Removal Of Precursors Research Articles

Influence of Ultraviolet Light Coupled with Hydrogen Peroxide Treatment on Organic Nitrogen and Carbon Precursors and Disinfection By-Product Formation

This study examined the relationships between organic matter composition and disinfection by-product formation potential (DBPFP) following water chlorination. Laboratory synthetic water with various compositions of organic carbon and nitrogen were treated with ultraviolet light, coupled with hydrogen peroxide (UV/H2O2), to assess the effects of UV/H2O2 on their DBPFPs. Biologically treated wastewater effluent and histamine dihydrochloride were spiked in the tested solutions to represent complex organic matter compositions and nitrogenated aromatic structure. It was found that carbon-containing precursors were relatively easier to mineralize by UV/H2O2 treatment than the nitrogen-containing compounds. UV/H2O2 processes successfully reduced the precursors of trihalomethanes and haloacetic acids (HAAs); however, the treatment efficiency was lower for N-nitrosodimethylamine (NDMA) precursors. It was also observed that the degree of precursor removal was reduced when raw water was contaminated by domestic wastewater effluents. In comparison to untreated water, UV/H2O2-treated water produced a higher ratio of HAAs than trihalomethanes after chlorination. This suggests that a higher fraction of hydrophilic compounds was obtained after UV/H2O2 treatment. Raw water impaired by wastewater effluent also altered the formation and species distribution of DBPs, because higher ratio of HAAs and brominated DBPs were observed.

THMs precursor removal by an integrated process of ozonation and biological granular activated carbon for typical Northern China water

The removal of trihalomethanes (THMs) precursor and natural organic matter (NOM) by an integrated process of ozonation and biological granular activated carbon filtration (BGAC) as a deep water treatment process was investigated in pilot-scale tests. A comparison is also made with granular activated carbon filtration (GAC). The characteristics of the THMs precursor and the THMs formation potential (THMFP) were investigated by resin adsorption and ultrafiltration. The results show that the integrated process of ozonation and BGAC (O 3/BGAC) is obviously superior to GAC for the removal of the THMs precursor because a considerable synergetic effect occurs between the ozonation and the BGAC. Although ozonation can limitedly remove dissolved organic carbon (DOC), it can cut down the molecular weight of the NOM, change its polarity, decrease the THMFP, and obviously enhance the efficiency of the BGAC. The BGAC could efficiently remove the hydrophobic base (HoB), hydrophobic neutral (HoN), weakly hydrophobic acid (WHoA), and low molecular weight fraction DOC that was produced in the optimized ozonation process. However, the BGAC stage should be carefully controlled to avoid the leakage of microbes and/or the products of metabolism because it has a high risk for producing THMs in following chlorination process.

Fabrication of catalytic ceramic membranes for water filtration

The paper describes the use of the layer-by-layer technique to coat ceramic membranes with iron and manganese oxide nanoparticles. The coatings are thin (<50 nm) and relatively uniform. These coatings enhance the performance of the hybrid ozonation-filtration process. With the coated membranes it is possible to significantly reduce fouling, improve the removal of DBP precursors and more effectively kill Escherichia coli bacteria.

Progress and Challenges in Colorectal Cancer Screening and Surveillance

Colorectal cancer is a leading cause of cancer death throughout the world. There is evidence that screening of average-risk individuals can result in mortality reduction with early cancer detection and cancer prevention by detection and removal of cancer precursor lesions. The optimal form of screening is not clear. Fecal screening tests can be performed at home at low initial cost, but current versions lack high sensitivity for cancer precursor lesions, and tests need to be repeated at regular intervals. Adherence to repeat testing for negative tests and referral for colonoscopy for positive tests are important elements of program effectiveness. Structural examinations of the colon are more invasive and may result in detection of both early cancer and cancer precursor lesions. Every screening program has advantages and limitations, but each program ultimately depends on quality and patient adherence.

