Wastewater treatment fluoride

FIGURE 22.3 General wastewater treatment process flow diagram at an aluminum fluoride plant. 

The raw minerals mined from natural deposits comprise mixtures of different specific minerals. An early step in mineral processing is to use crushing and grinding to free these various minerals from each other. In addition, these same processes may be used to reduce the mineral particle sizes to make them suitable for a subsequent separation process. Non-ferrous metals such as copper, lead, zinc, nickel, cobalt, molybdenum, mercury, and antimony are typically produced from mineral ores containing these metals as sulfides (and sometimes as oxides, carbonates, or sulfates) [91,619,620], The respective metal sulfides are usually separated from the raw ores by flotation. Flotation processes are also used to concentrate non-metallic minerals used in other industries, such as calcium fluoride, barium sulfate, sodium and potassium chlorides, sulfur, coal, phosphates, alumina, silicates, and clays [91,619,621], Other examples are listed in Table 10.2, including the recovery of ink in paper recycling (which is discussed in Section 12.5.2), the recovery of bitumen from oil sands (which is discussed further in Section 11.3.2), and the removal of particulates and bacteria in water and wastewater treatment (which is discussed further in Section 9.4). 

MBR processes is usually low since the As species remain in soluble form. Few cases showed how major role was played by the problematic layers such as fouling and clogging layers. Consequently, other processes should be integrated if enhanced As removal is required. Fluoride removal in urban wastewater is variable depending on the operating conditions of the urban wastewater treatment plant. Research data concerning the fate and removal of trace U in urban wastewater is very limited. Selenium removal by MBR is moderate to low. Both U and Se are met in very low concentrations in municipal wastewater. 

Poly(vinylidene fluoride) (PVDF) is one of the promising polymeric materials that has prominently emerged in membrane research and development (R D) due to its excellent chemical and physical properties such as highly hydrophobic nature, robust mechanical strength, good thermal stability, and superior chemical resistance. To date, PVDF hollow-fiber membranes have dominated the production of modem microfiltration (MF) ultrafiltration (UF) membrane bioreactor (MBR) membranes for municipal water and wastewater treatment and separation in food, beverage, dairy, and wine industries. In the last two decades, increasing effort has been made in the development of PVDF hollow fibers in other separation applications such as membrane contractors [6,7], membrane distillation (MD) [8-11], and pervaporation [12,13]. 

Precipitation is often applied to the removal of most metals from wastewater including zinc, cadmium, chromium, copper, fluoride, lead, manganese, and mercury. Also, certain anionic species can be removed by precipitation, such as phosphate, sulfate, and fluoride. Note that in some cases, organic compounds may form organometallic complexes with metals, which could inhibit precipitation. Cyanide and other ions in the wastewater may also complex with metals, making treatment by precipitation less efficient. A cutaway view of a rapid sand filter that is most often used in a municipal treatment plant is illustrated in Figure 4. The design features of this filter have been relied upon for more than 60 years in municipal applications. 

Some innovating treatment technologies may be introduced in the treatment of wastewater generated in the aluminum fluoride industry to make its effluent safer. The ion exchange process can be applied to the clarified solution to remove copper and chromium. At a very low concentration, these two pollutants can be removed by xanthate precipitation.24 A combination of lime and ferric sulfate coagulation will effectively reduce arsenic concentration in the wastewater. 

Nemerow [23] summarized the major characteristics of wastes from phosphate and phosphorus compounds production (i.e., clays, slimes and tall oils, low pH, high suspended solids, phosphorus, silica, and fluoride) and suggested the major treatment and disposal methods such as lagooning, mechanical clarification, coagulation, and settling of refined wastewaters. The... 

Hydrochloric, sulfuric, and nitric acids are used in soil remediation to extract metals. Because of the good solubility of basic salts (e.g., lead and zinc), it is also possible to use treatment with sodium hydroxide. Cyanides can also be converted with NaOH however, experience has shown that the treatment of iron cyanide in fines is difficult. The treatment of wastewater generated during the treatment of contaminated soil employs the same techniques as those used to treat industrial wastewater. Calcium oxide is most often used for the precipitation of metals as this process also removes sulfates, fluorides, phosphates, and arsenates. Most effective in the elimination of heavy... 

Only a few studies have been reported in the literature on the use of electrocoagulation for the treatment of distillery and/or brewery wastewater. Manisankar, Rani, and Viswanathan (2004) used electrocoagulation to remove COD, BOD and colour from distillery effluent using graphite electrodes and studied the effect of pH, current density and the halides (sodium fluoride, sodium chloride and sodium bromide) as supporting electrolytes on the treatment of distillery effluent. An influent COD value of 12,000 mg/L was reduced by 85.2% in the presence of sodium chloride electrolyte. Colour and BOD were also reduced by... 

Dolar, D., KoSutio, K. Vucic, B. (2011) RO/NF treatment of wastewater from fertilizer factory - removal of fluoride and phosphate. Desalination, 265 (1-3), 237-241. 

Fluoride ions were removed electrochemically from industrial wastewater by Shen et al. (2003) using a combined electrocoagulation and electroflotation process. The experimental results showed that weakly acidic conditions were favorable for this t)T)e of treatment, while too high or too low pH could affect the formation of the Al(OH)3 floes. The optimal retention time in their... 

Nowadays, water is a limited natural resource and in many cases there is a lack of water with the desired quality for both industrial and domestic use. Population growth and industrialization have led to a reduction of surface water sources, forcing populations around the world to depend on groundwater sources. Both types of water are not suitable for direct consumption due to high salt concentrations and in some cases also to naturally occurring hazardous contaminants, such as arsenic (As), fluoride (F ) and uranium (U) (US NRC, 1984). Therefore, extensive treatments are required prior to consumption. Another source of water is the one that can be obtained with appropriate treatments of both industrial and municipal wastewater. 

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