Advanced Water Treatment Plant Research Articles

Adsorption and desorption processes of trihalomethanes on different granulated activated carbons in a full-scale advanced water treatment plant

Abstract Trihalomethanes (THMs) are one of the main disinfection by-products generated in drinking water (DW). To control health risks caused by THMs several countries have established a maximum content of these chemicals in DW. THMs can be removed by granular activated carbon (GAC) and their adsorption processes have been studied by different authors. However, there are few studies on their desorption from GAC and no data are available on their desorption at a full scale. This paper summarises the results obtained in the monitoring of the adsorption and desorption processes of THMs at a full-scale DW plant considering different types and stages of GACs, as well as several types of influent waters. This research was carried out during 3 years in a full-scale advanced DW plant (6.25 m3·h−1) that can use four different pre-oxidants. An increase on THMs concentration in the outlet of the AC filters due to desorption processes were checked, although the obtained doses were always far below the established European limit (100 μg/L).

Dissolved Organic Matter Fractions and Their Removal in Full-Scale Drinking Water Treatment Process

Objectives:The objective of this study is to investigate characteristics about removal of dissolved organic matter (DOM) and its fraction for improving operation efficiency in an advanced water treatment plant. Methods:The monitoring of water quality was conducted at five processes such as raw water, pre-oxidation, after sedimentation, post-ozonation, after biological activated carbon (BAC) from July 2020 to August 2021 in advanced water treatment process (AWTP) supplying 180,000m<sup>3</sup>/day. The concentration of DOC (dissolved organic carbon) and number of algae were monitored and LC-OCD was used to fractionate DOC to four species, biopolymer (BP), humic substance (HS), building blocks (BB), and low molecular weights (LMWs). Results and Discussion:The characteristics of raw water showed that the concentration of DOC and the number of algae increased with an increase in water temperature. The portion of BP and HS significantly increased at low and high water temperature, respectively, while BB and LMWs maintained the similar portion. The removal efficiency of DOC in the AWTP was achieved at 59% with each species of BP, HS, BB, and LMWs obtaining removal efficiency of 87%, 65%, 26%, and 52%, respectively. Coagulation/sedimentation/filtration showed removal efficiency of 84%, 56%, 20%, and 18% for BP, HS, BB, and LMWs, respectively, corresponding to their molecular weight. The effect of post-ozonation would be negligible except for BP. In BAC, removal efficiency of 49% and 12% were obtained for LMWs and BB (low molecular weight, respectively. As a result, the BP portion significantly decreased due to high removal efficiency, while BB portion was increased in the final treated water compared to raw water. Conclusion:Most of DOM was removed in coagulation/sedimentation/filtration and BAC, whereas oxidation process such as pre-chlorination, pre-ozonation and post-oxidation did not have an effect on DOM removal. In coagulation/sedimentation/filtration, 84% and 54% of the BP and HS were removed, while BAC removed 49% and 12% of LMWs and BB, respectively. It has been recommended to improve the removal efficiency of BB, which obtained the lowest removal efficiency in AWTP, and to enhance the removal efficiency of LMWs in BAC to inhibit microbial regrowth in the distribution system.

Removal of natural organic matter in full-scale conventional and advanced water treatment plants: Assimilable organic carbon and its precursors

This study aimed to investigate the performance of three full-scale long-time water treatment plants with influent from Taihu Lake for the removal of natural organic matter (NOM) and assimilable organic carbon (AOC), emphasizing on the processes of pre- and post-ozonation and biological activated carbon filtration (BACF). High-performance size exclusion chromatography (HPSEC) separation, hydrophilicity/hydrophobicity resin fractionation and excitation-emission matrix (EEM) fluorescence spectroscopy were applied to determine NOM fraction variation in purification processes and their relationships with AOC. The results indicated that NOM fractions with high hydrophilicity (NHPI) and lower molecular weight (1 kDa - 10 kDa) likely contributed to the majority of AOC. The advanced water treatment processes behaved negative removals of AOC since the BACF with long-time operation introduced large amounts of AOC precursors and could cause drastic rebound of AOC upon chlorination disinfection. Finally, during exposure to ozone, the formation rate of AOC showed a linear relationship with UV254 and total fluorescence intensity (TFI) and each regional fluorescence intensity (RFI) with slight interference by the presence of particulate organic matter (POM). This study provides useful information for variation of NOM and its associated bio-availability during conventional and advanced processes in full-scale water treatment plants.

