Laboratory-grade Water Research Articles

The influence of natural organic matter and cations on fouled nanofiltration membrane effective molecular weight cut-off

This study investigated the influence of water matrix characteristics, specifically natural organic matter (NOM) and divalent cations, on fouled nanofiltration (NF) membrane rejection by size exclusion. Membrane bioreactor effluent, Lake Ontario water and laboratory-prepared waters were filtered and the membrane effective molecular weight cut-off (MWCO) was measured. Analysis of the results for the laboratory-prepared waters showed that NOM caused a statistically significant reduction in effective MWCO (from 385 ± 13 Da to 343 ± 12 Da) whereas neither the influence of cations nor the interaction of NOM and cations was significant. The MWCO of the NF membrane was reduced from 385 ± 13 Da to 222 ± 46 Da and 348 ± 28 Da following filtration with the MBR effluent and Lake Ontario water, respectively. A previous study by the authors [A.M. Comerton, R.C. Andrews, D.M. Bagley, C. Hao, The rejection of endocrine disrupting and pharmaceutically active compounds by NF and RO membranes as a function of compound and water matrix properties, J. Membr. Sci., 313 (2008) 323] observed an increase in the rejection of endocrine disrupting compounds (EDCs) and pharmaceutically active compounds (PhACs) from MBR effluent and Lake Ontario water by the NF membrane when compared to laboratory-grade water. However, in this study the effective MWCO measured following filtration with Lake Ontario water was larger than the molecular weight of all 22 compounds (<300 Da) from the previous study. This implies that compound interaction and association with organic matter in the water matrix itself may have contributed to previously observed increases in EDC and PhAC rejections.

Determination of inorganic oxyhalide disinfection by-products in bottled water by EPA Method 326.0 for trace bromate analysis

An ion chromatography method with post-column reaction and optical detection, according to EPA Method 326.0, for the determination of bromate has been developed and validated in water samples. Optimization of reaction and operating conditions (post-column reagent and sulphuric acid regenerant flow rate) made possible to minimize the background noise and attain low detection limit. Employing a carbonate elluent (9.0 mM Na 2CO 3) at a flow rate of 1.1 ml/min and a sample loop of 250 μl, a detection limit for bromate of 0.33 μg/l and a quantification limit (LOQ) of 0.99 μg/l were generated. Under these conditions bromate and chlorite were separated (resolution factor >2.5) in an analysis time of less than 6.5 min and the important validation parameters were evaluated. Calibration curve in laboratory-grade water produced excellent regression in the range from LOQ up to 20μg/l in the order of r 2=0.99, whereas a range of applicability of 0.99 μg/l to 100 μg/l was confirmed. UV detector response (AU ⁎min/(μg/l)) was almost constant (± 2%) at various concentration levels. The recoveries obtained in the accuracy test for all aqueous matrices studied were in the 93.1–106% range and the intraday and interday precisions (expressed as coefficient of variation, CV) were smaller than 13.5%. Expanded uncertainty (95%) was calculated at various concentration levels according to propagation error theory (1±0.28 μg/l, 5±0.44 μg/l, 10±0.60 μg/l).

The rejection of endocrine disrupting and pharmaceutically active compounds by NF and RO membranes as a function of compound and water matrix properties

This study examined the rejection of 22 endocrine disrupting compounds (EDCs) and pharmaceutically active compounds (PhAC) from raw and 5-μm filtered Lake Ontario water, membrane bioreactor effluent and laboratory-grade water (Milli-Q ®) by ‘loose’ and ‘tight’ nanofiltration (NF) membranes and a reverse osmosis (RO) membrane. Rejection by the ‘tight’ NF membrane was most strongly correlated with compound log K ow and water solubility with the more hydrophobic compounds showing higher rejection. The RO membrane provided efficient EDC and PhAC removal (>90%). Conversely, in general, the ‘loose’ NF membrane offered poor and variable compound removal. Fouling and the presence of organic matter likely contributed to higher rejections of EDCs and PhACs while higher concentrations of divalent ions appeared to result in lower EDC and PhAC rejection by the membranes.

Membrane adsorption of endocrine disrupting compounds and pharmaceutically active compounds

Adsorption is one of the main mechanisms contributing to compound removal by membrane filtration, in addition to size exclusion and charge repulsion. In this study, the adsorption of 22 endocrine disrupting compounds and pharmaceutically active compounds by ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes was investigated using 24-h bottle tests at 21 and 4 °C. Two natural waters (Lake Ontario and effluent from a membrane bioreactor (MBR)) and one laboratory-grade water were examined. Adsorption was strongly correlated with compound log K ow and membrane pure water permeability, and moderately correlated with compound water solubility. Adsorption was observed to be highest by the UF membrane followed by the NF and RO membranes. The influence of temperature on adsorption in the range examined was found to be insignificant. Three compounds for which deuterium-labelled surrogates were available (acetaminophen, carbamazepine, gemfibrozil) were examined to determine the influence of water matrix on adsorption. Adsorption of gemfibrozil may have been hindered due to competition for adsorption sites from the organic matter present in the lake water and MBR effluent.

