Coagulation flocculation

Makeup. Makeup treatment depends extensively on the source water. Some steam systems use municipal water as a source. These systems may require dechlorination followed by reverse osmosis (qv) and ion exchange. Other systems use weUwater. In hard water areas, these systems include softening before further purification. Surface waters may require removal of suspended soHds by sedimentation (qv), coagulation, flocculation, and filtration. Calcium may be reduced by precipitation softening or lime softening. Organic contaminants can be removed by absorption on activated carbon. Details of makeup water treatment may be found in many handbooks (22—24) as well as in technical Hterature from water treatment chemical suppHers. 

Suspended matter in raw water suppHes is removed by various methods to provide a water suitable for domestic purposes and most industrial requirements. The suspended matter can consist of large soflds, settleable by gravity alone without any external aids, and nonsettleable material, often colloidal in nature. Removal is generally accompHshed by coagulation, flocculation, and sedimentation. The combination of these three processes is referred to as conventional clarification. 

For color removal, ozonization has achieved the greatest practical importance as seen by the plethora of articles and patents on this method (147—163). Ozonization in combination with treatments such as coagulation, flocculation, carbon adsorption, uv irradiation, gamma radiation, and biodegradation significantly and successfully remove dye wastes and reduce costs (156,164—170). 

Control philosophies for clarifiers are based on the idea that the overflow is the most important performance criterion. Underflow density or suspended sohds content is a consideration, as is optimal use of flocculation and pH control reagents. Automated controls are of three basic types (I) control loops that optimize coagulant, flocculant, and pH control reagent additions (2) those that regulate underflow removal and (3) rake drive controls. Equahzation of the feed is provided in some installations, but the clarifier feed is usually not a controlled variable with respect to the clarifier operation. 

Precipitation is nonselective in that compounds other than those targeted may be removed. Both precipitation and flocculation are nondestructive and generate a large volume of sludge which must be disposed of. Coagulation, flocculation, sedimentation, and filtration, are typically followed by chlorination in municipal wastewater treatment processes. 

Coagulation, flocculation, sedimentation, and filtration will remove many contaminants. Perhaps most important is the reduction of turbidity. This treatment yields water of good clarity and enhances disinfection efficiency. If particles are not removed, they harbor bacteria and make fmal disinfection more difficult. 

It should be noted that the total loss of head of a filter bed is in inverse ratio to the depth of penetration of the matter in suspension. In a normal wastewater treatment plant, the water is brought onto a series of rapid sand filters and the impurities are removed by coagulation-flocculation-filtration. Backwashing is typically performed in the counterfiow mode, using air and water. One type of common filter is illustrated in Figure 6, consisting of closed horizontal pressurized filters. 

Corrective Action Increase coagulant/flocculant doses. 

Most external treatment processes involve the use of large items of capital equipment (although some consumable chemicals also may be used to aid or improve the process, such as coagulants, flocculants, filter-aids, dispersants, and the like). 

On the other hand, Palma de Mallorca is also a successful example of urban water reuse within an integrated water management framework. Since the end of the nineties, tertiary treated (coagulation, flocculation, sand filtration and gaseous chloride disinfection) water is used for public parks, landscape and golf courses irrigation. About 7 Mm year are currently used, thus saving equal amounts of potable water. This is the most efficient water reuse apphcation in Palma. 

Different technologies have been developed in recent years to treat the wastewaters contaminated with heavy metals. Chemical precipitation, coagulation-flocculation, flotation, ion exchange, and membrane filtration can be employed to remove heavy metals from contaminated wastewater.6 However, they have inherent limitations in application mainly due to the lack of economical feasibility for the treatment of large volumes of water with a low metal concentration. Furthermore, the major disadvantage of conventional technologies is the production of sludge.9... 

In this treatment process, unit operations such as chemical coagulation, flocculation, and sedimentation followed by filtration, activated carbon, ion exchange, and reverse osmosis are employed to remove significant amounts of nitrogen, phosphorus, heavy metals, organic matters, bacteria, and viruses present in wastewater.2 It is always the last process step in the wastewater treatment plant that finally renders the treated wastewater reusable and disposable into the environment without any adverse effect (Figure 22.1). 

Amuda, O.S., Amoo, I.A., and Ajayi, O.O., Performance optimization of some coagulants/flocculants in the treatment of a beverage industrial wastewater, Journal of Hazardous Materials, B129, 69-72, 2006. 

Amuda, O.S. and Alade, A., Coagulation/flocculation process in the treatment of abattoir wastewater, Desalination, 196, 22-31, 2006. 

Pretreatment is necessary for the treatment of the food industry wastewater. Pretreatment options such as flow equalization and neutralization, screening, FOG separation, acidification, coagulation-flocculation, sedimentation, and DAF are available. Selecting the appropriate technology depends on the wastewater characteristics. 

Liu, J.C. and Lien, C.S., Pretreatment of bakery wastewater by coagulation—flocculation and dissolved air flotation, Water Science and Technology, 43, 131-137, 2001. 

Any process which brings about destabilisation of a latex to such an extent that the particles coalesce. Depending on the form resulting from the agglomeration, the coacervation may be described as either coagulation, flocculation or gelation. 

Table VI Critical Coagulation/Flocculation Concentration and the slope of log W vs log C plot...

The coagulation, flocculation, and adsorption processes were modeled mathematically using classical coagulation theory as a starting point. The Smoluchowski equation for orthokinetic coagulation in laminar flow is written (18)... 

Golab V, Vinder A, Simonic M (2005) Efficiency of the coagulation/flocculation method for the treatment of dye bath effluent. Dyes Pigm 67 93-97... 

Treatment of dye wastewater involves physical, physico-chemical, chemical, and biological methods. Physical processes are dilution, filtration, and gamma radiation. Physico-chemical includes adsorption, coagulation, flocculation, precipitation, reverse osmosis, ion exchange, etc. 

Chemical processes include reduction and oxidation. Conventional chemical (coagulation-flocculation) and advanced oxidation processes (AOPs), such as chemical oxidation (ozonation, Fenton oxidation, Fe2+/H202), ultrasonic chemical oxidation, photocatalysis oxidation (UV/H2Q2, UV/O3, and W/O3/H2O2),... 

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