APTsorb

Finally, an economical solution for wastewater treatment! From stormwater treatment and mine dewatering to process water polishing, APTsorb is the new go-to tool for today’s water remediation engineer. APTsorb is a proven performer against dissolved heavy metals, and yet is cost-effective from initial start-up to final disposal.

If you’ve had experience with using peat-based products in the past, and they have underwhelmed you, let APTsorb change your thinking. There’s a reason why Mother Nature finds wetlands and organic soils so valuable. The toxin-filtering ability of wetlands is well-documented, but until now, natural peat has not been a viable alternative for wastewater treatment.

APTsorb is a chemically- and thermally-treated product that takes all the attractive characteristics of natural peat and packages it in an effective, easy-to-use granule. And there’s more; the future is bright for the line of APTsorb products. On-going research indicates that the active and complex structure of the media’s surface can be modified to target specific pollutants such as mercury and sulfates.

Look over the tabs below to learn what APTsorb can do for you, and what future developments lay ahead. American Peat Technology continues to pioneer the market of alternative sorption media, and we look forward to showing you what our products can do.

Description

Product Usage

Advantages

Properties

Downloads

Description

Peat: A good start to a great solution

The story of APTsorb starts 8,000 years ago in the low-lying depressions of the northern boreal forests. After the last glacial retreat, bodies of water naturally aged and filled with vegetation, helped along by cold climate and poor drainage. This unique combination of an anaerobic decomposition environment and cool temperatures resulted in partially decayed plant matter, called peat, with a different kind of chemistry.

Numerous classifications of peat land systems exist. The botanical classification focuses on vegetation, and in general, two types of peat dominate: sphagnum and reed-sedge. Sphagnum peat consists primarily of partially decayed mosses of the Sphagnum genus. It generally looks very fibrous and is commonly sold at home improvement stores in tightly compressed bales or bags. Reed-sedge peat, as the name implies, consists of partially decayed reeds, sedges, grasses and cattails. When decayed long enough, reed-sedge peat is dark and looks like rich humus soil.

Reed-sedge peat is a complex material consisting mostly of lignin, hemicellulose, cellulose and humic substances. These constituents bear functional groups such as alcohols, aldehydes, ketones carboxylic acids, phenolic hydroxides, esters and ethers that are primed and ready for chemical bonding. Further, it’s the negative charge of these functional groups that make peat a star performer against toxins with a positive charge, including the cationic form of many heavy metals.

Natural peat, however, has too many short-comings to be used as is. After filtering surface and ground water for thousands of years, many of the sorption sites on raw peat are already filled with innocuous cations. In addition, raw peat does not have favorable hydraulic characteristics; water simply doesn’t want to flow through unprocessed peat. Also, raw peat is dusty, it’s difficult to wet, and its low density makes shipping a challenge.

APTsorb harnesses all the attractive qualities of peat while overcoming the shortfalls. APTsorb is a hardened granular media that lends itself well to hydraulic loading. It wets readily and has minimal dust. Most importantly, though, APTsorb has been chemically treated to free up the functional groups, making it an even better performer than its parent material.

With such an extensive list of functional groups, it’s little wonder that the mechanisms of sorption for both APTsorb and natural peat remain under debate. There are five commonly recognized mechanisms for the reaction of peat with metals:

• Ion-exchange

• Surface adsorption

• Chemisorption

• Complexation

• Adsorption-Complexation

As the name implies, ion-exchange is simply an exchange of one ion, often a hydrogen ion on a carboxyl group, for another ion, such as a metal cation. This mechanism is often employed by traditional ion-exchange resins and is thought to be the predominate mechanism of APTsorb.

Surface adsorption is a weak, non-chemical attraction between the granule surface and a metal ion. This type of bond is easily reversed.

Chemisorption, or chemical adsorption, is a chemical bond between the surface of the media and a metal cation. Unlike ion-exchange, there is no exchange of ions, but electrons may be shared or exchanged at the active site. Chemisorption results in a strong bond that is not easily broken.

