Entry for February 25, 2008

In this posting we are going to talk about “good” and “bad” ozone in the environment.  The discussion of bad ozone comes from the US EPA website.  The discussion of the good ozone comes from the NASA website.

Ground-level or “bad” ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOC.

Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma. Ground-level ozone also can reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue.

Ground-level ozone also damages vegetation and ecosystems. In the United States alone, ozone is responsible for an estimated $500 million in reduced crop production each year.

Under the Clean Air Act, EPA has set protective health-based standards for ozone in the air we breathe. EPA and others have instituted a variety of multi-faceted programs to meet these health-based standards.

Throughout the country, additional programs are being put into place to cut NOx and VOC emissions from vehicles, industrial facilities, and electric utilities. Programs are also aimed at reducing pollution by reformulating fuels and consumer/commercial products, such as paints and chemical solvents that contain VOC. Voluntary and innovative programs also encourage communities to adopt practices, such as carpooling, to reduce harmful emissions.

Good ozone is found in the ozone layer.  The ozone layer refers to the ozone within stratosphere, where over 90% of the earth’s ozone resides.   The stratosphere is located between 10 and 50 km above the surface of the earth.

The ozone layer absorbs 97-99% of the sun’s high frequency ultraviolet light, light which is potentially damaging to life on earth. Every 1% decrease in the earth’s ozone shield is projected to increases the amount of UV light exposure to the lower atmosphere by 2%.  Because this would cause more ozone to form in the lower atmosphere, it is uncertain how much of UV light would actually reach the earth’s surface. Recent UV measurements from around the northern hemisphere indicate small UV increases in rural areas and almost no increase in areas near large cities.  The concern is that elevated UV levels may have adverse effects on plant and animal life on the earth.

The water treatment industry artificially creates ozone using an ozone generator to purify water by removing contaminants and inactivating pathogens.  This is another example of good ozone in the environment.  Spartan Environmental Technologies supplies ozone water treatment systems. 

 

 

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Entry for February 15, 2008

This posting is our third in a series discussing the use of ultra sonic systems for the control of algae.  In this note we will ultra sound in the context of a total water management system.  As noted in the previous note we discussed how ultra sound can damage the hard outer cell wall of certain algae species.  This damage leads to the eventual death of the algae so affected.  There are other factors to consider in the overall approach to algae control.

If the environmental in the water allows for aggressive growth of the algae and the algae is already well entrenched in the water.  Ultrasound alone might take a long time to impact the population.  This process can be helped along by other water management practices that have value beyond the control of algae.

One of these factors is the dissolved oxygen content of the water at all water depths.  Oxygen supports animal life for fish and bacteria.  Clearly, to keep the fish in the water body healthy the oxygen content of the water must be at a minimal level.  Less obvious is the need to support the bacterial community in the water.  One of the reasons that the algae have become entrenched in a body of water is the presence of nutrients that supports their growth.  If the water is low in oxygen, bacteria can not compete with the algae and the algae tend to get out of control.  If the bacteria in the pond have a good level of oxygen, then they can compete with the algae and reduce the nutrient that both rely on.  In addition, the bacteria can also decompose the algae that die in a healthy manner improving the water quality and appearance of the water.

In order to maintain the proper oxygen level the water needs to be aerated.  This aeration needs to be done in a fashion that will promote good oxygen levels throughout the body of water and at all depths.  A variety of aerations depths are available to do this and experienced personnel can guide the owner of the water body to select the proper type and size of aeration device.  A rule of thumb is that the amount of aeration should be equal to the one horse power for the aeration pump for each acre foot of water.  Moving the water will also equalize the temperature in the water.  The warmer the water the more algae there will be.

The natural bacteria in a body of water may have been seriously depleted by the competition and water quality.  As a result it may be necessary to add good bacteria to the water along with enzymes that will assist the bacteria to break down nutrients.  This should only be done once the oxygen levels in the pond have been adjusted properly.  The application of the bacteria is easy to do.  Typically the treatment is done only once or twice a season.

The combination of aeration, bacteria and ultrasound should eliminate the presence of algae in most bodies of water.  This process can be accelerated to some extent by the use of dyes to darken the water.  Food grade dyes are applied to reduce the amount of light that the algae receive from the sun.  Algae are plants and thus they use photosynthesis to grow.  As the light is reduced, they will have difficulty growing and competing with the good bacteria in the water.  This will hasten their removal from the water.  The dye will break down naturally in the water over time.  So, if the algae remain a problem the process might need to be repeated.

The use of ultrasound, naturally occurring bacteria and aeration represent a way to quickly control algae growth in a body of water in an environmentally friendly fashion that won’t harm fish or aquatic plants.  Once the pond is properly balanced, no further addition of bacteria or dye will be needed and the use of toxic heavy metals (such as copper) can be eliminated.  Spartan Environmental Technologies can help you with developing an environmentally friendly solution to your algae control problem.  Contact Spartan for further information.

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Entry for February 10, 2008

In this posting we will talk a little more about ultrasonic algae control.  The discovery that ultrasonic waves in water kill algae was made over sixty years ago in submarine sonar experiments.  It took some before this observation was applied to the control of algae in ponds, pools and other water bodies.

