Color of natural water

Their natural source of production is om the degradation of lignin (31,32) and sofl humic polymers. In nature, humic substances are by-products of lignin. Ligninand humic substances are compile aromatic polymers that constitute a major fraction of organic compounds in natural water and their presence in the wastewaters has been a problem fricii the water industry. The yellow to brown color of natural water is mainly due to the probI n of aquatic humic acids. Some of the nnportant characterisdes exhibited by all humic fractions are their resistance to microbial (gradation, and the... 

The apparent source materials for forming such a hypothetical humic polymer would be lignin degradation products or plant polyphenols such as flavonoids. Because it has little relationship with the physical or chemical characteristics of actual humic materials, this type of model has fallen out of favor almost completely, except for ambiguous statements, still occasionally encountered, that the color of natural waters is due to tannins. ... 

The coloring of natural water varying from pale yellow to brown is due to the presence of humus substances. Their decolorization is carried out by adsorption on coagulated Al(OH)j or Fe(OH)j. The increasing demand for fresh water requires the use of more colored water, which however is pre-chlorinated, and then subject to adsorption up to their complete decolorization. 

Silica. The siUca content of natural waters is usually 10 to (5 x lO " ) M. Its presence is considered undesirable for some industrial purposes because of the formation of siUca and siUcate scales. The heteropoly-blue method is used for the measurement of siUca. The sample reacts with ammonium molybdate at pH 1.2, and oxaUc acid is added to reduce any molybdophosphoric acid produced. The yellow molybdosiUcic acid is then reduced with l-amino-2-naphthol-4-sulfoiiic acid and sodium sulfite to heteropoly blue. Color, turbidity, sulfide, and large amounts of iron are possible interferences. A digestion step involving NaHCO can be used to convert any molybdate-unreactive siUca to the reactive form. SiUca can also be deterrnined by atomic... 

All aqueous extracts are brown colored, and so is the Hillsborough River where samples of hydrilla are found. Examination of Table II, however, suggests that the location of the second peak in this water sample is significantly different from the other five samples. Presently, chromatograms of natural waters and the distribution of hydrilla are being obtained and compared with a view to being able to understand those factors that may limit the growth and spread of this noxious aquatic plant. 

Acid-Base. The pH of natural waters is determined primarily by the carbonate equilibria. However, organisms may produce amounts of organic matter or ammonia sufficient to influence the pH and buffer capacity of the waters. It would be of interest to determine titration curves of high organic, high color, low alkalinity waters leached from some marshes. It is possible that these waters contain sufficient amounts of organic acids to be significant. 

Packham, R. F. (1964). Studies of organic color in natural water. Proc. Soc. Water Treatment Exam. 13, 316-334. 

The colors of azo compounds vary with the nature of the aryl group with its substituents and with pH Substituents also affect the water solubility of azo dyes and how well they... 

In unalloyed steel containers formamide discolors slowly during shipment and storage. Both copper and brass are also subject to corrosion, particularly in the presence of water. Lead is less readily attacked. Aluminum and stainless steel are resistant to attack by formamide and should be used for shipping and storage containers where the color of the product is important or when metallic impurities must be minimized. Formamide attacks natural mbber but not neoprene. As a result of the solvent action of formamide, most protective paints and finishes are unsatisfactory when in contact with formamide. Therefore, formamide is best shipped in containers made of stainless steel or in dmms made of, or coated with, polyethylene. Formamide supphed by BASF is packed in Lupolen dmms (230 kg) or Lupolen canisters (60 kg) both in continental Europe and overseas. 

Phosphate. Phosphoms occurs in water primarily as a result of natural weathering, municipal sewage, and agricultural mnoff The most common form in water is the phosphate ion. A sample containing phosphate can react with ammonium molybdate to form molybdophosphoric acid (H2P(Mo202q)4). This compound is reduced with stannous chloride in sulfuric acid to form a colored molybdenum-blue complex, which can be measured colorimetrically. SiUca and arsenic are the chief interferences. 

---