Soft water testing

The water quality (air content) and the water flow influenced the measurements using one channel. Therefore the four channel system was first tested in the laboratory with a stationary tube. The best results were obtained using tap water and a well controlled flow in a water-filled chamber. A great difference in the concentration of air in the different grades of water was obvious, and the tap water was superior to soft water during these measurements. 

Hardness breakthrough can be particularly troublesome at those small, hard-working facilities that employ just one automatic softener. The problem may develop gradually and go unnoticed for some time. This may be because the softened water is not tested daily or, more usually, because the soft water is tested soon after resin regeneration rather than immediately before the point of exhaustion (which may be many hours later, but perhaps still 2 or 3 hours before the end of a working shift or plant shutdown). 

Toxaphene is extremely toxic to freshwater and marine biota. In laboratory tests of 96-h duration, 50% mortality was recorded for the most sensitive species of freshwater and marine teleosts, marine crustaceans, and freshwater insects at nominal water concentrations of less than 10 pg/L of toxaphene, and, in several cases, less than 1 pg/L (Table 27.2). Bioassays of longer duration, based on exposure of aquatic organisms for the entire or most of the life cycle, produced significant adverse effects on growth, survival, and reproduction at toxaphene concentrations between 0.025 and 1.0 pg/L (Table 27.3). Toxaphene was most toxic to freshwater fishes in soft water at elevated temperatures (Saleh 1991). Based on its high toxicity and extensive use, it is not surprising that toxaphene was considered a major cause of nationwide fish kills in 1977 (USEPA 1980b). 

Slowly pour soft water into test tube S until you reach the marked height. 

A student added 1 mL of hard water to one test tube, 1 mL of soft water to another, and 1 mL of distilled water to a third. The hard water sample contained Ca2+ and Mg2+. The soft water contained lower concentrations of these ions. 

It is suggested that the standard soft water should contain 34.2mg/kg calculated as calcium carbonate (WHO standard water), not 20.0mg/ kg (CIPAC standard water) and that the preparation of WHO standard hard water and WHO standard soft water should be published as WHO test methods (see Annex 2 in this report). 

In standard soft water. Any separation, including creaming/oiling at the top and oiling/sedimentation at the bottom of 100ml of emulsion prepared in WHO standard soft water (WHO method WHO/M/30 see Annex 2, section II) with 5ml of emulsion, oil in water, shall not be visible when tested as described in WHO/M/13.R3 (/). 

Add about 1 ml of hard water to a small test tube, about 1 ml of soft water to another small test tube, and about 1 ml of distilled water to a third small test tube. 

Stonelly bioassay was done at Denver, Colorado, and at Salt Lake City, Utah. Denver tests were in soft water (35 mg 1 ... 

TDS), non-aerated, 60 F. Salt Lake City tests were in hard water (150 mg 1 TDS), aerated, 48-50 F. Response was death. — Daphnia pulex and Simocephalus serrulatus bioassay was done at Denver, Colorado, in soft water (35 mg 1 TDS), non-aerated, 60 F. Daphnia magna bioassay was done at Pennsylvania State University in hard water (146 mg 1 TDS), non-aerated, 68 F. Response was immobilization. 

In this study, the stability of bromate in water samples with different matrix constituents was investigated. Water samples ranged from soft to hard and were spiked with 1 mg/L bromide, 0.5 mg/L chlorite and 0.5 mg/L chlorate. These levels are considered to be higher than those normally observed in waters for these three anionic species. Each sample was also spiked with 2.5, 10 and 25 pg/L of bromate. Fiuthermore, a 5 pg/L of bromate standard in deionized water was also prepared. Brown glass bottles capped with polypropylene tops and PTFE inserts were used as sample containers. Samples were stored in the dark at 4 °C. Tables 2.5 and 2.6 summarize matrix constituents of each sample, preservation method spike levels and results of analyses. The results clearly demonstrate that for the two high and low total hardness waters tested, samples containing 2.5 to 25 pg/L bromate were stable for at least 20 days and that the addition of 50 mg/L ethylenediamine (EDA) preservative did not affect the results, as illustrated in Table 2.6. The results also confirm that 5 pg/L bromate standard made up in deionized water had the same stability over this period. 

---