Reducing customers’ activated carbon footprint

Oct. 10, 2012

Dealers and industry professionals continue to grow waste and sustainability awareness.

In many ways water treatment dealers serve as an industry advisor for customers. While these suppliers can help in recommending sound, practical solutions to customers and communities for problem water, these companies are also in position to follow through all the way to the disposal of spent product or equipment. By establishing a recycling program or partnering with sustainable-minded manufacturers, dealers can augment cradle-to-cradle sales relationships.

Why change

Although many aspects of our industry are green by nature, such as removing environmental contaminants for safe consumption, water treatment processes, especially on the municipal side, have traditionally followed some wasteful practices with environmentally unsafe consequences.

According to Leo Zappa, director, municipal water market for Calgon Carbon, for years, many municipal water treatment plants have used powdered activated carbon (PAC) to remove taste and odor compounds from water. “While effective in this regard, PAC also constitutes a waste product that has to be hauled away and disposed of as a sludge. Some water plants later converted to granular activated carbon (GAC), which is a more efficient means of employing activated carbon for the removal of targeted compounds. However, until recently, this GAC, once exhausted, was removed and disposed of either in landfills or via incineration,” he explains.

Issues associated with traditional means of disposal are coming to the forefront. The public is more aware of groundwater contamination as research has evolved and government attention has been shifted in this direction.

Discharges and spills from manufacturing facilities, which are not uncommon today, also have the potential to produce growing amounts of identified toxins in water sources, including chemical fertilizers, benzene, toluene, xylene, fuel oil, jet fuel, gasoline and more.

“This is highly worrisome to municipalities whose water intakes might be along major tributaries or groundwater supplies,” continues Zappa. “Added to the concern of discharges and spills is the EPA’s Stage 2 Disinfectants and Disinfection Byproducts Rule. Since monitoring technologies have evolved and are able to measure contaminants to the µg/L [and] mg/L level in our water today, communities are demanding municipalities address drinking water concerns without increasing rates.”

One way municipalities are overcoming these issues is through GAC contactors followed by disinfection. Not only has GAC proven to be an effective and viable protection from organic spills and discharges, informs Zappa, it has supplied customers with a multitude of additional benefits.

“DBP control, protection from many emerging contaminants, less chlorine usage and improved taste and odor are just a few. GAC has provided municipalities and customers with greater public health protection, water quality which meets or exceeds government regulations, all while satisfying customer expectations and securing community trust and confidence,” says Zappa.

Makes sense to reactivate

For municipal customers, dealers can educate decision-makers on recycling options as well. Some of the wasteful, but not necessarily harmful, practices in the water treatment industry is the disposal of spent activated carbon, which is activated carbon after it can no longer meet its treatment objective for water discharge values.

“At the municipal level where large volumes of activated carbon are employed and the spent carbon in the majority, if not all, cases is considered non-hazardous, there is a great opportunity to ‘reactivate’ the carbon and reuse it. At the consumer level, or what I consider the home treatment system, it is logistically too challenging and not cost effective at the moment to remove the spent carbon from the consumer for reactivation,” says Kim Walsh, vice president of marketing for Carbon Resources.

And, when municipal customers consider that reactivation of carbon can equate to less than 20 percent of the greenhouse gases compared to new carbon production and reduces landfill waste, most will want to take advantage to reduce their carbon footprint.

In just the past few years, continues Walsh, companies have dedicated reactivation furnaces to handle municipal spent carbon and have received NSF certification on the reactivated product.

“Companies involved in reactivating spent carbon from municipalities typically have to test a representative sample to assure that it is non-hazardous,” explains Walsh. “The spent carbon is then hydraulically removed directly from the plant into a tanker truck where any residual water is drained on-site. The tanker then transports the spent carbon to the reactivation site where it is discharged into holding tanks. The spent carbon is then gradually fed into the reactivation unit for reactivation.

“During and after reactivation, activated carbon samples are taken to determine the activation level according to standard ASTM D-28 testing protocols where they target to reach a pre-determined activity level.

Reactivation and regeneration

In the reactivation process, the spent activated carbon is heated in furnaces with a low oxygen level using steam as a selective oxidant. The adsorbed organics are either volatilized from the activated carbon or pyrolized to a carbon char. The volatile organics are destroyed in the furnace’s afterburner and acid gases are removed by means of a chemical scrubber. The high-temperature reaction with steam serves to restore the adsorptive capacity of the activated carbon.

For reactivating the GAC, temperatures may approach up to 1,800° F. “Approximately 90-95 percent of the original activated carbon activity may be restored,” asserts Walsh. “About 10 percent of the activated carbon is burned up or lost in this process.”

On the other hand, regeneration usually refers to a process where the spent carbon is washed with either water or a chemical agent to remove a portion of the contaminants adsorbed by the carbon. For regeneration, the GAC is treated in the adsorption vessel (in-situ), adds Walsh. The temperature is usually less than 250° F and only about 5-50 percent of the original activity of the activated carbon is restored, depending upon the contaminants on the activated carbon and regeneration conditions.

“Generally speaking,” adds Zappa, “activated carbons used in municipal water treatment can’t be effectively regenerated, though some companies market chemical solutions that can be used to remove some mineral buildups on the carbon, which can facilitate more effective thermal reactivation.”

As municipal customers become more conscious about protecting their location’s resources, such as landfills and water sources, these sustainable and practical solutions will continue to emerge.

While not commonplace in residential water treatment today, some experts envision a future where homeowners will be able to take advantage of carbon recycling practices. Grow awareness and position your company as a cradle-to-cradle focused business.

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