Analysis of Perfluorinated Compounds (PFCs) in Water using a Delay Column and an On-line SPE LC-MS/MS System

To ensure the safety of the citizens of Daegu with respect to drinking water sources, we continuously monitored trace pollutants in the Nakdong River basin. Perfluorinated compounds (PFCs) had been detected in the Nakdong River previously; thus, further low-concentration detection is required. We developed an LC-MS/MS analysis method using the online SPE approach for fast and simple detection of low-concentration PFCs. In this process, a delay column was used to assess PFC contamination. As a result, quality control analysis of eight standard PFCs using this method showed strong correlations, with correlation coefficients of 0.991 and more, and the limit of quantification was 0.5 to 1.7 ng/L. The recovery rates of PFCs from samples ranged from 75.3% ± 1.23% to 118.0% ± 1.39%, suggesting robustness of this method. Analyses of PFC at seven sampling points in the Nakdong River basin showed high PFC concentrations at the point where effluent from a sewage treatment plant was introduced. PFHxS, PFOA, and PFOS values, which were used as drinking water monitoring standards of treated water at the Daegu advanced water treatment plant, did not exceed the monitoring standards. Therefore, these results demonstrate that the established method is appropriate as an analytical tool for assessing low-concentration PFCs in drinking water. Key Words: Nakdong River, PFCs, Delay column, on-line SPE, PFHxS

A Study on the Comparative Analysis of 2-MIB Treatment Characteristics and Optimization of Process Operation in 2-types of Advanced Water Treatment Plants in the Han River Water Supply System

Objectives:In this study, through the results of the high-concentration 2-MIB (2-Methyl Isoborneol) treatment by two different types of advanced treatment plants (Post Peroxone+GAC, UV/H2O2+GAC F/A) which intake raw water from the same water intake facility, the 2-MIB removal characteristics by oxidation process of each WTPs (Water Treatment Plants) were compared and analyzed, and optimal operation methods were derived.Methods:The 2-MIB removal rate was compared and analyzed according to each AOP (Advanced Oxidation Process) operating conditions (Post Peroxone+GAC of the G WTP and UV/H2O2+GAC F/A of the I WTP). The optimal equations of chemical injection were derived through the correlation between the operating conditions of the AOP for each WTPs and 2-MIB removal rate. By analyzing the operating characteristics of each WTPs, the cost and unit price for optimal operation were calculated according to the 2-MIB concentration of raw water and water production. Optimal operating conditions were derived through the performance of oxidation facilities and chemical injection equations of each WTPs, and economical operating plans were reviewed through linked operation of 2 WTPs.Results and Discussion:The 2-MIB removal rates for each WTPs were 70~100% for the G WTP and 50~96% for the I WTP. The operating conditions affecting the 2-MIB removal were [O3 injection×contact time], H2O2/O3 for Post Peroxone of the G WTP, and [UV dose×H2O2 injection] for UV/H2O2 of the I WTP. As a result of comparing the operating cost(electric power cost + chemical cost) of each WTPs, I WTP was 6.6~24.3 KRW/m3 higher than G WTP. It is considered to be because the H2O2 injection was 11~43 times for UV/H2O2 than Post Peroxone. Optimal operating conditions could be derived through the performance evaluation of each oxidation facilities and chemical injection equations of each WTPs. The G WTP and the I WTP are equipped with pipe line for linked operation in the water supply pipes, so the water production for each WTPs can be distributed. In the case of the same water production, it was confirmed that the unit price can be reduced when the water production ratio of the G WTP is increased. Because the decrease in cost of the I WTP is higher than the increase in cost of the G WTP.Conclusions:It was confirmed that both Post Peroxone+GAC of G WTP and UV/H2O2+GAC F/A of I WTP were effective in 2-MIB treatment. As for the operating cost, it was analyzed that UV/H2O2 had higher unit pice than Post Peroxone because of the large amount of H2O2 injection. Considering the 2-MIB removal rate and operating cost of each WTPs, it was possible to derive the optimal operating conditions for each WTPs and a linked operation plan.

