Removal of Humic Substances by Coagulation

Measurements and modeling of the adsorption of natural organic matter (NOM) on oxide surfaces are presented and compared. Agreement is good and supports the view that the adsorption of NOM on oxides depends significantly on complex formation reactions between specific sites on oxide surfaces and functional groups on the NOM. Coagulant requirements can and often are set by the total organic carbon (TOC) concentration in a water source. Frequently there is a stoichiometric relationship between the required coagulant dosage and the TOC of the water to be treated. Other important factors include pH and the concentration of divalent cations. Ozone may benefit or retard coagulation, depending on coagulant type and the water quality characteristic that is dominant in setting the optimum coagulant dose.

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Ozone: its effect on coagulation and filtration

Water Science & Technology Water Supply ◽

10.2166/ws.2001.0070 ◽

2001 ◽

Vol 1 (4) ◽

pp. 81-88 ◽

Cited By ~ 4

Author(s):

W.C. Becker ◽

C.R. O'Melia

Keyword(s):

Water Quality ◽

Organic Matter ◽

Metal Salt ◽

Drinking Water Treatment ◽

The United States ◽

Quality Characteristic ◽

Cationic Polymers ◽

Water Quality Characteristic ◽

Treatment Train ◽

Coagulation And Filtration

The interest in ozone for drinking water treatment in the United States has increased dramatically in recent years due to new regulations and concern over Cryptosporidium. Ozone has many benefits, however, its expense is significant and its placement in the treatment train should be chosen with a sound understanding of its effect on other unit processes. The goal of this paper is to provide an overview of the effect of ozone on the coagulation and filtration processes. This is important given the enhanced coagulation requirements of the disinfection by-product rule and the filtered water quality goals of the Partnership for Safe Water. The effect of ozone on coagulation is shown to be dependent on the coagulant type and on the water quality characteristic that is setting the optimum coagulant dose. For waters with moderate to high dissolved organic carbon (DOC) levels, the coagulant dose is set by the DOC. Ozonation converts NOM into smaller, more oxygenated compounds, e.g. oxalic acid, that exert a greater metal salt coagulant demand than the parent compounds. In this case, higher dosages of alum or ferric chloride are needed. For low DOC waters, the coagulant dose is set by the particle and the adsorbed organic matter. Ozone may react with adsorbed DOC and alter the amount and conformation of adsorbed organic matter, which can lead to a decrease in the optimum coagulant dose. Finally, because cationic polymers react with particles and large organic matter (and not the smaller compounds formed after ozonation), the optimum polyelectrolyte coagulant dose after ozonation is reduced. Ozonation prior to filtration (intermediate ozonation) is shown to be beneficial for significantly reducing filtered water particle counts by as much as an order of magnitude.

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Assessment of Coagulation–Flocculation Process Efficiency for the Natural Organic Matter Removal in Drinking Water Treatment

Water ◽

10.3390/w13213073 ◽

2021 ◽

Vol 13 (21) ◽

pp. 3073

Author(s):

Corina Petronela Mustereț ◽

Irina Morosanu ◽

Ramona Ciobanu ◽

Oana Plavan ◽

Andreea Gherghel ◽

...

Keyword(s):

