Removal Of Trace Contaminants Research Articles

Investigating the fouling layer of polyamide nanofiltration membranes treating two different natural waters: internal heterogeneity yet converging surface properties

This study investigated the fouling of four polyamide nanofiltration membranes by two surface waters that differed substantially in major properties. The emphasis was on determining the characteristics of the fouling layer on the membranes. The rates of fouling for the two waters differed considerably, with a more rapid flux decline being observed for the water having higher biopolymer and major ion concentrations. Measurements of membrane roughness, contact angle and zeta potential in general showed considerable differences for each of these properties among the virgin membranes. However, values of each of these parameters tended to converge for all membranes after fouling, regardless of which water had been used. This result is very significant (for example for the removal of trace contaminants, which in many cases may depend on membrane properties) because in practice a membrane spends virtually all of its operating life fouled to some degree. Several techniques including transmission electron microscopy (TEM) were used to conduct detailed investigations of the fouling layer. These results demonstrated the great heterogeneity within that layer, despite the similar overall properties mentioned above. This heterogeneity is significant for quantitative understanding of the relationship between fouling and flux and for strategies to reduce or remove fouling.

An adapted purification procedure to improve the quality of 90Y for clinical use

Abstract There is an increasing interest for 90Y for radionuclide therapy. However, radioimmunotherapy, one of the most important applications for 90Y, demands a very high purity product. Obtaining a high quality 90Y is difficult not only because of the complex and time consuming production schemes but also because of the quality control which has challenging tasks like the determination of 90Sr at very low concentrations. The present paper investigates a reported purification procedure for the removal of stable metal trace contaminants from an 90Y solution, seeking for its potential use in the elimination of the radioactive contaminant 90Sr and its fast determination. For this purpose a washing step with HNO3 acid is introduced to elute 90Sr, the order of each acid solution is rearranged to reduce the potential contaminants present in acids and the size of the column is reduced to further optimize the procedure. As a result, an improved purification method is obtained, which allows the removal of both trace metal contaminants and 90Sr from an 90Y solution and the measurement of 90Sr/90Y ratios of the order of 10-7, which are well below the established pharmacopeia limit of 2×10-5.

Removal of inorganic trace contaminants by electrodialysis in a remote Australian community

Water provision for developing countries is a critical issue as a vast number of lives are lost annually due to lack of access to safe drinking water. The presence and fate of inorganic trace contaminants is of particular concern. Trace inorganic contaminants have been found in elevated concentrations in drinking waters supplied directly from brackish groundwaters in developing countries. Desalination and the removal of trace inorganic contaminants from bore water sources from a remote community in Australia using electrodialysis (ED) were investigated. The influence of applied voltage on the removal of the trace contaminants was evaluated. While the results from this study demonstrated that ED is an effectual method for the removal of total dissolved solids and a number of trace inorganic contaminants from brackish groundwaters to below drinking water guideline levels, the deposition of trace contaminants on the membranes (fouling) influenced the ED process in relation to ionic flux and the effectiveness of trace contaminant removal.

Effect of ozone exposure on the oxidation of trace organic contaminants in wastewater

Three tertiary-treated wastewater effluents were evaluated to determine the impact of wastewater quality (i.e. effluent organic matter (EfOM), nitrite, and alkalinity) on ozone (O 3) decomposition and subsequent removal of 31 organic contaminants including endocrine disrupting compounds, pharmaceuticals, and personal care products. The O 3 dose was normalized based upon total organic carbon (TOC) and nitrite to allow comparison between the different wastewaters with respect to O 3 decomposition. EfOM with higher molecular weight components underwent greater transformation, which corresponded to increased O 3 decomposition when compared on a TOC basis. Hydroxyl radical ( OH) exposure, measured by parachlorobenzoic acid ( pCBA), showed that limited OH was available for contaminant destruction during the initial stage of O 3 decomposition ( t < 30 s) due to the effect of the scavenging by the water quality. Advanced oxidation using O 3 and hydrogen peroxide did not increase the net production of OH compared to O 3 under the conditions studied. EfOM reactivity impacted the removal of trace contaminants when evaluated based on the O 3:TOC ratio. Trace contaminants with second order reaction rate constants with O 3 ( k O 3 ) > 10 5 M −1 s −1 and OH ( k OH) > 10 9 M −1 s −1, including carbamazepine, diclofenac, naproxen, sulfamethoxazole, and triclosan, were >95% removed independent of water quality when the O 3 exposure ( ∫ O 3 ⅆ t ) was measurable (0–0.8 mg min/L). O 3 exposure would be a conservative surrogate to assess the removal of trace contaminants that are fast-reacting with O 3. Removal of contaminants with k O 3 < 10 M − 1 s − 1 and k OH > 10 9 M −1 s −1, including atrazine, iopromide, diazepam, and ibuprofen, varied when O 3 exposure could not be measured, and appeared to be dependent upon the compound specific k OH. Atrazine, diazepam, ibuprofen and iopromide provided excellent linear correlation with pCBA ( R 2 > 0.86) making them good indicators of OH availability.

