At the International Ozone Association meeting in Boston a couple of months back, Frederick Laskey, who is the executive director of the Massachusetts Water Resource Authority (MWRA) gave one of the keynote addresses. MWRA supplies 220 MGD of drinking water and treats 350 MGD of wastewater. Boston once had, or at least what was called, the dirties harbor in America.
MWRA invested $3.8 billion to improve water quality in the harbor and is on track to have the cleanest harbor beach in America by 2011. MWRA’s Carrol Drinking water plant employs ozone water treatment for taste and odor control and produces some of the best tasting water in the US. In addition, the water is free of pharmaceutical products found in other drinking water systems. Further improvements are being planned to meet the next generation of regulations such as the EPA’s LT2 standards.
This is great progress, but it did not come without some cost. Prior to the capital spenidng program, a Bostonian household paid $100/year for water, now they pay closer to $1,000/year. If we assume that the average person uses 150 gallons/day of water and the average household has 2.5 people, the cost per $1,000 gallons is about $7.50. Not an unreasonable price for such an important commodity.
As we have discussed in previous posts, certain pharmaceutical, personal care products, flame retardants and perfuorooctanoic acid have found their way into public drinking water systems. In addition, most water treatment systems are not designed to remove these contaminants. The concensus, until now, has been that this compounds are in concentrations that do not pose a threat to public health.
The EPA is now asking permission from the Office of Management and Budget to conduct a survey at 25 water utilities to determine the prevalence of 200 emerging contaminants. This would appear to be the first step to regulating the presence of these compounds in drinking water.
Some water and wasterwater utilities have begun to be concerned about these issues. The Clark County in Nevada is looking at building an ozone disinfection system for their wastewater with the additional goal of removing emerging contaminants from the water. they have been aided by the Southern Nevada Water District (SNWD)which treats drinking water from the same source Clark County discharges to.
SNWD is an expert in the use ozone having one of the larger ozone water treatment processes in the country for disinfecting their drinking water. In addition, SNWD has also done considerable research showing that ozone is quite effective in removing these contaminants from water.
Check out the Federal Register for April 8, 2009 pp 15965-15967 for more information.
We are always interested in new applications for ozone water treatment. In the current issue of Ozone News, researchers describe a process for using ozone to reduce excess sludge from an activated sludge process.
The activated sludge process is a biological process that uses bacteria to breakdown organic compounds in wastewater prior to their discharge into the environment. A tank with bacteria is constantly supplied with air/oxygen along with the feed of wastewater. As the bacteria convert the organics to CO2, the amount of sludge increases. This excess sludge must be removed from the process, dried and disposed of. The handling and disposal of the excess sludge represents a major portion of the cost associated with running a wastewater treatment plant.
The researchers found that by adding ozone to a portion of the sludge that is recycled back to the process, the overall production of sludge can be reduced. Previous work had found that this was possible, but the amount of ozone required made the approach uneconomical. The current development appears to have overcome this problem by improving the reactor design.
Disposal of sludge from wastewater treatment plants is becoming increasing difficult due to limited land fill locations willing to accept the sludge as well as reduced opportunities to employ the sludge for agricultural application. So economical processes for reducing sludge production are wlecomed.
This development may create a major new application for ozone generators in wastewater treatment plants. In teh past, the ozone was primarily used as a disinfectant.
There are many reasons why ozone is used to treat drinking water, but one of the most noticeable is that it makes water taste better. A further example of this comes from the state of Georgia.
There are 1,600 public water systems in Georgia and 100 of those systems competed for the title of best tasting water sponsored by the Georgia Association of Water Professionals. The testing was done using a double blind tasting. The state is divided into sections which compete with one another.
The 2009 winners included Forsyth County. Forsyth County uses ozone to disinfect its water, which means less chlorine than many water treatment facilities. Ozone drinking water treatment also aids in filtration and helps removed dissolved organics that can add an off taste to water.
Forsyth will face off against the other six winners for the state championship in August. The winner of that contest will compete nationally against other state winners next year in Texas.
We continue to scan news releases about new water treatment facilities employing ozone to improve water quality around the US and Canada. As we have noted in previous posts, ozone offers multiple benefits for drinking water treatment. Below is another example of a large water system switching to ozone water treatment.
