Groundwaters softening

Analytical Errors. Errors associated with these data arise from uncertainties in the analytical methods and from impurities introduced into or present in the textile. These added materials include inorganic salts from groundwaters, dye materials, and organic materials introduced in the conservation laboratory to soften friable artifacts (9). 

Sodium is present in soils and water as NaCl. In arid environments, NaCl accumulates in the surface and groundwater owing to irrigation and high evapotranspiration. Other activities such as road salting and water softening may also contribute NaCl to natural waters. For additional information on human health effects and drinking water levels, see Shelton (1989). 

Micro-, ultra-, and nano-filtration can separate smaller particles using media with defined porous sizes (i.e., 10 1—1 pm in microfiltration, 10 2—10 pm in ultrafiltration, and 10 3— 10 2 pm in nanofiltration). Residual colloidal and suspended solids can be removed by microfiltration. Selected salts, most organic compounds, bacteria, protozoan cysts, oocysts and viruses are removed by nanofiltration, so that the treated water will be disinfected. This advanced filtration is used for the treatment of effluents for indirect potable reuse applications such as groundwater injection, water softening, decoloriza-tion, or removal of micropollution. 

Well water samples were collected from residential taps prior to any in-place water softening units. Water samples taken during a spring flood water period were collected from inside taps after a full open flush of 30 minutes. This assured that the sample collected was groundwater withdrawn from the carbonate aquifer some distance from the well. Stream samples were taken at the center of the channel near the stream surface. The cross sectional stream samples were taken equidistant apart at 1/3 the water depth at each lateral position. Water samples were stored less than a week at 5°C. 

Applications for NF-50 membrane potentially include industrial separations, partial water softening, removal of trihalomethane precursors from groundwaters, and point-of-use filtration of high purity water for semiconductor chip manufacturing. 

In some types of groundwaters, the content of Ca and Mg must be reduced to the set value, and this is mostly performed by decarbonization (water softening). On the other hand, some surface waters require increased amounts of calcium and magnesium salts (water hardening). 

Fig. 2 A typical water treatment plant for treating groundwater, using lime softening...

Groundwater is typically not turbid (cloudy), so it does not require the type of treatment used for surface water. At minimum, it requires disinfection. Removal of iron and manganese by aeration may be needed, and if the water is very hard, it may be softened by ion exchange. 

Freshwater sources, groundwater, and surface water reservoirs and streams usually contain less than 10 mg/dm chloride. Higher analysis results indicate contamination by industrial effluents (water softening, paper works, oil wells, galvanic industries), by sewage from hog farms or other agricultural or communal facilities by snow- or ice-melting road treatments. 

Groundwater generally has a stable composition, but it is often too hard for use as process water or drinking water. Softening is necessary in many cases. Nanofiltration is here a competitive alternative for lime softening a comparison between both for application in Florida by Bergman (1995) showed that for lime softening operation and maintenance... 

---