Iron salts, coagulation

Chemical precipitation can remove 95 percent of the suspended solids, up to 50 percent of the soluble organics and the bulk of the heavy metals in a wastewater. Removal of soluble organics is a function of the coagulant chemical, with iron salts yielding best results and lime the poorest. Metal removal is primarily a function of pH and the ionic state of the metal. Guidance is available from solubihty product data. 

Rotary vertical shaft turbine units as shown in Figure 10 and other rotary or reciprocating equipment are other examples. Tapered flocculation may be obtained by varying reel or paddle size on horizontal common shaft units or by varying speed on units with separate shafts and drives. In applications other than coagulation with alum or iron salts, flocculation parameters may be quite different. Lime precipitates are granular and benefit little from prolonged flocculation. 

Precipitation Softening. This process depends on sufficient holdup time within a vessel to allow sedimentation and clarification to occur. A coagulation chemical such as alum or iron salts added to the solution will improve the process efficiency. 

Ion exchange, in contrast, creates an effluent that contains between two and five times the mass of inorganic material removed from the product water. Coagulation with aluminum or iron salts creates a sludge, which creates a disposal problem. Green pressure, especially in Switzerland and mid-west USA, which lie in the middle of large land masses, has started to force industrialists to install alternative membrane processes to avoid these discharges. 

Ferrous sulfate (copperas), (FeS04) 7H20 This is similar to ferric sulfate. The optimum coagulation pH level for these last two iron salts is typically 8.0 to 9.0 but may need to be lowered. 

Concurrent use of the fluoroquinolones with theophylline causes an increase in serum theophylline levels. When used concurrently with cimetidine, the cimetidine may interfere with the elimination of the fluoroquinolones. Use of the fluoroquinolones with an oral anticoagulant may cause an increase in the effects of the oral coagulant. Administration of the fluoroquinolones with antacids, iron salts, or zinc will decrease absorption of the fluoroquinolones. There is a risk of seizures if fluoroquinolones are given with the NSAIDs. There is a risk of severe cardiac arrhythmias when the fluoroquinolones gatifloxacin and moxifloxacin are administered with drains that increase the QT interval (eg, quini-dine, procainamide, amiodarone, and sotalol). 

Many chemicals are added to water to remove contaminants such as organic matter, suspended or dissolved solids, and microbial pathogens. Among those added are alum, iron salts, polymeric coagulant aids, chlorine, and other oxidizing agents, all of which may leave residues or byproducts in the finished water. Chlorine gas often contains... 

This chapter applies the techniques of the unit process of coagulation to the treatment of water and wastewater for the removal of colloids that cause turbidity and color. It also discusses prerequisite topics necessary for the understanding of coagulation such as the behavior of colloids, zeta potential, and colloid stability. It then treats the coagulation process, in general, and the unit process of the use of alum and the iron salts, in particular. It also discusses chemical requirements and sludge production. 

Alum (aluminum salts) Iron (iron salts) Cationic polymers Nonionic polymers Anionic polymers Starch Coagulation and flocculation for removal of particulate... 

Lime is the largest tonnage chemical used in the treatment of potable and industrial water supplies. In conjunction with alum or iron salts it is urod to coagulate suspended solids and remove turbidity. It is also used in water softening to remove lempotaty (bicarbonate) hardness. Typical reactions ate ... 

Precipitation and dissolution phenomena are extremely important in both natural waters and water treatment processes. Dissolution of minerals is a prime factor in determining the chemical composition of natural waters. Natural water chemical composition can be altered by precipitation of minerals and the subsequent sedimentation of these solids from supersaturated solutions. Water and wastewater treatment processes such as lime-soda softening, iron removal, coagulation with hydrolyzing metal salts, and phosphate precipitation are based on precipitation phenomena. 

Dying solutions and wastewaters are usually purified by using conventional methods such as decolourisation by chemical means, coagulation by lime, aluminium or iron salts, adsorption on activated carbon, and by biological oxidation techniques. 

---