Current and Long-Term Effects of Delta Water Quality on Drinking Water Treatment Costs from Disinfection Byproduct Formation

Sea level rise and the failure of subsided western islands are likely future conditions for the Sacramento-San Joaquin Delta. This study explores the current and long-term effects of changes in the Delta’s water quality on drinking treatment costs for alternative disinfection and additional disinfection byproduct (DBP) precursor removal. Current and likely future Delta water qualities were investigated for electrical conductivity and the concentrations of bromide, and organic carbon. With roughly 1.5 million acre-feet (af) per year of Delta water used for urban water supplies, the drinking water treatment cost differences of taking water from the south Delta and the Sacramento River upstream could amount to $30 to $90 million per year currently, and could rise to $200 to $1000 million per year in the future, with lower water quality and urban use of Delta waters rising to 2 million af annually. From these results, waters drawn directly from the Delta will likely become more difficult and expensive to treat, making the Delta less desirable as a conventional water source.

The impact of Moringa oleifera as a coagulant aid on the removal of trihalomethane (THM) precursors and iron from drinking water

Chlorine is used as a disinfectant and an oxidant in drinking water treatment to protect the public health from pathogenic microorganisms. However, if applied to raw water with humic materials, it leads to the formation of halogenated organic compounds that are a potentially serious environmental and health problem. This renders pre-chlorination of raw waters to oxidise iron inappropriate. Coagulation, the principal treatment process for removal of THM precursors, is therefore essential for chlorination by-product control. In this study, the impact of pre-chlorination and the performance of Moringa oleifera as a coagulant aid at Masaka waterworks were assessed. An average increase of trihalomethanes of over 4,000% at aeration and pre-chlorination stage was observed at the plant. From the jar tests, alum with Moringa oleifera reduced dissolved organic concentration by 47.1%. The treated water after sedimentation tasted salty but after filtration and chlorination, the salty taste disappeared. Residual iron values of 1.38 mg/L and 3.05 mg/L were achieved with MOC-SC as coagulant aid and alum alone respectively. The jar test results indicated that use of alum with Moringa oleifera as coagulant aid is promising as a first stage in the treatment train for waters with humic materials and high content of iron.

Disinfection by-product formation of natural organic matter surrogates and treatment by coagulation, MIEX ® and nanofiltration

Potentially the most effective means of controlling disinfection by-products (DBPs) is to remove precursors before disinfection. To understand relationships between physical properties, treatability and DBP formation, nine natural organic matter (NOM) surrogates were studied. Their DBP formation and removal by coagulation, MIEX ® anion exchange resin and two nanofiltration membranes was measured. Whereas treatability of NOM surrogates was explained in terms of their physicochemical properties, the same was not true of DBP formation. Hence it was not possible to selectively remove compounds which generate high amounts of DBPs. Instead, precursor removal strategies based upon empirical DBP formation potential testing are more apt. Under conditions simulating full-scale performance, MIEX ® did not offer improved performance over coagulation. A hydrophobic nanofiltration membrane proved successful for removing neutral, hydrophilic surrogates, and hence is also suitable for DBP precursors of this character.

Parallel Factor Analysis of Excitation–Emission Matrices to Assess Drinking Water Disinfection Byproduct Formation During a Peak Formation Period

Parallel factor (PARAFAC) analysis was applied to the fluorescence excitation–emission matrices (EEM) of a water treatment plant's source and coagulated water during a peak chlorinated byproduct formation period. Water plant operations included the use of surface water only and surface/ground water mixtures. Three statistically significant components were obtained through PARAFAC analysis and were correlated to dissolved organic carbon (DOC), chlorine consumption, and individual disinfection byproduct (DBP) formation potential. Multifactor linear regression of select component scores showed linear relationships to individual chloro-DBP compounds providing insight to possible precursor locations within the EEM and organic matter, as well as, organic compound characteristics responsible for chloro-DBP formation. Likewise, linear relationships were also observed between component scores and empirically estimated precursor concentration methods reported in the literature. These results suggest PARAFAC analysis of EEM may be an effective tool for monitoring source water, measuring treatment process effectiveness (removal of specific DBP precursor), and estimating DBP precursor concentrations and individual DBP compound formation potential.

