A model for predicting contaminant removal by adsorption within the International Space Station water processor: 1. Multicomponent equilibrium modeling

Abstract

A thermodynamic model is developed to predict adsorption equilibrium in the International Space Station water processor's multifiltration beds. The model predicts multicomponent adsorption equilibrium behavior using single-component isotherm parameters and fictitious components representing the background matrix. The fictitious components are determined by fitting total organic carbon and tracer isotherms with the ideal adsorbed solution theory. Multicomponent isotherms using a wastewater with high surfactant and organic compound concentrations are used to validate the equilibrium description on a coconut-shell-based granular activated carbon (GAC), coal-based GAe, and a polymeric adsorbent. Water Environ. Res., 70, 14 (]998).A substantial amount of potable water is required for life support of the crew aboard the International Space Station (ISS). Water for drinking, food preparation, and personal hygiene accounts for more than 90% by weight of the basic consumables (water, oxygen, and food) required for survival aboard the ISS. Life support of a four-person crew would require transport of approximately 20 900 kg (46 100 Ib) of water per year to the ISS without onboard water recycling. The economic limitations of transporting water to the ISS necessitate onboard recovery and reuse of the aqueous waste streams (Carter et ai., 1991).The aqueous waste streams processed by the ISS water processor include urine distillate, waste shower and hand wash water, humidity condensate, ora] hygiene and wet shave waste, and a mixture of humidity condensate and evaporated urine from the Research Animal Holding Facility. These waste streams are complex mixtures of unknown composition. Wastewater is recycled aboard the ISS using a series of four treatment processes. In one stage of the treatment process, adsorption media and ionexchange resins are combined in multi filtration beds (MFBs) for removal of ionic and non ionic contaminants from the wastewater. A schematic of an MFB is shown in Figure I. The empty bed contact time is also reported for each layer of the MFB.A technique termed the fictive component analysis (FCA) was developed to model adsorption equilibrium for wastewaters of unknown composition on the MFB adsorbents. The FCA uses imaginary compounds (fictive components [FCs]) to represent the background compounds making up the overall total organic carbon (TOC) in unknown mixtures (Sontheimer et at., 14 1988). The FC parameters are determined such that the FCs give the same competitive adsorption effect as the unknown mixture. Hubele andFrick and used the FCA to predict adsorption isotherms of TOC, where each FC represented a portion of the total TOC, and the sum of the FC TOC concentrations equaled the overall TOC concentration. Crittenden et at. (1985) used the FCA to predict the adsorption isothenns of tracer compounds in the presence of a multicomponent background matrix made up of similar-sized organic compounds. Crittenden et at. (1993) also used the FCA to predict removal of dissolved organic carbon in fixe...

Humic matter and contaminants. General aspects and modeling metal ion binding

“…The concentration of dissolved humics is typically 1000 times higher than the pesticide concentration, so a well-designed experimental set-up is required to obtain an economically feasible process. To avoid expensive largescale test experiments, the results of small-scale laboratory experiments are often used to predict the behavior for full-scale columns [39,40]. Some problems encountered with this approach have been discussed by Heijmans et al [41].…”