Biological filtration for membrane pre-treatment and other applications: towards the development of a practically-oriented performance parameter

Research Article| June 01 2008 Biological filtration for membrane pre-treatment and other applications: towards the development of a practically-oriented performance parameter P. M. Huck; P. M. Huck 1University of Waterloo, Waterloo, Ontario, Canada Tel.: 1-519-888-4567 ext.32707; E-mail: pm2huck@uwaterloo.ca Search for other works by this author on: This Site PubMed Google Scholar M. M. Sozan´ski M. M. Sozan´ski 2Technical University of Poznan, Poznan, Poland Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2008) 57 (4): 203–224. https://doi.org/10.2166/aqua.2008.010 Article history Received: May 15 2007 Accepted: October 12 2007 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation P. M. Huck, M. M. Sozan´ski; Biological filtration for membrane pre-treatment and other applications: towards the development of a practically-oriented performance parameter. Journal of Water Supply: Research and Technology-Aqua 1 June 2008; 57 (4): 203–224. doi: https://doi.org/10.2166/aqua.2008.010 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Biological processes have a long history of use in drinking water treatment. In recent decades, rapid biological filtration has achieved increasing acceptance. In terms of organic carbon, the classical application of biofiltration has been for the removal of easily biodegradable material, along with the related objectives of reduction in disinfectant demand and byproduct formation. Additional objectives receiving emphasis more recently include the removal of trace contaminants and the use of biofiltration as a membrane pre-treatment to reduce fouling. Although various models for biofiltration have been developed, these are generally complicated and research-oriented, and no modeling approach or performance parameter has found general acceptance in practice.The paper summarizes previous modeling approaches and illustrates the usefulness of a previously developed index of contact time, X*, referred to as dimensionless contact time. In addition to empty bed contact time, X* contains other factors which are important for biofiltration performance: the reactor surface area available for biofilm development and substrate biodegradability and diffusivity. This paper shows how X* can be simplified and also illustrates its application to the removal of trace contaminants (e.g. pharmaceuticals, endocrine disrupting substances or odorous compounds such as geosmin). A major section of the paper analyzes the requirements for biofiltration when used as a membrane pre-treatment to reduce fouling, and illustrates the applicability of X* for this use of biofiltration. Thus X* is presented as an overall unifying parameter. The last section of the paper introduces a new practically-oriented parameter, the Biofiltration Factor (BF). The use of this parameter, which is directly related to X*, is proposed for biofiltration design and operation, once some additional work has been undertaken. biofiltration, dissolved bacterial product material, drinking water, geosmin and MIB, membrane fouling, trace contaminants This content is only available as a PDF. © IWA Publishing 2008 You do not currently have access to this content.

Removal of Trace Contaminants from Water Using New Chelating Resins

The modification of cross‐linked polyacrylamide (CPAAm) and incorporation of methyl thiourea (MeTU) or phenyl thiourea (PhTU) group were utilized in the preparation of two new chelating resins CPAAm‐EDA‐MeTU (resin I) and CPAAM‐EDA‐PhTU (resin II), [EDA=ethylenediamine]. The prepared resins were characterized by elemental analysis and IR spectroscopy. The sorption behaviors of Cd(II), Pb(II), and Zn(II) ions on the prepared resins were studied and the optimum sorption conditions for the tested metal ions were determined. The optimum pH value for the sorption of Cd(II) and Zn(II) ions on both resins I and II was ranged between 7–8. The prepared new resins show very little affinity towards Pb(II) ion. The maximum experimental sorption capacities of resin I towards Cd(II) and Zn(II) ions were 3.2 and 0.6 mmol g−1, respectively, and that of resin II were and 0.6 mmol g−1 in the same prescribed order. Langmuir and Freundlich isotherm constants and correlation coefficients for the present system were calculated and compared. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) for cadmium and zinc sorption on the prepared resins were also determined from the temperature dependence.

