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Herein, we isolate the rate-determining intermediate species in the photo-assisted Sabatier reaction on La promoted NiOx/TiO2 by in-situ isotopic spectroscopy. Specifically, adsorbed intermediate species formed during the photo-assisted Sabatier reaction were directly probed using Steady-State Isotopic Kinetic Analysis coupled with Diffuse Reflectance Infrared Fourier Transform Spectroscopy (SSITKA-DRIFTS). The photo-activation of the formate adsorbate (HCO2*) offers an eight-fold photo-enhancement on NiOx/La2O3@TiO2.

Efficient and low-cost electrocatalysts for water splitting are essential for solar fuel production. Herein, we report that nanoarrays of CoP supported on carbon cloth are an efficient bifunctional catalyst for overall water splitting. The catalyst exhibits remarkable activity for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media, delivering a current density of 10mAcm(-2) at an overpotential of 281mV for OER and 95mV for HER. During electrocatalysis, the surface of the CoP catalyst was covered with a layer of CoOx, which was the active species. However, the CoP core and the nanoarray morphology contributed significantly to the activity.

Zinc is a heavy metal that is essential for human health at trace levels. Zinc also has antibacterial properties and these were investigated on microbiological mediated monochloramine decay (measured as a microbial decay factor, Fm) occurring in chloraminated drinking water. Water samples displaying rapid chloramine decay were obtained using a field based novel design pilot-plant distribution system (PDS), located at the Tailem Bend water treatment plant, South Australia. The PDS comprised 1 kL tanks each holding 900m of polyethylene tubing with sampling points at 300m intervals. Flow rates were applied to achieve hydraulic retention times (HRTs) that simulated those of the full-scale distribution system. Total (k(t)) and microbiological mediated (k(m)) decay rates were determined for chloraminated waters as these passed through the PDS. Highest Fm values (2.1 +/- 0.7) were found for waters collected at the outflow of the PDS pipework, demonstrating increase in microbiological mediated monochloramine decay with increased HRT. Zinc (0.6-60 mg/L) added to water samples was found to lower k(t), k(m) and consequently Fm, as its concentration was increased. Mathematical models (R-2 > 0.9 and Ttest value > 0.8) were developed that describe reductions in monochloramine decay rates with the zinc addition. Reduction in kt and Fm in response to zinc were found to have an inverse correlation with initial microbial activity in the chloraminated waters. Zinc concentration below drinking water aesthetic limits (< 3.0 mg/L, ADWG) was also found to lower the monochloramine decay rate, indicating potential benefit at such levels in chloraminated distribution systems. Refereed/Peer-reviewed

This paper reports the effects of pre-oxidation processes including ozone and ultraviolet (UV) irradiation prior to chloramination on microbiologically assisted monochloramine decay. Water samples with varying water qualities were pre-oxidated by ozone and UV irradiation, followed by determination of chemical and microbiological monochloramine decay (F m ). Both ozone and UV could effectively improve the reduction of microbial-like compounds responsible for monochloramine decay in treated water samples. Reductions in F m values were observed for ozone contact times (Ct) greater than 5 mg min/L and UV doses greater than 30 mJ/cm 2 . However, UV was less effective than ozone in reducing F m values in raw water samples. Complete removal of the microbiological component of the decay for raw water samples was not found either with ozone (even with Ct of 50 mg min/L) or UV (even with UV dose of 120 mJ/cm 2 ). The effects of pre-oxidation processes on chemical (k c ) and microbial (k m ) decay coefficients were assessed. Increasing both ozone Ct and UV dose ahead of chloramine did not affect the chemical decay component, but they changed the microbiological component of decay. Changes in organic matter after ozonation were also characterized using three-dimensional fluorescence excitation–emission matrix (3D-FEEM) spectroscopy, and correlations between 3D-FEEM spectroscopy results and F m values were found. Intensities of humic-like, fulvic-like, microbial protein-like and aromatic protein-like substances were reduced by pre-ozonation. Based on the 3D-FEEM results, we can confirm that the slowdown of monochloramine decay rate is due to the reduction of marine humic-like substances and soluble microbial protein-like compounds by pre-ozonation. Refereed/Peer-reviewed

A model was developed for estimation of N-nitrosodimethylamine (NDMA) concentration in a case study of a chloraminated water distribution system in Australia using influencing parameters that had an impact on NDMA formation via a hybrid genetic algorithm method. The model was based on hydraulic retention time, temperature, and monochloramine residual. The genetic algorithm and quasi-Newton optimization with a Broyden-Fletcher-Goldfarb-Shanno Hessian updating method were combined into a hybrid parameter optimization scheme for robust calibration of NDMA model parameters. In order to test the applicability and the accuracy of the proposed model, NDMA concentration and water quality characteristics for 220 post-disinfection water samples collected between 2006 and 2016 were used. Good agreement between measured and estimated NDMA concentrations was observed by performing statistical analysis on an independent set of water sample data (R2 = 0.93). This modeling approach has the potential to be used as a decision support tool in order to manage and improve the chloramine disinfection process. Refereed/Peer-reviewed

