[Show abstract][Hide abstract] ABSTRACT: The application of ceramic membranes in water treatment is becoming increasing attractive because of their long life time and excellent chemical, mechanical and thermal stability. However, fouling of ceramic membranes, especially hydraulically irreversible fouling, is still a critical aspect affecting the operational cost and energy consumption in water treatment plants. In this study, four ceramic membranes with pore sizes or molecular weight cut-off (MWCO) of 0.20 μm, 0.14 μm, 300 kDa and 50 kDa were compared during natural surface water filtration with respect to hydraulically irreversible fouling index (HIFI), foulant composition and narrowing of pore size due to the irreversible fouling. Our results showed that the hydraulically irreversible fouling index (HIFI) was proportional to the membrane pore size (r2=0.89) when the same feed water was filtrated. The UF membranes showed lower HIFI values than the MF membranes. Pore narrowing (internal fouling) was found to be a main fouling pattern of the hydraulically irreversible fouling. The internal fouling was caused by monolayer adsorption of foulants with different sizes that is dependent on the size of the membrane pore.
Separation and Purification Technology 06/2015; DOI:10.1016/j.seppur.2015.04.039 · 3.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper presents an outline of the effects of photoelectrocatalytic operating parameters in a batch reactor on the kinetics of photo(electro) catalytic (PEC) oxidation, using phenol as a model compound. Process parameters and electrode configuration were varied to examine which mechanism becomes dominant under which conditions. The parameters studied were: the effect of the TiO2 layer thickness, agitation, different light intensities (UV300–400), and the initial concentration of phenol in an aqueous solution as encountered in practice.
Journal of Photochemistry and Photobiology A Chemistry 06/2015; 305. DOI:10.1016/j.jphotochem.2015.03.009 · 2.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sewage is a nutrient rich reliable water source that is rather consistent in quality, volume and temperature, and is available in large amounts in urban areas. Decentralised reclamation of water including its constituents from municipal sewage, further referred to as sewer mining, is a concept in which municipal sewage is considered a resource instead of a waste stream.
In this research, water reclamation in the sewer mining concept was studied using ceramic tight ultra- (UF) and ceramic nanofiltration (NF). In our current approach, ceramic membrane filtration is proposed as pre-treatment for reverse osmosis (RO) to produce demineralised water for industries from municipal sewage. The objectives of this research are to study (i) the membrane performance, (ii) the organic matter and ion rejection, and (iii) the biofouling potential of RO using permeate water from the ceramic filtration.
The application of ceramic tight UF and ceramic NF for direct treatment of domestic sewage has been demonstrated in this study. The cross flow ceramic tight UF and NF fed with filtered sewage, can be operated for 1–4 days without any cleaning required. The membrane performance remained high with chemical cleaning with NaClO (0.1%) and HCl (0.1 mol L−1) solutions. On average about 81% of organic matter was rejected by both ceramic tight UF and NF membranes. Finally, the pressure drop increase in the MFS fed with ceramic NF permeate was low during an operation of 14 days. These results were comparable with the increase in pressure drop of an MFS fed with Dutch drinking water.
[Show abstract][Hide abstract] ABSTRACT: Loose deposits (LD) accumulate in drinking water distribution systems (DWDS) and may lead to tap water discoloration incidents upon resuspension. While inconvenient for the consumers and the water companies, discoloration may be accompanied by degradation of the microbiological quality of the water, and possibly to the transport of bacteria. The presence of heterotrophic bacteria towards LD with different characteristics was investigated. Bacterial loads in discoloured water samples and LD concentrated over different settling times were analysed. Total heterotrophic (TH) bacteria numbers did not relate to turbidity or to suspended solids in discoloured waters. Higher affinities of TH were observed for slower-settling LD (<24 h), which were also richer in microbial extracellular polymeric substances. The detection of viable iron-oxidizing bacteria in LD supported their possible roles in LD formation and may be related to microbial growth/regrowth in DWDS. Results suggest that LD may exhibit low affinities to hold and transport bacteria, at least to TH in chlorinated water supplies.
Journal of Water Supply: Research and Technology - AQUA 02/2015; DOI:10.2166/aqua.2015.062
[Show abstract][Hide abstract] ABSTRACT: Alkalizing amines such as cyclohexylamine and dimethylamine have great potential for protecting steam-water cycles against corrosion, but their thermal stability is limited and anionic decomposition products are a concern due to increased corrosion risk. In this study morpholine, ethanolamine, cyclohexylamine, dimethylamine and 3-methoxypropylamine were exposed to 500, 530 and 560 ˚C at 9.5, 13.5 and 17.5 MPa to investigate the influence of temperature and pressure on amine thermolysis kinetics. The surface:volume ratio of the reactor tube was 0.4 mm-1, close to the value of superheater tubes in steam-water cycles. All amines thermolyzed by first order kinetics, with the exception of dimethylamine. The Arrhenius constants Ea, ln(A) and Va were obtained from the experimental data for all investigated amines. The influence of pressure on thermolysis kinetics was less pronounced than in previous studies and was different for each amine. Dimethylamine did not degrade below 20 and 10% at 500 and 530 ˚C respectively, in spite of longer retention times being applied, suggesting synthesis may occur. Limited practical data showed some promise for the applicability of the model to steam-water cycles. More plant data is necessary to fully validate the model. In all cases, thermolysis of the amines led to the formation of between 150 and 600 ppb organic acid anions. In most cases the concentrations increased linearly with increasing degradation percentage. Acetate and formate were found as major degradation products, with some propionate and traces of glycolate. Cationic degradation products were ammonia and some amines, meaning that the complete thermolysis of an amine does not necessarily lead to acidic conditions.