Electro-biosorptive accumulation for use in enhanced detection of fluorogenic tracers and the removal of toxic entities from dilute solutions

An accumulating process based on electric field-assisted biosorption is described to facilitate the accumulation and enhanced detection of organic fluorogenic marker species in aqueous solution. Fluorescein was detected at concentrations as low as 0.6 microg l(-1). Using a mammalian cell-based bioassay, we demonstrate the use of the system to remove the toxic effects of species such as ethidium bromide and doxorubicin from complex solutions such as tissue culture medium. The use of such a system for the detection and removal of trace contaminants is discussed.

Membrane fouling in the nanofiltration of landfill leachate and its impact on trace contaminant removal

Nanofiltration (NF) is an attractive option for the treatment of landfill leachate. However, membrane fouling can be a major obstacle in the implementation of this technology. In this study, bench-scale filtration experiments were carried out to study the fouling behaviour during the NF of a synthetic landfill leachate. The results indicate that calcium in combination with organic matter could play a major role in governing the fouling process. Membrane fouling depended on the calcium concentration in the feed solution. Moreover, the results also indicate a significant influence of membrane fouling on the retention of Bisphenol A (BPA). It was hypothesised that pore blocking and the presence of the fouling layer resulted in an enhanced sieving effect, which subsequently increased the retention of BPA. On the other hand, cake layer enhanced concentration polarisation could hinder BPA from back diffusing into the bulk solution, which would eventually result in a lower BPA retention.

Removal of trace contaminants using molecularly imprinted polymers

This work was conducted to study the potential of molecularly imprinted polymers (MIPs) for the removal of oestradiol at trace concentrations (1 ppm-1 ppb). An MIP synthesised with 17beta-oestradiol as template was compared to non-imprinted polymers (NIP) synthesised under the same conditions but without template, a commercial C18 extraction phase and granulated activated carbon. At 1 ppb oestradiol was recovered by 98 +/- 2% when using the MIP, compared to 90 +/- 1, 79 +/- 1, and 84 +/- 2% when using the NIP, a C18 phase, or granulated activated carbon, respectively. According to these levels, the MIP was capable of producing an effluent with a quality 5-10 times higher than the other materials. The same levels of oestradiol recovery were achieved with the MIP when supplying 17beta-oestradiol at 0.1 ppm. Phenolic compounds added as interferences bound less to the MIP than to the NIP, confirming the selectivity of the MIP. Oestradiol biodegradation was also demonstrated at high concentrations (50 ppm), showing the pollutants can be safely destructed after being enriched by molecular extraction. This study demonstrates the potential of molecular imprinted polymers as a highly efficient specific adsorbent for the removal of trace contaminants.

Mars life support systems

Background: A critical element of planning human to Mars involves life support systems. The requirements for air, food, water and waste disposal materials in human to Mars total well over 100 metric tons and possibly as much as 200 metric tons. Translated back into an equivalent mass required in low Earth orbit, this figure would increase by at least a factor of seven, depending on mission architecture, requiring at least half a dozen heavy-lift launches solely for life support, and thus driving the cost and complexity of human to Mars beyond any reasonable limit. Recycling and possibly in situ utilization of indigenous Mars water resources are therefore critical enabling capabilities for human to Mars. Previous design reference missions assumed that high-performance life support systems would function flawlessly for the ~ 2.7 year round trip to Mars. However, life support systems developed for the International Space Station do not appear to have the longevity and reliability needed for Mars. As NASA moves forward with the current human exploration initiative, we need some means of estimating the required mass of life support system that goes beyond wild optimistic guesses. NASA's Advanced Life Support (ALS) project has been advancing the technology of recycling of water and air resources in human space for some time. Emphasis has been placed on recovery percentage and trace contaminant removal. Method: Mass estimates for physical plant and back-up caches are provided by NASA. A critical review was carried out based on NASA reports dealing with life support systems and these were judged in the context of design reference missions for humans making the round trip to Mars. Conclusion: ALS estimates of masses of life support systems are based on research and analysis, but the sources of reported performance data are not traceable to experimental data, and the reliability and lifetime of these systems is very uncertain. These estimates are optimistic, and when translated into engineering systems requiring margins, spares and fail-safe performance, are likely to increase significantly. Nevertheless, even these optimistic estimates require a significant initial mass in low Earth orbit, estimated as 210 metric tons. Life support remains at best, a significant mass, cost and risk factor for human to Mars, and at worst a major show stopper.

