Effect of Water Hardness

The presence of polyvalent cations, notably Ca2+ and Mg2+, in the bath water is invariably detrimental to the cleaning process for a number of reasons  

Adsorption of polyvalent cations onto solid soil particles dispersed in the bath can reduce their (negative) electrical potentials and cause them to flocculate and redeposite onto the substrate. 

At high polyvalent cation concentrations, the corresponding metal salts of anionic surfactants and other anions (e.g., phosphates, silicates) in the bath may precipitate onto the substrate. In some cases, this may mask the presence of soil on the substrate (Rutkowski, 1971) or produce other deleterious effects (Vance, 1969 Brysson, 1971). 

---

FIG. 26 Effect of water hardness on foam height of AOS, LAS, AS, AES, and a-SFMe in phosphate-built formulation. (From Ref. 5.)... 

Everall, N.C., N.A.A. Macfarlane, and R.W. Sedgwick. 1989b. The effects of water hardness upon the uptake, accumulation and excretion of zinc in the brown trout, Salmo trutta L. Jour. Fish Biol. 35 881-892... 

Paulauskis, J.D. and R.W. Winner. 1988. Effects of water hardness and humic acid on zinc toxicity to Daphnia magna Straus. Aquat. Toxicol. 12 273-290. 

Dyer, S.D., J.R. Coats, S.P. Bradbury, G.J. Atchison, and J.M. Clark. 1989. Effects of water hardness and salinity on the acute toxicity and uptake of fenvalerate by bluegill (Lepomis macmchirus). Bull. Environ. Contam. Toxicol. 42 359-366. 

Maier, K.J. and A.W. Knight. 1991. The toxicity of waterborne boron to Daphnia magna and Chironomus decorus and the effects of water hardness and sulfate on boron toxicity. Arch. Environ. Contam. Toxicol. 20 282-287. 

Stendahl, D.H. and Sprague, 3.B., 1982. Effects of water hardness and pH on vanadium lethality to Rainbow Trout. Water Res., 16 1479-1488. 

Examine the causes and effects of water hardness. Considered several methods for softening hard water. 

Moni, S. and S, Manohar-Dhas. 1989. Effects of water hardness on the toxicity of zinc to Sarotherodon mossambicus (Peters), Uttar Pradesh J. Zool. 9(2) 263-270. 

The term water hardness incorrectly attributes identical chemical and biological properties to calcium and magnesium. Positive or negative effects of water hardness mostly do not relate to the total calcium and magnesium concentrations, but only to the concentration of one of them. For example, from the viewpoint of the formation of incrustations in pipes, calcium plays a more important role than magnesium. There are also differences in biological and health aspects. It is therefore invariably more appropriate to evaluate the effects of calcium and magnesium separately [4]. 

Inorganic ligands that complex metal ions can alter the effects that metal ions exert in natural waters. For example, the literature on fish toxicity contains references to the effects of water hardness on the toxicity of heavy metals. The general observation made is that heavy metals are much less toxic to fish in hard water than they are in soft water. We can provide an explanation of this result in terms of complex formation between the heavy metal copper and the alkalinity ions (HCOa" and COs "), since the alkalinity usually increases together with the water hardness. 

GUhs, P.L., R.J. Mitchell, A.N. Schwalh, et al. 2008. Sensitivity of the glochidia (larvae) of freshwater mussels to copper Assessing the effect of water hardness and dissolved organic carhon on the sensitivity of endangered species. Aquat. Toxicol. 88 137-145. 

Linho, T.L., D.H. Baldwin, J.K. McIntyre, et al. 2009. Effects of water hardness, alkalinity, and dissolved organic carbon on the toxicity of copper to the lateral line of developing fish. Environ Toxicol. Chem. 28 1455-1461. 

Markich, S.J., A.R. King, and S.R Wilson. 2006. Non-effect of water hardness on the accumulation and toxicity of copper in a freshwater macrophyte Ceratophyllum demersum) How useful are hardness-modified copper guidelines for protecting freshwater biota Chemosphere 65 1791-1800. 

Morgan, T.P., C.M. Guadagnolo, M. Grosell, et al. 2005. Effects of water hardness on the physiological responses to ehronie waterborne silver exposure in early life stages of rainbow trout Oncorhynchus myldss). Aquat. Toxicol. 74 333-350. 

The reason for the above procedure is because both temperature and water hardness have a major effect on the performance of ECs. This was illustrated previously [8], showing the effect of water hardness on the amount of cream that separates... 

Polymer solutions lose their potency with age. The more dilute the polymer, the quicker is the deterioration. Making up with hard water also makes deterioration more rapid. Thus, in preference, it is better to make up with soft water as concentrated as possible, and only dilute to the required dilution just before use. Figure 5.3 shows some results of work testing the effect of water hardness. The dewaterability of the sludge was gauged by the amount of supernatant produced after a set spin in a laboratory bottle centrifuge. Note the correlation of the fall in polymer solution viscosity with increased water hardness and resulting decrease in polymer efficiency. 

Figure 5.3. The effect of water hardness on polyelectrolyte solutions.

Builders are used to enhance the performance of the surfactant system, using several different mechanisms. Probably the most important functions of a builder system are to reduce the deleterious effects of water hardness, to provide an alkaline buffer, and to prevent soil redeposition. Until about 15 years ago, all the builder systems were based on sodium phosphates (pyrophosphate, tripolyphosphate). Due to eutrophication of lakes and rivers, phosphate levels were regulated and, in some countries, totally banned. As a result, different builder systems were developed, based on zeolites and citrate with acrylic acid polymers and copolymers. 

Figure 5 shows the effects of monovalent and a divalent cation on the initial foam height of a C14-SME [20]. Again, the effects of water hardness are also shown in the same graph. In soft water, the magnesium and anunonium salts... 

SLS and cause the surfactant to become significantly less water soluble. Surfactant solutions will typically become hazy and over time the surfactant can precipitate. If a surfactant precipitates, it is not available for foam generation, cleaning, wetting, etc. These surfactant properties require a surfactant be available at an interface, not sitting on the bottom of a container. SMEs are not affected by hard water. In other words, their divalent salts are water soluble. Sulfonated fatty acids are affected by hard water and can precipitate in cold water [3]. The effects of water hardness on detergency will be discussed later. 

Uses Dispersant for cotton and poiyester dyeing soiubiiizer for reactive dyes increases sait toierance of dye carriers and disperse dyes controis effects of water hardness in dyeing improves ieveiness of dyeings reduces dye and carrier stain probiems reduces deposits on dyeing machines ideai in one-bath disperse/ direct or disperse/reactive dye formuias in aii types of equip. 

Features Nonfoaming solv.-free inc. dye salt tolerance and solubility eliminates effects of water hardness and reduces trimer buildup produces cleaner, smoother dyeings with better fixation and quicker wash-out Properties 45% act. 

Uses Reduces the effect of water hardness by removing calcium and magnesium ions and increases the effectiveness of the detergent Trade Names Containing Montanov L C16-18 alcohols. See Cetearyl alcohol C16-20 alcohols EINECS/ELINCS 283-068-6 Synonyms Alcohols, C16-20... 

---