Date: July 29, 2014
Due to climate change, population growth, and rapid urbanization as well as industrialization,
water scarcity is a growing concern in many areas of the world.
In light of potential water shortages, cities have increasingly recognized the importance of water conservation and water demand management as a long term water supply option. However, in some cases, water conservation is not enough to close the water supply-demand gap, and alternatives for augmenting water supply must be considered.
Reclaimed water -wastewater that has been treated to levels suitable for reuse can provide a safe and reliable source for bothnon-potable and potable water supply. Recent technological advances have reduced the technical and economic barriers to reusing wastewater; however, political, cultural, and regulatory challenges remain. The starting point is wastewater reclamation, which refers to the treatment or processing of wastewater to control biodegradable organics, nutrients and pathogens thereby making it reusable, and water reuse is the use of treated wastewater for beneficial purposes that include non-potable uses such as agricultural irrigation and industrial process & cooling purpose. Reclaimed water is a treated effluent that is considered to be of appropriate quality for an intended water reuse application. In addition, direct water reuse requires the existence of pipes or other conveyance facilities for delivering reclaimed water to theend-user. Indirect reuse, through discharge of an effluent to a receiving water or groundwater for assimilation and withdrawals downstream, is recognized to be important but does not constitute planned direct water reuse. In contrast to direct water reuse, water recycling normally involves only one use or user
and the effluent from the user is captured, treated, and redirected back into the original use or a use that has lower water quality requirements.
Water pollution control efforts have advanced to the point that treated effluent from municipal/ industrial effluent treatment plants ETP is suitable and economical for augmenting traditional water supplies at source, particularly when compared to the alternatives such as importing water through costly conveyance systems or constructing dams and reservoirs. The reclaimed water provides a reliable water supply located near the point of use, reducing pumping costs and eliminating the need to negotiate with neighbors for new water supplies. Conventional treatment plants use physical, biological, and chemical processes to treat wastewater. Historically, secondary treatment has been sufficient for many non-potable reuse applications and for environmental release. However, as regulations for both reuse and environmental releases have become stricter, tertiary and advanced treatment are becoming more prevalent. Primary and secondary treatment processes and technology have not changed significantly, but innovations in tertiary and advanced treatment technology, four of which are described below, have resulted in increased economic and physical efficiency, increased reliability, and, in some cases, safer conditions for workers. This has lowered historical barriers to wastewater reuse such as cost, energy use, and public health risk.
1. Membrane filtration technologies:
Membrane filtration replaces or supplements traditional filtration methods to treat water to tertiary and advanced levels. A membrane allows certain molecules to flow through it, acting as a very fine filter. Micro-filtration MF and Ultra-filtration UF are used as part of secondary treatment while nano-filtration NF and reverse osmosis RO filter to advanced treatment levels. However, reverse osmosis has better salt removal ability. Advances in technology have resulted in less expensive and more efficient membranes, reducing the high energy costs of membrane filtration.
2. Membrane bioreactors technology:
Membrane bioreactor MBR can be used as secondary treatment. This technology combines the biological component of secondary treatment with membrane filtration process like micro-filtration or ultra- filtration, reducing the space necessary for treatment while providing higher quality
effluent than traditional secondary treatment. This allows you to treat wastewater to reuse levels. MBR processes can produce effluent of high quality enough to be discharged to surface or to be reclaimed for urban irrigation. Other advantages of MBRs over conventional processes include small footprint, easy retrofit and upgrade of old wastewater treatment plants.
Recent technical innovation and significant membrane cost reduction have enabled MBRs to become an established process option to treat wastewaters. As a result, the MBR process has now become an attractive option for the treatment and reuse of industrial and municipal wastewaters, as evidenced by their constantly rising numbers and capacity. Two MBR configurations exist : internal/submerged, where the membranes are immersed in and integral to the biological reactor; and external/sidestream, where membranes are a separate unit process requiring an intermediate pumping step. The lower operating cost obtained with the submerged configuration along with the steady decrease in the membrane cost encouraged an exponential increase in MBR plant installations from the mid 90s. Since then, further improvements in the MBR design and operation have been introduced and incorporated into larger plants.
3.Advance oxidation technologies:
It is also important to note that these advancements in treatment technology have been accompanied by a simultaneous increased in wastewater effluent pollutants and chemical complexity. Advanced Oxidation Technology (AOT) has provided innovative, highly cost- effective, catalyzed chemical oxidation processes for treatment of contaminated wastewater. Advance oxidation process AOP refers to a set of chemical treatment procedures designed to remove organic (and sometimes inorganic) materials in water and waste water by oxidation through reactions with hydroxyl radicals (·OH). Hydroxyl radicals are produced with the help of one or more primary oxidants (e.g. ozone, hydrogen peroxide, oxygen) and/or energy sources (e.g. ultraviolet light) or catalysts (e.g. titanium dioxide, Fe, etc).
The AOT is particularly useful for cleaning biologically toxic or non-degradable materials such as aromatics, pesticides, petroleum constituents, and volatile organic compounds in waste water. Additionally, AOPs can be used to treat effluent of secondary treated wastewater which is then called tertiary treatment. The various catalyst, in combination with a variety of oxidants, allows for the treatment of a wide variety of recalcitrant chemicals. The contaminant materials are converted to a large extent into stable inorganic compounds such as water, carbon dioxide and salts, i.e. they undergo mineralization.
4. Disinfection technologies: Water is one of the body’s most essential nutrients. People may survive six weeks without any food, but they couldn’t live more than a week or so without water. That’s because water is the cornerstone for all body functions. It’s the most abundant substance in the body, accounting for up to 75 percent of body weight. It helps keep body temperature constant at about 98.6 degrees, and it transports nutrients and oxygen to all cells and carries waste products away. Water helps maintain blood volume, and it helps lubricate joints and body tissues such as those in the mouth, eyes and nose. And water is truly a liquid asset for a healthy weight—it’s sugar free, caffeine free, and—most importantly—calorie free.
How Much Water Do Kids Need?
The daily amount of water that a child or teen needs will depend on factors such as age, weight and gender. Air temperature, humidity, a person’s activity level and his or her overall health affect daily water requirements, too. The Kids’ Total Daily Water Requirements chart below can help you identify about how many liters of water your child or teen needs each day (one liter is about four cups of liquid). These water recommendations are set for generally healthy kids living in temperate climates; therefore, they might not be perfect for your child or teen.
The amount of water that your child or teen needs each day might seem like a lot, but keep in mind that the recommendations in the chart are for total water, which includes water from all sources: drinking water, other beverages and food. Notice that fruits and vegetables have a much higher water content than other solid foods. Their high water content helps keep the calorie level of fruits and vegetables low while their nutrient level remains high—another perfectly great reason for kids to eat more from these food groups.
So how do you apply total water recommendations to your kid’s day? As a rule of thumb, to get enough water, your child or teen should drink at least six to eight cups of water a day and eat the recommended number of servings of fruits and vegetables every day. Also pay special attention to your child’s or teen’s water consumption when he or she is physically active. Before, during and after any physical activity, kids need to drink plenty of water, especially in hot weather. The goal is to drink one-half to two cups of water every 15 to 20 minutes while exercising
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