[Show abstract][Hide abstract] ABSTRACT: Forward osmosis (FO) processes, due to internal concentration polarisation, are limited with regards to flux. Improved flux performance will allow FO to compete with fluxes achieved by hydraulically driven membrane processes. Pressure assisted osmosis (PAO) is proposed to enhance FO performance, by adding hydraulic pressure (0.1-0.8 bar) on the feed side. An FO mass transport model (active layer to feed side orientation) incorporating pressure was developed to describe the fluxes in PAO. Continuous and discontinuous PAO operations on laboratory scale were proposed and evaluated using draw solutions equivalent to 24 bar osmotic pressure. The fluxes increased with increasing hydraulic feed pressures for all PAO experiments, including activated sludge feeds, owing to the increased driving force and membrane deformation. Discontinuous PAO was found to have an adverse effect on the salt fluxes, due to the subsequent pressure release. This study emphasizes the benefits of PAO for use in innovative membrane systems, while illustrating the importance of developing more rigid membranes and better support designs.
[Show abstract][Hide abstract] ABSTRACT: Literature shows that water demand forecasting models which use water demand as single input, are capable of generating a fairly accurate forecast. However, at changing weather conditions the forecasting errors are quite large. In this paper three different forecasting models are studied: an Adaptive Heuristic model, a Transfer/-noise model, and a Multiple Linear Regression model. The performance of the models was studied both with and without using weather input, in order to assess the possible performance improvement due to using weather input. Simulations with the models showed that when using weather input the largest forecasting errors can be reduced by 11%, and the average errors by 7%. This reduction is important for the application of the forecasting model for the control of water supply systems and for anomaly detection.
[Show abstract][Hide abstract] ABSTRACT: Pipe bursts in a drinking water distribution system lead to water losses, interruption of supply, and damage to streets and houses due to the uncontrolled water flow. To minimize the negative consequences of pipe bursts, an early detection is necessary. This paper describes a heuristic burst detection method, which continuously compares forecasted and measured values of the water demand. The forecasts of the water demand were generated by an adaptive water demand forecasting model. To test the method, a dataset of five years of water demand data in a supply area in the Western part of the Netherlands was collected. The method was tested on a subset of the data (only the winter months) in which 9 (larger) burst events were reported. The detection probability for the reported bursts was 44.4%, at an acceptable rate of false alarms of 5.0%. The results were compared with the CUSUM method, which is a general statistical process control (SPC) method to identify anomalies in time series. The heuristic and CUSUM methods generated comparable results, although rate of false alarm for the heuristic method was lower at the same detection probability.
[Show abstract][Hide abstract] ABSTRACT: Tap water discolouration occurs due to resuspension of loose deposits (LD) that accumulate in drinking water distribution systems. Strategies for discolouration control involve network pipe cleaning and replacement of cast-iron pipes. However, the sole application of such measures is not generally effective. Therefore, a deeper understanding on processes associated with LD origin and development is required. Transparent (but covered) test rig pipes (Ø = 23 mm) continuously supplied with drinking water at steady flow through mode (7-9 months) were used to investigate LD build-up under laminar flow (0.2-4.1 cm/s) conditions. Rather than continuously and homogeneously, LD developed as spots, and predominantly at the pipes' bottom. Results suggested that particle attachment may be added to settling as a LD build-up process. This is consistent with LD cohesive-adhesive properties, as shown by LD repose angle tests, as well as to the occurrence of flocculent extracellular polymeric substances-EPS in LD.
Urban Water Journal 12/2014; DOI:10.1080/1573062X.2014.938762 · 1.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Soil deformation is believed to play a crucial role in the onset of failures in the underground infrastructure. This article describes a method to generate a replacement-prioritisation map for underground drinking water pipe networks using ground movement data. A segment of the distribution network of a Dutch drinking water company was selected as the study area. Failure registration data comprising 868 failures registered over 40 months and geographical network data were obtained from the water utility. Ground movement was estimated using radar satellite data. Two types of analyses were performed: cell and pixel based. For the cell-based analysis, asbestos cement (AC) pipes exhibited the highest failure rates. Older AC pipes were also shown to fail more often, whereas failure rates for PVC were the lowest. For the pixel-based analysis, ground movement was demonstrated to play a role in the failure of all materials combined. Therefore, a replacement-prioritisation map for AC was generated which combined ground movement data and pipe-age data. This method can be a beneficial resource for network managers for maintenance and continuous monitoring.
