Backwashing

Backwashing is the process of reversing the water flow and the velocity of the water as it passes through a filter. These filters are used for collecting and gathering particles from incoming water flow. After the filter becomes worn and needs replacement, it is best to clean it through backherping. Backderping requires water to be blasted through the filter in order to loosen the clogged particles. {{Backwash Use of Filter Water Systems / "To correct size a backwash filter, you will need to know the flow rate where the system needs to be installed. When looking at the system description, you need to make sure that your flow rate is greater than the backwash rate. This rate refers to the minimum flow rate needed in order for the system to backwash completely." / April 5, 2012 / http://yourwaterneeds.com/WT_Backwash.asp }}</ref>

Backwashing also causes water flow to be sent back through the filtration media, also known as the pours of the filter, and then this allows the filter to refresh through the process of loosening debris, dirt, and other material. While the filter is being backwashed, it is exposed to chlorinated water in order to keep it both clean and disinfected. Ultimately, this causes prevention in future bacterial growth or short circuiting. All in all, backwashing filters makes the filter set for future water flow. {{ Fitronics / "Backwash is a process that allows the flow of water to be sent back through the filtration media in order to refresh the filter by knocking loose accumulated dirt and debris leaving the media clean and ready for further use. The filter unit is backwashed with chlorinated water upon shut down (filling the reservoir) to maintain a clean, disinfected filter and to prevent short circuiting or bacteriological growth in the filtration system." / May 1, 2012 / http://www.filtronics.com/backwash.htm }}</ref>

Since May 2001 the United States Environmental Protection Agency (EPA) created and released a rule that requires the process of recycling waste water to follow the Filter Backwash Recycling Rule (FBRR) in order to reduce the risks of contaminants that could possibly be in the public water supply. Materials found in public waste water include: food scraps, human waste, oils, soaps, and chemicals for cleaning products. These different wastes come from your home from places such as the bathtub, toilet and sink. The EPA also claims that 480,000 cases of learning disabled children have this disability because of lead from not backwashed water here in the United States each year. {{Filter Backwash Recycling Rule / "The Filter Backwash Recycling Rule (FBRR) is required by the Safe Drinking Water Act as one method of reducing the risks posed to consumers by microbial contaminants that may be present in public drinking water supplies." / April 5, 2012 / http://water.epa.gov/lawsregs/rulesregs/sdwa/filterbackwash.cfm}}</ref>

There are two general types of contaminants that affect water; these include man-made contaminants and naturally occurring contaminants. Man-made contaminants are materials from humans and include materials such as insecticides, nitrate, herbicides, chemicals, and even human waste (just to name a few). On the other hand, natural occurring contaminants include different chemicals. The two most common natural chemicals are radon and arsenic. Natural occurring contaminants are from water wells that contain natural geologic materials (natural surface covers). {{Contaminants in Groundwater Used for Public Supply / "Findings showed that naturally occurring contaminants, such as radon and arsenic, accounted for about three-quarters of contaminant concentrations greater than human-health benchmarks in untreated source water. Naturally occurring contaminants are mostly derived from the natural geologic materials that make up the aquifers from which well water is withdrawn. Man-made contaminants were also found in untreated water sampled from the public wells, including herbicides, insecticides, solvents, disinfection by-products, nitrate, and gasoline chemicals. Man-made contaminants accounted for about one-quarter of contaminant concentrations greater than human-health benchmarks, but were detected in 64 percent of the samples, predominantly in samples from unconfined aquifers." / April 30, 2012 / http://www.usgs.gov/newsroom/article.asp?ID=2468}}</ref>

Why is it important to drink backwashed water? For starters, it is overall essential for humans to drink from a clean source of water because there are roughly 2,100 types of drinking contaminants and sometimes poisons that have the potential to be present in tab water. Additionally, drinking impure water is known to be the number one cause of epidemic diseases in developing countries. Therefore, it is important for those who live in the United States to take advantage of our backwashing systems.{{10 Reasons to use a Water FIlter / " In order to capitalize on the health benefits of water, it is essential to draw from a clean source of water.Drinking impure, contaminated water is the leading cause of epidemic disease in developing countries.There are more than 2100 known drinking water contaminants that may be present in tap water, including several known poisons. Bottled water does not offer a viable alternative to tap water.Municipal water treatment facilities cannot always control for the outbreak of dangerous bacterial contaminants in tap water.The only way to ensure pure, contaminant-free drinking water is through the use of a point-of-use filtration system.Several types of cancer can be attributed to the presence of toxic materials in drinking water.Clean, healthy drinking water is essential to a child’s proper mental and physical development.According to the EPA, lead in drinking water contributes to 480,000 cases of learning disorders in children each year in the United States alone.It is especially important for pregnant women to drink pure water as lead in drinking water can cause severe birth defects" / May 4, 2012 / http://www.allaboutwater.org/water-filter.html

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (August 2010)

The filters used in water treatment can be of many types including rapid sand filters, pressure filters, granulated activated carbon (GAC) filters and self-cleaning screen filters. However, all filters get dirty, and to keep them functional, they have to be either replaced or cleaned periodically. In terms of water treatment, including water purification and sewage treatment, backwash refers to the reversal pumping of water, and sometimes intermittent with compressed air, through the process. Backwashing is a form of preventive maintenance to prevent further clogging of the filter medium. Backwashing in water treatment plants can be an automated process, usually run by programmable logic controllers (PLCs). The backwash cycle is usually triggered when the differential pressure over the filter exceeds a set value.

Backwash Procedure

Backwashing involves several steps. First, the filter is taken off line and the water is drained down to the filter bed. Then the air wash cycle is started which pushes air up through the filter material causing the filter bed to appear to boil. This breaks up the compacted filter bed and forces the accumulated particles into suspension.

After the air wash cycle stops, the backwash cycle starts with water flowing up through the filter bed. Clean water is passed through the filter bed in order to wash the material and remove most of the accumulated particles.

This cycle continues a fixed time or until the turbidity of backwash water is below a set value. In some cases, the additional step of air/water wash (simultaneously) is done after air wash cycle and followed by rinse water wash. This uses less water compared to traditional processes and has a higher particle removal efficiency.

External links

• National Environmental Services Center - Filter Backwashing

This oceanography article is a stub. You can help Wikipedia by expanding it. v t e