Effective ultrasonic algae control devices transmits a complex pattern of ultrasonic vibrations through the water causing the vacuoles inside the algae cells to resonate and break  the same vibrations are harmless to humans, animals, fish and aquatic plants. Once broken, the algae cells no longer possess the ability to grow and reproduce. The pond or pool will become clearer and healthier from destruction of algae and other harmful root-parasitic fungi (single-celled) without having to apply environmentally harmful chemicals for this purpose. The microscopic pictures  show the ultrasonic effects on healthy, dying and dead algae cells.

It is important to note that not all organisms called algae are killed by ultrasonic waves.   Species that are killed might take longer than others to die.  In swimming pools for example, the toughest ones are the black algae which mostly grow in the joints of the tiles; however, they surely will be killed in due time.  Another hard type is filamentous algae.  Some patience is definitely required here, as they bond together forming masses which absorb the ultrasonic vibrations hindering the overall effective range. They will be killed, it just takes longer.

There are over twenty thousand kinds of algae, which react in various ways after their demise. The most common algae are the so-called “roaming algae”, which enter the water by wind and rain, these will be killed the quickest. Others may take a couple of weeks, but will be dead in due time. Even though some algae die rather fast, others may take up to six weeks before the effects are visible to the naked eye.   There are some species with different cell structures that are unaffected by ultrasound.  The only way to be sure is to have a sample of the algae tested by a trained biologist who can identify the species in the water.  Spartan Environmental Technologies and its partner Algae Control US provide this service free of charge.

Spartan supplies the LG Sonic brand of algae control systems.  The LG Sonic algae control devices are scaled for different sized water systems with application ranges of 10, 30, 50, 100, and 150 meters, so you can fit your system with the right device or combination of devices from a water garden to a 4.5 acre pond with a single unit or lakes, and reservoirs with multiple units.  Contact Spartan for more information on ultrasonic algae control to see if it is correct for you pond, pool or lake.

 

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Entry for February 5, 2008

In our postings up to this point we have focused on on oxidation technologies.  Spartan also offer ultrasonic algae control products.  Our partner in this area is Algae Control US.  The following information on teh use of ultrasonics for biofilm control was provided by the Vice President for Engineering of Algae Control US, George Hutchinson.  George writes:

“Ultrasonic units help to eliminate the biofilm growth that acts as a host and

attachment point for algae. The ultrasound will prevent most of the planktonic bacteria from becoming strongly attached sessile bacteria that forms the base layer of the biofilm. Bio-film typically start forming as quickly as 20 minutes to 3 hours. Bacteria are not killed by the LG Sonic device although they are being affected. The ultrasonic sound waves vibrate the bacteria and their pili retract as if they are in turbulent water. They do not excrete the polysaccharide glue they use to attach to a surface. The influence of the ultrasound actually slows down biofilm growth on surfaces. Thus, if you start with a very clean surface, the formation of biofilm is nearly inhibited. The LG Sonic has had very positive results on preventing

bio-film in the following applications: WWTP clarifiers, potable water basins and vnotch weirs, swimming pools, viewing glass windows and

aquarium tanks at a zoo.

Biofilm reduction is a large benefit to our clients for overall algae control.”

If algae is a problem in your ponds or water treatment facilites, ultrasonics might be a good option versus chemical oxidation and disinfection.  Contact Spartan for further inforamtion.

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Entry for February 4, 2008

In this posting we will discuss measurement of dissolved ozone.  Knowing dissolved ozone concentration is important in a variety of situation, most especially in water disinfection.  The ozone residual is critical for calculating the CT value as we have discussed in previous postings.  CT in turn is the key parameter for determining pathogen inactivation.  In applications where organic destruction is being considered, the residual ozone can help establish the mass balance for ozone in the process and therefore the amount of ozone required to treat a given amount of water.  It may also be a useful marker for the end point in the end point of the reaction indicating that further ozone addition is not needed.

Measurement of dissolved ozone can be done directly or indirectly using both wet chemical methods and analytical instruments.  Direct measurement of ozone in water can be done using UV or electrochemical methods.  Measurement can accurately be made in the ppb range.  The electrochemical method uses selective polarographic membrane sensors, dissolved ozone can be monitored interference-free.  

The UV method employs UV absorption method.   The amount of UV radiation absorbed is directly proportional to the amount of ozone in solution.  Measurements in the low ppm range are possible with this approach.  Both UV and electrochemical monitors provide direct digital readout ozone concentration.  As a result they are extensively used in the water treatment industry.

In terms of wet chemical methods, the indigo method relies of the fact that in acidic solution ozone decolorizes indigo.  The decrease in absorbance is linear with increasing concentration of ozone.    A colorimeter can be used to measure absorbance.  Alternatively a color wheel can be used, although the measurement than relies on the operator to judge the match between the color wheel and the change in color in the water.  The indigo method is quantitative, selective and simple.  It can be used to calibrate the digital instruments based on the electrochemical or UV method.

If the absolute value of ozone concentration is not needed, the oxidation reduction potential (ORP) can  provide the operator with a rapid and single-value assessment of the  disinfection potential of water and an indirect measure of ozone concentration.   ORP monitors are generally less expensive than other ozone monitors, but since they do not give a direct read out of ozone concentration they are also less valuable.  In addition, ORP is not specific to ozone and will measure any oxidant present in the water, e.g. chlorine.  So if there is a chance for interference, ORP should not be employed.

 

 

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