Water Quality ◽

Drinking Water ◽

Organic Matter ◽

Natural Organic Matter ◽

Oxygen Demand ◽

Principal Component ◽

Drinking Water Treatment ◽

Water Source ◽

Process Efficiency ◽

Aluminum Concentration

Natural organic matter (NOM) represents a range of heterogeneous hydrophobic and hydrophilic components naturally occurring in the water source and, due to the fact that they can act as precursors for the disinfection, by-products may have a considerable impact on drinking water quality. Coagulation–flocculation (C/F) is among the most applied processes for NOM removal from water sources (especially rivers). In this study, C/F efficiency for a river water supply was investigated in cold and warm conditions, by varying the coagulant dose and mixing conditions. In this study, polyhydroxy aluminum chloride PAX XL 60, and polyacrylamide FloPam AN 910 SEP were used as coagulant and flocculant, respectively. Multiple water quality indicators were determined, such as turbidity, chemical oxygen demand (COD), dissolved organic carbon (DOC), and residual aluminum concentration. Some unconventional parameters relevant for NOM removal were also considered, like absorbance at 254 nm (A254), at 280 nm (A280), and at 365 nm (A365), as well as the ratios A254/DOC, A254/280, and A254/A365. After coagulation–flocculation, turbidity was completely removed in all the studied conditions. The DOC content was reduced by up to 22.65% at a low temperature and by up to 31.81% at a high temperature. After the addition of polyelectrolyte in cold conditions, the efficiency in terms of A254 increased by up to 37.4%, while the specific absorbance decreased. The high molecular weight NOM increased after C/F, based on the A254/A365 ratio. Chemometric analysis was employed in order to determine the effect of the coagulant dose on the process efficiency. The optimum coagulation–flocculation conditions were corroborated by means of the principal component analysis.

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Application of a fractionation technique for better understanding of the removal of natural organic matter by alum coagulation

Water Science & Technology Water Supply ◽

10.2166/ws.2002.0200 ◽

2002 ◽

Vol 2 (5-6) ◽

pp. 427-433 ◽

Cited By ~ 4

Author(s):

J. van Leeuwen ◽

C. Chow ◽

R. Fabris ◽

N. Withers ◽

D. Page ◽

...

Keyword(s):

Organic Matter ◽

Natural Organic Matter ◽

High Performance ◽

Relative Proportion ◽

Water Source ◽

Size Exclusion ◽

Gas Chromatography Mass Spectrometry ◽

Pyrolysis Gas ◽

Alum Treatment ◽

Hydrophobic Acids

To gain an improved understanding of the types of organic compounds that are recalcitrant to water treatment, natural organic matter (NOM) isolates from two drinking water sources (Mt. Zero and Moorabool reservoirs, Victoria, Australia) were separated into fractions of distinct chemical behaviour using resins. Four fractions were obtained from each water source and were organics absorbed to: (1) XAD-8 (very hydrophobic acids, VHA); (2) DAX-4 (slightly hydrophobic acids, SHA); (3) bound to an anion exchange resin (charged organics, CHAR); and (4) not absorbed or bound to resins (neutrals, NEUT). These fractions were then tested to determine the capacity of alum to remove them from water and to correlate this with the character of each isolate. The fractions were characterised by the application of high performance size exclusion chromatography (HPSEC), bacterial regrowth potential (BRP), trihalomethane formation potential (THMFP), pyrolysis gas-chromatography mass spectrometry (Py-GC-MS) and thermochemolysis. The highest removals of dissolved organic carbon (DOC) by alum treatment were in waters spiked with the CHAR fractions while the NEUT fractions were the most recalcitrant. The number average molecular weights (Mn) of DOC of the CHAR fractions before treatment were the highest, whilst those of the NEUT fractions were the lowest. After alum treatment, the Mn of the NEUT fractions were only slightly reduced. Results from Py-GC-MS and thermochemolysis indicate that the NEUT fractions had the highest relative proportion of saccharide derived organic material. Nonetheless, the BRP of waters spiked with the NEUT fractions differed markedly, indicating that organics recalcitrant to alum treatment can vary substantially in their chemical composition and capacity to support microbial growth.

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Stability of Fe-oxide nanoparticles coated with natural organic matter under relevant environmental conditions

Water Science & Technology ◽

10.2166/wst.2014.454 ◽

2014 ◽

Vol 70 (12) ◽

pp. 2040-2046 ◽

Cited By ~ 6

Author(s):

L. Chekli ◽

S. Phuntsho ◽

L. D. Tijing ◽

J. L. Zhou ◽

J.-H. Kim ◽

...

