Backwashing of Industrial Media Filters

BACKWASHING PRINCIPLE

Water Filtration is to collect or gather impurities from the incoming water flow. When the pores of filters logged, it has to be cleaned by forcing out the accumulated particles by reversing the flow and increasing the velocity of water passing back through the filter. It is called backwashing. We can improve the quality of water by doing it at regular intervals.

BACKWASHING PROCEDURE

First the filter is taken off line and the water is drained to a level that is above the surface of the filter bed. Next, compressed air is pushed up through the filter material causing the filter bed to expand, breaking up the compacted filter bed and forcing the accumulated particles into suspension for 20-30 minutes.

After the air scour cycle, clean backwash water is forced upwards through the filter bed, causing the filter bed to expand and carrying the particles in suspension into backwash troughs suspended above the filter surface. In some applications, air and water streams are simultaneously pushed upwards through the granular media. Backwashing continues for 30 minutes to one hour time, or until the turbidity of the backwash water is below an established value. A filter bed should have as much expansion as possible upto 30 to 50 percent of bed volume without loosing media or displacing the support gravel. At the end of the backwash cycle, the upward flow of water is terminated and the filter bed settles by gravity in its initial configuration.

After allowing sufficient time for the filter bed to settle by gravity, rinsing can be done with clear water for 30 minutes until the crystal clear water comes out as the output. Then water to be filtered is passed through the filter and the service cycle can be from 16hrs to 20hrs.

SILT DENSITY INDEX (SDI)

In order to measure the degree of the fouling problem, a measure called Silt Density Index (SDI) is used. Here filtration rates are calculated by exposing a 0.45-micron filter to the feed water under pressure. An SDI of less than 5 is typically considered acceptable for a reverse osmosis systems.(RO). If the value of SDI is higher than 6, stop passing the feed through RO membranes and the pretreatment cycle should be carried out to bring down the SDI levels to less than 4.

In any pretreatment system the SDI reduction in multi grade filters (MGF) should be brought down significantly. If the size of the impurities in the raw water is less than 25 microns, suitable coagulants/flocculants should be added in the raw water to increase the size of the particles (Impurities) and improve the filtering efficiency of MGF.

In carbon filters (CF) SDI reduction across the CF should be minimum. If a significant reduction in SDI is seen across the CF, it will foul very frequently. The remedy is to improve the particle removal efficiency of the MGF.

TURBIDITY SPIKE

A turbidity spike can occur if the filter bed is not allowed to settle by gravity for a reasonable time. For small plants back washing can be carried out at the end of the day and allow the filter to settle by gravity at night time.

CONCLUSION

A carefully designed pretreatment plant aimed at reducing the SDI to as low as possible will go a longway in trouble free operation of the RO plants.

Kalbon JULIA Wood Carbon Powder Series

Wood based Activated Carbons are rising in popularity, with applications which in the past utilized coal or coconut carbon products, with regard to industrial applications.

Wood carbons possess outstanding decolorizing attributes due to their particular unique porosimetry.  Their high surface area seen as a significant percentage of mesopores and macropores generates a fairly low density along with an environmentally friendly and renewable supply of raw materials.  Wood Based Powder Activated Carbon is used for decolorizing in sugar liquors, juices, soybean, and food industries.

Wood powder activated carbon is non-toxic, without taste and it has the appearance of a fine black powder. Offering a sizable surface area, and robust adsorption abilities, it is perfectly suited to water clarifying and purifying within the production of sugars, pharmaceuticals, beverages and also wines.  It is also used around the globe for waste water treatment as well as in the decolorizing, refining, and purification of organic solvents.

Kalbon PAC Powder Series

PAC is made from organic materials with high carbon contents such as wood, lignite and coal. 

PAC typically has a diameter less than 0.1 mm and an apparent density ranging between 23 and 46 lb/ft3, depending on the material used and manufacturing process. Iodine and molasses numbers are typically used to characterize PAC.  These numbers describe the quantity of small and large pore volumes in a sample of PAC.  A minimum iodine number of 500 is specified for PAC by AWWA standards.
PAC is used by water treatment plants on either a full time basis or as needed for taste and odour control or removal of organic chemicals. PAC can be fed as a powder using dry feed equipment or as a slurry using metering pumps. Dry feed systems are typically used for smaller dosages.  PAC can also be mixed with water and fed as a slurry. Slurry systems are normally used when PAC is frequently added and the required dosages are high. 

