Wastewater treatment processes

Wastewater treatment processes are generally classified in order as... 

Chevron s WWT (wastewater treatment) process treats refinery sour water for reuse, producing ammonia and hydrogen sulfide [7783-06-04] as by-products (100). Degassed sour water is fed to the first of two strippers. Here hydrogen sulfide is stripped overhead while water and ammonia flow out the column bottoms. The bottoms from the first stripper is fed to the second stripper which produces ammonia as the overhead product. The gaseous ammonia is next treated for hydrogen sulfide and water removal, compressed, and further purified. Ammonia recovery options include anhydrous Hquid ammonia, aqueous Hquid ammonia, and ammonia vapor for incineration. There are more than 20 reported units in operation, the aimual production of ammonia from this process is about 200,000 t. 

Ex situ bioremediation may use various biological wastewater treatment processes, soil piles, or land appHcation. With in situ bioremediation, the basic process is the same microbes, soil, and water working together as a bioreactor. Where the in situ techniques differ are in how contaminants and microbes are brought in contact and how oxygen, nutrients, and other chemical supplements ate distributed in the soil—water—air matrix. Typical in situ bioremediation techniques include natural or intrinsic attenuation, air sparging, and bioventing. 

U.S. Environmental Protection Agency, SITE demonstration Bulletin ZenoGem - Wastewater Treatment Process, ZENON Environmental Systems, EPA/540/MR-95/503, Cincinnati, Ohio, 1995. 

Water Environment Eederation (formerly Water Pollution Control Eederation) and American Society of Civil Engineers, xleration Wastewater Treatment Process, Manual of Practice No. FD-13, Alexandria, Va. and New York (1988). 

Fig. 18. Anaerobic wastewater treatment processes (a) anaerobic filter reactor (b) anaerobic contact reactor (c) fluidized-bed reactor (d) upflow anaerobic...

In many cases, the quality of a stream or another water source can be adequately improved by removing more BOD or suspended solids. In other iastances, the effluent is prepared for groundwater recharge which may require only the removal of nutrient. A classification of wastewater treatment processes is given ia Table 3. Table 4 summarizes water quality criteria for various iadustrial uses (10). 

Biological wastewater treatment processes also affect solids characteristics and hence solids separation. Activated sludge solids have been found to have a distinct bimodal distribution with one mode in the supracolloidal to settleable range and another near the border between the colloidal and supracolloidal fractions. The concentrations and size limits in each range are affected by conditions in the... 

Quantities of the chemical released to surface impoundments that are used merely as part of a wastewater treatment process generally must cal be reported in this section. However, if the impoundment accumulates sludges containing the chemical, you must include an estimate in this section unless the sludges are removed and otherwise disposed of (in which case they should be reported underthe appropriate section of the form). For the purposes of this reporting, storage tanks are not considered to be a type of disposal and are not to be reported in this section of the form. 

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. 

There are commercially available clarifier simulation software for comprehensive (2D) analyzes of wastewater treatment processes in circular and rectangular clarifiers. With these software, you can predict processes like ... 

Attached growth processes Wastewater treatment processes in which the microorganisms and bacteria treating the wastes are attached to the media in the reactor. The wastes being treated flow over the media. Trickling filters, bio-towers, and RBCs are attached growth reactors. These reactors can be used for removal of BOD, nitrification, and denitrification. 

Pathogenic organisms Bacteria, viruses or cysts which cause disease (typhoid, cholera, dysentery) in a host (such as a person). There are many types of bacteria (non-pathogenic) which do NOT cause disease. Many beneficial bacteria are found in wastewater treatment processes actively cleaning up organic wastes. 

Primary treatment A wastewater treatment process that takes place in a rectangular or circular tank and allows those substances in wastewater that readily settle or float to be separated from the water being treated. 

Secondary Treatment A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. Usually the process follows primary treatment by sedimentation. The process commonly is a type of biological treatment process followed by secondary clarifiers that allow the solids to settle out from the water being treated. Sedimentation The process of subsidence and deposition of suspended matter from a wastewater by gravity. 

Thomas PM, Foster GD (2005) Tracking acidic pharmaceuticals, caffeine, and triclosan through TFIE wastewater treatment process. Environ Toxicol Chem 24(l) 25-30... 

Ma, M., Li, J., and Wang, Z.J. (2005). Assessing the detoxication efficiencies of wastewater treatment processes using a battery of bioassays/biomarkers. Archives of Environmental Contamination and Toxicology 49, 480-487. 

The application of a dynamic PCA strategy to a full-scale industrial wastewater treatment plant has demonstrated the feasibility and effectiveness of the proposed dynamic process monitoring approach. The methodology is relatively simple, only based on the historical operation data sets, and can easily be applied to most biological wastewater treatment processes. 

Reuse the spent reagents from the process baths in the wastewater treatment process. 

Several unit processes can be used in the washing process. The soil is mixed with washing agents and extraction agents that remove the contaminants from the soil and transfer them to the extraction fluid. The soil and washwater are then separated. The soil can be further rinsed with clean water. The soil is removed as clean product, ready to put back into the original excavation, and the washwater is ready to be treated by conventional wastewater treatment processes as addressed in the next subsection. 

Residual wastes from wastewater treatment processes may contribute to existing local and regional disposal problems. 

Wastewater treatment systems can be a significant source of cross-media pollutant transfer. For example, waterborne particulates and some chlorinated compounds settle or absorb onto treatment sludge and other compounds may volatilize during the wastewater treatment process. 

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

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