A novel mathematical template for developing fDOM probe fluorescence signal correction models for freshwaters.

The reliable application of field deployable fluorescent dissolved organic matter (fDOM) probes is hindered by several influencing factors which need to be compensated. This manuscript describes the corrections of temperature, pH, turbidity and inner filter effect on fluorescence signal of a commercial fDOM probe (fDOMs). For this, Australian waters with wide ranging qualities were selected, e.g. dissolved organic carbon (DOC) ranging from ∼1 to ∼30 mg/L, specific UV absorbance at 254 nm from ∼1 to ∼6 L/m/mg and turbidity from ∼1 to ∼ 350 FNU. Laboratory-based model calibration experiments (MCEs) were performed. A model template was developed and used for the development of the correction models. For each factor, data generated through MCEs were used to determine model coefficient (α) values by fitting the generated model to the experimental data. Four discrete factor models were generated by determination of a factor-specific α value. The α values derived for each water of the MCEs subset were consistent for each factor model. This indicated generic nature of the four α values across wide-ranging water qualities. High correlation between fDOMs and DOC were achieved after applying the four-factor compensation models to new data (r, 0.96, p < 0.05). Also, average biases (and %) between DOC predicted through fDOMs and actual DOC were decreased by applying the four-factor compensation model (from 3.54 (60.9%) to 1.28 (16.7%) mg/L DOC). These correction models were incorporated into a Microsoft EXCEL-based software termed EXOf-Correct for ready-to-use applications.

A cross-sectional study of the welfare of calves raised in smallholder dairy farms in Meru, Kenya, 2017.

AIM: This study was aimed at describing calf comfort and determining the individual and pen level factors that affect comfort status (in particular, calf leg hygiene scores) of smallholder dairy farms in Meru County, Kenya. MATERIALS AND METHODS: A cross-sectional study was carried out on 52 calves that were up to 1 year old in 38 dairy farms (mean±standard deviation: Herd size=1.71±0.7 milking cows and milk production=6.7±3.1 L/day) in Meru, Kenya, in 2017, with the intention to describe their comfort and determine the factors associated with leg hygiene as a critical parameter for calf comfort assessment. Calves' biodata, health status, and leg hygiene were assessed, along with pen characteristics such as area, hygiene, and knee impact and knee wetness scores, while a questionnaire was administered to the farmers to gather information regarding calf housing management practices in the farm. RESULTS: The calves had a mean body weight of 85.2±32.8 kg and average daily weight gain of 0.50±0.45 kg per day. 71% of calves had a good body condition score (≥2.5), and the mean space allowance per calf was 2.52±1.56 m2. Approximately 75% of the calves (39/52) were kept in pens, and the rest were reared outdoors. For 39 calves kept indoors, 26% (10/39) of them had wooden or concrete floors while 74% (29/39) had dirt floors. Nearly two-thirds (62%) of indoor calves (26/39) were reared in pens with bedding, and 23% (9/39) and 33% (13/39) of the calves reared indoors were kept in pens displaying a failed knee impact test and failed knee wetness test. Indoor housed calves had an increased probability of having dirty calf legs (cleanliness score of >2.5) by 8.6 times (p=0.031), compared to outdoor-housed calves. In the final multivariable logistic regression model of 39 calves in pens, concrete or wood floors (odds ratio [OR]=7.9, p=0.047), poor body condition (OR=17.1, p=0.020) and use of bedding (OR=12.5, p=0.046) appeared to be positively correlated with dirtiness of calf legs, compared to dirt floors, good body condition, and no bedding, respectively. CONCLUSION: Overall, some calf comfort aspects were covered for the majority of calves examined, but 69% of the pens were categorized as dirty, especially those with wooden or concrete floors and poor bedding management. Smallholder dairy farmers in Kenya should be trained on calf housing management to improve calf comfort and productivity.

Study of the impacts of process changes of a pulp and paper mill on aerated stabilization basin (ASB) performance.