PAC is normally added early in the treatment process and is subsequently removed either by sedimentation or by the filter beds during backwashing. The PAC application point should allow for (1) an adequate contact time between the PAC and organics, and (2) avoid coating PAC particles with other water treatment plant chemicals.  A minimum contact time of about 15 minutes is required for most taste and odour compounds; however, significantly longer contact times may be required for Methyl-Iso-Borneol (MIB) and Geosmin removal.

PAC dosages can range between 1 to 100 mg/L depending on the type and concentrations of organic compounds present.  Dosages of 1 to 20 mg/L are typical for nominal taste and odour control.  Application of PAC generates additional sludge which is not able to be regenerated as is spent GAC.  PAC sludge will contain elevated concentrations of the contaminants removed and must be disposed in accordance with State and federal laws; however, it is not likely to be classified as a hazardous waste.

Kalbon GCF Cigarette Filter Series

Cigarette smoking is the world’s single most preventable cause of disease and death.

It is estimated that each year over five million people throughout the world die from cigarette related illness.  Cigarette smoke contains more than 4000 compounds.  Among these Nicotine is the primary source of tobacco dependence and others are toxins and carcinogens. 

Tobacco is an ever changing and extremely complex mixture of chemicals.  It is formed when tobacco itself, a complex mixture of over 2000 chemical constituents, is burnt during the smoking of cigarettes, cigars, or pipes.  When a cigarette burns, thousands of chemical substances are generated and they are distributed between the gas phase and the particles that constitute the smoke aerosol. 

Cellulose Acetate filtered cigarettes contain substantial amounts of p-BenzoSemiQuinone (p-BSQ) which is about 100 to 200 µg /cigarette.  It has been determined that when a Cellulose Acetate filter is replaced by a Charcoal filter, the amount of p-BSQ in the mainstream smoke is reduced by 73-80% and prevents protein carbonyl formation to the extent of 70– 90%.

Kalbon GFL Filter Series

Kalbon GFL filter series are designed for efficient use in fixed beds for the purification and decolorization of many aqueous and organic liquids.

The particle size of GFL filter series carbon has been selected to give maximum adsorption rates and reasonable pressure drop characteristics with liquors of relatively low viscosity. 

It is made from a superior quality activated carbon with low ash, sulphur, and phosphorous content.  It has a large surface area, high pore volume, high mechanical hardness and chemical stability, longer operating life, and it is easy to regenerate.

20x50 is a virgin granular activated carbon designed specifically for point-of-use water treatment applications where impurities are removed in drinking water filtering units with short contact times

Kalbon GVP Vapor Phase Series

Vapor-phase Granular Activated Charcoal (GAC) is a treatment technology that removes contaminants from air. Contaminated air is passed through one or more vessels containing GAC.

Contaminants absorb onto the surfaces of the activated carbon grains. The thermal processing of carbon, often from coconut shells, creates small porous particles with a large internal surface area. This processing activates the carbon. The activated carbon attracts and adsorbs organic molecules as well as certain metal and inorganic molecules. When the concentration of contaminants in the vapor exiting the vessels exceeds a certain level, the carbon must be replaced. Spent carbon can be regenerated in place; removed and regenerated at an off-site facility; or most commonly, removed and disposed.

Vapor Phase Carbon Adsorption Systems are designed to remove certain gaseous contaminants, including Dioxins/ Furans, Hydrogen Sulphide, Hydrogen Chloride, Ammonia and Mercaptans. 
Rapid economic development and urban population growth have triggered a series of challenges to the endeavors of maintaining the clean air.  Urban air is cause of public concern, largely as a result of instances of smog and health problems. 

New pollutants are being increasingly recognized.  Air pollution sources have grown and so also the pollutants. Some of these have led to the emission of some hazardous air pollutants like Volatile Organic Compounds (VOC).  VOCs are chemicals that have high vapor pressure exceeding 0.5 kPa at 25⁰ C, like benzene, toluene, xylene, formaldehyde, and methylene chloride.  Major VOC emission sources are automobiles exhaust (45%) followed by industrial sites (41%) and remaining from solid waste disposal and from miscellaneous sources. 

The acute and chronic effects of VOCs on health and environment include eye-nose-throat irritation, cancer, liver damage, and kidney damage.  Hence, many VOCs have been identified as toxic and carcinogenic.  Approximately 235 million tons of VOCs are released every year into the atmosphere by man-made sources.  The subject has become important because of the impact on environment and human.

