Entry for January 25, 2008

Here is an update on the International Ozone Association (IOA) Technical Conference to be held in Orlando this August.

1.  You can make you hotel reservations at the special IOA conference rate at http://www.disneyurl.com/Ozone2008.  Please note the special benefits you receive from the Disney resort including “Complimentary Transportation” from to and from the property and the Orlando airport.

2. Please use the following link to purchase Disney theme park tickets online.  This link offers advanced purchase savings and expires 20 August so order early if you plan to come early or stay late with family and friends!  http://www.disneyconventionear.com/ioaac  Please note that you must have the Macromedia Flash player installed on your computer in order to view the website.

3. Abstracts for the conference are due before 01 March 2008 for consideration for oral presentation.  Follow this link  for more information: http://www.io3a.org/Call_for_Papers-Orlando_2008.pdf

Spartan Environmental Technologies looks forward to seeing you at the conference!

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Entry for January 23, 2008

In this post we would like to talk about pilot and lab testing of ozone water treatment and advanced oxidation applications.  Typically, pilot and lab tests are conducted to first see if ozone or other advanced oxidation processes will address the water treatment objectives, or to assess the economics of using ozone or other advanced oxidation processes.

As we have discussed in other posts, it is difficult to predict with accuracy the amount of oxidant required to destroy dissolved organics in water.  This is especially true if the specific organic constituents are not known or the variety of such contaminants is large.  In many cases, the only analytical data available are broad based measures of organic species such as BOD, COD and TOC.  In the case of ozone, some organic species react readily with ozone while others are not reactive at all.

In the case of advanced oxidation processes, the primary reactant involved, the hydroxyl radical, will react with most organic species; other materials in the water may interfere with these reactions.  One such species are carbonate ions that can scavenge hydroxyl radicals out of the water.  High concentration of these ions will limit the effectiveness of advanced oxidation processes.

Given the complexity of the chemistry that can be involved, it is sometimes better to run laboratory and pilot tests to measure actual results which can then be scaled up to predict the results in a commercial scale installation.  To be effective, proper measurement of the amount of oxidant applied is important.

In the case of ozonation, we first need to know how much ozone has been produced.  Ozone generators are usually supplied with production curves that show ozone production as a function of gas feed and power applied.  With time ozone generator characteristics may change, so these curves should be checked using a high quality flow meter and a high concentration ozone monitor.

Only a portion of the ozone applied to the water will dissolve and thus be able to react with the organics in the water.  The percentage of ozone that transfers to the water is measured as the ozone transfer efficiency.  Using a high concentration ozone monitor, one can measure the off gas from the process to see how much ozone did not dissolve into the water.  By subtraction one can arrive at the amount that did enter the water and is available to react.

While not as critical, measuring dissolved, but unreacted oxidant at the end of the process can be done with a dissolved ozone monitor or other analytical method depending on the oxidant used.  This information might suggest what will need to be done to maximize the use of the reactant.  Being able to measure a oxidant residual may also point to a process control option.  If ozone residual is present it might be able to serve as an indication that the organic destruction reaction has reached its end point.  This could be useful in the final design of the commercial installation.

While the economics of the process are dictated by the total amount of ozone applied, regardless of whether it dissolved or not, pilot processes may not be as efficient as commercial scale processes.  A short bubble column that allows the ozonated gas to enter in large bubbles could easily have a ozone transfer efficiency of less than 10% while a well design ozone injection and mixing system can achieve 95% efficiency.  Such a large difference would make the applied dose useless to know without the ozone transfer efficiency data.

Using the information gathered at the pilot stage, adjustments can be made to accurately assess the amount of ozone needed in an efficient commercial process.  In other advanced oxidation processes, measurement of peroxide and UV radiation applied would be needed as well.

Besides the amount of oxidant applied, before and after results for the relevant measure of the dissolved organic (BOD, COD and/or TOC) will be needed.   This will be correlated to the amount of applied oxidant, e.g. mg Ozone/mg COD removed.  This ratio along with the ozone transfer efficiency data will allow for a cost estimate to be made for the entire system.

Spartan Environmental Technologies can provide both laboratory and pilot testing of ozone and advanced oxidation processes.  Contact us if you would like to see if ozone or advanced oxidation processes may be able to solve your dissolved organic contamination issue.

