H. Moon

Biofilter in Water and Wastewater Treatment

Biofilter is one of the most important separation processes that can be employed to remove organic pollutants from air, water, and wastewater. Even though, it has been used over a century, it is still difficult to explain theoretically all the biological processes occurring in a biofilter. In this paper, the fundamental of biological processes involved in the biofilter is critically reviewed together with the mathematical modeling approach. The important operating and design parameters are discussed in detail with the typical values used for different applications. The most important parameter which governs this process is the biomass attached to the medium. The relative merits of different methods adopted in the measurement of the biomass are discussed. The laboratory-and full-scale applications of the biofilter in water and wastewater treatment are also presented. Their performances in terms of specific pollutant removal are highlighted.

Adsorption of phosphorus in saturated slag media columns

Abstract Adsorption of phosphorus (P as phosphates) in saturated slag media (dust and cake) columns was studied to assess the slag medias capability in removing P from wastewater. Prior to the experiments, slag media were completely washed to rinse off the soluble metal ions which are generally responsible for forming insoluble precipitates. Experimental data revealed that the adsorption capacities of washed slag media are still much higher than that of a sandy roam soil. Two dynamic models were tested for simulating the adsorption behavior of phosphorus in columns packed with slag media. The model employing the intraparticle transport through surface diffusion is successful, while a simplified model based on the linear driving force approximation (LDFA) could not predict the column behavior properly at low concentrations, particularly on the cake slag.

Application of a PAC-Membrane Hybrid System for Removal of Organics from Secondary Sewage Effluent: Experiments and Modelling

As world supplies of clean, fresh water come under increasing pressure and the need for water reuse rises, membrane technology is becoming increasingly important as a possible solution. However, membrane fouling is a major obstacle to the successful operation of the membrane process in wastewater treatment. In this study, a submerged hollow-fiber membrane with powdered activated carbon (PAC) adsorption was investigated for the removal of organics from secondary sewage effluent from a sewage treatment plant. The use of PAC in the membrane system was found to be very effective, not only in removing refractory organics, but also in reducing membrane clogging. A simple mathematical model was developed to predict the effluent quality [in terms of total organic carbon (TOC)] of the submerged membrane–adsorption hybrid system.

Adsorption equilibria, kinetics, and column dynamics of chlorophenols on a nonionic polymeric sorbent, XAD-1600

Abstract Adsorption equilibrium, kinetics, and column dynamics of chlorophenols [2‐chlorophenol (2‐CP) and 2,4‐dichlorophenol (2,4‐DCP)] dissolved in water were studied using a hydrophobic resin, XAD‐1600, without ion‐exchange functional groups. In addition, a hydrophilic nonionic polymer resin, XAD‐7, and an activated carbon, F400, were chosen for comparative analysis. Adsorption equilibrium data were correlated with the well‐known Langmuir, Freundlich, and Sips isotherms. The adsorption amount was in the order of F400 > XAD‐1600 > XAD‐7. Desorption from polymeric resins adsorbed with chlorophenols was conducted by using two organic solvents [methanol and isopropyl alcohol (IPA)] as desorbates. The intraparticle diffusion mechanism was assumed to be the surface diffusion or pore diffusion. It was found that the diffusivity in desorption step was considerably slower than the diffusivity in adsorption step within polymeric resins. To confirm the possibility of the resin as a sorbent for the removal of chlorophenols, adsorption breakthrough curves were measured under key operating conditions, such as concentration, flow rate, and column length. A simple dynamic model was also formulated to describe both the adsorption and desorption breakthrough curves of chlorophenols.

Comparative Studies on Coagulation and Adsorption as a Pretreatment Method for the Performance Improvement of Submerged MF Membrane for Secondary Domestic Wastewater Treatment

Abstract Membrane fouling is the main limitation of water and wastewater treatment. Coagulation and adsorption can remove organic materials which play an important role in fouling phenomena. Thus, this study focused on the comparison of the hybrid process of coagulation and adsorption coupled with microfiltration (MF) membrane for the secondary domestic wastewater from an apartment complex in Gwangju city, South Korea. Coagulation and adsorption were adopted as a pretreatment method prior to MF treatment. Three different powdered activated carbon (PAC) and ferric chloride were used as an adsorbent and as a coagulant. MF was operated in a submerged mode using hollow fiber polyethylene membrane with pore size of 0.4 µm for the separation of suspended organic solids resulted from coagulation or PAC particles, which are used for adsorbing organics dissolved in wastewater. Prior to study on the hybrid system, the performance of coagulation and adsorption processes were optimized individually for the removal of organics. Then, the overall performance for the hybrid system of coagulation/MF and PAC/MF was evaluated based on TOC removal, turbidity removal, and flux decline. It was found that the combined coagulation/MF and PAC/MF showed similar performance for TOC removal while coagulation/MF resulted in a significant decrease of the flux decline.

