By Dennis Abraham Thazhamon
The supply of clean, fresh water is rapidly becoming more and more constrained as populations rise and demand for high quality water grows around the world. The challenge is multifaceted. Increasing regulatory pressures require tighter and tighter limits on various contaminants in drinking water supplies and wastewater discharges. Increasing standards of living dictate consumer demand for better tasting water that is free of off-colors and odors. Increasing industrial processes also require cleaner feed water quality. Providing clean water for people to drink is one of the biggest challenges facing our world. Some countries struggle with water-borne diseases. Others face natural pollutants such as arsenic or man-made pollutants like textile dyes and pharmaceuticals.
Technology is constantly evolving and changing to meet the needs of humanity and one of those needs is for clean water. The water treatment industry is always researching, testing and developing new and improved ways in which to treat wastewater and drinking water that are both efficient and environmentally friendly. For hundreds of years, humans have utilized the resources provided by nature to improve our quality of life. Sometimes we use them in the manner they are available in the environment and other times, we find new and innovative ways they can be implemented.
Water is a huge part of manufacturing industries. The water used in the manufacturing industries can get contaminated during the process and needs to be treated before it’s released into the environment. Likewise, some industries need water to be treated before it can be used for manufacturing. Activated carbon is a powerful adsorbent used prolifically throughout water purification efforts to remove contaminants. While activated carbon can be used in a wide range of water treatment applications, it is a critical tool used throughout municipal and industrial water treatment facilities to treat drinking water, wastewater, and municipal water for process use.
The unique, porous structure and vast surface area of activated carbon, combined with attraction forces, allows activated carbon to capture and hold various types of materials onto its surface. Activated carbon comes in many forms and varieties. It is produced by processing a carbonaceous material, most often coal, wood, or coconut husks, in a high temperature environment (such as a rotary kiln) in order to activate the carbon and create the highly porous surface structure.
Activated carbon is one of the most used products in the water treatment industry. It is extremely porous with a large surface area, which makes it an efficient adsorbent material. Activated carbon belongs to group of porous carbon materials that have high adsorption capacity and reactivation capability. Many substances are used as a base material to produce AC. The most common of those used in water purification are coconut shell, wood, anthracite coal and peat.
Various forms of activated carbon exist, each offering different material characteristics that make it ideally suited for specific applications. As such, manufacturers offer a wide array of activated carbon products. Depending on the application, activated carbon may be used in powdered, granular, extruded, or even liquid form. It may be used alone, or combined with different technologies, such as UV disinfection. Water treatment systems typically employ either granular or powdered activated carbon, with granular activated carbon (GAC) from bituminous coal being the most commonly utilized form. Coconut shell has emerged as one of the best forms of activated carbon for water filtration system needs. Coconut shell- based activated carbons are micro-pores. These small pores match the size of contaminant molecules in drinking water and thus are very effective in trapping them. Coconuts are a renewable resource and readily available throughout the year. They grow in large numbers and can be preserved for a long time.
Water may contain contaminants which can affect health and quality of life. Water intended for human consumption must be free from organisms and from concentrations of chemical substances that may be hazardous to health. The water we drink daily must be free from any pollution. There are two types of drinking waters: pure water and safe water. It is important to distinguish between these two types of drinking waters.
Pure water may be defined as water that is free of extraneous substances whether harmless or not. From a practical standpoint, however, pure water is hard to produce, even with current sophisticated equipment. On the other hand, safe water is water that is not likely to cause undesirable or adverse effects. Safe water may contain some contaminants but these contaminants will not cause any risks or adverse health effects in humans. The contaminants must be in an acceptable range.
For example, chlorination is used to disinfect water. This process, however, introduces trihalomethanes (THMs) into the finished product. THMs pose potential health risks. Long- term drinking of chlorinated water appears to increase a risk of developing bladder cancer as much as 80 percent, according to a study published in the journal of the National Cancer Institute (St. Paul Dispatch & Pioneer Press, 1987).
As the population of the world increases and demands for using safe water increases more than ever before, it will be of great concern in the near future that water treatment facilities be more effective. On the other hand, water supplies to households are still threatened by contaminants like chemicals and microorganisms.
Drinking water contaminants are more likely to cause chronic health effects. Usually, chronic health effects happen when humans are repeatedly exposed to small amounts of chemical in the drinking water. Examples of chronic health effects are cancer, liver and kidney damage. Drinking water contaminants that may lead to health effects are divided into five groups, including microorganisms, dissolved salts, dissolved organics, suspended solids and dissolved gases.
Activated carbon has been used as a water filtering medium for purification of drinking water for many years. It is widely used for the removal of contaminants in water due to its high capacity for adsorption of such compounds, resulting from their large surface area and porosity. Activated carbons have varied surface characteristics and pore size distribution, characteristics that play an important role in adsorption of contaminants in water.