Effects of ozonation on disinfection by-product formation potentials and biostability in a pilot-scale drinking water treatment plant with micro-polluted water

ABSTRACT The accelerated urbanization in China has caused intensified micro-pollution problems for drinking water sources, severely challenging drinking water treatment efficiencies and its biostability. This study mainly investigated the effects of ozonation on disinfection by-product formation potentials (DBPFPs) and biological dissolved organic carbon (BDOC) in a pilot-scale ozonation-biological activated carbon advanced drinking water treatment plant with micro-polluted raw water. The results indicated that the micro-polluted water would be effectively treated in the advanced treatment processes with DBPFPs significantly eliminated. The total removal rates of trihalomethane formation potentials (THMFPs) and haloacetic acid formation potentials (HAAFPs) increased with the elevated ozone dosage to finally a relatively stable stage, and the maximum removal rates of 77.3% and 57.0%, respectively, were achieved at the ozone dosage of 2 mg/L. The bromine incorporation in total THMFPs (TTHMFPs) was dramatically suppressed after integrated advanced treatment processes, while that in total HAAFPs (THAAFPs) was promoted with the corresponding increment of up to 25.3% for bromine incorporation factor, which caused relatively high brominated HAAFP proportions in the treated water than in the raw water. In addition, the BDOC generation rate and THAAFP removal rate during the post-ozonation treatment displayed apparent positive correlation, and a similar relationship was observed for the BDOC degradation rate and TTHMFP removal rate during the BAC treatment in the studied ozone dosage (1 ∼ 5 mg/L). The findings strongly implied a promising alternative to measure DBPFP removal rate instead of BDOC level for more sensitive and convenient monitoring of the biostability in the reclaimed water.

Behavior of perfluorinated compounds in advanced water treatment plant

Behavior of perfluorinated compounds in advanced water treatment plant

Seasonal occurrence and removal of organophosphate esters in conventional and advanced drinking water treatment plants

In this study, the fate of organophosphate esters (OPEs) in conventional and advanced drinking water treatment plants (DWTPs) was investigated in field scale. In addition, the risk of OPEs by drinking water was assessed. The average total OPE concentrations in raw and treated water were lower in the rainy season (94.3 and 57.1 ng/L, respectively) than dry season (163 and 84.2 ng/L, respectively). Advanced DWTPs showed better removal efficiencies of major OPEs rather than those in conventional DWTPs. The average removal rates for two chlorinated OPEs, including tris(2-chloroethyl)phosphate (TCEP) and tris(1-chloro-2-propyl)phosphate (TCIPP), were negative (TCEP: −87%, TCIPP: −41%) for a conventional DWTP but positive (TCEP: 46%, TCIPP: 49%) for advanced DWTPs using granular activated carbon filtration. The average removal rates for advanced DWTPs were statistically higher for the alkyl/aryl OPEs, tri-n-butyl phosphate (TNBP: 67%) and tris(2-butoxyethyl) phosphate (TBOEP: 63%), than those for the conventional DWTPs (TNBP: 21%, TBOEP: 25%). The hazardous quotient (HQ) of major OPEs were lower for advanced DWTPs and water irrigated from upstream sties/reservoir compared to that of conventional DWTPs and water irrigated from downstream sites. We believe that this is the first comparison of OPE removal efficiencies achieved in conventional and advanced DWTPs.

Identification of emerging contaminants and their transformation products in a moving bed biofilm reactor (MBBR)-based drinking water treatment plant around River Yamuna in India.

