Kinetic modeling for dye removal using polyelectrolyte enhanced ultrafiltration.

A generalized kinetic model is proposed for the first time for dye removal using polyelectrolytes in application of polyelectrolyte enhanced ultrafiltration. Three polyelectrolyte-dye systems, reported in the literature have been taken up for case studies. Different cases, namely, nature of dye and polyelectrolyte system and their concentration, effect of solution pH and electrolyte concentration have been included in the general framework of the modeling. The equilibrium constants are evaluated by minimizing the errors involved in the measured and experimental values of dye retention data. The matching between the calculated and the experimental data is found to be adequate. A general phase space analysis involving the equilibrium constants has also been carried out to determine the region of feasible solution, in order to facilitate dye removal using engineered polyelectrolyte.

Extraction of phenol from aqueous solutions by means of supported liquid membrane (MLS) containing tri-n-octyl phosphine oxide (TOPO).

This paper deals with the liquid-liquid extraction and the facilitated transport through a supported liquid membrane (SLM) system of aqueous phenol using tri-n-octyl phosphine oxide (TOPO) dissolved in an appropriate organic solvent. Phenol has been quantitatively extracted from aqueous acidic solutions using TOPO dissolved in kerosene as organic phase. The effect of TOPO concentration dissolved in kerosene on the extraction efficiency reveals that TOPO combined with phenol in the ratio of 1:1. Using a flat-sheet SLM (FSSLM) system, more than 65% of the initial phenol content in the feed phase was extracted and stripped in a NaOH aqueous receiving phase. The important operational variables affecting the facilitated transport of phenol through the FSSLM system studied are concentration of TOPO, membrane viscosity, feed phase pH, initial phenol concentration, polymeric support type and membrane stability. Regardless of its comparatively low extraction efficiency of phenol, the SLM based on TOPO exhibits higher long-term stability as compared to tributyl phosphate (TBP). Elaborated SLM system retained its stability and initial performance during the 5 days long experiment contrary to the TBP-SLM system where a time dependent negative tendency (transport efficiency decline) was observed.

Spectral study of Eriochrome Blue Black R in different cationic surfactant solutions.

Interactions of anionic dye Eriochrome Blue Black R (EBBR) with various cationic micelles of surfactants n-alkyltrimethylammonium CnTAB (n=12; 14; 16 and 18) have been investigated spectrophotometrically at 25°C in premicellar and postmicellar region. The results have shown that with increasing the alkyl chain length of surfactants, the maximum absorbance of EBBR shifted to a higher wavelength and the binding constants of EBBR to cationic micelles (Kb) increases. This confirms that the surfactant micelle, which has a longer alkyl hydrocarbon chain, enables greater solubilization of dye. Thus, the hydrophobic interaction of the dye with micelles increases in the order: C12TAB

Characterization of endotoxic indicative organic matter (2-keto-3deoxyoctulosonic acid) in raw and biologically treated domestic wastewater.

The aim of this research is to characterize the organic matter showing endotoxicity in domestic wastewater. It is assumed that endotoxicity is caused by lipo-polysaccharide (LPS), particularly large and hydrophobic molecules. In this study, a batch experiment (decay test for 12 h) was conducted to confirm whether LPS is the cause of endotoxicity or not. 2-keto-3deoxyoctulosonic acid (KDO) was used as an indicator of presence of LPS.A size and structural characterization of several samples from raw and domestic wastewater was also carried out in order know which fractions are causing endotoxicity. Endotoxin and KDO patterns were found to be similar, peaking at the same time. Thus, organic matter showing endotoxicity, such as LPS was released in the decay test. Moreover, the organic matter released from bacteria during decay test was partly biodegradable. Results from size characterization (Molecular Weight Distribution) showed that the majority of endotoxin (up to 82%), in domestic sewage and secondary effluents,is composed of molecules larger than 100 kDa and less than 0.1 µm. Similarly, structural characterization (hydrophobic and hydrophilic) showed that the majority of endotoxin, ranging from 59% to 83% of the total endotoxicity, is hydrophobic fractions. Therefore, removing large and hydrophobic molecules from wastewater can be an effective way to achieve a significant decrease in its endotoxicity.

Survey on LPS endotoxin in rejected water from sludge treatment facility.