Effects of pre-ozonation on the removal of THM precursors by coagulation

Pre-ozonation in combination with enhanced coagulation was used to remove NOM from lake water as to control the formation of disinfection by-products, DBPs. The effect of the hydrophobicity/hydrophilicity nature of NOM on the performance of the combined pre-ozonation and coagulation process was studied. The hydrophilicity/hydrophobicity property of NOM was characterized in terms of mass distribution of the phydrophilic and the hydrophobilic fractions of NOM. The optimal condition for the combined pre-ozonation–coagulation was established: pH = ca. 9.0 and ozone dose = 0.45 mg-O 3/mg-DOC. Under the optimal condition, it was able to achieve ∼ 60% of THMFP removal. In terms of THMPF, results also indicated that the distribution between the hydrophilic and the hydrophobic fractions of NOM was 57.3 and 98.7 µg-THMFP/mg-DOC, respectively. Ozonation alters the structures and characteristics of NOM thereby affecting the coagulation effectiveness. Pre-ozonation was effective in removing the hydrophobic NOM, with a decrease of THMFP by ∼ 20% versus ∼ 10% for the hydrophilic fraction. The dosage of coagulant also governed DOC removal. The removal of hydrophobic and hydrophilic NOM were in the range of 27–41 and 2.5–22.7%, respectively at alum dosage of 0.41–1.65 (in Al/DOC) and 0.41–1.65 (in Al/DOC) and ozone dose of 0.58–2.93, mg/mg respectively. The adsorption characteristics of the hydrophilic and the hydrophobic fractions of NOM on aluminum hydroxide (from coagulant alum) were studied. Results indicated that the modified Langmuir isotherm of competitive adsorption was able to describe the adsorption of NOM onto hydrous aluminum hydroxide formed during alum coagulation of the lake waters.

Effective removal of disinfection by-products and assimilable organic carbon: An advanced water treatment system

The purpose of this work is to investigate an advanced water treatment system changes on disinfects by-products (DBPs) precursors removal efficiencies of treatment plant and associated trihalomethanes (THMs) and haloacetic acids (HAA 5) formation and assimilable organic carbon (AOC) in reduction from raw water through finished water of Fong-shan Water Treatment Plant (FSWTP) in Kaohsiung City, Taiwan. Drinking water samples were collected from an advanced water treatment plant during March–October 2008. In the formation of DBPs, advanced water treatment processes efficiently removed THMs and HAA 5. The concentrations of THMs and HAA 5 in finished water were reduced to 13.97 μg/L and 17.67 μg/L, respectively. In this investigation, the AOC was reduced effectively by ozonation and biological activated carbon (BAC) processes. Experimental results of this 6-month investigation indicate that AOC concentrations in the finished water can meet the WTP criterion of 50 μg acetate-C/L in the world. Results of this study provide a valuable reference for solving DBPs and AOC control of water treatment plants and the setting of regulations in Taiwan.

Characterization and carbonylic hydrogenation of methyl oleate over Ru-Sn/Al 2O 3: Effects of metal precursor and chlorine removal

Hydrogenation of methyl oleate to oleyl alcohol was evaluated over Ru-Sn/Al 2O 3 catalysts, prepared from different precursors, at 270 °C and 5.0 MPa. Two kinds of metal precursors were employed: chlorine-free precursors and inorganic chlorides. In addition, several methods for chlorine removal of metal-chloride-based catalysts were studied. Catalysts were characterized by EDX, XRF, DRX, BET and TPR analyses. Selectivity toward unsaturated alcohol was higher with the bimetallic catalyst based on chlorine-free precursors than with the catalyst based on metal chlorides, owing that chlorine avoids, at certain extent, an effective interaction between ruthenium and tin species. However, the most selective catalyst was the bimetallic one based on chloride precursors and reduced with NaBH 4, due to elimination of residual chlorine and higher dispersion of Ru-Sn species.