A laboratory scale (LS) and a field-based pilot plant (PP), designed to simulate aerobic stabilization basin (ASB) operation, were utilized to assess the potential impacts of changes in pulp and paper (P&P) mill operations on full-scale (FS) ASB performance. Two stages of investigation were conducted. The first was undertaken to determine the potential of pre-alum treatment of pulp mill wastewaters on ASB performance. The second investigation was conducted to assess ASB performance where wastewaters transitioned from being coagulated pulp and paper mill wastewaters to paper mill wastewaters only. Simulation ASB performance was assessed based on removals of BOD5, colour, UV@254 nm and nutrients [total phosphorus (TP) and nitrogen compounds (TN)]. Pre-alum treatment of pulp mill wastewaters with subsequent ASB treatment following mixing with paper mill wastewaters showed high percentage removals of BOD5. Despite low TP concentrations (≤0.05 mg/L) and low nutrient to BOD5 ratios of wastewaters in the LS-ASB trial, the high % BOD5 removal indicated recycling of nutrients from sludge [sourced from the FS-ASB]. Despite coagulation of pulp mill wastewater being performed using a very high alum dose (∼2000 mg/L) to remove colour and its precursors, colour formation remained high throughout the simulated ASB trials. Simulation of discontinuation of pulping indicated that colour would reduce rapidly to low levels in ASB wastewaters, but that TP and TN concentrations would persist for longer periods of time and decline slowly. Survey data of water qualities of the FS-ASB system obtained before, during and 2 years after discontinuation of pulping are presented.

Field based pilot-scale drinking water distribution system: Simulation of long hydraulic retention times and microbiological mediated monochloramine decay.

Drinking water distribution systems with long hydraulic retention times (HRTs) commonly encounter rapid microbiological-mediated monochloramine decay that results in microbial regrowth and nitrification with reduction in alkalinity. In this paper, we report the design and operation of a field-based pilot-scale distribution system (PDS) operated at flows that simulate long HRTs (∼10 days) to promote rapid microbiological monochloramine decay over long periods. The PDS is designed to enable the testing of chemical treatment for the control of nitrification and monochloramine decay. The PDS has two identical cylindrical polyethylene tanks (DS1 & DS2), each of 1 m diameter and 1.8 m height (∼1 kL) holding 900 m of polyethylene (PE) tubing with sampling points every 300 m intervals. Microbial mediated decay (determined by the Fm test) of monochloramine occurred as treated (alum coagulated and flocculated) and chloraminated water passed through the DSs. In this manuscript we report: •An inexpensive, flexible and compact system that can be readily set-up at a full-scale water treatment plant, requiring minimal supervision for operation.•A 'draw & fill' system for achieving control on HRT's through the pipes.

Evaluation and comparison the performance of titanium and zirconium(IV) tetrachloride in textile wastewater treatment.

Wastewater treatment is a key challenge in the textile industry. The current treatment methods for textile wastewater are insufficient or ineffective for complex dyes generated from the textile industry. This study evaluated the performances of two novel inorganic coagulants with high cationic charges, namely, titanium tetrachloride (TiCl4) and zirconium tetrachloride (ZrCl4). They were utilised to treat textile industry wastewater. Both coagulation processes were performed under the same experimental operational conditions. Turbidity, suspended solids (SS), colour, chemical oxygen demand (COD) and ammonia were measured to assess the efficiencies of the coagulants. Results indicated that ZrCl4 and TiCl4 exhibited high potentials for textile wastewater treatment. ZrCl4 presented high removal efficiency in COD and SS, whereas TiCl4 showed excellent removal in ammonia.

Modelling of THM formation potential and DOM removal based on drinking water catchment characteristics.

Catchment properties influence the character and concentration of dissolved organic matter (DOM). Surface and subsurface runoff from discrete catchments were collected and DOM was measured and assessed in terms of its treatability by Enhanced Coagulation and potential for disinfection by-product (trihalomethane, THMFP) formation potential. Models were developed of [1] DOM character [i.e. SUVA and SpCoL] and concentration (measured as dissolved organic carbon), [2] treatability of DOM by coagulation/flocculation processes and [3] specific THMFP based on the catchment features including: (a) surface and sub-surface soil texture (% clay: 5-25%), (b) topography (% slope: 5-15%) and (c) vegetation cover [i.e. high photosynthetic vegetation, low photosynthetic vegetation and bare soil] extracted from RapidEye satellite imagery using spectral mixture analysis. From these models, a catchment management decision support tool was designed for application by catchment managers to support decision-making of land-use and expected water quality related to water resources for drinking water supply. SOFTWARE AND DATA AVAILABILITY: Data sets used for models developing presented in this paper have been published in Research Data Australia (RDA) under the title of "Impacts of catchment properties on DOM and nutrients in waters from drinking water catchments".1 These data sets are available in open access and published in June 2017. A catchment management decision support model (CMDSM) tool was developed. Macros created using Visual Basic for Applications in Excel 2010. Excel 2010 or higher is required to open the CMDSM tool. The tool is provided by the University of South Australia (UniSA) and is not currently available on-line so please contact the corresponding author for access or further information.