Competitive Effects of Natural Organic Matter: Parametrization and Verification of the Three-Component Adsorption Model COMPSORB

Natural organic matter (NOM) hinders adsorption of trace organic compounds on powdered activated carbon (PAC) via two dominant mechanisms: direct site competition and pore blockage. COMPSORB, a three-component model that incorporates these two competitive mechanisms, was developed in a previous study to describe the removal of trace contaminants in continuous-flow hybrid PAC adsorption/membrane filtration systems. Synthetic solutions containing two model compounds as surrogates for NOM were used in the original study to elucidate competitive effects and to verify the model. In the present study, a quantitative method to characterize the components of NOM that are responsible for competitive adsorption effects in natural water was developed to extend the application of COMPSORB to natural water systems. Using batch adsorption data, NOM was differentiated into two fictive fractions, representing the strongly competing and pore blocking components, and each was treated as a single compound. The equilibrium and kinetic parameters for these fictive compounds were calculated using simplified adsorption models. This parametrization procedure was carried out on two different natural waters, and the model was verified with experimental data obtained for atrazine removal from natural water in a PAC/membrane system. The model predicted the system performance reasonably well and highlighted the importance of considering both direct site competition and pore blockage effects of NOM in modeling these systems.

Microfibrous entrapment of small catalyst or sorbent particulates for high contacting-efficiency removal of trace contaminants including CO and H2S from practical reformates for PEM H2–O2 fuel cells

The four catalyst systems, Pt-Co/Al2O3, Pt/Al2O3, Au/α-Fe2O3, and CuO-CeO2, which demonstrated promising catalytic activity among more than 150 catalysts investigated for the preferential oxidation (PROX) of CO from practical reformate in our previous studies [B. Chang, L. Chen, B.J. Tatarchuk, unpublished work], were further examined in differential reactor in the absence of heat and mass transfer limitations in order to compare their specific activities. Differential reactor studies reveal that the cobalt promoted Pt/Al2O3 (Pt-Co/Al2O3) is the best candidate among those four catalyst systems for the preferential oxidation (PROX) of CO from practical reformate for PEM fuel cells. A high void and tailorable sintered microfibrous carrier consisting of 5 vol% 4 and 8 μm diameter Ni fibers was used to entrap 15 vol% 150–250 μm Al2O3 particulates. SEM images showed the microstructures of the thin microfibrous entrapped alumina support particles. The alumina support particulates were uniformly entrapped into a well sinter-locked three-dimensional network of 4 and 8 μm Ni fibers. Cobalt and platinum were then dispersed onto the microfibrous entrapped alumina support particles by impregnation method so as to prepare microfibrous entrapped Pt-Co/Al2O3 catalysts. The composite catalysts possessed 80 vol% voidage. The microfibrous entrapped Pt-Co/Al2O3 catalysts showed stable long-term activity for the preferential CO oxidation in wide temperature range. A microfibrous entrapped H2S sorbent layer was then placed upstream of a microfibrous entrapped PROX catalyst layer to remove both H2S and CO from a sulfur-contaminated practical reformate stream. Operating in this fashion, an outermost H2S sorbent layer promotes the activity maintenance of a secondary non-poison tolerant PROX CO catalyst, which ultimately serves to provide activity maintenance to CO-intolerant precious metal-based MEA assemblies in PEM fuel cells.

Preparation and characterization of a new class of polymeric ligand exchangers for selective removal of trace contaminants from water

Trace organic and inorganic contaminants possessing strong ligand characteristics are widely found in aquatic systems. Sorption processes such as activated carbon (AC) adsorption and ion exchange (IX) have been frequently employed to achieve the required degree of removal. However, AC-based processes are not effective in removing ionic species such as various pesticides carrying carboxylic and/or phenolic groups, and conventional IX resins are not selective for contaminants such as phosphate or arsenate in the presence of various omnipresent anions such as sulfate. Polymeric ligand exchangers (PLE) are a class of promising sorbents that sorb chemicals based primarily on their ligand characteristics rather than ionic charges. Consequently, selective removal of trace contaminants that are strong ligands can be achieved using PLEs. This paper reports the preparation and characterization of an innovative PLE for selective removal of trace organic and inorganic contaminants in the presence of various competing ions. It was observed that chelating resins with nitrogen donor atoms can serve as excellent metal hosting polymers and pyridine-nitrogen atoms in the polymer phase binds with metal ions more effectively than amine-nitrogen atoms. The nitrogen donor atoms in the chelating polymers interact with various metal ions in accord with the Irving–Williams series, with the highest affinity being observed for Cu 2+. A novel PLE, designated as DOW 3N–Cu was prepared by immobilizing Cu 2+ ions onto a chelating polymer with high content of pyridine-N donor atoms. Equilibrium and column run results indicated that the PLE is highly selective for trace inorganic contaminants such as phosphate, arsenate and ionizable organic contaminants such as 2,4,6-trichlorophenol (TCP). For neutral organic molecules such as atrazine, the PLE was not as effective as hydrophobic sorbents such as XAD-4. The DOW 3N–Cu's sorption rates for inorganic ligands are quite comparable to standard macroporous IX resins. The sorption rate for TCP by both DOW 3N–Cu and IRA-900 (a commercial resin) was rather slow, and lengthy gradual breakthrough profiles of TCP were observed. While brine can efficiently regenerate phosphate- or arsenate-exhausted DOW 3N–Cu, a mixture of brine and methanol at 70 °C was needed to desorb TCP from DOW 3N–Cu. The ligand exchange (LE) process may provide a cost effective alternative to help water utilities comply with increasingly stringent regulations.