The prevalence of emerging contaminants of concern in water regimes is very common these days. High anthropogenic intervention is leading to occurrence of various types of microcontaminants of concern in drinking water systems. Their removal using conventional form of treatment systems employed in water treatment plants is not widely researched upon. Their fate in the conventional as well as advanced water treatment system needs to be focused upon for efficient and safe water disposal. Some compounds may leave the system unchanged or some might transform into much more toxic byproduct. Moreover, understanding level of occurrence of these emerging contaminants in source water bodies is also quintessential for assessing their fate in treatment plant itself as well as in the final treated water. Here in this study, the occurrence and removal of various classes of emerging contaminants were investigated in a moving bed biofilm reactor (MBBR)-based advanced drinking water treatment plant (ADWTP) alongside one conventional drinking water treatment plant, both of which use River Yamuna as the source of water. Non-target analysis utilizing high-performance liquid chromatography combined with time of flight (HPLC-QToF) identified more than 300 compounds. Pharmaceuticals accounted for a major fraction (58%) of the identified compounds, followed by plasticizers and insecticides. Nine parent compound and their transformation products were additionally identified using solid-phase extraction followed by analysis using gas chromatography mass spectrometry and HPLC-QToF. The degradation pathway of the parent compounds in MBBR-based ADWTP was also analyzed in depth. The efficiency of each unit process of MBBR-based drinking water treatment plant was studied in terms of removal of few emerging contaminants. Pharmaceutical compound like diclofenac supposedly was persistent, even, toward the end of the treatment train. Semi-quantitative analysis revealed ineffective removal of pyridine, hydrochlorothiazide, and diethyl phthalate in the outlet of ADWTP. ADWTP was able to remove a few emerging contaminants, but a few were recalcitrant. Likewise, it was established that although some parent compounds were degraded, much more toxic transformation products were formed and were prevalent at the end of the treatment.

Monitoring NDMA precursors throughout membrane-based advanced wastewater treatment processes by organic matter fluorescence

This study investigates the potential of fluorescence excitation/emission matrices (EEM) measurement as a tool to predict N-Nitrosodimethylamine (NDMA) formation in water reuse applications. In particular, samples from a pilot-scale membrane biological reactor (MBR) followed by nanofiltration (NF) advanced water treatment plant, are used for the study. Concentrations of both, specific NDMA precursors and NDMA formation potential (FP) are correlated with different EEM peaks. The specific precursors investigated are: erythromycin, azithromycin, clarithromycin, venlafaxine, o-desmethylvenlafaxine, ranitidine and citalopram, while the NDMA FP is conventionally measured by the NDMA formation potential test. EEM peaks investigated are obtained by fluorescence regional integration as well as by the peak picking method generating I1, I2, I3, I4, and I5 peaks. Results showed that protein-like materials are correlated with the bulk NDMA FP and specific NDMA precursors. Additionally, selected fluorescence peaks such as I1, I2 and I4 are strongly correlated with NDMA precursors throughout the MBR-NF pilot plant. The removal of NDMA precursors and EEM peaks also correlated well (R2 > 0.8). This data shows that fluorescence EEM can be a promising tool to monitor the concentration of NDMA precursors and their removal in water reuse application.

Characterization of natural organic matter and assimilable organic carbon from an advanced full-scale drinking water treatment plant to tap

Characterization of natural organic matter and assimilable organic carbon from an advanced full-scale drinking water treatment plant to tap

Pilot Plant Performance Comparing Carbon-Based and Membrane-Based Potable Reuse Schemes

