet varying loads and up to 40 to 60 TPD, PCI has many blower package options and configurations which will depend on operating parameters. This is just an example of a 20 TPD plant.
Pci Oxygen In Water Treatment
PCI VSA Oxygen Systems<br />Pure Oxygen in Water & Wastewater Treatment<br />March, 2010<br />
Oxygen in Water & Wastewater<br />Odor Control – Lift Stations/Headworks<br />Replace traditional aeration in WWTP<br />Lake oxygenation<br />Ozone disinfection feed gas<br />Remediation (ozone and HIPOX)<br />
Traditional Aeration<br />Many different types of aerators; surface, course bubble, fine bubble, etc. <br />Most significant energy consumption >60% of plant energy use.<br />Mixing and oxygen transfer inherently linked.<br />May be susceptible to fouling incurring high maintenance & energy costs, and oxygen transfer limitations.<br />Clogged Polyurethane diffuser plate after 9 months of use.<br />
Pure Oxygen Use in WWT<br />UNOX – Introduced by Linde in 1968<br />OASES – Developed by Air Products/now owned by Kruger<br />Many gas companies use technology to sell their molecules – Captive Technology<br />Schematic of UNOX Process.<br />
Why Pure Oxygen<br />Water solubility of pure oxygen at 25oC and 1 atm. is 40 mg/L water.<br /> Using air the oxygen partial pressure is 0.2 atm. <br /> This results in oxygen dissolution of 40X 0.2 = 8 mg O2/L in water.<br />D.O. is often a limitation in WWT that can be addressed by exploiting properties of pure oxygen.<br />Pure O2 can significantly increase DO levels<br />Oxygen (Using Air) Solubility in Clean Water<br />
Advantages of Pure Oxygen<br />Reduced reactor size/footprint<br />Reduced energy consumption<br />Reduced VOC stripping and odors<br />Reduced foaming issues<br />Separate mixing and oxygen requirements<br />Less susceptible to low alpha factors<br />To achieve benefits of pure oxygen, take advantage of 1/5 volume of gas and higher dissolution capabilities.<br />Pure oxygen alone is not the answer Must be coupled with synergistic application technology<br />
Exploiting Potential of Pure Oxygen<br />Speece Cone from<br />ECO2 System dissolves O2 at 90-95% absorption efficiency to achieve D.O. concentrations of 50 to >150 mg/L<br />Applications:<br />Odor Control<br />Reservoir Oxygenation<br />
Exploiting Potential of Pure Oxygen (2)<br />SDOXTMfrom<br />SDOX System dissolves O2 at 99% absorption efficiency to achieve D.O. concentrations of 300 to 350 mg/L<br />Applications:<br />Odor Control<br />WWTP<br />Reservoir Oxygenation<br />
Exploiting Potential of Pure Oxygen (3)<br />Dissolved Oxygen Augmentationfrom Dynamox<br />Dynamox system dissolves O2 at 99% absorption efficiency to achieve D.O. concentrations of 800 mg/L<br />Applications:<br />Odor Control<br />WWTP<br />Reservoir Oxygenation<br />
Exploiting Potential of Pure Oxygen (4)<br />OxyMBRfrom <br />Suitable for flows < 25,000 m3/day<br />High Strength Wastes 2,500 – 50,000 COD<br />Applications:<br />Industrial & Municipal WWT<br />
Exploiting Potential of Pure Oxygen (5)<br />Biobooster PBR & MBR from<br />Targeted for high strength wastes<br />Applications:<br />Typically Industrial WWT<br />
Exploiting Potential of Pure Oxygen (6)<br />UnderWaterOxygenator (UWO) from<br />Oxygen injection in<br />wastewater aeration basins: 9.35 lbs O2/hp-h<br />Applications:<br />Secondary treatment at WWTP’s<br />
Exploiting Potential of Pure Oxygen (7)<br />HiPox – Ozone/ Hydrogen Peroxide Remediation<br />Ex-Situ Remediation <br />Applications:<br />Remediation of contaminated ground water<br />
Oxygen Supply Map<br />Cyl<br />2 Bed VSA<br />PSA<br />O2 Purity (%)<br />1 Bed VSA<br />TPD or 000 SCFH<br />
O2 Product Offering: Small to Medium Size<br />-15-<br /><ul><li> DOCS 66 –140 SCFH / 280 lbs/day
DOCSOperating Cost Examples<br />-19-<br />Product Platform<br />DOCS 200<br />845 lbs/day<br />DOCS 66 <br />280 lbs/day<br />DOCS 500<br />2100 lbs/day<br />DOCS<br />Operating Cost <br />per ccf <br />(per m3)<br />$0.31($0.11)<br />$0.25<br />($0.09)<br />$0.21<br />($0.07)<br />Typical PSA<br />Operating Cost<br />per ccf <br />(per m3)<br />$0.55 - $0.85<br />($0.20 - $0.30)<br />LOX <br />Delivered Cost<br />per ccf<br />(per m3)<br />$0.35 – more than $10.00<br />($0.12 – more than $3.00)<br />Notes:<br />- ccf is hundred cubic feet which is a common term in the industrial gas industry<br />- @ 55 psig (~ 4 barg) output pressure and 93% purity.<br />*DOCS 66 delivers ~ 5 m3/hr, DOCS 200 delivers ~ 15 m3/hr @ 90% purity.<br />- Includes energy ($0.10/kWh) and Preventive Maintenance cost. <br />
Typical Oxygen Application Examples<br />-20-<br />DOCS 500 at PCI Open House<br />DOCS 200 at Industrial WWTP<br />Aquaculture<br />Mobile Field Hospital<br />Wastewater: <br />Odor Control <br />at Lift Station<br />GroundwaterRemediation<br />
Summary<br />Long history of oxygen use in Water Treatment<br />UNOX, OASES<br />Emerging Applications – Speece Cone, Blue In Green, Grundfos<br />It all starts with low cost, reliable oxygen supply<br />PCI’s Oxygen VSA Technology Advantages<br />Extremely low power consumption <br />Very few components – low maintenance cost<br />Leading to very low operating cost<br />Best on-site oxygen solution available<br />Your questions, please!<br />-21-<br />