Pharmaceuticals, Personal Care Products, and Endocrine Disruptors in Water: Implications for the Water Industry

For over 70 years, scientists have reported that certain synthetic and natural compounds could mimic natural hormones in the endocrine systems of animals. These substances are now collectively known as endocrine-disrupting compounds (EDCs), and have been linked to a variety of adverse effects in both humans and wildlife. More recently, pharmaceuticals and personal care products (PPCPs) have been discovered in various surface and ground waters, some of which have been linked to ecological impacts at trace concentrations. The majority of EDCs and PPCPs are more polar than traditional contaminants and several have acidic or basic functional groups. These properties, coupled with occurrence at trace levels (i.e., <1 μg/L), create unique challenges for both removal processes and analytical detection. Reports of EDCs and PPCPs in water have raised substantial concern among the public and regulatory agencies; however, very little is known about the fate of these compounds during drinking and wastewater treatment. Numerous studies have shown that conventional drinking and wastewater treatment plants can not completely remove many EDCs and PPCPs. Oxidation with chlorine and ozone can result in transformation of some compounds with reactive functional groups under the conditions employed in water and wastewater treatment plants. Advanced treatment technologies, such as activated carbon and reverse osmosis, appear viable for the removal of many trace contaminants including EDCs and PPCPs. Future research needs include more detailed fate and transport data, standardized analytical methodology, predictive models, removal kinetics, and determination of the toxicological relevance of trace levels of EDCs and PPCPs in water.

Three-component competitive adsorption model for flow-through PAC systems. 2. Model application to a PAC/membrane system.

A three-component competitive adsorption kinetic model, developed and validated in part 1 of this study, was applied to a continuous-flow PAC/membrane system to study the effects of various system and operating parameters on organic removal. The model quantitatively describes the two competitive adsorption mechanisms that occur during adsorption of trace organic compounds by powdered activated carbon (PAC) in flow-through systems where the PAC is retained in the system: pore blockage and direct competition for adsorption sites. Model simulations were conducted to investigate the effects of influent water composition, membrane cleaning water quality, PAC pore size distribution, and system operation conditions such as hydraulic retention time, membrane cleaning interval, and PAC dosing method on treatment efficiency. Effects of these factors on adsorption capacity as well as surface diffusion rate and consequent removal of the trace organic compound were discussed. It was found that optimal operating conditions for maximum trace organic compound removal must be determined on the basis of the adsorption properties and concentrations of the competing compounds in the influent. For the conditions investigated in this study, the small strongly competing compound, p-DCB, had greater impact on atrazine removal than the large pore-blocking compound, PSS-1.8k. Various process design and operating parameters had complex and interrelated effects on the impact of competitive adsorption and corresponding trace contaminant removal efficiency in hybrid PAC/membrane systems.

Particle interactions and removal of trace contaminants from water and wastewaters

The adsorption of trace contaminants on natural particles is of great interest as this adsorption enhances the possibility of removing these with low pressure filtration such as MF and UF. This study shows that natural hormones such as estrone and estradiol will adsorb to natural particles both organic and inorganic. Experiments have shown that the adsorption capacity of organics is a factor of 10 higher than for inorganics. Ultrafiltration of a solution containing NOM and estrone also indicated this adsorption as the retention of estrone showed strong relationship to the concentration of organic material in the permeate. For practical application of this finding it was investigated if it applied to activated sludge. It was found that activated sludge does adsorb the natural hormones and that activated sludge during ultrafiltration develops a dynamic membrane which enhances the retention of the hormones.

