Wastewater physical

F. W. Keith, Jr. and R. T. Moll in R. A. Young and P. Cheremisinoff, eds., Wastewater Physical Treatment Processes, Ann Arbor Science Publishers, Ann Arbor, Mich., scheduled 1978. 

Wastewater physical treatment is directed toward removal of certain pollutants with the least effort. Three treatment steps are presented below. 

Primary or pretreatment of wastewater prior to biological treatment involves both physical and chemical treatment depending on the nature of the emission. 

M. P. Freeman andj. A. Fitzpatrick, eds.. Physical Separations, Engineering Foundation, New York, 1980 A. J. Rubia, ed., Chemisty of Wastewater Technology, Ann Arbor Sci., Ann Arbor, Mich., 1978. 

The general proportions may be varied from one end of the tower to the other to accommodate changing liquid volumes and physical properties. These towers have been used in diameters ranging from a few inches for laboratory work up to 2.4 m (8 ft) in diameter by 12.2 m (40 ft) tall for purposes of deasphalting petroleum. Other commercial services include furfural extraction of lubricating oils, desulfurization of gasoline, phenol recoveiy from wastewaters, and many others. Columns up to 4.5 m in diameter and up to 50 m in height have been constructed. 

Calculate the mass or weight of chemical in the wastestream being treated by multiplying the concentration (by weight) of the chemical in the wastestream by the flow rate. In most cases, the percent removal compares the treated effluent to the influent for the particular type of wastestream. However, for some treatment methods, such as Incineration or solidification of wastewater, the percent removal of the chemical from the influent wastestream would be reported as 100 percent because the wastestream does not exist in a comparable form after treatment. Some of the treatments (e.g., fuel blending and evaporation) do not destroy, chemically convert, or physically remove the chemical from its wastestream. For these treatment methods, an efficiency of zero must be reported. 

In applying these general criteria, one should focus on the intended application. In wastewater treatment applications, filtration can be applied at various stages. It can be applied as a pretreatment method, in which case the objective is often to remove coarse, gritty materials from the waste-stream. This is a preconditioning step for waste waters which will undergo further chemical and physical treatment downstream. 

Lime is among a family of chemicals which are alkaline in nature and contain principally calcium, oxygen and, in some cases, magnesium. In this grouping are included quicklime, dolomitic lime, hydrated lime, dolomitic hydrated lime, limestone, and dolomite. The most commonly used additives are quicklime and hydrated lime, but the dolomitic counterparts of these chemicals (i.e., the high-magnesium forms) are also widely used in wastewater treatment and are generally similar in physical requirements. 

Air stripping is used to remove 90% of the toluene (molecular weight = 92) dissolved in a 10 kg/s (159 gpm) wastewater stream. The inlet composition of toluene in the wastewater is 500 ppm. Air (essentially free of toluene) is compressed to 202.6 kPa (2 atm) and bubbled through a stripper which contains sieve trays. In order to avoid fire hazards, the concentration of toluene in the air leaving the stripper is taken as 50% of the lower flammability limit (LFL) of toluene in air. The toluene-laden air exiting the stripper is fed to a condenser which recovers almost all the toluene. A schematic representation of the process is shown in Fig. 2.11. Calculate the annual operating cost and the fixed capital investment for the system. The following physical and economic data are available ... 

Table 4 summarizes the efficiency of membrane filtration as preliminary treatment in the hybrid process to obtain regenerated water for industrial reuse. Working with the adequate cleaning cycle to avoid fouling and to keep a constant flux (10 1 min ) important reduction in suspended solids (90%) and turbidity (60%) of the wastewaters is achieved but there is no significant reduction of other chemical or physical parameters, e.g., conductivity, alkalinity or TDS, or inactivation of E. coli. 

Inputs from WWTP effluents can also affect the hydrologic and nutrient concentration regimes of recipient streams at different temporal scales. Daily variations of these parameters may be exacerbated in streams below the WWTP input by the diel patterns of the effluent discharge associated with plant operation [46]. In contrast, at the annual scale, seasonal variations of physical and chemical parameters upstream of the WWTP may be dampened by the constant input of additional water and nutrients from the WWTP. At its extreme, naturally intermittent or ephemeral streams may turn into permanent streams downstream of WWTPs [28, 30]. In these effluent-dominated streams, the relative contribution of WWTP inputs may vary widely on an annual basis, as shown by the 3-100% range measured in a Mediterranean stream [47]. Finally, WWTP inputs also cause shifts in the relative availability of N and P as well as in the relative importance of reduced and oxidized forms of N in the stream [30, 47]. The magnitude of these shifts depends on the level of wastewater treatment (i.e., primary, secondary, or tertiary treatment), the type of WWTP infrastructure (e.g., activated sludge reactor. 

Various physical, chemical, and biological methods have been used for the treatment of dye-containing wastewater. However, these conventional technologies have disadvantages like poor removal efficiency and high running cost. Therefore, low-cost sorbents which can bind dye molecules and be easily regenerated have been extensively searched and tested [3-7]. 

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