Chloramine demand estimation using surrogate chemical and microbiological parameters.

A model is developed to enable estimation of chloramine demand in full scale drinking water supplies based on chemical and microbiological factors that affect chloramine decay rate via nonlinear regression analysis method. The model is based on organic character (specific ultraviolet absorbance (SUVA)) of the water samples and a laboratory measure of the microbiological (Fm) decay of chloramine. The applicability of the model for estimation of chloramine residual (and hence chloramine demand) was tested on several waters from different water treatment plants in Australia through statistical test analysis between the experimental and predicted data. Results showed that the model was able to simulate and estimate chloramine demand at various times in real drinking water systems. To elucidate the loss of chloramine over the wide variation of water quality used in this study, the model incorporates both the fast and slow chloramine decay pathways. The significance of estimated fast and slow decay rate constants as the kinetic parameters of the model for three water sources in Australia was discussed. It was found that with the same water source, the kinetic parameters remain the same. This modelling approach has the potential to be used by water treatment operators as a decision support tool in order to manage chloramine disinfection.

Developing a chloramine decay index to understand nitrification: A case study of two chloraminated drinking water distribution systems.

The management of chloramine decay and the prevention of nitrification are some of the critical issues faced by water utilities that use chloramine as a disinfectant. In this study, potential association between high performance size exclusion chromatography (HPSEC) data obtained with multiple wavelength Ultraviolet (UV) detection from two drinking water distribution systems in Australia and nitrification occurrence was investigated. An increase in the absorbance signal of HPSEC profiles with UV detection at λ=230nm between apparent molecular weights of 200 to 1000Da was observed at sampling sites that experienced rapid chloramine decay and nitrification while its absorbance signal at λ=254nm decreased. A chloramine decay index (C.D.I) defined as the ratio of area beneath the HPSEC spectra at two different wavelengths of 230 and 254nm, was used in assessing chloramine decay occurrences. The C.D.Is of waters at locations that experienced nitrification were consistently higher than locations not experiencing nitrification. A simulated laboratory study showed that the formation of nitrite/nitrate and/or soluble microbial products and/or the release of extracellular polymeric substances (EPS) during nitrification may contribute to the C.D.I. increase. These findings suggest that C.D.I derived from HPSEC with multiple wavelength UV detection could be an informative index to track the occurrence of rapid chloramine decay and nitrification.

Influence of coagulation mechanisms and floc formation on filterability.

Minimizing particles in water is a key goal for improving drinking water quality and safety. The media filtration process, as the last step of the solid-liquid separation process, is largely influenced by the characteristics of flocs, which are formed and controlled within the coagulation process. In a laboratory-based study, the impacts of the physical characteristics of flocs formed using aluminum sulfate on the filtration treatment of two comparative water samples were investigated using a photometric dispersion analyzer and a filterability apparatus. In general, the optimum dosage for maximizing filterability was higher than that for minimizing turbidity under neutral pH conditions. For a monomeric aluminum-based coagulant, the charge neutralization mechanism produced better floc characteristics, including floc growth speed and size, than the sweep flocculation mechanism. In addition, the charge neutralization mechanism showed better performance compared to sweep flocculation in terms of DOC removal and floc filterability improvement for both waters, and showed superiority in turbidity removal only when the raw water had high turbidity. For the different mechanisms, the ways that floc characteristics impacted on floc filterability also differed. The low variation in floc size distribution obtained under the charge neutralization mechanism resulted in the flocs being amenable to removal by filtration processes. For the sweep flocculation mechanism, increasing the floc size improved the settling ability of flocs, resulting in higher filter efficiency.

Seasonal variation in the nature of DOM in a river and drinking water reservoir of a closed catchment.

