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Monitoring low levels of ammonia in chloraminated water can be challenging but is important for effectively managing potable water disinfection. The lower the concentration of free ammonia that can be determined, the tighter the control at the disinfection point, which supports better maintenance of chloramine residuals in the distribution system. In this study a micro-distillation technique was used to selectively separate ammonia into a boric acid solution allowing determination by conductance (i.e., micro-distillation and conductance measurement instrument - Micro-DCMI). The optimised technique had a linear calibration range of 0.01–60 mg NH 3 L−1 with a limit of detection (LOD) of 0.014 mg L−1 and limit of quantification (LOQ) of 0.045 mg L−1. With the optimum operational parameters of 80 °C distillation temperature, 0.3 L min−1 air flow rate, 0.1 mol L−1 boric acid concentration and 8 min pre-concentration time, a sample throughput of 7 samples per hour was achieved. A laboratory comparison between Micro-DCMI and the standard ammonia selective electrode method was conducted on water samples obtained from a chloraminated drinking water distribution system. The results showed that the ratios of the free ammonia values determined by Micro-DCMI and an ammonia selective electrode were between 0.82 and 1.2 for 11 water samples. A custom-built automated analytical system was evaluated at a water treatment plant in Australia and the results compared favourably with the in plant online ammonia ion selective analyser. This study indicated that the Micro-DCMI method was a simple, robust and low cost online monitoring system suitable for determining low concentration ammonia to manage chloramination. fx1 • A new monitoring technique, using microstill and conductance detection, for low level ammonia in chloraminated water. • The Micro-DCMI successfully determined low level ammonia at the water filtration plant. • The Micro-DCMI provided precise ammonia measurement compared with ammonia selective electrode method. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Insufficient dissolved organic matter removal results in higher residual organics (measured as dissolved organic carbon, DOC) in the treated water which can act as precursors for disinfection by-products (DBPs) and consequently increases the potential for health risk. This study aims to use drinking water treatment sludge (DWTS) as a coagulant-aid to improve the DOC removal efficiency. The effect of various DWTS doses (between 0.5 and 3 g/L) on the coagulation performance (by alum) to treat natural surface water that has relatively low turbidity and high DOC at optimum pH (~6) was examined using standard jar tests procedure. Although addition of DWTS at doses lower than 1.5 g/L improved the DOC removal efficiency (by 4% and 12% at DWTS dose of 0.5 and 1.0 g/L, respectively), the turbidity levels increased. In comparison to optimum dose of alum without DWTS, the addition of DWTS at 3 g/L led to reduce the alum dose to ~50% to achieve similar removal efficiency of organics (70% DOC removal). Further, addition of DWTS improved the floc's characteristics (achieve larger flocs and rapid growth rate; measured by photometric dispersion analyser, PDA) and settling rate significantly, and the produced sludge volume decreased by ~50% compared to the figure with no DWTS addition. Trihalomethane formation potential (THMFP) was also reduced (up to ∼ 30%) when DWTS used. The results indicate that DWTS reuse as a coagulant-aid has the potential to reduce DOC and control DBPs formation when the organic loads require high coagulant dose exceeding the WTP design limits. [Display omitted] • Drinking water treatment sludge (DWTS) used as a coagulant-aid. • DWTS improved organics removal effectively and reduced the required alum dose. • Floc settling ability enhanced greatly by DWTS addition and produced less sludge volume. • DWTS improved the removal of humic substances with molecular weight in the range of 1–3 kDa. • DWTS decreased the trihalomethanes formation potential (THMFP). [ABSTRACT FROM AUTHOR]

Abstract: Observations from many countries around the world during the past 10–20 years indicate increasing natural organic matter (NOM) concentration levels in water sources, due to issues such as global warming, changes in soil acidification, increased drought severity and more intensive rain events. In addition to the trend towards increasing NOM concentration, the character of NOM can vary with source and time (season). The great seasonal variability and the trend towards elevated NOM concentration levels impose challenges to the water industry and the water treatment facilities in terms of operational optimisation and proper process control. The aim of this investigation was to compare selected raw and conventionally treated drinking water sources from different hemispheres with regard to NOM character which may lead to better understanding of the impact of source water on water treatment. Results from the analyses of selected Norwegian and Australian water samples showed that Norwegian NOM exhibited greater humic nature, indicating a stronger bias of allochthonous versus autochthonous organic origin. Similarly, Norwegian source waters had higher average molecular weights than Australian waters. Following coagulation treatment, the organic character of the recalcitrant NOM in both countries was similar. Differences in organic character of these source waters after treatment were found to be related to treatment practice rather than origin of the source water. The characterisation techniques employed also enabled identification of the coagulation processes which were not necessarily optimised for dissolved organic carbon (DOC) removal. The reactivity with chlorine as well as trihalomethane formation potential (THMFP) of the treated waters showed differences in behaviour between Norwegian and Australian sources that appeared to be related to residual higher molecular weight organic material. By evaluation of changes in specific molecular weight regions and disinfection parameters before and after treatment, correlations were found that relate treatment strategy to chlorine demand and DBP formation. [Copyright &y& Elsevier]