Gilbert and Chandler Arizona have completed a new $102 MM treatment plant that will process 24 MGD of Colorado River water. Officials expect that residents will notice an improvement in the taste of the water.
The new plant uses a new process called “ballasted flocculation,” which uses ozone, sand and coal to remove bacteria and particles from the water within about 15 minutes. The process previously took about two hours and required much more space. The ozone is the facility is produced by ozone generators. Phoenix’s Lake Pleasant Water Treatment Plant converted to ballasted flocculation last summer.
Poche Beach, a county-owned spit of sand between Dana Point and San Clemente, California had a problem with water quality as a result of storm water runoff with pollutants and bacteria that flowed right into the Pacific making the water unsafe for bathers. Recently, officials in the area dedicated a $3 MM treatment facility using UV to reduce the amount of bacteria entering the beach area.
The city of Dana Point in 2006 invested in a $6 million treatment plant in Salt Creek. That project used ozone instead of ultraviolet light, the first time ozone was used to treat urban runoff. Ozone was used against runoff in Dana Point because the Salt Creek water was not clear enough for UV light to penetrate it and kill bacteria. The state contributed $4 million to that project. Salt Creek has not had a single water-quality advisory while the plant was running. Dana Point also has added a smaller ozone system to a creek that runs between San Juan Creek and Dana Point Harbor.
The project demonstrates that ozone can be an effective means to treat storm water runoff to reduce bacterial loads. In this case, to make the beach safer for those who want to enjoy ocean bathing, ozone can provide excellent disinfection, especially where the water cannot be economically treated with UV. Ozone not only purifies the water, but also leaves behind no residual that other disinfectants such as chlorine might.
Research in ozone generation technology continues to provide new approaches to improving the cost and effectiveness of ozone for a variety of applications. The two technologies that were discussed at the recent International Ozone Association conference pointed out the promise of these new approaches. One approach involved electrochemical formation of ozone using artificial diamond electrodes and the other employed a new Xe Excimer UV lamp. In this post I will discuss the latter development and in a future post will cover the electrochemical approach.
UV Solutions has developed a new extremely efficient light source converts more than 50% of input energy to 172 nm light. By exposing air or oxygen to the radiation from this lamp, high concentration ozone can be produced with high energy efficiency. This is because one photon of 172 nm UV light produces two molecules of ozone. As with other gas phase ozone generation methods, results depend on temperature, pressure and humidity. Nonetheless at 300 degrees K, the lamp was able to produce 40 wt% ozone at 50 g/Kwh. This concentration is not possible to produce at that energy level by any conventional technology employed today.
It is expected at concentrations currently employed for water treatment (8-10%), that ozone made using this UV process will reduce energy consumption by 45%. Since energy is one of the major costs associated with the production of ozone, this is a substantial improvement over current technology employing the corona discharge method. Total cost for UV produced ozone using this method is expected to cost $0.60/lb versus $0.80/lb for the conventional method.
This technology is only at the laboratory scale, but the potential of the technology is great if the process can be scaled up to larger sizes comparable to those used in ozone water treatment applications.
Spartan has introduced its SPARTOX ozone water treatment system. The SPARTOX system is a completely self contain ozone water treatment system mounted on a skid which requires only a connection for the water to be treated and electrical power. The on board systems include a compressor/oxygen concentrator, ozone generator and ozone water mixing system with integrated booster pump.
The SPARTOX package is easy to install and use. The system has an automatic control featuring a touch screen computer control system. Optional dissolved ozone monitor or ORP monitor with built in PID controllers can pace ozone generator output to targt a specific ozone or ORP target value in teh treated water. The panel door is interlocked to shut down the system should the door be opened by unauthorized personel during operation. All electrical connections are fused for protection of the equipment.
Applications include bottled water facilities, small drinking water treatment systems, bottle washing applications, clean in place (CIP) applications, small industrial wastewater treatment system and many other water treatment applications.
Spartan is shipping SPARTOX unit currently to various customers in North America.
SPARTOX Ozone Water Treatment System
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Another town is looking to add ozone for drinking water treatment to meet new EPA regulations. Manistique, MI will add ozone water treatment as part of a two step improvement to their water treatment plant. The funds will come from the US Department of Agricultures Rural Development (RD) fund. The RD funding is 75% grant and 25% low interest loan.
An increasing number of communities are beginning to view ozone as an important option for meeting increasingly stringent EPA drinking water standards.