Complexation is another type of chemical bond, but this time between two or more functional groups and a metal cation. The functional groups are often carboxyl and hydroxyl groups, and during the formation of the bond, the morphology of the media surface may change. A hydrogen ion may be released, depending on the functional group.

Lastly, adsorption-complexation is a hybrid type of mechanism, with a weak physical attraction forming between the media surface and a metal-anion molecule while a functional group, such as a hydroxyl group, forms a chemical bond with the same molecule to balance out the charge.

Obviously, APTsorb is a complex media. We continue our efforts to chemically describe APTsorb, relying on the skill of Igor Kolomitsyn, Ph.D., of the Natural Resources Research Institute of the University of Minnesota, to spearhead research into fully describing and optimizing this exciting new technology. At the same time, we seek to uncover new and innovative solutions to environmental problems. Check out the product development link under Technology to see what goals are on our research horizon.

Product Usage

APTsorb is a versatile water treatment media that meshes well with many existing industries and standard equipment. In addition, once the media is spent, disposal is easy to handle because generally, the media meets the EPA’s TCLP limits and can be disposed of as non-hazardous solid waste.

Industrial uses include:

Stormwater remediation

Parking lots
Construction sites
Galvanized roof runoff

Process water treatment

Laboratories
Manufacturing facilities
Plating shops

Mining

Acid mine drainage sites
Mine dewatering
Abandoned mine remediation

APTsorb lends itself well to conventional filtration equipment, including:

Columns
Open-top or passive containers
Standard sand filters
Pressurized contactors
Boom socks
Potentially, as an amendment in contaminated soils

In general, APTsorb cannot be regenerated. The complex chemical nature of the bonding mechanisms result in surface-metal bonds that are not easily broken. Regeneration is costly and incomplete. However, the strength of those bonds also translates into favorable leaching results. Although it is up to the end user to determine if spent media meets TCLP limits for non-hazardous waste disposal, current data suggest that spent APTsorb meets EPA guidelines when used in conventional conditions. Contact us for guidance on meeting TCLP limits.

Advantages

A Cost-Effective Solution

Unlike most synthetic resins, APTsorb’s diverse mechanisms of sorption result in unusual loading curves. Simply put, different cations approach different functional groups in different ways. In that respect, coefficients of kinetic loading are not uniform throughout the life of the granule. That presents some challenges to using APTsorb, but also makes it an attractive solution for many applications.

As mentioned under the Description tab, ion-exchange is most likely one of the primary mechanisms of adsorption. Those sites are extremely active, making APTsorb an excellent candidate for a final polishing step in a conventional treatment regime. If residence times are within limits, APTsorb is simply unwilling to let most metals with a 2+ valance, and some with a 3+ valance, through. Much of our research has centered on cadmium, and current data indicate that the ion-exchange sites, by themselves, can be loaded to about 3.5 mg Cd per gram of APTsorb.

The other functional groups are also active against cadmium. Our data indicate that APTsorb’s total capacity approaches 25 mg Cd per gram. The different coefficients across the loading mechanisms suggest, and our research confirms, that attacking a wastewater with a counter-current stream is effective. As the upstream granule is spent, it is replaced with fresh media at the end of the stream. This takes advantage of the different coefficients of loading and uses the granule to its fullest extent.

APTsorb’s cost-effective pricing structure, which is about a tenth of traditional resins, translates into larger contactors that can address increased flow volumes. For this reason, APTsorb is an ideal candidate for stormwater remediation or applications where large volumes of water are complicated by relatively low concentrations of contaminants.

Although much of our research has focused on cadmium remediation, we have also partially described APTsorb’s activity against copper and lead, and to a lesser extent, nickel, zinc, cobalt, chromium and manganese. Contact us for more information about how APTsorb will perform with your particular wastewater.

An Environmentally-Friendly Alternative

Traditional sorption resins are synthetic, petroleum-based polymers. They are an effective tool for wastewater remediation, but in the long run, they are not sustainable. The economic and environmental costs of producing oil can only increase as competing manufacturing sectors continue to demand slices of an-already uncertain natural resource. Even now, factors such as sustainability and actual environmental costs enter more often into thoughtful purchasing decisions. Being green is no longer a secondary, abstract consideration.