Two pilot-scale advanced water treatment plants using tertiary-treated biological nutrient removal wastewater effluent were operated simultaneously to demonstrate and compare treatment performances and process operations. Final effluent from both the plants was compared for its suitability to recharge a potable water supply aquifer. The two treatment approaches included a carbon-based treatment process (flocculation/sedimentation, ozone-biofiltration, granular activated carbon (GAC) adsorption, ultraviolet (UV) disinfection; 20,000 L/day) and a membrane-based treatment process (ultrafiltration, reverse osmosis, UV-hydrogen peroxide advanced oxidation; 160,000 L/day). Both processes were found to be reliable in producing water that met all United States Safe Drinking Water Act's primary maximum contaminant levels (MCLs). The carbon-based process often exceeded the secondary MCL for total dissolved solids due to background salinity in the source water. Results showed that both systems performed comparably with respect to removal of pathogens, fecal indicators, and contaminants of emerging concern. Total organic carbon (TOC) was removed to below 0.5 mg/L by the membrane-based process. For the carbon-based process, GAC media exhaustion over the course of the pilot operation resulted in an increase in finished water TOC from <0.5 to ∼4 mg/L. Disinfection byproducts, including trihalomethanes and haloacetic acids were not measured above their respective MCL after 8 h of free chlorine contact in a simulated distribution system test. N-nitrosodimethylamine was removed below 10 ng/L by the GAC with 20 min of empty bed contact time after 20,000 bed volumes.

Occurrence and removal of microplastics in an advanced drinking water treatment plant (ADWTP)

Microplastics (MPs) have attracted worldwide attention as the emerging persistent pollutants. Since they have been detected in raw water and the treated water of drinking water treatment plants (DWTPs), there was an urgent need to explore the properties and fates of microplastics in DWTPs. The characteristics of the effluent MPs from each treatment unit in an advanced drinking water treatment plant (ADWTP) were studied, and the relationship between the variations of MPs and the removal performances of treatment processes was also explored. Overall, both the coagulation combined with sedimentation and the granular activated carbon (GAC) filtration performed well in removing microplastics. The former had a removal efficiency of about 40.5–54.5%, mainly for fibres' removal, and the presence of GAC filtration reduced the microplastic abundance by about 56.8–60.9%, mainly for small-sized MPs. It was worthy of attention that a larger amount of polyacrylamide (PAM) was detected in the effluent of the sedimentation compared to raw water, which was caused by the usage of coagulant containing PAM. Specially, the number of 1–5 μm MPs in the effluent of ozonation tank was increased by 2.8–16.0%, resulting in a negative removal efficiency in ozonation. The removals of microplastics were depended primarily on their physical properties (size and shape).

Wastewater recycling in Antarctica: Performance assessment of an advanced water treatment plant in removing trace organic chemicals

The Australian Antarctic Division (AAD) operates Australia's Davis Station in the Antarctic. In 2005, Davis Station's wastewater treatment plant failed and since then untreated, macerated effluent has been discharged to the ocean. The objectives of this study were to determine whether an advanced water treatment plant (AWTP) commissioned by the AAD and featuring a multi-barrier process involving ozonation, ceramic microfiltration, biologically activated carbon filtration, reverse osmosis, ultraviolet disinfection and chlorination was capable of producing potable water and a non-toxic brine concentrate that can be discharged with minimal environmental impact. The AWTP was tested using water from a municipal wastewater treatment plant in Tasmania, Australia. We used spot water and passive sampling combined with two multi-residue chromatographic-mass spectrometric methods and a range of recombinant receptor-reporter gene bioassays to screen trace organic chemicals (TrOCs), toxicity and receptor activity in the Feed water, in the environmental discharge (reject water), and product water from the AWTP for six months during 2014–15, and then again for three months in 2016. Across the two surveys we unambiguously detected 109 different TrOCs in the feed water, 39 chemicals in the reject water, and 34 chemicals in the product water. Sample toxicity and receptor activity in the feed water samples was almost totally removed in both testing periods, confirming that the vast majority of the receptor active TrOCs were removed by the treatment process. All the NDMA entering the AWTP in the feed and/or produced in the plant (typically < 50 ng/L), was retained into the reject water with no NDMA observed in the product water. In conclusion, the AWTP was working to design, and releases of TrOCs at the concentrations observed in this study would be unlikely cause adverse effects on populations of aquatic organisms in the receiving environment or users of the potable product water.