Keyword(s):

Organic Matter ◽

Natural Organic Matter ◽

Environmental Conditions ◽

Divalent Cations ◽

Oxide Nanoparticles ◽

Fe Oxide ◽

Coated Nanoparticles ◽

Aggregation Behaviour ◽

Physico Chemical ◽

The Stability

Manufactured nanoparticles (MNPs) are increasingly released into the environment and thus research on their fate and behaviour in complex environmental samples is urgently needed. The fate of MNPs in the aquatic environment will mainly depend on the physico-chemical characteristics of the medium. The presence and concentration of natural organic matter (NOM) will play a significant role on the stability of MNPs by either decreasing or exacerbating the aggregation phenomenon. In this study, we firstly investigated the effect of NOM concentration on the aggregation behaviour of manufactured Fe-oxide nanoparticles. Then, the stability of the coated nanoparticles was assessed under relevant environmental conditions. Flow field-flow fractionation, an emerging method which is gaining popularity in the field of nanotechnology, has been employed and results have been compared to another size-measurement technique to provide increased confidence in the outcomes. Results showed enhanced stability when the nanoparticles are coated with NOM, which was due to electrosteric stabilisation. However, the presence of divalent cations, even at low concentration (i.e. less than 1 mM) was found to induce aggregation of NOM-coated nanoparticles via bridging mechanisms between NOM and Ca2+.

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Triclosan removal by NF from a real drinking water source – Effect of natural organic matter

Chemical Engineering Journal ◽

10.1016/j.cej.2015.07.065 ◽

2016 ◽

Vol 283 ◽

pp. 330-337 ◽

Cited By ~ 16

Author(s):

Abdullah Ogutverici ◽

Levent Yilmaz ◽

Ulku Yetis ◽

Filiz B. Dilek

Keyword(s):

Drinking Water ◽

Organic Matter ◽

Natural Organic Matter ◽

Water Source ◽

Drinking Water Source ◽

Source Effect

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Natural organic matter removal by ion exchange at different positions in the drinking water treatment lane

Drinking Water Engineering and Science ◽

10.5194/dwes-6-1-2013 ◽

2013 ◽

Vol 6 (1) ◽

pp. 1-10 ◽

Cited By ~ 29

Author(s):

A. Grefte ◽

M. Dignum ◽

E. R. Cornelissen ◽

L. C. Rietveld

Keyword(s):

Water Quality ◽

Drinking Water ◽

Organic Matter ◽

Water Treatment ◽

Organic Carbon ◽

Natural Organic Matter ◽

Drinking Water Treatment ◽

Biological Stability ◽

Sand Filtration ◽

Slow Sand Filtration

Abstract. To guarantee a good water quality at the customers tap, natural organic matter (NOM) should be (partly) removed during drinking water treatment. The objective of this research was to improve the biological stability of the produced water by incorporating anion exchange (IEX) for NOM removal. Different placement positions of IEX in the treatment lane (IEX positioned before coagulation, before ozonation or after slow sand filtration) and two IEX configurations (MIEX® and fluidized IEX (FIX)) were compared on water quality as well as costs. For this purpose the pre-treatment plant at Loenderveen and production plant Weesperkarspel of Waternet were used as a case study. Both, MIEX® and FIX were able to remove NOM (mainly the HS fraction) to a high extent. NOM removal can be done efficiently before ozonation and after slow sand filtration. The biological stability, in terms of assimilable organic carbon, biofilm formation rate and dissolved organic carbon, was improved by incorporating IEX for NOM removal. The operational costs were assumed to be directly dependent of the NOM removal rate and determined the difference between the IEX positions. The total costs for IEX for the three positions were approximately equal (0.0631 € m−3), however the savings on following treatment processes caused a cost reduction for the IEX positions before coagulation and before ozonation compared to IEX positioned after slow sand filtration. IEX positioned before ozonation was most cost effective and improved the biological stability of the treated water.

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