APTsorb is not made from petroleum products. It is made from easily-accessible, environmentally-safe peat. From field harvest to final shipping, we strive to be a good steward of the resource entrusted to us. And in many ways, our raw material makes it easy for us. Harvesting peat is much more like farming than mining. The material is essentially harmless at all stages: in the deposit itself, in processing, in transport and in use by the consumer. Unlike petroleum, the site where peat is harvested, while certainly disturbed, is not inhospitable. We often see wildlife on our peat fields, and we comply with strict de-watering regulations to ensure that we are not sending any problems downstream.

Technically, and according to the US definition, peat is not a renewable resource. Finland is the only country to classify peat as renewable. At an accumulation rate of about 3 centimeters per year, most long-range business plans, including our own, take into account the value of the current resource. We have acquired a core of knowledge about alternative raw materials in our desire to produce a truly sustainable product. For instance, we already know that certain composting processes can produce a raw material not unlike our current peat. Our research includes efforts to produce a consistent, high-quality raw material using natural and native vegetation. We hope that in the future we will be offering a filtration media that is 100 percent sustainable, through the use of low-value, diverse cover crops that convey environmental benefits during the growing season. In the meantime, we will continue to judiciously harvest our current deposit so that we can explore the market for a safe and environmentally-friendly alternative to petroleum-based resins.

Check out our Plant Operations page under the Technology link for more information about how we continually seek to green our production of our entire line of products.

Our harvesting operation uses low-impact equipment to gently remove only the top several inches of our peat deposit each year. There are no open pits or gaping scars in our peat fields. Our deposit is only a mile away from our processing plant, which means that we are not using precious resources to truck raw material long distances. Inside our processing plant itself, we use a bio-fuel combustor to do the bulk of our drying operations.

Properties

APTsorb is an innovative, environmentally-friendly sorption media for dissolved heavy metals. It is made of physically-, thermally-, and chemically-modified red-sedge peat harvested from the abundant reserves of North America. It capitalizes on the known sorption mechanisms and capacities of natural peat while improving on those qualities that have limited peat’s use in wastewater treatment in the past.

APTsorb is a low-cost alternative to traditional resins and excels in applications such as polishing prior to discharge, storm water treatment, and waste waters with low pHs.

Properties¹

Physical form	Granules
Matrix	Reed-sedge peat
Mechanisms of sorption	Chemical: ion-exchange, chemisorption, complexation Physical: surface adsorption Combination: adsorption-complexation
Ionic form	H⁺, Na⁺
Total capacity²	44.5 meq/100 g
Capacity at 50 ppb equilibrium³	14 meq/100 g
Bulk density	0.7 g/cm³
Particle size	12 X 50 mesh (>90 percent of granules)
Particle density	1.55 g/cm³
Moisture content as shipped	9-14 percent
Expansion	up to 65 percent
pH of media¹	4.9-5.2
Ash content	15-17 percent

Suggested Operating Conditions

Maximum operating temperature	77⁰C (170⁰F)
pH of water	2 - 8.5
Recommended BV/hour	6
Column pretreatment	Flush with five bed volumes clean water, discharge to drain
Bed ratio	Depth/width = 1/1.25 = 0.75
Contact time	5 to 20 minutes
Regeneration	Not recommended
Sparging/fluffing	Water, air, CO₂ or N₂
Expansion precautions	Pre-wet media or allow for expansion, air sparge if needed

Elemental analysis⁴

Element		Element	(ppm)	Element	(ppm)	Element	(ppm)
C	48 – 52 %	Be	<1	Li	<5	Na	<4800
H	4 – 5 %	B	<20	Mg	<1200	Sr	<18
N	2 – 3 %	Cd	<7	Mn	<31	Tl	<10
O	29 – 35 %	Ca	<5100	Hg	<60 ppb	Sn	<10
	(ppm)	Cr	<7	Mo	<3	Ti	<100
Al	<3500	Co	<2	Ni	<7	V	<6
Sb	<5	Cu	<6	K	<550	Zn	<10
As	<4	Fe	<3900	Se	<2
Ba	<65	Pb	<7	Ag	<2