Developing a comprehensive framework for eutrophication management in off-stream artificial lakes

In this paper, a comprehensive and interdisciplinary framework for management of eutrophication in off-stream artificial lakes in semi-arid and arid regions is proposed. Identification of the lake’s water resources system components and stakeholders, simulation of Phosphorus (P) export from upstream watershed, simulation of the lake water quality as well as simulation of water demands and supply, development of management scenarios for the lake and selecting the best scenario using social choice methods (i.e. discrete and fuzzy Borda counts) are the four main parts of the framework. The proposed framework is applied on Chitgar Artificial Lake (ChAL), the largest intra-urban artificial lake in Tehran which has been constructed in 2010–2013 for recreational purposes. The Load Apportionment Model (LAM) is used for the simulation of P loads from the point and non-point (diffusive) sources and the LakeMab model is used for the simulation of P dynamics in the lake. The management scenarios contain optimized rule curves for water intake/outtake blended with P management plans (i.e. removal of point sources of P load in the upstream watershed, construction of a hydroponic bio-filter or an advanced water treatment plant beside the lake for reduction of external loading of P and recycling lake water, alum treatment of lake sediments for controlling the internal loading of P as well as construction of a dry detention basin). The most preferred scenarios selected by the discrete Borda count are the low-cost alum treatment and dry detention basin, while the most preferred scenario according to fuzzy Borda count, which considers the uncertainty of model inputs, is the costly water treatment plant. In all preferred scenarios, water intake is conducted from flood flows in order to avoid conflict with downstream agricultural demands. In addition to decentralized decision making and stakeholders’ participation, the proposed framework promotes the integration of the technical aspects such as the role of internal loading in lake eutrophication and separation of flood and non-flood flows in the off-stream lakes’ systems.

Economics of alternative water resources with an emphasis on aquifer storage and recovery

Abstract This paper demonstrates a comprehensive methodology for assessing the comparison of unit water production cost (UWPC) between alternative water resources including desalination, freshwater reservoirs, single-purpose dams, underground dams and two indirect water in take technologies – riverbank filtration and aquifer storage and recovery (ASR). This study considers the Monte Carlo simulation as the only viable solution to tackle this critical question, which can be used to evaluate the economics of diverse water supply schemes incorporating those alternatives and prepare long-term water supply planning. Built upon actual and conceptual cost data for each alternative, total project cost and operation and management cost estimation models for each alternative were developed and used for generating mean UWPC information using the Monte Carlo simulation approach. The mean UWPC differences between alternative water supply schemes were found to be statistically significant and the simulation results revealed that ASR is the lowest-cost option to provide drinkable water for both cases when a conventional water treatment plant (WTP) and advanced WTP were used as a connected post-treatment process.

Erratum to: A Visual Basic simulation software tool for performance analysis of a membrane-based advanced water treatment plant.

A Visual Basic simulation software (WATTPPA) has been developed to analyse the performance of an advanced wastewater treatment plant. This user-friendly and menu-driven software is based on the dynamic mathematical model for an industrial wastewater treatment scheme that integrates chemical, biological and membrane-based unit operations. The software-predicted results corroborate very well with the experimental findings as indicated in the overall correlation coefficient of the order of 0.99. The software permits pre-analysis and manipulation of input data, helps in optimization and exhibits performance of an integrated plant visually on a graphical platform. It allows quick performance analysis of the whole system as well as the individual units. The software first of its kind in its domain and in the well-known Microsoft Excel environment is likely to be very useful in successful design, optimization and operation of an advanced hybrid treatment plant for hazardous wastewater.

Characterization of suspended bacteria from processing units in an advanced drinking water treatment plant of China.

