Powdered Activated Carbon Treatment (PACT) is a wastewater technology in which powdered

activated carbon Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that increase the surface area availa ...

is added to an

anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...

aerobic treatment system An aerobic treatment system (ATS), often called an aerobic septic system, is a small scale sewage treatment system similar to a septic tank system, but which uses an Cellular respiration, aerobic process for digestion rather than just the Fermentat ...

.Jafarinejad, S. “Activated sludge combined with powdered activated carbon (PACT process) for the petroleum industry wastewater treatment: A review.” Chemistry International. 3(4) (2017) 26. The carbon in the biological treatment process adsorbs recalcitrant compounds that are not readily biodegradable, thereby reducing the chemical oxygen demand of the wastewater and removing toxins.Meidl, John. “Use of the PACT System to Treat Industrial Wastewaters for Direct Discharge or Reuse.” Jubilee XX Conference of Science & Technology. The carbon also acts as a "buffer" against the effects of toxic organics in the wastewater. In such a system, biological treatment and carbon

adsorption Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a ...

are combined into a single, synergistic treatment step. The result is a system which offers significant cost reduction compared to

activated sludge The activated sludge process is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa. It uses air (or oxygen) and microorganism ...

and granular carbon treatment options. The addition of the powdered activated carbon stabilizes biological systems against upsets and shock loading, controls color and odor, and may reduce disposal costs while removing soluble organics.Ruiz-Lopez, Salvador and Clayton Maugans. “Wastewater Treatment.” Hydrocarbon Engineering. May 2004.

System Description

In an

, influent first enters an

aeration Aeration (also called aerification or aeriation) is the process by which air is circulated through, mixed with or dissolved in a liquid or other substances that act as a fluid (such as soil). Aeration processes create additional surface area in ...

tank where the powdered carbon is added, making up a portion of mixed liquor suspended solids.Meidl, John. “An Overview of PACT Wastewater Treatment for the Petroleum and Petrochemical Industries.” Symposium – Environmental Successes in the Chemical Industry, 203rd American Chemical Society Meeting. Once the

is completed, the treated

wastewater Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industrial ...

and the carbon-

biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bio ...

slurry A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal p ...

are allowed to settle. In cases where complete solids separation is needed, such as for reuse, an MBR may be used in place of the clarifer. Following treatment, a portion of the carbon and biomass slurry is wasted to solids handling. Due to the presence of the powdered activated carbon, the sludge settles, thickens, and dewaters better compared to conventional activated sludge processes. These solids can be wasted and disposed of as a slurry, dewatered to a compact, stable cake, or pumped as a slurry to a wet air oxidation unit for further processing to regenerate the

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...

and destroy the biological solids.

Commercial Applications

The system as it exists today was developed in the 1970s under a collaborative effort between DuPont and Zimpro. PACT systems can be used to treat very difficult to treat

s including * refinery, petrochemical, pharmaceutical, chemical, textile/dye and other industrial wastewaters * landfill

leachate A leachate is any liquid that, in the course of passing through matter, extracts soluble or suspended solids, or any other component of the material through which it has passed. Leachate is a widely used term in the environmental sciences wh ...

* highly contaminated surface water or groundwater. Powdered activated carbon is also used in the processing of drinking water at treatment facilities, primarily on a seasonal basis in order to deal with aesthetic problems with the water such as odor and taste issues associated with Geosmin and 2-MIB. Today there are over 100 PACT systems worldwide. Some of these installations have been retrofits to existing conventional activated sludge processes to meet more stringent effluent requirements. Several PACT systems have been built in China in recent years as a result of higher treatment regulations for difficult-to-treat industrial wastewaters. PACT systems have also been used to meet bioassay and toxicity requirements as well as allow for

water reuse Water reclamation (also called wastewater reuse, water reuse or water recycling) is the process of converting municipal wastewater (sewage) or industrial wastewater into water that can be reused for a variety of purposes. Types of reuse include: ...

References

* {{DEFAULTSORT:Powdered Activated Carbon Treatment Waste treatment technology Powders

System Description

Commercial Applications

See also

References