Evaluation of UV irradiation for photolytic and oxidative degradation of pharmaceutical compounds in water

A medium-pressure (MP) ultraviolet (UV) system was used to investigate the UV photolysis and UV/H 2O 2 oxidation of pharmaceutically active compounds (PhACs) that belong to different therapeutic classes and were found to occur in the aquatic environment. The results obtained in laboratory-grade water (LGW) and surface water (SW) were compared with low-pressure (LP) results reported previously. Overall, MP lamps proved to be more efficient to maximize the bench-scale degradation of the selected group of compounds (ketoprofen, naproxen, carbamazepine, ciprofloxacin, clofibric acid, and iohexol) by both UV photolysis and UV/H 2O 2 oxidation. Fundamental direct and indirect photolysis parameters obtained in LGW are reported and used to model the MP-UV photolysis and MP-UV/H 2O 2 oxidation of the pharmaceuticals in SW, predicting the experimental results very well.

Impact of flocculated particles on low pressure UV inactivation of E. coli in drinking water

This study investigated the impact of coagulated/flocculated particulate matter on low-pressure (LP) UV inactivation of spiked Escherichia coli under drinking water conditions using a standard bench scale collimated beam apparatus. The effect of floc particles in both coagulated river water and coagulated process (treatment plant) water was assessed. Laboratory grade water and uncoagulated river water were used as controls. The dose-response curves of spiked E. coli were determined at UV doses of 5, 10, 15, 25, and 40 mJ/cm2. The results indicated that surface water particles (turbidity from 12 to 32 NTU essentially have no influence on UV inactivation of spiked E. coli if they are appropriately accounted for in the UV transmittance determination. However, the presence of floc particles formed by coagulation and flocculation led to significantly lower inactivation of E. coli by LP UV. A limited investigation of medium pressure UV inactivation undertaken as part of the study indicated that shielding effects for medium pressure UV warrant further investigation. The support for the inactivation results provided by the particle size analysis carried out suggests that criteria related to particle size may be very useful in addition to turbidity for UV regulation and operation. The results emphasize the need for UV disinfection/inactivation to be placed following filtration, because a sedimentation upset (i.e. where some floc particles may reach a downstream UV unit) could potentially compromise disinfection/inactivation.

UV Degradation Kinetics and Modeling of Pharmaceutical Compounds in Laboratory Grade and Surface Water via Direct and Indirect Photolysis at 254 nm

Direct and indirect photolysis of pharmaceutically active compounds (PhACs) was investigated in laboratory-grade water (LGW) and a local surface water using a low-pressure ultraviolet batch reactor. The PhACs selected in this study belong to different therapeutic classes and are known to occur in environmental samples. Fundamental photolysis and advanced oxidation process parameters obtained in LGW (such as the decadic molar absorption coefficient, quantum yield, and degradation rate constants) are reported and discussed. These parameters, together with the incident photon irradiance, solution depth, and solution absorbance were used to develop UV and UV/ H202 photolysis models that were compared with experimental results obtained in the surface water. The model predicted the experimental UV photolysis removals well but underestimated the UV/H2O2 photolysis results. These models were used to discuss the effects of optical path length and H2O2 concentration on the UV-based rate constant predictions.

Elucidation of the Substrate Specificity of the C1s Protease of the Classical Complement Pathway

The complement system is a central component of host defense but can also contribute to the inflammation seen in pathological conditions. The C1s protease of the first complement component, the C1 complex, initiates the pathway. In this study we have elucidated the full specificity of the enzyme for the first time using a randomized phage display library. It was found that, aside from the crucial P(1) position, the S(3) and S(2) subsites (in that order) played the greatest role in determining specificity. C1s prefers Leu or Val at P(3) and Gly or Ala residues at P(2). Apart from the S(2)' position, which showed specificity for Leu, prime subsites did not greatly affect specificity. It was evident, however, that together they significantly contributed to the efficiency of cleavage of a peptide. A peptide substrate based on the top sequence obtained in the phage display validated these results and produced the best kinetics of any C1s substrate to date. The results allow an understanding of the active site specificity of the C1s protease for the first time and provide a basis for the development of specific inhibitors aimed at controlling inflammation associated with complement activation in adverse pathological situations.

Evaluation of Disinfectants against Salmonella enteritidis

Five classes of disinfectants (phenol, quaternary ammonium, chlorine, glutaraldehyde, and a combination of quaternary ammonium and formaldehyde) were diluted in "field" water (well, stream, or pond water) and compared with dilutions of the disinfectants in laboratory-grade water for their efficacy against the AOAC (Association of Official Agricultural Chemists) test organism Salmonella cholerasuis (ATCC 10708), S. enteritidis isolated from the spleen of an infected laying hen, and an egg-invasive S. enteritidis isolate. In all cases when S. cholerasuis was used, there was a significant association between the use of well, pond, and stream water and the growth of the bacterium. If we exclude glutaraldehyde, there was also a significant association between the use of "field" water and the growth of both isolates of S. enteritidis. There was no significant association when glutaraldehyde was used. There was a significant association between the use of lab water and the growth of S. enteritidis. The results suggested that the inability to remove S. enteritidis from layer houses may in part be associated with the source of water. Variables in pH, hardness, conductivity, nitrate content, or bacterial contamination of the water did not appear to affect the ability of the disinfectant to kill S. enteritidis. If "field" water is used for disinfection against S. enteritidis, the use of quaternary ammonium, the combination (quaternary ammonium/formaldehyde), or phenol should be considered.