Kalbon GAU Gold Recovery

Kalpaka Chemicals offers unique line of products that caters to Gold Industry. 

Our GAU series Kalbon carbon products offers superior performance in terms of providing the highest gold adsorption capacity (K value), rate of adsorption (R value), superior hardness and abrasion resistance.  Our Gold Carbon products provide our customers with exceptional value by maximizing yield while minimizing loss.

Activated carbon is a highly porous organic material comprised of a series of graphitic plates, which are interconnected by carbon-carbon bonds. This creates a highly porous structure and gives an extensive internal surface area, where “adsorption” occurs.  Adsorption is a surface reaction that causes compounds to “stick” to the surface of the carbon.  The phenomenon is the result of intermolecular attractions or forces inherent to the carbon surface.

In gold recovery applications, adsorption forces remove gold from solutions and adhere the metal complex to the carbon surface.  Because the reaction occurs at the surface of the carbon, the adsorption process is relatively easy to reverse, a process called “desorption.”  While it is important to maximize the adsorption of gold from the solution, it is equally as important to subsequently desorb the gold from the carbon.  Any molecules that remain adsorbed after elution or stripping translate into gold that cannot be recovered.  As a result, it is important to select an activated carbon that efficiently adsorbs and desorbs to maximize overall yield and profitability.

In physical adsorption, contaminants are adsorbed and held on the internal Activated Carbon Structure surface of activated carbon due to Van der Waals Forces of attraction between the carbon atom and the molecule.  The force of attraction diminishes as the distance between the pore wall and the adsorbate molecule increases.

Gold alone is not soluble, and will not be readily adsorbed by activated carbon until it is cyanidated, forming a gold-cyanide coordination complex called dicyanoaurate.  It is this gold-cyanide complex that is attracted to the tremendous surface area available on activated carbon, allowing for a variety of recovery techniques.  One handful of activated carbon has a surface area equivalent to that of a football field.  The massive surface area of activated carbon makes the material an ideal adsorbent.
Activated carbon can be produced from a variety of different precursors, including coal, coconut, wood, and lignite, which are the primary materials used to make commercial-scale activated carbon. The starting material dictates the pore size distribution of the final activated carbon product. Typically, coconut is the precursor for gold recovery applications because of its tight pore structure, high activity pores, and hardness.

Kalbon PET Effluent Treatment

Activated carbon adsorption is most commonly applied in industrial wastewater treatment to meet stringent regulations for discharge into receiving waters. 

In industrial wastewater treatment, activated carbon adsorption can be utilized as a separate unit process. It may be placed after various physicochemical treatment steps such as coagulation/clarification, filtration, and dissolved air flotation.  Another alternative is to use activated carbon adsorption prior to biological treatment to remove compounds which might be toxic to a biological system.

Nowadays, activated carbon finds wide application in the treatment of wastewaters generated from industries such as food, textile, chemical, pharmaceutical, pesticides and herbicides production, coke plant, munitions factories, petroleum refineries and storage installations, organic pigments and dyes, mineral processing plants, insecticides, pesticides, resins, detergents, explosives, and dyestuffs.  It is also employed in the treatment of sanitary and hazardous landfill leachates.

Kalbon GAQ – Aqua Series

Homeowners are increasingly concerned about contaminants in their water supply that may affect health or cause taste and odour problems.

Sources of these contaminants might include solvents, pesticides, industrial wastes, or contaminants from leaking underground storage tanks.

Contaminants such as benzene, chlorobenzenes, trichloroethylene, carbon tetrachloride, methylene chloride, and vinyl chloride in drinking water may pose health risks if they are present in quantities above the EPA Health Advisory Level (HAL).  Pesticides, such as Atrazine, also can pose a health risk if present in quantities above EPA guidelines. Activated carbon (AC) filtration can effectively reduce some of these organic chemicals as well as certain harmless taste and odour-producing compounds.

Some drinking water may be disinfected with chlorine or chloramines.  During disinfection the reaction of chlorine with organic matter can produce compounds such as trihalomethanes (THMs) as byproducts.  These disinfection byproducts may increase the risk of certain cancers.  The EPA mandates that public systems have less than 80 parts per billion (ppb) of THMs in their treated water.  Activated Carbon filtration can be effective in removing chlorine, chloramines, and some disinfection byproducts.