Adsorption of Radionuclides from Aqueous Solutions by Inorganic Adsorbents

Abstract Radionuclides such as 137Cs and 85Sr were removed from dilute aqueous solutions by means of inorganic adsorbents, MS-13X and chabazite. Adsorption data of radionuclides on the inorganic adsorbents were satisfactorily correlated by the Dubinin-Astakov (DA) equation. Gaussian-type distributions of adsorption energies were obtained from the parameters of the DA equation by applying the condensation approach. A surface diffusion model was applied to estimate the intraparticle mass transfer of radionuclides. The range of surface diffusion coefficients estimated was 3.2 × 10−12 to 3.5 × 10−11 m2/s. The adsorption model, which describes the surface diffusion mechanism with the DA equation, satisfactorily simulated the adsorption behavior of radionuclides on zeolites in batch adsorbers.

Heterogeneous Adsorption Characteristics of Volatile Organic Compounds (VOCs) on MCM‐48

Abstract This work focuses on the fundamental studies of heterogeneous adsorption characteristics of mesoporous adsorbent. MCM‐48 was synthesized to investigate the adsorption properties of eight different volatile organic compounds (benzene, cyclohexane, n‐hexane, toluene, methanol, acetone, methyl ethyl ketone (MEK), and trichloroethylene (TCE)). The gravimetric method was used to measure the adsorption equilibrium amount. Several simple and reliable methods such as isosteric enthalpy of adsorption, thermodynamic properties, condensation pressure, organophilicity, and adsorption energy distribution were evaluated to understand the surface heterogeneity of the VOCs+MCM‐48 adsorption system. This work shows that the unique features of the VOCs+MCM‐48 adsorption system are highly dependent on the adsorption step, ionization potential, and Debye dipole moment of VOCs. W. G. Shim and J. W. Lee contributed equally to this work.

Equilibrium and Fixed‐Bed Adsorption of n‐Hexane on Activated Carbon

Equilibrium and fixed‐bed adsorption of n‐hexane on pelletized activated carbon (SLG‐2PS) was studied between 298.15°K and 318.15°K. Equilibrium data was obtained in a gravimetric method. Adsorption isotherms were predicted by various model equations. Based on a comprehensive comparison of various single component isotherm models, the Langmuir–Freundlich isotherm was found to provide the best fit overall for the adsorption of the adsorbates on activated carbon. Their results could also be used to simulate the adsorption and temperature experimental data. A simple mathematical model was developed to calculate the concentration and temperature curves for the fixed bed adsorber. Model parameters were estimated from experiments and from correlations available in the literature. The mathematical model provides a good representation of the experimentally observed behavior of the breakthrough curves and temperature curves for n‐hexane on activated carbon.

Effects of biodegradation and background inorganic substances on granular activated carbon adsorption of wastewater

Background inorganic substances are thought to disrupt the adsorption process used in wastewater treatment systems. In this study, a low-strength synthetic wastewater was investigated for biodegradation and adsorption onto granular activated carbon, with and without the presence of background inorganic compounds. Overall, organic compounds in the synthetic wastewater underwent slow biodegradation, but when a solution was prepared with only one or two individual organic components present in the wastewater, biodegradation ceased. This effect was noticed both in the presence and absence of inorganic compounds. The association theory was found to describe the overall adsorption equilibrium of the system better than the more commonly used Freundlich isotherm. The isotherm patterns of the synthetic wastewater indicated that the dissolved inorganic substances had unfavorable effects on the adsorption of dissolved organic substances.

Phosphorus removal by slag: experiments and mathematical modeling

Publisher Summary This chapter focuses on the removal of phosphorus (P) by slag. A detailed study on P removal using soil and slag media from steel industries indicates that slag media have higher sorption capacities for P compared to other substrata, such as natural soils. The slag particles contain significant amounts of soluble metal ions such as magnesium and calcium. Those metal ions are responsible for chemical precipitation and complexation at high pH. The chapter presents the results of several column experiments to show the dynamic behavior of P in the column with slag at various operating conditions. Nonequilibrium, dynamic models based on surface or pore diffusion inside slag media have been used for simulating the adsorption behavior of P. At high pH, P retention by chemical precipitation is significant. The soluble metal ions react with P in the solution to form insoluble precipitates such as calcium phosphate. At high pH, when P removal is both by adsorption and precipitation—to obtain the exact adsorption isotherms—the real adsorption amount has to be used after subtracting the amount of precipitation from the total uptake.