Regulation of Heparan Sulfate and Chondroitin Sulfate Glycosaminoglycan Biosynthesis by 4-Fluoro-glucosamine in Murine Airway Smooth Muscle Cells

The importance of the pathological changes in proteoglycans has driven the need to study and design novel chemical tools to control proteoglycan synthesis. Accordingly, we tested the fluorinated analogue of glucosamine (4-fluoro-N-acetyl-glucosamine (4-F-GlcNAc)) on the synthesis of heparan sulfate (HS) and chondroitin sulfate (CS) by murine airway smooth muscle (ASM) cells in the presence of radiolabeled metabolic precursors. Secreted and cell-associated CS and HS were assessed for changes in size by Superose 6 chromatography. Treatment of ASM cells with 4-F-GlcNAc (100 microM) reduced the quantity (by 64.1-76.6%) and decreased the size of HS/CS glycosaminoglycans associated with the cell layer (K(av) shifted from 0.30 to 0.45). The quantity of CS secreted into the medium decreased by 65.7-73.0%, and the size showed a K(av) shift from 0.30 to 0.50. Treatment of ASM cells with 45 microM and 179 microM 4-F-GlcNAc in the presence of a stimulator of CS synthesis, 4-methylumbelliferyl-beta-D-xyloside, reduced the amount of the xyloside-CS chains by 65.4 and 87.0%, respectively. The size of xyloside-CS chains synthesized in the presence of 4-F-GlcNAc were only slightly larger than those with xyloside treatment alone (K(av) of 0.55 compared with that of 0.6). The effects of 4-F-GlcNAc to inhibit CS synthesis were not observed with equimolar concentrations of glucosamine. We propose that 4-F-GlcNAc inhibits CS synthesis by inhibiting 4-epimerization of UDP-GlcNAc to UDP-GalNAc, thereby depleting one of the substrates required, whereas HS elongation is inhibited by truncation when the nonreducing terminus of the growing chain is capped with 4-F-GlcNAc.

Effect of Aluminum Speciation and Structure Characterization on Preferential Removal of Disinfection Byproduct Precursors by Aluminum Hydroxide Coagulation

Humic acid was coagulated by aluminum chloride and pokyaluminum (PACl) at different pH conditions. Aluminum speciation was investigated in details through combining electrospray ionization mass spectrometer (ESI-MS) with solid-state 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR). Freeze-dried flocs from coagulation precipitates were analyzed by Fourier transform infrared (FTIR) and solid-state 13C cross-polarization magic angle spinning (CPMAS) NMR. This study also evaluated removal of disinfection byproduct (DBP) precursors by PACI and AlCl3 coagulation during coagulation process. Particular emphasis was paid to the role of aluminum speciation and structure characterization in the preferential removal of precursors by coagulation. The results indicated that prehydrolyzed or in situ formed Al13 species during coagulation process exhibited preferential removal for corresponding DBP precursors with relative structures. On one hand, for DBP precursors with aromatic and carboxylic structures, in situ Al13 species were preferentially bound to these DBP precursors. Thus, more DBP precursors with aromatic and carboxylic structures were removed by AlCl3 than those by PACl at pH 5.0. On the other hand, for DBP precursors with aliphatic structures, aluminum coagulation was not responsible for reducing these precursors. However, oligomeric aluminum species and preformed Al13 species were weak preferentially bound to DBP precursors with aliphatic structures.