In this study, we applied the Limulus amebocyte lysate (LAL) test to rejected water samples from a sludge treatment facility in Sapporo, Japan. The endpoint LAL test was performed using a commercial kit and involved incubating a mixture of water samples and LAL reagent at 37 degrees C. We have observed that all of the rejected water showed endotoxic activity. Overflow from thickener and dewatering are the main contributor to this high concentration in the influent of treatment plants receiving return flow from sludge treatment facilities. The LAL test was also applied to sample batch tests, where sewage was mixed with rejected waters and aerated for 12 hours. It was found that the low biodegradability of endotoxic material in the mixture led to higher endotoxicity in comparison to the sewage and sludge aerated without rejected water. Several batch tests were also operated using sewage, sludge and different types of rejected water (overflow from thickener, dewatering, dehumidification, and desulfurization). The findings indicated that samples from reactors using water from thickener and dewatering had significant concentrations and these contributed to the high values of the effluent.

Removal of Eriochrome Blue Black R from wastewater using micellar-enhanced ultrafiltration.

Micellar-enhanced ultrafiltration (MEUF) represents a potentially attractive tool for the removal of different contaminants from wastewater. In this study, MEUF was carried out to investigate the retention of Eriochrome Blue Black R (EBBR), an anionic dye, from aqueous stream. N-Alkyltrimethylammonium bromide i.e. dodecyltrimethylammonium bromide (C(12)TAB), tetradecyltrimethylammonium bromide (C(14)TAB), cetyl-trimethylammonium bromide (C(16)TAB) and octadecyltrimethylammonium bromide (C(18)TAB) were taken as cationic surfactants, and NaCl, Na(2)SO(4), Na(2)HPO(4) as electrolytes. A hydrophilic membrane made of cellulose (molecular weight cut-off 10000 Da) was used in a cross-flow ultrafiltration unit. The removal of EBBR was studied as a function of dye and surfactant concentrations, ionic strength, transmembrane pressure and pH. The MEUF experiments showed that the highest dye rejection was about 99% for the used range of dye and surfactant concentrations. This retention depended slightly on dye and surfactant concentrations, ionic strength, pH and transmembrane pressure. However, permeate flux changed significantly with those parameters due mainly to concentration polarisation and osmotic pressure.

Treatment of textile wastewater by a hybrid electrocoagulation/nanofiltration process.

Untreated effluents from textile industries are usually highly coloured and contain a considerable amount of contaminants and pollutants. Stringent environmental regulation for the control of textile effluents is enforced in several countries. Previous studies showed that many techniques have been used for the treatment of textile wastewater, such as adsorption, biological treatment, oxidation, coagulation and/or flocculation, among them coagulation is one of the most commonly used techniques. Electrocoagulation is a process consisting in creating metallic hydroxide flocks within the wastewater by the electrodissolution of soluble anodes, usually made of iron or aluminium. This method has been practiced for most of the 20th century with limited success. In recent years, however, it started to regain importance with the progress of the electrochemical processes and the increase in environmental restrictions in effluent wastewater. This paper examines the use of electrocoagulation treatment process followed by nanofiltration process of a textile effluent sample. The electrocoagulation process was studied under several conditions such as various current densities and effect of experimental tense. Efficiencies of COD and turbidity reductions and colour removal were studied for each experiment. The electrochemical treatment was indented primarily to remove colour and COD of wastewater while nanofiltration was used to further improve the removal efficiency of the colour, COD, conductivity, alkalinity and total dissolved solids (TDS). The experimental results, throughout the present study, have indicated that electrocoagulation treatment followed by nanofiltration processes were very effective and were capable of elevating quality of the treated textile wastewater effluent.

Assessment of endotoxin activity in wastewater treatment plants.

Endotoxic material, commonly associated to biological reactions, is thought to be one of the most important constituents in water. This has become a very important topic because of the common interest in microbial products governed by the possible shift to water reuse for drinking purposes. In this light, this study was conducted to provide an assessment of endotoxic activity in reclaimed wastewater. A bacterial endotoxin test (LAL test) was applied to water samples from several wastewater treatment plants (WWTP) in Sapporo, Japan keeping in view the seasonal variation. Samples were taken from several points in WWTP (influent, effluent, return sludge, advanced treatment effluent). The findings of this study indicated that wastewater shows high endotoxin activity. The value of Endotoxin (Endo) to COD ratio in the effluent is usually higher than that of the influent. Moreover, it is found that wastewater contains initially endotoxic active material. Some of those chemicals are biodegradable and but most of them are non-biodegradable. Batch scale activated sludge studies were undertaken to understand the origin of endotoxic active material in the effluent. This study showed that those chemicals are mainly produced during biological reactions, more precisely during decay process. Moreover, raw wastewater (RWW) contains high amounts of organic matter having endotoxicity which remains in the effluent.