Design of new materials for environmental control

AbstractDuring the past several years we have pursued a program here at UIUC to tailor the pore size and surface chemistry of activated carbon fibers (ACFs) to greatly increase their efficiency and selectivity for removal of trace contaminants from the environment. In addition we have evolved new ways of preparing the ACFs to sharply reduce their cost (typically ∼$100/lb) to be more competitive with activated carbon granules ($1‐2/lb), but also to greatly improve the abrasion resistance of the fibers. This was accomplished by coating glass fibers with a phenolic resin and then activating the coating under a controlled atmosphere to produce a variety of tailored micropores. Using chemically tailored ACFs, we describe major improvements over current activated carbons for adsorption of environmental contaminants.

Adsorption processes in spacecraft environmental control and life support systems

The environmental control and life support system on a spacecraft maintains a safe and comfortable environment in which the crew can live and work by supplying oxygen and water and by removing carbon dioxide, water vapor, and trace contaminants from cabin air. Although open-loop systems have been used successfully in the past for short-duration missions, the economics of current and future long-duration missions in space will make nearly complete recycling of air and water imperative. A variety of operations will be necessary to achieve the goal of nearly complete recycling. These include separation and reduction of carbon dioxide, removal of trace gas-phase contaminants, recovery and purification of humidity condensate, purification and polishing of wastewater streams, and others. Several of these can be performed totally or in part by adsorption processes. These processes are good candidates to perform separations and purifications in space due to their gravity independence, high reliability, relative high energy efficiency, design flexibility, technological maturity, and regenerative nature. For these reasons, adsorption has historically played a key role in life support on U.S. and Russian piloted spacecraft. Among the life support applications that can be achieved through use of adsorption technology are removal of trace contaminants and carbon dioxide from cabin air and recovery of potable water from waste streams. In each of these cases adsorption technology has been selected for use onboard the International Space Station. The requirements, science, and hardware for these applications are discussed. Human space exploration may eventually lead to construction of planetary habitats. These habitats may provide additional opportunities for use of adsorption processes, such as control of greenhouse gas composition, and may have different resources available to them, such as gases present in the planetary atmosphere. Separation and purification processes based on adsorption can be expected to continue to fulfill environmental control and life support needs on future missions.

Dynamic Modelling of Trace Contaminant Removal in a Municipal Sewage Treatment Plant

The variability of influent and effluent concentrations of trace contaminants at a full-scale municipal sewage treatment plant (STP) was measured by intensive sampling at two hour intervals for eight consecutive days. From these data, the technique of time series analysis was used to generate predictive models describing the process response. The data indicated that municipal STPs are capable of efficient trace contaminant removal and significantly attenuate the variability of these contaminants in the raw influent. Significant correlations were identified between influent characteristics and effluent concentrations for selected contaminants. For three metals and three trace contaminants, adequate time series models were developed. Such models are valuable tools for the development of strategies to control trace contaminants in discharges from municipal STPs.

A regenerable carbon dioxide removal and oxygen recovery system for the Japanese experiment module

The Japanese Space Station Program is now under Phase B study by the National Space Development Agency of Japan in participation with the U.S. Space Station Program. A Japanese Space Station participation will be a dedicated pressurized module to be attached to the U.S. Space Station, and is called Japanese Experiment Module (JEM). Astronaut scientists will conduct various experimental operations there. Thus an environment control and life support system is required. Regenerable carbon dioxide removal and collection technique as well as oxygen recovery technique has been studied and investigated for several years. A regenerable carbon dioxide removal subsystem using steam desorbed solid amine and an oxygen recovery subsystem using Sabatier methane cracking have a good possibility for the application to the Japanese Experiment Module. Basic performance characteristics of the carbon dioxide removal and oxygen recovery subsystem are presented according to the results of a fundamental performance test program. The trace contaminant removal process is also investigated and discussed. The solvent recovery plant for the regeneration of various industrial solvents, such as hydrocarbons, alcohols and so on, utilizes the multi-bed solvent adsorption and steam desorption process, which is very similar to the carbon dioxide removal subsystem. Therefore, to develop essential components including adsorption tank (bed), condensor, process controller and energy saving system, the technology obtained from the experience to construct solvent recovery plant can be easily and effectively applicable to the carbon dioxide removal subsystem. The energy saving efficiency is evaluated for blower power reduction, steam reduction and waste heat utilization technique. According to the above background, the entire environment control and life support system for the Japanese Experiment Module including the carbon dioxide removal and oxygen recovery subsystem is evaluated and proposed.