(Z)-cyclooctene epoxidation and cyclohexane oxidation on Ni/alumina-pillared clay catalysts

This work reports the synthesis of Ni-clay catalysts by impregnation of Al-pillared saponite with various Ni salts, using several Ni loadings. The catalysts were characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric and differential thermal analysis, nitrogen adsorption, temperature-programmed reduction studies, and ultraviolet–visible spectroscopy. All the solids displayed good structural properties. FTIR spectroscopy confirmed the total removal of the anionic precursors after calcination of the solids at 500 °C. The presence of NiO and NiAl 2O 4 in the nickel particles formed on the surface of the solids was demonstrated. Deconvolution of TPR curves allowed to identify three Ni-reduction effects, their temperature and relative intensity depended on the preparation of each sample. The catalytic behaviour of the solids for (Z)-cyclooctene epoxidation and cyclohexane oxidation by either iodosylbenzene (a model oxidant) or hydrogen peroxide (a clean oxidant) was studied. In the case of the epoxidation reactions, there was 100% selectivity for the epoxide. As for cyclohexane oxidation, only cyclohexanone was formed, whereas no cyclohexanol was detected. The use of radical scavengers indicated that the high-valent oxo-nickel species is responsible for the oxygen transfer between the oxidant and the substrates.

Chemical and biological oxidation of NOM surrogates and effect on HAA formation

Formation of disinfection by-products (DBPs) can be controlled by removal of disinfection by-product precursors before disinfection. Variable success has been reported, depending on the treatment used and water tested. Chemical and biological oxidations are candidate technologies to control DBP formation. Given the uncertainty over the identity of DBP precursors, the use of surrogates of natural organic matter (NOM) allows fundamental probing of the links between compound character, removal and DBP formation. Nine compounds were chosen to represent NOM and their removal by two advanced oxidation processes (AOPs), UV-C irradiation and biological treatment compared while haloacetic acid (HAA) formation before and after treatment was measured. Although AOPs were able to fully remove all compounds, incomplete mineralisation led to increased HAA levels, dramatically in the case of two amino acids. Biological treatment was effective in removing amino acids but also moderately increased the HAA formation potential (HAAFP) of hydrophilic compounds. These findings indicate waters with high amino acid concentrations will be susceptible to raised HAA levels following AOP treatment and careful process selection for HAA control is required in such cases.

Natural organic matter removal and enhanced coagulation as a link between coagulation and electrocoagulation

Although coagulation has historically been used for turbidity removal, drinking water regulations have emerged in recent years expanding the use of this process beyond its traditional role to include disinfection by-products (DBP) precursors removal. Effective removal of DBP precursors is the one of the major challenges in modern drinking water treatment. DBP precursors are present in all surface water supplies existing as natural organic matter (NOM), and this type of precursors can be characterised by the following measurements of dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254), specific ultraviolet absorbance (SUVA), and disinfection by-products formation potential (DBPFP). The effort to remove DBP precursors results in reduction of DBP formation in potable water. However, scientists discovered that chlorination of organic matter in raw water resulted in formation of DBPs. Because of concerns over the health effects of these organic byproducts, several industrial countries have...

Monitoring the prevalence of nitrosamines in South African waters and their removal using cyclodextrin polyurethanes

The prevalence of nitrosamines, especially N-nitrosodimethylamine (NDMA), was monitored in three South African water supplies. NDMA a disinfection by-product (DBP) and potent carcinogen, has recently been detected in many drinking water supplies internationally. Besides direct industrial or human-derived contamination, nitrosodimethylamine can be formed through a chemical reaction between monochloroamine and an organic based compound such as dimethylamine which is frequently detected in surface water. It has been suggested that chloramination of surface waters with a high concentration of dissolved organic carbon (DOC) could result in elevated NDMA formation. Growing evidence suggests that NDMA occurs more frequently and at higher concentrations in drinking water systems that practise chloramination compared to systems that use chlorination. In gauging the extent of water contamination by nitrosamines in water distribution systems, especially NDMA, water samples collected from three different water treatment plants that practise chemical drinking water disinfection were qualitatively analysed for the presence of nitrosamines. Solid phase microextraction (SPME) was employed in the extraction of nitrosamines from the water samples and gas chromatography–mass spectrometry (GC–MS), was used in the analysis of the water samples. Trace amounts of NDMA were detected at one of the water treatment plants and in the distribution network. The application of water-insoluble cyclodextrin (CD) polymers in the removal of nitrosamines and potential amine precursors from the water samples was tested. Quantitative removal of NDMA (based on peak area) from the water samples was achieved which suggests that in the water treatment train the use of these nanosponges can be applied in the mitigation of trace contaminants such as NDMA.