Water treatment facilities
While not overtly obvious, the water we use every day – whether for bathing, drinking, swimming, or otherwise – is frequently brought to us in purified form, courtesy of activated carbon. In drinking water treatment systems, activated carbon helps to ensure that drinking water not only smells and tastes satisfactory, but is also safe for consumption. Drinking water treatment focuses on:
• Removal of contaminants. Activated carbon helps to ensure that water destined for consumption is free of most harmful contaminants such as pesticides, endocrine disruptors and pharmaceutical products.
• Taste and odor control. Activated carbon is also employed in reducing components that result in undesirable tastes and odors.
• DBPs. Activated carbon has also been more recently utilized in controlling DBPs at drinking water treatment facilities. DBPs are formed when disinfectants used to treat water combine with the natural organic matter (NOM) present in the water to form harmful byproducts. Activated carbon offers an effective approach in removing the precursors (NOM) of DBPs.
How does activated carbon adsorb contaminants?
Activated carbon has great adsorption properties, which help to bind different chemicals. When activated carbon comes in contact with water or gas, it attracts and takes away one or more atoms, molecules, or ions on its surface. Activated carbon for water treatment comes in various forms:
• Granular activated carbon – ideal for water and wastewater treatment purposes
• Powdered activated carbon – perfect for treating specific trace synthetic chemicals
• Extruded activated carbon – used for de-chlorination and chemical removal
Activated carbon’s capability to adsorb contaminants of all kinds make it an ideal choice for water treatment plants for industries where harmful chemicals and metals used for manufacturing. It also has the capacity to remove contaminants from liquid and gas.
Wastewater treatment facilities
Activated carbon is also employed in both municipal and industrial wastewater treatment facilities. The effluent discharged, either as municipal wastewater, or the discharge from an industrial process, can contain a variety of components that must be removed before they are discharged into waterways or reused. In these settings, activated carbon helps to protect waterways from contaminants such as pesticides, fuels and various solvents, to name a few. Here again, activated carbon captures the targeted components for removal, rendering the water sufficient for discharge or its intended reuse application.
In addition to dedicated water treatment facilities, many industrial facilities may host their own on-site operation to treat incoming municipal water for use in their specific industrial process. Process water used in the production of beverages, pharmaceutical products and the like, must often meet highly strict requirements so as not to damage equipment or result in an inferior product. Process water applications commonly rely on activated carbon to ensure that water quality meets the requirements of its intended use. For all of these water treatment applications, activated carbon can be employed in a number of ways. In each setting, activated carbon may be used alone, or in combination with other treatment methods, such as UV disinfection and/or particulate filtration systems.
Additional water treatment uses
It’s worth noting that while activated carbon is a key component in large-scale water treatment facilities, it can also extend to small-scale and POU applications as well. Activated carbon helps to keep aquatic environments free of contaminants that could harm inhabitants. A variety of in-home water filters such as those found in refrigerators, or that can be affixed to faucets, also rely on activated carbon to purify water.
Cost savings when reactivated
Activated carbon can be regenerated, meaning that spent carbon can be processed to be reused; the adsorbed components can be desorbed and the spent carbon reactivated, allowing it to be reused repeatedly. Not all activated carbons are reactivated (powdered activated carbon is typically disposed of). Reactivation, however, is an attractive feature because it costs significantly less than purchasing virgin activated carbon and also results in a lower carbon footprint. It takes much less energy to reactivate carbon than it does to produce virgin carbon.
Depending on the location and capacity requirements of a treatment facility, on-site reactivation may offer economic benefits. Remote or isolated operations may find that the shipping costs required to transport spent carbon to a commercial reactivation facility will outweigh the cost of an on-site reactivation operation.
Water is the world’s most valuable resource. As the world’s population grows, the efficient treatment of existing water resources will continue to grow in importance as well. Activated carbon offers an effective solution in many water treatment facilities, whether it’s to ensure drinking water is safe for consumption, to protect waterways from potentially harmful effluent discharge, or to help create products of premium quality.
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https://feeco.com/spent-carbon-reactivation/. Accessed May 11, 2021.
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About the author
Dennis Abraham Thazhamon, Managing Director of Josab India Pvt Ltd for the India and Southeast Asian regions, is a highly qualified marketing and management professional with a primary focus on entering new markets. A water expert who focuses on sustainable living for everyone, he has been honored with the 51 Fabulous Global Water and Water Management Leaders award. Abraham is currently working toward making a difference in the lives of people via natural treatment of water so they can continue enjoying good health by drinking treated, natural water.
About the company
Josab India Pvt Ltd, a fully owned subsidiary of Josab Water Solutions AB, Stockholm, Sweden, has been providing safe drinking water solutions in India since its launch in 2012. The company produces and sells products, solutions and services for ecologically sound water purification. Because of the Aqualite™ filter material, large volumes of water can be purified in an ecologically safe way at a low cost, leading to long-term sustainability. The company’s primary focus is on rural areas, where access to safe drinking water is barely minimal. Since its launch in India, Josab’s Aqualite-based technology has been approved and acclaimed by various public and private entities. Currently Josab India is expanding its territories in terms of acquiring market and diversification where the requirement for pure water is pivotal.