This granular activated carbon is used for water treatment applications in fixed bed media filters.  It is used for removal of taste, odour, chlorine, and dissolved organic contaminants from potable and process water.  It is also used in DM plant filters, Tap water filters, Desalination plants, and Aquariums.

Kalbon GAQ – Aqua Series

Homeowners are increasingly concerned about contaminants in their water supply that may affect health or cause taste and odour problems.

Sources of these contaminants might include solvents, pesticides, industrial wastes, or contaminants from leaking underground storage tanks.

Contaminants such as benzene, chlorobenzenes, trichloroethylene, carbon tetrachloride, methylene chloride, and vinyl chloride in drinking water may pose health risks if they are present in quantities above the EPA Health Advisory Level (HAL).  Pesticides, such as Atrazine, also can pose a health risk if present in quantities above EPA guidelines. Activated carbon (AC) filtration can effectively reduce some of these organic chemicals as well as certain harmless taste and odour-producing compounds.

Some drinking water may be disinfected with chlorine or chloramines.  During disinfection the reaction of chlorine with organic matter can produce compounds such as trihalomethanes (THMs) as byproducts.  These disinfection byproducts may increase the risk of certain cancers.  The EPA mandates that public systems have less than 80 parts per billion (ppb) of THMs in their treated water.  Activated Carbon filtration can be effective in removing chlorine, chloramines, and some disinfection byproducts.

This granular activated carbon is used for water treatment applications in fixed bed media filters.  It is used for removal of taste, odour, chlorine, and dissolved organic contaminants from potable and process water.  It is also used in DM plant filters, Tap water filters, Desalination plants, and Aquariums.

Kalbon Crystal is an acid washed high purity high activity granular activated carbon

Kalbon Crystal is an acid washed high purity high activity granular activated carbon manufactured by steam activation from carefully selected coconut shells.

This activated carbon is produced for use in ultra-pure water treatment systems requiring low conductivity and exceptionally high purity.  This activated carbon is also specifically designed for the removal of heavy hydrocarbons from recovered condensate. The acid washing process removes soluble silica from the matrix of the activated carbon to prevent leaching into the condensate.

 

Some of the benefits of Acid Wash carbon include Dechlorination of water, better taste, removal of bad odors, removal of color from water, removal of organic substances, etc.  Acid wash carbon has extensive internal structure, neutral surface, maximum hardness, extended operational life, high volume activity, and rapid pH stabilization.

Acid wash carbon is used in various applications such as Condensate de-oiling, semiconductor process water, dialysis treatment, point of entry treatment units, and protection of reverse osmosis membranes from chlorine and organic fouling.

Kalbon Crystal is an acid washed high purity high activity granular activated carbon

Kalbon Crystal is an acid washed high purity high activity granular activated carbon manufactured by steam activation from carefully selected coconut shells.

This activated carbon is produced for use in ultra-pure water treatment systems requiring low conductivity and exceptionally high purity.  This activated carbon is also specifically designed for the removal of heavy hydrocarbons from recovered condensate. The acid washing process removes soluble silica from the matrix of the activated carbon to prevent leaching into the condensate. 


Some of the benefits of Acid Wash carbon include Dechlorination of water, better taste, removal of bad odors, removal of color from water, removal of organic substances, etc.  Acid wash carbon has extensive internal structure, neutral surface, maximum hardness, extended operational life, high volume activity, and rapid pH stabilization.
Acid wash carbon is used in various applications such as Condensate de-oiling, semiconductor process water, dialysis treatment, point of entry treatment units, and protection of reverse osmosis membranes from chlorine and organic fouling.

Activated carbon

Kalbon Aquapura is a water washed high purity high activity granular activated carbon manufactured by steam activation from carefully selected coconut shells.
 
Water washing is primarily performed to remove ash content from the granular activated carbon.  Water wash is also used for regeneration of granular activated carbon.  Kalpaka Chemicals can perform water washing on different mesh sizes as per the customer’s requirement.

KALBON Activated Carbon

We are a global leader in the manufacturing and processing of Activated Carbon. Our activated carbon products are sourced from natural products such as coconut shell, coal, wood, etc.

Wemarket our products under the brand name KALBON Activated Carbon. It is manufactured by Kalpaka Chemicals Private Limited which is based in southern Indian port city of Tuticorin, India.

Kalbon activated carbon products are widely used by various industries in gas purification, decaffeination, gold purification, metal extraction, water purification, medicine, sewage treatment, air filters in gas masks and respirators, filters in compressed air, and many other applications.