Removal of disinfection by-product precursors by UF and NF membranes in low-SUVA waters

The performance of ultrafiltration (UF) and nanofiltration (NF) membranes on disinfection by-products (DBPs) precursor removal in a surface water having low-to-medium dissolved organic carbon (DOC) and specific ultraviolet absorbance (SUVA 254) levels was evaluated. While higher molecular weight (HMW) DOC fraction was successfully rejected (>90%), lower molecular weight (LMW) fraction could be removed only 1.5–30% by the tested four different membranes (two UF and two NF). This finding suggested that although NF and UF membranes with pore sizes of ≤1000 Da are highly effective on the removal of HMW NOM from waters having low-to-medium DOC and SUVA 254 levels, such membranes are not effective in these waters in rejecting LMW fractions (i.e., <2000 Da). NF membranes provided THM and HAA formation reductions above 90%. However, DOC and UVA 254 rejections could not be directly linked to DBP formation reductions by the tested membranes. Due to higher rejection of DOC than the bromide ion in UF and NF separation, Br/DOC ratio increased which further increased the relative occurrence of brominated THM and HAA species over chlorinated ones.

LibraGen and DSM link a deal to co-develop and produce enzymes

Enhanced Coagulation is a new regulatory requirement in the United States aimed at removing TOC by coagulation thereby controlling formation of disinfection byproducts. Coagulation principles are summarized for alum coagulation of natural organic matter (NOM). Negatively charged NOM creates a coagulant demand for positively charged Al species resulting in a stoichiometric relationship between the alum dosage and the raw water DOC that is pH dependent. The paper addresses coagulation with a broader view than Enhanced Coagulation, termed multiple objective coagulation. In general the objectives include: 1) to maximize particle and turbidity removals by downstream solid-liquid separation, 2) to maximize TOC and DBP precursor removals, 3) to minimize residual coagulant, 4) to minimize sludge production, and 5) to minimize operating costs. Optimum coagulation conditions are those that maximize pathogen removals, produce low turbidities and particle counts, and minimize residual Al. It is shown, for treatment of waters of low alkalinity, that the optimum alum dosage selected to minimize UV absorbance with strict pH control produced excellent treatment for turbidity, pathogens, and NOM. Full scale plant data are used to demonstrate a dual coagulation strategy of alum and cationic polymer that reduces sludge production and overall operating costs compared to alum alone.

Dissolved organic carbon and potential for disinfection byproducts in Kranji, Pandan and Tengah reservoirs in Singapore

Fresh water from three western reservoirs of Singapore was assessed for the formation of trihalomethanes and the removal of precursors in a pilot-scale study. Raw water was processed through flocculation-sedimentation modules in a pilot plant with a capacity of 45 m3/day. Alum was the primary coagulant. Normal coagulation removed 10–60% of THM precursors. Kranji Reservoir, which has a watershed with thick vegetation, had relatively higher levels of dissolved organic matter with correspondingly higher potential for the formation of THM than Pandan Reservoir; Pandan is largely an urban catchment. Land-use pattern and proximity to seashore seem to influence THM formation. UV254 and SUVA were found to be better surrogates than DOC for THM. A benchmark criterion (UV254&amp;lt;0.08 cm−1) for on-line monitoring of THM was deduced from SDS-THM data and this criterion would vary slightly among the water works.