Dissolved organic matter (DOM) in surface waters used for drinking purposes can vary markedly in character depending on its source within catchments and the timing and intensity of rainfall events. Here we report the findings of a study on the character and concentration of DOM in waters collected during different seasons from Myponga River and Reservoir, South Australia. The character of DOM was assessed in terms of its treatability by enhanced coagulation and potential for disinfection by-product i.e. trihalomethane (THM) formation. During the wet seasons (winter and spring), water samples from the river had higher DOC concentrations (X¯: 21 mg/L) and DOM of higher average molecular weight (AMW: 1526 Da) than waters collected during the dry seasons (summer and autumn: DOC: 13 mg/L; AMW: 1385 Da). Even though these features led to an increase in the percentage removal of organics by coagulation with alum (64% for wet compared with 53% for dry season samples) and a lower alum dose rate (10 versus 15 mg alum/mg DOC removal), there was a higher THM formation potential (THMFP) from wet season waters (treated waters: 217 µg/L vs 172 µg/L). For reservoir waters, samples collected during the wet seasons had an average DOC concentration (X¯: 15 mg/L), percentage removal of organics by alum (54%), alum dose rates (13 mg/mg DOC) and THMFP (treated waters: 207 µg/L) that were similar to samples collected during the dry seasons (mean DOC: 15 mg/L; removal of organics: 52%; alum dose rate: 13 mg/mg DOC; THMFP: 212 µg/L for treated waters). These results show that DOM present in river waters and treatability by alum are highly impacted by seasonal environmental variations. However these in reservoir waters exhibit less seasonal variability. Storage of large volumes of water in the reservoir enables mixing of influent waters and stabilization of water quality.

Impact of prechlorination on organophosphorus pesticides during drinking water treatment: Removal and transformation to toxic oxon byproducts.

Prechlorination is commonly used to minimize operational problems associated with biological growth as well as taste and odor control during drinking water treatment. However, prechlorination can also oxidise micropollutants into intermediate byproducts. This could impose profound effects on the safety of the finished water if the transformed byproducts are more toxic and less removable. This study investigated the effect of prechlorination on decomposition and subsequent removal of the four organophosphorus pesticides (OPPs): chlorpyrifos, diazinon, malathion and tolclofos-methyl using a simulated conventional water treatment process of powdered activated carbon assisted coagulation-sedimentation-filtration (PAC-CSF) and postchlorination. It was found that, following prechlorination, not only did the percentage of OPPs oxidation vary significantly, but also the concentration of transformed oxons, which are more toxic than their parent compounds, increased as the major identified oxidation byproducts in water. Removal of these oxons proved to be more difficult by the PAC-CSF than their parent OPPs, because they are more water soluble and more hydrophilic. Both the OPP oxidation and oxon formation increased with chlorine dose during prechlorination. Meanwhile, the continuing chlorination of OPPs by residual free chlorine during PAC-CSF further complicated the pesticide removal processes, generally resulting in a gradually increased formation of oxons. Moreover, in the final treatment stage of postchlorination, the more chlorine-reactive pesticides, malathion and diazinon, were completely oxidised and the formation of corresponding oxons was increased with the prechlorine dose. In contrast, a certain amount of the less chlorine-reactive pesticide tolclofos-methyl still remained in solution after postchlorination, accompanied by an increased formation of tolclofos-methyl oxon with prechlorine dose. Since the oxons are resistant to further oxidation and less adsorbable during the PAC-CSF process, the gross removal of these pesticides and their oxons decreased with increase of the prechlorine dose. This led to an accumulation of the more toxic oxons in the finished water, especially at higher chlorine doses during prechlorination. The significance of this work is the demonstration that, under circumstances where prechlorination is used and source water contains traces of OPPs, alternative practices should be prioritized to avoid the potential risks involved in consumption of the treated water.

Roles of coagulant species and mechanisms on floc characteristics and filterability.

In full scale water treatment operation, the rapid filtration process, as the last step of solid-liquid separation, is largely influenced by floc characteristics. In this study, aluminium sulphate (alum) and nano-Al13 were investigated to understand the influence of coagulant species on the formation and filterability of flocs. At neutral pH, it was found that nano-Al13, a high MW polymer, showed better floc filterability than alum. This is because of the densely compacted and well-distributed size flocs from nano-Al13, even though floc sizes of alum were generally bigger. Al specie distributions of the two coagulants at different pH levels were compared by using electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) to further elucidate the reasons for the superiority of nano-Al13 in floc filterability. Depolymerisation/re-polymerisation of nano-Al13 occurred as pH changed, and Al species from nano-Al13were more abundant than that from alum, especially for the high molecular weight (MW) oligomers such as Al11, Al12, Al13 and Al14. Under the charge neutralisation mechanism, higher MW Al species was found to improve coagulation performance and floc filterability. In addition, breakage resistance and regrowth ability of nano-Al13 was better than alum, at weak acid condition. Flocs formed by the charge neutralisation mechanism readily regenerated after being thoroughly broken up. The floc regrowth ability of nano-Al13 at high shear rates (200 rpm and 300 rpm) was much better than at low shear and better than any shear applied to alum., and the flocs after breakage at 200 rpm and 300 rpm also showed better filterability than other conditions.

