Accumulation and Adsorption Capacity of PAC in a Slurry Recirculating Clarifier

Kassam, Karirn; Huck, Peter M.; Roodselaar, Albert van; Shariff, Riyaz

doi:10.1002/j.1551-8833.1991.tb07103.x

Cited by 12 publications

(2 citation statements)

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“…Floc blanket reactors have been shown to have solids residence times ranging from 12 to 48 h or more. 3,12,13 Such long PAC residence times in the reactor allow the process of adsorption onto the surface of the PAC to reach complete equilibrium. 14 PAC addition at the rapid mix chamber of a conventional treatment plant.…”

Section: Application Of the Cstr And Pfr Modelsmentioning

confidence: 99%

Mathematical modeling of PAC adsorption processes

Najm¹

1996

Journal AWWA

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Easy‐to‐use models for PAC adsorption processes are presented. Recently, great strides have been made in modeling the adsorption of organic compounds onto powdered activated carbon (PAC), specifically with the conversion of the partial differential equations of the homogeneous surface diffusion model to algebraic nonlinear equations. The solutions of these equations are easy to obtain using nonlinear equation‐solving techniques (such as Newton's method) and are as accurate as the partial differential equation solutions obtained using labor‐intensive numerical techniques. A new method using these algebraic equations has been developed to determine the value of the surface diffusion coefficient Ds from adsorption batch kinetic tests. A nondimensional parameter λ = (t Ds/R2) can be used to evaluate the performance of PAC in a continuous‐flow process. A λ value > 0.1 implies that the adsorption process is highly efficient, in that more than 75 percent of the PAC adsorption capacity is being utilized. On the other hand, a λ value < 0.01 implies that the adsorption process is highly inefficient, in that less than 30 percent of the PAC adsorption capacity is being utilized.

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Section: Application Of the Cstr And Pfr Modelsmentioning

confidence: 99%

Mathematical modeling of PAC adsorption processes

Najm¹

1996

Journal AWWA

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“…For practical-oriented research, PAC has been used in the Robert-Haberer process (Stukenberg and Hesby, 1991;Harberer and Norman-Schmidt, 1991), the upflow floc-blanket reactor (Najm et al, 1991c(Najm et al, , 1993, and the solids contact slurry recirculating clarifier (Kassam et al, 1991), jet flocculation systems (Sobrinho et al, 1997), and other reactors (Najm et al, 1991b;Qi et al, 1994). Najm et al (1991a) summarized the advantages and disadvantages of different points for PAC application and the important criteria for selecting these points.…”

Section: Introductionmentioning

confidence: 99%

Jar Tests for Evaluation of Atrazine Removal at Drinking Water Treatment Plants

Zhang¹,

Emary²

1999

Environmental Engineering Science

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The objective of this study was to evaluate the effects of major factors such as PAC dosage, pH, contact time, mixing energy, alum dosage, and enhanced coagulation on the effectiveness of atrazine removal. Jar tests and response surface methodology were used to simulate conditions found in different treatment facilities. The time course of atrazine concentration with an initial atrazine concentration of 12 /JLgfL and initial (Acticarb) PAC of 16 mg/L indicated that it took approximately 5 days to reach equilibrium with the maximum atrazine removal of about 73%. Therefore, in treatment facilities, the adsorption of atrazine with this kind of PAC will be less than the removal achieved at equilibrium, due to the short retention time in a dynamic process. Mixing energy is a major factor affecting atrazine absorption. With jar test times ranging from 30 to 60 min, increasing rpms from 5 to 100 (G = 4 to 321 s_1) resulted in atrazine removals ranging from 34 to 59%. Without addition of PAC, neither lime softening nor alum coagulation (conventional or enhanced dosages ranging from 6 to 18 mg/L) demonstrated atrazine removal. A synergistic relationship appears to exist between PAC dosage and enhanced coagulation (with pH adjusted to about 5.8); neither PAC nor enhanced coagulation resulted in as high a removal rate of atrazine as the two did together (greater than 60%). The results of this study are useful for evaluation of different PAC application points in conventional drinking water treatment plants.

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