Home filtration systems

Home Filtration Systems. The same filtration and purification methods used in large water treatment plants have been downscaled for home use. Faucet-mount filters use carbon filtration, ion-exchange filtration, and submicron filtration to reduce sediment, chlorine, lead, mercury, iron, herbicides, pesticides, insecticides, industrial solvents, volatile organic compounds, synthetic organic compounds, and tri-halomethanes (THMs, chlorine and its by-products). These apparatuses rapidly provide filtered water that tastes and smells better with less cloudiness. Shower filters typically use copper-zinc oxidation media and carbon filtration to remove chlorine for softer skin and hair. Whole-house-use water filters are plumbed into the main water line and commonly include a sediment pre-filter, then copper-zinc oxidation media and crushed mineral stone or natural pumice to reduce chlorine, then activated carbon to remove other chemicals. 

The concentration of indoor pollutants is a function of removal processes such as dilution, filtration, and destruction. Dilution is a function of the air exchange rate and the ambient air quality. Gases and particulate matter may also be removed from indoor air by deposition on surfaces. Filtration systems are part of many ventilahon systems. As air is circulated by the air-conditioning system it passes through a filter which can remove some of the particulate matter. The removal efficiency depends on particle size. In addition, some reactive gases like NOj and SOj are readily adsorbed on interior surfaces of a building or home. 

So we face a curious conundrum. We should be drinking more to flush carcinogens from our bladders (as well as for other health reasons), but the stuff most of us drink — namely, tap water — may itself contain some of those very carcinogens. What do we do Bottled waters are not chlorinated and therefore do not contain any thms. We can also remove these compounds with home water-filtration systems, usually with an efficiency rate of well over ninety percent. Just remember, though, that you have to change the filters in these systems regularly, or you ll end up drinking water that s of poorer quality than it is in its unfiltered form. 

The FDA regulates the quality of bottled water. The water passes through one or more purification steps (Figure 11.12). The three purification methods (which can also be done in home treatment systems)—distillation, carbon filtration, and reverse osmosis— have already been discussed as methods used for treating municipal water. The maximum levels of contaminants allowed by the EPA after these treatments are listed in Table 11.10. Each of these methods is expensive and results in a high cost per gallon of treated water. In the case of bottled water or home water treatment, the cost of treatment is not the major factor, because only the small amount of water needed for human consumption needs to be specially purified. Figure 11.12 shows... 

Many people today find that they want to further purify their drinking and cooking water. Often this is because of objectionable tastes in the municipal drinking water. People add filtration systems to appliances such as refrigerators and coffee pots or use home water filtration systems. People also buy bottled water for drinking and cooking. 

Charles River. Water from the river was more polluted than that from the wells, and therefore had to be filtered. The company installed a slow-sand filtration system, which not only eliminated bacterial contaminants, it also reduced the lead solvency of the river water." The introduction of these measures in 1902 and 1903 reduced the average water-lead levels in area homes from 1.39 ppm (627 times the modern EPA standard) to 0.27 ppm (175 times the modern EPA standard). Although 0.27 ppm is a high lead level by modern standards, it was well below the 0.5-ppm threshold then considered safe by the Massachusetts Board of Health." ... 

With windows open, the concentration of UFP inside a home is directly related to the outdoor concentration with an I/O ratio near 1.0. With windows closed, the concentration of UFP may still be related to the outdoor concentration but I/O ratios may drop as low as 0.3. Zhu et al. (2(X)5) investigated the indoor and outdoor variation of UFP near a highway under three ventilation conditions natural infiltration, fan on, and windows open. In the case of natural infiltration, the highest I/O ratio was observed for the largest particles. It was hypothesized that since the UFP in the smallest fractions are likely more volatile, their infiltration behaviour is likely very different than that of the older larger non-volatile particles. With windows open, the UFP I/O ratio was near 1.0 for all sizes. In the case of mechanical ventilation (fan on), the I/O ratio was below 1.0 for all sizes and it was hypothesized that some filtration of outdoor air was provided by the ventilation system itself. 

In contrast to common clothing and home textiles, so-called technical textiles are a growing and important market for high performance products. Technical textiles find application in fields as diverse as medical engineering, aerospace and automotive industry, modem architecture and constmction, filtration, and transport systems. Increasingly super-hydrophobic character is required for these products to... 

Yebra et al. [83] used a continuous-flow procedure for the indirect determination of sodium cyclamate by flame atomic absorption spectrometry (FAAS). This method is based on oxidation of the sulfamic group derived from cyclamate to sulfate in acidic conditions and in the presence of sodium nitrite. The procedure is adapted to a flow system with precipitate dissolution (Figure 24.11), where sulfate formed is continuously precipitated with lead ion. The lead sulfate formed is retained on a filter, washed with diluted ethanol, and dissolved in ammonium acetate (because of the formation of soluble lead acetate) for online FAAS determination of lead, the amount of which in the precipitate is proportional to that of cyclamate in the sample. In this work a home-made filtration device was used made of a Teflon tubing packed with a cotton pulp and the ends of the filter column were plugged with filter paper (chamber inner volume 141 J,L). This precipitate collector was effective in retaining the precipitate and did not produce excessive back-pressure if the precipitate was dissolved following each precipitation cycle. 

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