Nitrogen compounds removal from brackish water by electrodialysis at fixed electric potential and dynamic current density operations

Nitrogen (N) compounds can occur in water resources from natural and anthropogenic activities. It is ideal that these contaminants be removed before water consumption. As water quality has been affected by increased salinity and pH variation, more advanced and robust technologies such as electrodialysis (ED) can be considered for simultaneous desalination and pollutant removal. In this context, the removal of N-species (NO3-, NO2-, NH4+, and CH4N2O) from brackish water by ED was investigated for different feed water quality, considering increased salinity (0 - 10g/L NaCl) and pH variation (3 - 11), under limit current density (LCD) at fixed electric potential condition. The applied electric potential (5 - 25V) under, at, and over the LCD at fixed electric potential and dynamic current density (DCD), as a percentage of LCD (0.4 - 1.2), were analyzed to improve the process. In addition, energy efficiency in the form of specific energy consumption (SEC) and current efficiency (CE) were assessed for ED at fixed electric potential and DCD. The results showed that, at extreme pH of the feed water, the removal of NO2- and NH4+ can be affected, while NO3-was the most stable compound with pH variation. An increase in feed water salinity just slightly impacted the removal of N-compounds, due to the similar characteristics of the ions in the water. The increase in electric potential at fixed electric potential or DCD increased the removal and molar flux of N-compounds. However, operating over the LCD increased the SEC of the ED process while changes in removal were not significant. DCD procedures resulted in higher CE and shorter run time of the experiments. Therefore, ED proved to be a suitable treatment technique to produce fresh water due to the selective removal of the studied ions, especially at 15V (fixed electrical potential) and 0.8 LCD (DCD) related to removal, molar flux, and run time to achieve guidelines.

Pilot-scale removal of persistent and mobile organic substances in granular activated carbon filters and experimental predictability at lab-scale

Present knowledge about the fate of persistent and mobile (PM) substances in drinking water treatment is limited. Hence, this study assesses the potential of fixed-bed granular activated carbon (GAC) filters to fill the treatment gap for PM substances and the elimination predictability from lab-scale experiments. Two parallel pilot filters (GAC bed height 2 m, diameter 15 cm) with different GAC were operated for 1.5 years (ca. 47,000 BV throughput) alongside rapid small-scale column tests (RSSCT) designed based on the proportional diffusivity (PD) and the constant diffusivity (CD) approaches. Background dissolved organic matter (DOM) and a set of 17 target substances were investigated, among them 2-acrylamido-2-methylpropane sulfonate (AAMPS), adamantan-1-amine (ATA), melamine (MEL) and trifluoromethanesulfonic acid (TFMSA). Nine substances were predominantly present in the drinking water used as pilot filter influent (frequencies of detection above 80 %, median concentrations 0.003-1.868 μg/L) and their breakthrough behaviors could be observed: TFMSA was not retained at all, four substances including AAMPS and ATA reached complete breakthrough below 20,000 BV, three compounds were partially retained until the end of operation and oxypurinol was retained completely. The comparable PM candidate and DOM removal performances of both GAC aligns with their very similar surface characteristics and elemental compositions. The agreement of results between RSSCT with the pilot-scale filters were substance specific and no superior RSSCT design could be identified. However, CD-RSSCT provide a conservative removal prediction for most studied compounds. MEL adsorption was significantly underestimated by both RSSCT designs. Using the criterion of a carbon usage rate (with respect to 50 % breakthrough) below 25 mg_GAC/L_water for an economic retention by fixed-bed GAC filters, five (out of nine) substances met the requirement.

Predicting Water Flux in Forward Osmosis with Unknown Feed Solution Composition: An Empirical Approach Based on Thermodynamical Properties

This study investigated the predictability of forward osmosis (FO) performance with an unknown feed solution composition, which is important in industrial applications where process solutions are concentrated but their composition is unknown. A fit function of the unknown solution's osmotic pressure was created, correlating it with the recovery rate, limited by solubility. The osmotic concentration was derived and used in the subsequent simulation of the permeate flux in the considered FO membrane. For comparison, magnesium chloride and magnesium sulfate solutions were used since these show a particularly strong deviation from the ideal osmotic pressure according to Van't Hoff and are, thus, characterized by an osmotic coefficient unequal to 1. The simulation is based on the solution-diffusion model with consideration of external and internal concentration polarization phenomena. Here, a membrane module was subdivided into 25 segments of equal membrane area, and the module performance was solved by a numerical differential. Experiments in a laboratory scale for validation confirmed that the simulation gave satisfactory results. The recovery rate in the experimental run could be described for both solutions with a relative error of less than 5%, while the calculated water flux as a mathematical derivative of the recovery rate showed a bigger deviation.