Characterization of dissolved organic matter for prediction of trihalomethane formation potential in surface and sub-surface waters.

Dissolved organic matter (DOM) in surface waters used for drinking purposes can vary markedly in character dependent on their sources within catchments. The character of DOM further influences the formation of disinfection by products when precursor DOM present in drinking water reacts with chlorine during disinfection. Here we report the development of models that describe the formation potential of trihalomethanes (THMFP) dependent on the character of DOM in waters from discrete catchments with specific land-use and soil textures. DOM was characterized based on UV absorbance at 254 nm, apparent molecular weight and relative abundances of protein-like and humic-like compounds. DOM character and Br concentration (up to 0.5 mg/L) were used as variables in models (R(2)>0.93) of THMFP, which ranged from 19 to 649 µg/L. Chloroform concentration (12-594 µg/L) and relative abundance (27-99%) were first modeled (R(2)>0.85) and from these, the abundances of bromodichloromethane and chlorodibromomethane estimated using power and exponential functions, respectively (R(2)>0.98). From these, the abundance of bromoform is calculated. The proposed model may be used in risk assessment of catchment factors on formation of trihalomethanes in drinking water, in context of treatment efficiency for removal of organic matter.

Treatability of organic matter derived from surface and subsurface waters of drinking water catchments.

The treatability of NOM present in runoff and subsurface waters from discrete zero-order catchments (ZOCs) with three land management practices (Australian native vegetation, pine plantation, grasslands) on varying soil textures of a closed drinking water reservoir-catchment was investigated. Subsurface water samples were collected by lysimeters and shallow piezometers and surface waters by installation of barriers that diverted waters to collection devices. For small sample volumes collected, a 'micro' jar testing procedure was developed to assess the treatability of organics by enhanced coagulation using alum, under standardised conditions. DOM present in water samples was quantified by measurement of DOC and UV absorbance (at 254 nm) and characterized using these and F-EEM. The mean alum dose rate (mg alum per mg DOC removed or Al/DOC) was found to be lower for DOM from sandy soil ZOCs (21.1 ± 11.0 Al/DOC) than from clayey soil ZOCs (38.6 ± 27.7 Al/DOC). ZOCs with Pinus radiata had prominent litter layers (6.3 ± 2.6 cm), and despite differences in soil textures showed similarity in DOM character in subsurface waters, and in alum dose rates (22.2 ± 5.5 Al/DOC). For sandy soil ZOCs, the lowest alum dose rates (16.5 ± 10.6 Al/DOC) were for waters from native vegetation catchment while, for clayey soil ZOCs, waters from pine vegetation had the lowest alum dose rates (23.0 ± 5.0 Al/DOC). Where ZOCs have a prominent O horizon, soil minerals had no apparent influence on the treatability of DOM.

The effect of vegetation and soil texture on the nature of organics in runoff from a catchment supplying water for domestic consumption.

The influence of vegetation and soil texture on the concentration and character of dissolved organic matter (DOM) present in runoff from the surface and sub-surface of zero order catchments of the Myponga Reservoir-catchment (South Australia) was investigated to determine the impacts of catchment characteristics and land management practices on the quality of waters used for domestic supply. Catchments selected have distinct vegetative cover (grass, native vegetation or pine) and contrasting texture of the surface soil horizon (sand or clay loam/clay). Water samples were collected from three slope positions (upper, middle, and lower) at soil depths of ~30 cm and ~60 cm in addition to overland flows. Filtered (0.45 µm) water samples were analyzed for dissolved organic carbon (DOC) and UV-visible absorbance and by F-EEM and HPSEC with UV and fluorescence detection to characterize the DOM. Surface and sub-surface runoff from catchments with clay soils and native vegetation or grass had lower DOC concentrations and lower relative abundances of aromatic, humic-like and high molecular weight organics than runoff from sandy soils with these vegetative types. Sub-surface flows from two catchments with Pinus radiata had similar DOC concentrations and DOM character, regardless of marked variation in surface soil texture. Runoff from catchments under native vegetation and grass on clay soils resulted in lower DOC concentrations and hence would be expected to have lower coagulant demand in conventional treatment for potable water supply than runoff from corresponding sandy soil catchments. However, organics in runoff from clay catchments would be more difficult to remove by coagulation. Surface waters from the native vegetation and grass catchments were generally found to have higher relative abundance of organic compounds amenable to removal by coagulation compared with sub-surface waters. Biophysical and land management practices combine to have a marked influence on the quality of source water used for domestic supply.

