Chloride-containing waste waters

The ideal disposal method is a chemical treatment that can convert hazardous waste into environmentally benign materials. For example, trichloroethylene (CI2 C I CHCl) is highly toxic to aquatic life, but this compound can be made nontoxic by chemical treatment that converts its chlorine atoms into chloride anions. Similarly, the chromium-containing waste from electroplating operations contains highly toxic CrOq anions, but a chemical treatment that converts CrOq into Cr causes the chromium to precipitate from the solution as insoluble Cr (OH). This removal of chromium detoxifies the water. 

The rate of biological oxidation may vary considerably under different test conditions. Gotaas [205] reported that waste waters containing less than 10 000 mg/1 chloride diluted with fresh water had a rate of biological oxidation... 

The waste contained about 3.5% dissolved solids, 1.7% chlorides, 0.4% sodium hydroxide, and tens to hundreds of ppm of chlorinated hydrocarbons and chlordane its pH was generally greater than 13 (Brower et al., 1989). At the time of drilling, analysis of formation samples indicated that the injection zone was composed of nearly pure dolomite [CaMg(CC>3)2]. The carbonate formation was thought to be safe for accepting an alkaline waste water because carbonates are considered stable at high pH. 

Vessels for treatment of municipal waste water containing chloride ions ... 

Waste waters containing low concentrations of soluble organic lead in the presence of high concentrations of other diverse ions such as Cl pose a particularly difficult treatment problem. Generally, organic lead exists in solution as the tri- or dialkyl lead chloride species. These salts are not amenable to the conventional methods used to remove inorganic lead, viz., those of pH adjustment followed by settling. The technique of chemical conversion of the... 

In full-scale applications very fast corrosion (formation of holes over the course of weeks, especially at improper welds) has been observed in off-gas piping, even when made from stainless steel. The problem is most evident when aerosols, for example containing chloride, escape from the reactor into the pipes where they form a very corrosive wet film. But corrosion may also occur in stainless steel pilot or full-scale reactors, especially when treating waste waters. Such reactors are best made of stainless steel because of the possibility to operate them at elevated pressures, e. g. 200-600 kPa, which can readily be achieved with commercially available ozone generators (Masschelein, 1994). 

Thiocyanate is a monovalent polyanion that has the formula SCN-. This anion is rarely found in wastewaters. However, cyanide-containing wastes or waters on contact with sulfides can form thiocyanates. On chlorination, thiocyanate could react with chlorine to form highly toxic cyanogen chloride, CNC1. Thiocyanate in water may be analyzed using 1. colorimetric method and 2. spot test. The latter method is a rapid spot test that can give semiquantitative results. Preserve samples at pH below 2 and refrigerate. 

The work of Mosko [116] is important in that he is one of the few workers who have given serious consideration to the determination of nitrite in water. His paper is concerned with the determination of chloride, sulphate, nitrate, nitrite, orthophosphate, fluoride and bromide in industrial effluents, waste water and cooling water. Two types of analytical columns were evaluated (standard anion and fast run series). Chromatographic conditions, sample pretreatment and the results of interference, sensitivity, linearity, precision, comparative and recovery studies are described. The standard column provided separation capabilities which permitted the determination of all seven anions. The fast run column could not be used for samples containing nitrite or bromide owing to resolution problems. 

Atomic absorption spectroscopy (AAS) is the most prevalent analytical technique for measuring low levels of barium and its compounds (i.e., barium carbonate, barium sulfate, and barium chloride) in air, water, waste water, geological materials (calcium carbonate), unused lubricating oil, and diagnostic meals containing barium sulfate (see Table 6-2). 

Calcium phosphate has become a common problem with the increase in treatment of municipal waste-water for reuse. Surface waters can also contain phosphate. Calcium phosphate compounds can contain hydroxyl, chloride, fluoride, aluminum, and/ or iron. Several calcium phosphate compounds have low solubility, as shown in Table 7.2. Solubility for calcium carbonate and barium sulfate are also shown by comparison. The potential for scaling RO membranes with the calcium phosphate compounds listed in Table 7.2 is high and will occur when the ion product exceeds the solubility constant. This can occur at orthophosphate concentrations as low as 0.5 ppm. Sodium softening or antisealants together with low pH help to control phosphate-based scaling. 

A by-product aqueous stream is generated in the first washing step that contains dissolved HCl, alkylate and AICI3. The uses for this byproduct depend upon its purity. It has been used directly in industrial waste water treating and it has been shown to effectively remove phosphate from municipal sewage. In Japan it is converted to polyaluminum chloride, a highly desirable coagulant for waste water. 

Hydroxylated derivatives of PCDEs might also contain traces of PCDEs. There are no reports on the concentration of PCDEs in OH-PCDEs, but the manufacture of Triclosan was suggested as a source of PCDEs in Narrangesett Bay, Rhode Island [51]. PCDEs were observed in the waste water of a chemical manufacturing plant. OH-PCDEs can be prepared via five different routes [52] and one route, the coupling of chloroguaiacol and chlorodiphenyliodonium chloride, can be used in the preparation of PCDEs. 

An analyzer based upon AAS and containing a tin chloride elemental reduction device is employed to measure the mercury in an industrial waste water sample. The cold vapour mode is used. Three standard solutions and the solution of the sample to be measured give the following results ... 

Chlorinated hydrocarbons are frequently encountered in ground-, drinking, and waste waters. A method for the detection of organic chlorides has been developed [6]. It makes use of the Fujiwara color reaction, which is a general assay for organic compounds that contain two or more chlorine atoms. Reaction of alkaline pyridine with polychlorinated organic compounds yields a red fluorescent chromophore whose formation is detected. The formation of the fluorophore is irreversible, so the device is a probe rather than a sensor. 

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