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 = 230. nm between apparent molecular weights of 200 to 1000. Da was observed at sampling sites that experienced rapid chloramine decay and nitrification while its absorbance signal at λ = 254. nm 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 254. nm, 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. Refereed/Peer-reviewed

Natural organic matter (NOM) is a heterogeneous mixture of organic compounds that is ubiquitous in surface waters. The character of NOM varies according to source, age and season. This variability can have an impact on the NOM reactivity during water treatment. In the present study, NOM removal efficiencies by TiO(2) photocatalysis from two Australian surface water samples were assessed by monitoring the concentration, absorbance in the ultraviolet range (200-350 nm), molecular weight distribution and the chemical polarity of the source and treated water. In addition, the potential of the treated waters to form trihalomethanes (THM) after chlorination were evaluated. From the two surface waters after photocatalysis, similar product distributions were observed, which indicates that the degradation process can be described in terms of a similar reaction pathway. The organics remaining in the treated water consist mostly of low molecular weight hydrophilic compounds with weak UV absorbance at wavelength of 254-260 nm, and little reactivity with chlorine to form THM. Most importantly, use of multiple complementary analytical approaches resulted in a better understanding of the photocatalytic degradation process and its products. Refereed/Peer-reviewed

In this study, we investigated the relationship between water characteristics and removal of natural organic matter (NOM) using polyaluminium chloride (PACl) and a newly developed coagulant obtained by hybridising PACl with chitosan (PACl-chitosan) for two different types of water. Using UV-visible spectroscopy analysis, we showed that PACl-chitosan is more effective than PACl for treating water samples that contain higher levels of activated polyhydroxyaromatic moieties. As a result, a lower level of total trihalomethanes formation potential (THMFP) was detected for synthetic water treated with PACl-chitosan coagulant compared to water treated with PACl only. In contrast, no difference was observed for the total THMFP that were formed following coagulation with either coagulant, for water sample containing the same level of organic carbon concentration, but lower levels of polyhydroxyaromatic moieties. Our work shows how the complex characteristics and interactions of organic matter with coagulant component can affect the outcome of the treatment process, and in this case, enhance the treatment. The use of PACl-chitosan was also shown to produce larger floc for both water samples; this again, can lead to better removal. Refereed/Peer-reviewed

In this study, the formulation of a novel polyaluminum chloride-chitosan composite coagulant that improves the coagulation process for natural organic matter (NOM) removal was investigated. The performance of the composite coagulant was tested using two water sources (synthetic and natural water) to develop a better understanding on the behaviour of the composite coagulant. Fourier Transform-Infra red (FT-IR) spectroscopy, ferron analysis and zeta potential studies were performed to characterise the composite coagulant. FT-IR analysis showed that there is an intermolecular interaction between Al species and chitosan molecules, while ferron analysis indicated that the distributions of Al a, Al b, and Al c in PACl-chitosan are different from those in PACl. At a low Al dosage (2.16 mg L -1), a much higher removal of NOM from synthetic water, as evidenced from UV 254 and Dissolved Organic Carbon (DOC) measurements, was achieved by the composite coagulants in comparison to that removed by PACl or PACl and chitosan added separately. For natural water from the Myponga Reservoir, both polyaluminum chloride (PACl) and PACl-chitosan composite coagulants demonstrated similar dissolved organic carbon (DOC) percentage removal, whereas PACl-chitosan gave a slight improvement in removing the UV 254 absorbing components of NOM. Refereed/Peer-reviewed

The effect of TiO(2) photocatalytic oxidation on the natural organic matter (NOM) properties of two Australian surface waters were quantified using UV-vis spectroscopy, high performance size exclusion chromatography (HPSEC) with a multi-wavelength UV detector, liquid chromatography with organic carbon detector (LC-OCD), and trihalomethane formation potential (THMFP) analyses. Both the UV absorbance at wavelengths greater than 250 nm and dissolved organic carbon (DOC) content decreased significantly with treatment, although complete mineralization of NOM could not be achieved. Multiwavelength UV detection of HPSEC analysis was shown to be useful to display further changes to NOM composition and molecular weight profiles because the organic molecules was transformed into compounds that absorb weakly at the typical detection wavelength of 250-260 nm. The multi-wavelength HPSEC results also revealed that photocatalytic oxidation yields by-products with a low aromaticity and low molecular weight. The LC-OCD chromatograms indicated that low molecular acids and neutral compounds remained after photocatalytic oxidation. Those groups of compounds did not seem to contribute significantly to the formation of trihalomethanes. Refereed/Peer-reviewed