 

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Entry for January 16, 2008

In this posting we would like to discuss the use of ozone in recycling industrial process water.   Recycling water is becoming more important as the availability of high quality water is decreasing, the cost of purchased water increases, costs associated with discharging water increases and compliance and liability issues continue to be more serious.  Water reclaim is becoming especially important in industries where water use is high.  A key example is the semiconductor industry.

Ozone can offer the following benefits to industrial user:  First, in some industrial processes the build-up of organics in the water allows for the build-up of micro organisms.  Since ozone is an excellent biocide, it can prevent this build-up and allow for the recycling of water that otherwise might have to be discarded.  Second, ozone, either alone or in combination with UV or peroxide, can reduce organic chemical loading (BOD/COD/TOC) in water which may prevent its reuse as these levels rise with use.

Ozone is most likely to be a good solution when the organic loading are relatively low, most likely less than 100 ppm as measure as TOC.  Higher TOC levels may be economically treated if the total flow is low.

In determining the usefulness of an ozone based solution, it is important to characterize the nature of the organic and the treatment objective.  The treatment objective is directly related to the nature of the water reuse.  For example, water in the semiconductor industry can be recycled back to the ultra pure water treatment area or sent to a less demanding application such as cooling water make-up.  If the water is sent to ultra pure water make up system, the treatment objective is going to be similar to the requirements for drinking water.

In terms of the nature of the organic to be treated, certain molecules are not readily oxidized by ozone such as small chain aldehydes, ketones and carboxylic acids.  These compounds will need to be treated with an advanced oxidation process (AOP) that employs ozone in combination with UV, peroxide or some combination of both compounds.  Ozone alone is unlikely to breakdown most organics to CO2, so called mineralization.  If this is part of the treatment objective, an AOP would be required.

Certain geographic areas are becoming increasingly concerned about water use and the governments are limiting water supplies to industries located in their area of authority.  In some cases there are mandated recycling requirements.  It is expected that these requirements will continue to increase with time.

Spartan Environmental Technologies can supply ozone based solutions for water recycling applications.  We invite you to contact us with your water treatment challenges.

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Entry for January 8, 2008

In this posting we are going to discuss using an ozone generator in a system where the flow of water is intermittent.  An example would be a well pump that is feeding a pressurized system.  In these systems the pump comes on in response to a drop in system pressure.  It is not good practice to tie the operation of the ozone generator directly to the operation of the pump for three reasons: 

First, quickly turning the ozone generator on and off will reduce the lifetime of the dielectric elements which are critical components of the ozone generator.  Thus the overall lifetime of the system is put at risk.  Second, it takes some time for the ozone generator to reach steady state.  If the system is only on for a few minutes, it is not likely that steady state operation will be reached.  As a result, the amount of ozone production will not be accurately known.  Third, the size of the ozone system would have to be increased to meet the peak pump flow versus the average flow rate.  This means a larger ozone system would need to be built.

There are a few ways to apply ozone in situations with intermittent flow.  First, an equalization tank can be used to smooth the flow in the system.  The ozone system could then be positioned after the tank where it would receive a steady flow.  Let’s assume that the flow to the system is intermittent, but on average the flow is 10 gpm.  A properly sized tank can be positioned prior to the ozone generator whose level rises and falls, but the outfall is a constant 10 gpm. 

Second, the liquid could be treated in batches.  Even though this may be intermittent operation the period of operation could be extended to a longer period, e.g. hours of operation versus minutes of operation.  A tank is allowed to fill and contents treated over a suitable period of time.  The tank is emptied and then allowed to be filled again to repeat the process.

Third, for a small system, it might make sense to run the ozone generator continuously and waste the produced ozone when it is not needed.  Essentially, if the ozone is not needed it is vented instead of being mixed with the water.  During these periods the generator can be turned down to a low rate of production.  The excess gas would be passed through the same ozone destroyer employed for the vent gas from the process.  In this way, the ozone generator is not entirely shut down.

Fourth, an equalization tank could be used with an ozone system which is set up to recycled the water from the tank through ozone injection system continuously.  The tank level will rise and fall with the flow of water to the system.  A dissolved ozone monitor would control the ozone generator output to main the concentration of ozone in the tank.  While the output of the generator would vary, it would generally run continuously if properly designed in terms of size and flow.

These are a few options for handling intermittent flow to an ozone water treatment system.  These approaches will permit longer generator lifetime, better output control and optimized system size.  Spartan Environmental Technologies supplies complete ozone systems for a variety of water treatment applications.

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