Changes in the quality of river water before, during and after a major flood event associated with a La Niña cycle and treatment for drinking purposes.

The treatment of organics present in the lower reaches of a major river system (the Murray-Darling Basin, Australia) before (March-July 2010), during (December 2010-May 2011) and after (April-December 2012) a major flood period was investigated. The flood period (over 6months) occurred during an intense La Niña cycle, leading to rapid and high increases in river flows and organic loads in the river water. Dissolved organic carbon (DOC) increased (2-3 times) to high concentrations (up to 16mg/L) and was found to correlate with river flow rates. The treatability of organics was studied using conventional jar tests with alum and an enhanced coagulation model (mEnCo©). Predicted mean alum dose rates (per mg DOC) were higher before (9.1mg alum/mg DOC) and after (8.5mg alum/mg DOC) than during the flood event (8.0mg alum/mg DOC), indicating differences in the character of the organics in raw waters. To assess the character of natural organic matter present in raw and treated waters, high performance size exclusion chromatography with UV and fluorescence detectors were used. During the flood period, high molecular weight UV absorbing compounds (>2kDa) were mostly detected in waters collected, but were not evident in waters collected before and afterwards. The relative abundances of humic-like and protein-like compounds during and following the flood period were also investigated and found to be of a higher molecular weight during the flood period. The treatability of the organics was found to vary over the three climate conditions investigated.

Changes in the nature of dissolved organics during pulp and paper mill wastewater treatment: a multivariate statistical study combining data from three analytical techniques.

The paper-making process can produce large amounts of wastewater (WW) with high particulate and dissolved organic loads. Generally, in developed countries, stringent international regulations for environmental protection require pulp and paper mill WW to be treated to reduce the organic load prior to discharge into the receiving environment. This can be achieved by primary and secondary treatments involving both chemical and biological processes. These processes result in complex changes in the nature of the organic material, as some components are mineralised and others are transformed. In this study, changes in the nature of organics through different stages of secondary treatment of pulp and paper mill WW were followed using three advanced characterisation techniques: solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy, pyrolysis-gas chromatography mass spectrometry (py-GCMS) and high-performance size-exclusion chromatography (HPSEC). Each technique provided a different perspective on the changes that occurred. To compare the different chemical perspectives in terms of the degree of similarity/difference between samples, we employed non-metric multidimensional scaling. Results indicate that NMR and HPSEC provided strongly correlated perspectives, with 86 % of the discrimination between the organic samples common to both techniques. Conversely, py-GCMS was found to provide a unique, and thus complementary, perspective.

Using reverse phase high performance liquid chromatography as an alternative to resin fractionation to assess the hydrophobicity of natural organic matter.

Resin fractionation is the most widely used technique to isolate and characterize natural organic matter (NOM) based on its hydrophobicity and hydrophilicity, however, it is also recognized as a time consuming technique. This paper describes the use of reverse phase high performance liquid chromatography (RPHPLC) as a rapid assessment technique to determine the hydrophobicity/hydrophilicity of NOM. The optimum column separation condition was achieved and without the need for concentrating the sample prior to analysis and with good reproducibility of the peak retention time and the peak area. The characterization results were further compared with the traditional resin fractionation technique using DAX-8 and XAD-4 resins. The results demonstrated that the polarities defined by the two methods were different but consistent and also that the fractions absorbed onto XAD-4 were less hydrophobic than those absorbed onto DAX-8. The difference in definition between resin fractionation and RPHPLC were further investigated.

pH modeling for maximum dissolved organic matter removal by enhanced coagulation.

Correlations between raw water characteristics and pH after enhanced coagulation to maximize dissolved organic matter (DOM) removal using four typical coagulants (FeCl3, Al2(SO4)3, polyaluminum chloride (PACl) and high performance polyaluminum chloride (HPAC)) without pH control were investigated. These correlations were analyzed on the basis of the raw water quality and the chemical and physical fractionations of DOM of thirteen Chinese source waters over three seasons. It was found that the final pH after enhanced coagulation for each of the four coagulants was influenced by the content of removable DOM (i.e. hydrophobic and higher apparent molecular weight (AMW) DOM), the alkalinity and the initial pH of raw water. A set of feed-forward semi-empirical models relating the final pH after enhanced coagulation for each of the four coagulants with the raw water characteristics were developed and optimized based on correlation analysis. The established models were preliminarily validated for prediction purposes, and it was found that the deviation between the predicted data and actual data was low. This result demonstrated the potential for the application of these models in practical operation of drinking water treatment plants.