Modelling Forward Osmosis Treatment of Automobile Wastewaters

Forward osmosis (FO) has rarely been investigated as a treatment technology for industrial wastewaters. Within this study, common FO model equations were applied to simulate forward osmosis treatment of industrial wastewaters from the automobile industry. Three different models from literature were used and compared. Permeate and reverse solute flux modelling was implemented using MS Excel with a Generalized Reduced Gradient (GRG) Nonlinear Solver. For the industrial effluents, the unknown diffusion coefficients were calibrated and the influences of the membrane parameters were investigated. Experimental data was used to evaluate the models. It could be proven that common model equations can describe FO treatment of industrial effluents from the automobile industry. Even with few known solution properties, it was possible to determine permeate fluxes and draw conclusions about mass transport. However, the membrane parameters, which are apparently not solution independent and seem to differ for each industrial effluent, are critical values. Fouling was not included in the model equations although it is a crucial point in FO treatment of industrial wastewaters. But precisely for this reason, modelling is a good complement to laboratory experiments since the difference between the results allows conclusions to be drawn about fouling.

Two-photon photoemission spectroscopy of unoccupied electronic states at CuPc/PTCDA/Ag(1 1 1) interfaces

The unoccupied electronic structure of stacked layers of copper(II)phthalocyanine (CuPc) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on Ag(1 1 1) has been investigated by means of two-photon photoemission (2PPE). We find a rich electronic structure comprising at least five unoccupied electronic states which we identify based on their energetic position and their dispersion in momentum space. More specifically, we observe the first and the second image-potential states of the modified Ag(1 1 1) surface, as well as the metal-organic interface state (IS) inherent to the PTCDA/Ag(1 1 1) interface. Moreover, two additional molecular features are observed for the CuPc/PTCDA/Ag(1 1 1) system which we attribute to an unoccupied molecular orbital (LUMO  +  2) of CuPc. The 2PPE intensity of the IS exhibits a pronounced dependence on the pump photon energy, which closely follows the optical absorption of the outer molecular layer. This strongly points to charge transfer from the optically excited molecules to the interface state.

Forward osmosis treatment of effluents from dairy and automobile industry - results from short-term experiments to show general applicability

Forward osmosis (FO) is a potential membrane technology to treat wastewater energy efficiently with low fouling. In laboratory-scale experiments, six effluents from a dairy and an automobile production plant were tested to find out if FO is an applicable treatment technology. Permeate flux and reverse salt flux were determined in nine test series with three subsequent 5 h experiments each. In between, the membrane was cleaned with deionized water. Membrane performance tests before each experiment were used to monitor membrane performance and fouling. Samples were analysed and the T/M-value was introduced to indicate which substances caused fouling. Dairy cheese brine was a suitable DS. Here, permeate fluxes were 21.0 and 15.1 L/(m²·h). Automobile cooling tower water and wastewater from cathodic dip painting were also used as DS. However, permeate fluxes were below 1.1 L/(m²·h). The tested FS, reverse osmosis concentrate from dairy wastewater treatment, rinsing water and wastewater from automobile cathodic dip painting, as well as wastewater from automobile paint shop pre-treatment, showed good performance regarding the permeate flux of between 7.9 and 19.4 L/(m²·h). Membrane performance test showed that some of the effluents lead to permeate flux reduction due to fouling. Different cleaning-in-place methods were examined. Eventually, permeate flux was restored.

Research experiences in direct potable water treatment using coagulation/ultrafiltration

Recently, new concepts for direct or pre-treatment minimised processes for the treatment of surface waters to potable water have aroused more and more interest. The requirements of such concepts are various and express the desire for high flexibility, adaptation on various water qualities and expandability of the treatment process. These requirements can be nearly ideally achieved by membrane technology. This publication presents the actual approach in research, piloting and operation of selective plants, research institutions and universities for the hybrid process coagulation/ultrafiltration (UF), or microfiltration (MF) respectively. The focus is set on the discussion of the influences of the mass freight, coagulation conditions, temperature and theoretical considerations about the coating layer build-up in dead-end and IN/OUT-mode driven MF and UF capillary membranes with a coagulation step prior to membrane filtration.

Tissue reaction against a self-setting calcium phosphate cement set in bone or outside the organism

Calcium phosphate cements are able to set in situ when injected into bone tissue. We evaluated the tissue reaction occurring when a DCPD-based calcium phosphate cement was either set within the bone or implanted when already set. The samples were implanted in rabbit condyles and examined histologically after 8 and 16 weeks. The relative bone surface, the fibrous capsule around the implants and the implant section surface were measured. Solid material seemed to be better tolerated than paste implants. More bone was found at the solid implant contact whatever the implantation time and the solid material degraded much less rapidly. In conclusion, the physico-chemical modification of the biological environment occurring during setting increases the foreign body reaction against the material.