• Pozzolanic reactivity of drinking water sludge ash prevails after 7 days for curing. • The filler effect of sludge ash dominates the reaction kinetic at an early age. • Unreacted sludge ash may deteriorate the mechanical performance of cement composites. • Sludge ash alters hydration products' phases. • Concrete blocks incorporating 10% sludge ash exhibit competitive compressive strength. The effect of drinking water sludge ash (DWSA) on the properties of DWSA-cement pastes is investigated in this study using x-ray diffraction, scanning electron microscopy coupled with energy-dispersive spectrometry, and thermogravimetry techniques. The pozzolanic reactivity of DWSA is confirmed; the filler effect of DWSA can significantly and rapidly accelerate the hydration reaction at an early curing age. The presence of DWSA in blended pastes promotes the incorporation of aluminum into the C-(A)-S-H gel; the original 'Al-minor' C-(A)-S-H gel in pure cement paste is converted to 'Al-rich' C-(A)-S-H gel. The added DWSA leads to the formation of aluminum-bearing hydrates, such as ettringite and calcium aluminate hydrates (C-A-H). The compressive strength of sludge-derived concrete blocks is studied; blocks containing 10% DWSA exhibited higher compressive strength at a curing age of 90 d than the reference samples. Such benefits are not observed in block samples with 20 and 30% DWSA, which is attributed mainly to the physical effect of unreacted DWSA particles. [ABSTRACT FROM AUTHOR]

The spectra fingerprint of drinking water from a water treatment plant (WTP) is characterised by a number of light-absorbing substances, including organic, nitrate, disinfectant, and particle or turbidity. Detection of disinfectant (monochloramine) can be better achieved by separating its spectra from the combined spectra. In this paper, two major focuses are (i) the separation of monochloramine spectra from the combined spectra and (ii) assessment of the application of the machine learning algorithm in real-time detection of monochloramine. The support vector regression (SVR) model was developed using multi-wavelength ultraviolet-visible (UV-Vis) absorbance spectra and online amperometric monochloramine residual measurement data. The performance of the SVR model was evaluated by using four different kernel functions. Results show that (i) particles or turbidity in water have a significant effect on UV-Vis spectral measurement and improved modelling accuracy is achieved by using particle compensated spectra; (ii) modelling performance is further improved by compensating the spectra for natural organic matter (NOM) and nitrate (NO3) and (iii) the choice of kernel functions greatly affected the SVR performance, especially the radial basis function (RBF) appears to be the highest performing kernel function. The outcomes of this research suggest that disinfectant residual (monochloramine) can be measured in real time using the SVR algorithm with a precision level of ± 0.1 mg L−1. [ABSTRACT FROM AUTHOR]

In recent decades, industrial by-products have gained significant attention for their potential as components of more environmentally friendly construction materials. In this context, this paper presents the manufacture of concrete blocks (CB), in which sand was replaced with oven-dried drinking water treatment sludge (DWTS). In addition, CB with DWTS contents ranging from 0% to 30% by weight were exposed to early-age carbonation curing. Experiments were conducted to determine the compressive strength, splitting tensile strength, and water capillary absorption of CB subjected to normal or early-age carbonation curing. The results indicated that DWTS degraded durability and mechanical properties of CB because of the high-water absorption and high organic content of DWTS. However, early-age carbonation curing was found to improve the overall performance of CB with DWTS, such that the carbonated CB mixtures satisfied the strength requirement of load-bearing blocks. The pH values of CB after carbonation curing increased with increasing content of DWTS. Microstructural analyses showed that the addition of DWTS into CB caused the formation of ettringites because of the presence of alum and gypsum in DWTS, and early-age carbonation curing decomposed these ettringite into calcium carbonates. The results also showed that the production of crystalline CaCO 3 under carbonation had a filling effect that refined the pore sizes. Thus, the findings of this study indicate that utilisation of DWTS in CB offers significant environmental and health benefits via increased greenhouse gas absorption, as well as reduced DWTS disposal in landfills and unsustainable sand extraction. • Drinking water treatment sludge can be used as fine aggregate in concrete blocks. • Early-age carbonation curing mitigated the adverse effect of the sludge. • Microstructure revealed higher CaCO 3 and less ettringite in carbonated blocks. [ABSTRACT FROM AUTHOR]