For the drinking water treatment plant (DWTP), the organic pollutant removal was the primary focus, while the suspended bacterial was always neglected. In this study, the suspended bacteria from each processing unit in a DWTP employing an ozone-biological activated carbon process was mainly characterized by using heterotrophic plate counts (HPCs), a flow cytometer, and 454-pyrosequencing methods. The results showed that an adverse changing tendency of HPC and total cell counts was observed in the sand filtration tank (SFT), where the cultivability of suspended bacteria increased to 34%. However, the cultivability level of other units stayed below 3% except for ozone contact tank (OCT, 13.5%) and activated carbon filtration tank (ACFT, 34.39%). It meant that filtration processes promoted the increase in cultivability of suspended bacteria remarkably, which indicated biodegrading capability. In the unit of OCT, microbial diversity indexes declined drastically, and the dominant bacteria were affiliated to Proteobacteria phylum (99.9%) and Betaproteobacteria class (86.3%), which were also the dominant bacteria in the effluent of other units. Besides, the primary genus was Limnohabitans in the effluents of SFT (17.4%) as well as ACFT (25.6%), which was inferred to be the crucial contributors for the biodegradable function in the filtration units. Overall, this paper provided an overview of community composition of each processing units in a DWTP as well as reference for better developing microbial function for drinking water treatment in the future.

Small Scale Direct Potable Reuse (DPR) Project for a Remote Area

An Advanced Water Treatment Plant (AWTP) for potable water recycling in Davis Station Antarctica was trialed using secondary effluent at Selfs Point in Hobart, Tasmania, for nine months. The trials demonstrated the reliability of performance of a seven barrier treatment process consisting of ozonation, ceramic microfiltration (MF), biologically activated carbon, reverse osmosis, ultra-violet disinfection, calcite contactor and chlorination. The seven treatment barriers were required to meet the high log removal values (LRV) required for pathogens in small systems during disease outbreak, and on-line verification of process performance was required for operation with infrequent operator attention. On-line verification of pathogen LRVs, a low turbidity filtrate of approximately 0.1 NTU (Nephelometric Turbidity Unit), no long-term fouling and no requirement for clean-in-place (CIP) was achieved with the ceramic MF. A pressure decay test was also reliably implemented on the reverse osmosis system to achieve a 2 LRV for protozoa, and this barrier required only 2–3 CIP treatments each year. The ozonation process achieved 2 LRV for bacteria and virus with no requirement for an ozone residual, provided the ozone dose was &gt;11.7 mg/L. Extensive screening using multi-residue gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–mass spectrometry (LC–MS) database methods that can screen for more than 1200 chemicals found that few chemicals pass through the barriers to the final product and rejected (discharge) water streams. The AWTP plant required 1.93 kWh/m3 when operated in the mode required for Davis Station and was predicted to require 1.27 kWh/m3 if scaled up to 10 ML/day. The AWTP will be shipped to Davis Station for further trials before possible implementation for water recycling. The process may have application in other small remote communities.

Evaluation of interfacial sulfate complexation by a bis-thiourea ionophore at water-organic interfaces using microelectrochemistry and high resolution mass spectrometry

Simple, fast and low cost methods for the detection of sulfate are required for different applications. Electrochemistry at water/o-nitrophenyloctylether (W/NPOE) interfaces was employed to evaluate sulfate detection by ionophore-facilitated ion-transfer at an array of micro-interfaces. With ionophore 1,3-[Bis(3-phenylthioureidomethyl)]benzene present in the NPOE phase, the transfer of sulfate across the interface was determined by voltammetry at ca. −0.35V for 0.01M Na2SO4 on the Galvani potential scale. The potentiometric detection limit for sulfate was 0.6×10−6M, based on the shift in the half-wave transfer potential with concentration. Amperometric detection limits for forward and reverse ion transfer currents were determined to be 14×10−6M and 0.8×10−6M, respectively. Electrochemical analysis of the half-wave potential versus logCSO42−w and the corresponding electrospray ionisation – high resolution mass spectrometry (ESI-HRMS) analysis of W/NPOE emulsions indicated interfacial complexation via the formation of 1:1 sulfate:ionophore complexes. ESI-HRMS analysis of W/NPOE emulsions formed with water samples from an advanced water treatment plant revealed the binding of the ionophore to potential interferences from this environment, thus providing a guide to sensor development.