Osseointegration of composite calcium phosphate bioceramics

The resistance of macroporous calcium phosphate ceramics to compressive strength generally is low and depends on, among other factors, porosity percentage and pore size. A compromise always is adopted between high porosity, required for a good integration, and mechanical strength, which increases with material density. We improved the strength of macroporous calcium phosphate ceramics of interconnected porosity by filling the pores with a highly soluble, self-setting calcium phosphate cement made of TCP and DCPD. Cylinders of the resulting material were implanted in sheep condyles and subjected to histological analysis after 20, 60, and 120 days. Microradiographs were made of the histological sections. The control material consisted of ceramic that had not been loaded with cement. Progressive ingrowth of bone into the ceramic pores occurred as the cement was degraded during the first implantation period. Marked degradation of the cement was apparent after 2 months, with fragmentation of the cement in most of the pores and the presence of bone tissue between the fragments. All the cement had been replaced by bone after 4 months. Some fragments of cement still were embedded in the newly formed bone. There was no significant difference between the integration of loaded and nonloaded ceramics. Filling the macroporous ceramic pores with a calcium phosphate cement significantly improved the mechanical strength of these ceramics without modifying their integration in the healing bone.

Low molecular weight proteins secreted by peritoneal macrophages obtained from 2,3,7,8-tetrabromodibenzo-p-dioxin-treated NMRI mice

The protein secretion patterns in a macrophage-like cell line (CBrD), established from the peritoneal cells of NMRI mice treated with the dioxin analog 2,3,7,8-tetrabromodibenzo-p-dioxin (TBrDD), were analyzed by high resolution two-dimensional gel electrophoresis (2-D PAGE), and compared to the pattern of proteins secreted by control macrophages which were intraperitoneally activated by bacterial lipopolysaccharide. The most striking alterations were observed in the low molecular range. The transformed cells encode a number of low molecular mass proteins (10-20 kDa) which were not detected in control cells under identical experimental conditions. The protein pattern with respect to isoelectric point, molecular weight, optical density (OD) and area of the spot (in mm2) has been depicted by computer analysis in relation to a standardized spot outline and the spot's background (in OD). It is concluded that the transformation of murine peritoneal macrophages by TBrDD leads to an upregulation of proteins, in particular of low-molecular-weight proteins.

Expression of a reverse transcriptase activity in a cell line established from peritoneal macrophages of mice treated with N-methyl-N-nitrosourea

We have established a cell line from peritoneal macrophages of mice treated intraperitoneally with N-methyl-N-nitrosourea. The present communication describes the identification of an RNA-dependent DNA-polymerase activity in a particulate fraction from supernatants of the cell culture. This activity is similar to retroviral Reverse Transcriptase (RT) based on its template specificity and ionic preference. The proof of the retrovirus-like nature of RT was obtained by ultracentrifugation of the pelleted proteins secreted in the medium on a sucrose gradient. The main RT activity was obtained in fractions of 1.14-1.16 g/ml densities, which are comparable to those of type C retroviruses. The presented data support constitutive expression of the retrovirus gene in a chemically transformed cell line.

The establishment of a macrophage-like cell line (Ymnu) from NMRI mice treated with N-methyl-N-nitrosourea. II. Induction of differentiation of Ymnu cells: a cytochemical and immunocytochemical study

The Ymnu cell line established by us from peritoneal exudate cells of mice treated with methylnitrosourea is of macrophage origin. We have shown that 54% of these cells possess Fc-gamma receptors and can bind opsonized erythrocytes; 30% of these cells express the nonspecific esterase and 65% the Mac-1 antigen, indicating these cells are dedifferentiated. Treatment of the cells with various differentiation inducers led to time-dependent redifferentiation of the cells. The expression of the nonspecific esterase increased to 51.1% (TPA), 42.5% (RA), 63.6% (DMSO), 40.6% (SB). The fraction of Mac-1 positive cells increased to 90.5% (TPA), 80.6% (RA), 84.5% (SB) and decreased to 52.7% (DMSO). The maximal effects of the chemicals on expression of these two parameters were achieved at different times following treatment. While RA and SB were effective after one day, the maximum effect of TPA was seen at day 5.

The establishment of a macrophage-like cell line (Ymnu) from NMRI mice treated with N-methyl-N-nitrosourea. I. Characterization of the cell line

Here we describe the establishment of a cell line from peritoneal exudate cells for NMRI-mice treated with methylnitroso urea, which we designate Ymnu. Tests for macrophage specific characteristics have shown that 54% of Ymnu cells possess Fc-gamma receptors, 30% are nonspecific esterase positive and 65% possess the macrophage specific antigen Mac-1, indicating their macrophage origin. Although of macrophage origin, the majority of these cells are round, 13 microns in diameter. The cells grow partially in suspension and have doubling times varying from 3 to 1.75 days depending on serum concentration. Cultures of Ymnu cells achieve after 14 days densities 4 times higher than those achieved by NIH-3T3 cells. Ymnu cells have lost the anchorage dependence of growth and grew very well on semi-solid media. In addition, they possess an oncogenic potential and build tumors when injected subcutaneously in nude mice.