The management of abundant drinking water treatment sludge (DWTS) in landfill remains an important issue. The reuse of DWTS as construction material could contribute to the development of greener concrete product and to mitigating the detrimental environment effect from excessive production of DWTS. This paper investigates the potential of using DWTS as sand replacement in Concrete Paving Blocks (CPB). Five CPB mixtures were designed and the replacement ratios of sand by DWTS were 0%, 5%, 10%, 15%, and 20%, by weight. Properties of CPB such as compressive strength, water absorption, abrasion resistance, sulfate attack and metal leachability were determined. The results indicated that above 10% of DWTS, the replacement was detrimental to such properties of the CPB. Microstructure analysis proved the addition of DWTS could result in ettringite formation and the interfacial transition zone (ITZ) between the cement matrix and DWTS was more porous than that of sand. In addition, the metal leachability test of CPB demonstrated that the addition of high-copper DWTS into CPB was safe. • Drinking water treatment sludge has potential as aggregates for paver production. • Reduction in strength and durability of pavers was observed, except 5% sludge type. • Maximum 10% of sand replaced by sludge is feasible for paving blocks. • SEM and XRD analyses confirm the formation of ettringite induced by sludge. [ABSTRACT FROM AUTHOR]

Abstract: In order to understand and improve drinking water treatment process operations, many techniques have been established to characterize natural organic matter (NOM). Resin fractionation is the most widely used technique to isolate NOM based on its hydrophobicity and hydrophilicity, these can be used to determine the treatability of NOM, 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 of the hydrophobicity/hydrophilicity of NOM. The reduction of total RPHPLC peak area correlated well with dissolved organic carbon (DOC) and UV absorbance at 254nm (UV254) removal efficiency. After resolving the RPHPLC profile using a peak fitting technique, the ratio between hydrophobic and hydrophilic peak area can be used to quantify the treatability of NOM (particularly DOC removal). Further statistical analysis grouped the resolved peaks into three groups (two groups of hydrophilic and one group of hydrophobic) and established an expression to link peak area with UV254 and DOC removal. The characterization results were further compared by the traditional resin fractionation technique using DAX-8 and XAD-4 resins (combined). The results confirmed that despite the definition that hydrophobic and hydrophilic components measured by both methods could be different, both methods confirm that the hydrophilic fraction was recalcitrant after coagulation and is of small molecular weight. [Copyright &y& Elsevier]

Abstract: Cyanobacterial metabolites, both toxic and non-toxic, are a major problem for the water industry. Nanofiltration (NF) may be an effective treatment option for removing organic micropollutants, such as cyanobacterial metabolites, from drinking water due to its size exclusion properties. A rapid bench scale membrane test (RBSMT) unit was utilised to trial four NF membranes to remove the cyanobacterial metabolites, microcystin, cylindrospermopsin (CYN), 2-methylisoborneol (MIB) and geosmin (GSM) in two treated waters sourced from the Palmer and Myponga water treatment plants. Membrane fouling was observed for both treated waters; however, only minor differences were observed between feed waters of differing natural organic matter (NOM) concentration. Low molecular weight cut-off (MWCO), or ‘tight’ NF, membranes afforded average removals above 90% for CYN, while removal by higher MWCO, or ‘loose’ NF membranes was lower. MIB and GSM were removed effectively (above 75%) by tight NF but less effectively by loose NF. Microcystin variants (MCRR, MCYR, MCLR, MCLA) were removed to above 90% by tight NF membranes; however, removal using loose NF membranes depended on the hydrophobicity and charge of the variant. Different NOM concentration in the treated waters had no effect on the removal of cyanobacterial metabolites. [Copyright &y& Elsevier]

Abstract: Cyanobacteria are a major problem for the world wide water industry as they can produce metabolites toxic to humans in addition to taste and odour compounds that make drinking water aesthetically displeasing. Removal of cyanobacterial toxins from drinking water is important to avoid serious illness in consumers. This objective can be confidently achieved through the application of the multiple barrier approach to drinking water quality and safety. In this study the use of a multiple barrier approach incorporating coagulation, powdered activated carbon (PAC) and ultrafiltration (UF) was investigated for the removal of intracellular and extracellular cyanobacterial toxins from two naturally occurring blooms in South Australia. Also investigated was the impact of these treatments on the UF flux. In this multibarrier approach, coagulation was used to remove the cells and thus the intracellular toxin while PAC was used for extracellular toxin adsorption and finally the UF was used for floc, PAC and cell removal. Cyanobacterial cells were completely removed using the UF membrane alone and when used in conjunction with coagulation. Extracellular toxins were removed to varying degrees by PAC addition. UF flux deteriorated dramatically during a trial with a very high cell concentration; however, the flux was improved by coagulation and PAC addition. [Copyright &y& Elsevier]