Structure and Infrastructure Engineering 12/2014; DOI:10.1080/15732479.2014.938660 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Amines like ethanolamine and morpholine have great potential for protecting steam–water cycles against corrosion, but their thermal stability is limited and acidic decomposition products are a concern because of increased corrosion risk. In this study, metal catalysis of amine thermolysis caused by oxides on the inner surface of superheater tubes has been investigated by using a flow reactor and metal tubes of varying sizes and elemental composition. The kinetics of morpholine and ethanolamine thermolysis decreased as the tube size increased. The relationship between the S:V ratio and the degradation rate constant k was linear. Heterogeneous thermolysis accounted for 82–92% of the value of the degradation rate constant k at an S:V ratio of 4.65 mm–1. This decreased to only 6–17% at an S:V ratio of 0.4 mm–1. Although the results varied between the two applied materials, there is no consistent trend that can link thermolysis kinetics to the tube wall composition. Organic acid anion production was weakly related to the amine structure, temperature, and tube diameter but strongly related to the metal oxide composition, with formate and acetate altering as the dominant organic acid anion. A distinction between homogeneous and heterogeneous thermolysis has been made, but the results indicate that a laboratory study with a large enough tube diameter will lead to more reliable predictions.
[Show abstract][Hide abstract] ABSTRACT: Algae organic matter (AOM), including intracellular organic matter (IOM) and extracellular organic matter (EOM), are major membrane foulants in the treatment of algae-polluted water. In this study, the effects of EOM and IOM (at dissolved organic concentrations of 8 mg/L) on the fouling of a polyethersulfone ultrafiltration (UF) membrane were investigated using a dead-end down-flow UF unit. Changes in the membrane pore geometry and the interaction energy between the membrane and foulants were analyzed based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. The data (relative standard deviation within 10%) showed that UF was able to retain 57% and 46% of IOM and EOM respectively, while the corresponding membrane fluxes rapidly reduced to 28% and 33% of their respective initial values after a specific filtration volume of only 3.75 mL/cm2. The fouling model implied that cake formation was the major mechanism. Specifically, IOM foulant had a much greater free energy of cohesion (-59.08 mJ/m2) than EOM foulant (3.2 mJ/m2), leading to the formation of a compacted cake layer on the membrane surface. In contrast, small molecules of hydrophobic EOM tended to be adsorbed into the membrane pores, leading to significant reduction of the pore size and membrane flux. Therefore, the overall fouling rates caused by EOM and IOM were comparable when both of the above mentioned mechanisms were considered.
[Show abstract][Hide abstract] ABSTRACT: Ultrasound, closed-circuit television (CCTV) and Panoramo® are capable of inspecting drinking water pipes and joints of any pipe material. The three tools were tested for their accuracy and reproducibility for gap width sizing in double-socket push-fit joints. The tests were performed at laboratory scale (PVC pipes and joints) in the field (asbestos cement pipes and joints) and in three full-scale tests (PVC) inside pipes used to supply drinking water. In the laboratory tests both accuracy and reproducibility were evaluated. In the field and full-scale tests only reproducibility of the tools was tested. CCTV proved to be the most accurate and reproducible for the application. This straightforward approach is considered to be a surrogate measure for joint's condition.
Urban Water Journal 11/2014; 11(8). DOI:10.1080/1573062X.2013.806562 · 1.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The draw solution is the driving force of the forward osmosis (FO) process; however, the solute loss of the draw solute to the feed side is a general, financial limitation for most applications. The anthropogenic amino acid ethylenediaminetetraacetic acid (EDTA) was investigated as a draw solution for FO. At concentrations of approximately 1.0 osmol/kg, EDTA demonstrated comparable water fluxes (Jv = 5.29 L/m(2) h) to the commonly used salt, NaCl (Jv = 4.86 L/m(2) h), and both produced better water fluxes than glucose (Jv = 3.46 L/m(2) h). EDTA showed the lowest solute loss with Js (reverse solute loss or solute leakage) = 0.54 g/m(2) h. The molecular weight, degree of ionisation and charge of EDTA played a major role in this efficiency and EDTA was therefore well rejected by the membrane, showing a low Js/Jv ratio of 0.10 g/L. Owing to the low solute loss of EDTA and its resistance to biodegradation, this compound has the potential to be used as a draw solute for FO during long periods without requiring much replenishment.
[Show abstract][Hide abstract] ABSTRACT: The appearance of pharmaceuticals in wastewater has become a significant concern to both the water treatment industry as well as consumers. The availability of advanced treatment methods has optimized the removal of these compounds present in wastewater sources. The latest development in polymers as flocculants and combining it with other treatment helps to reduce the quantities of these pharmaceuticals in the final wastewater effluent. This paper gives an insight on the potential usage of polymer flocculants and its combination with particles, organic substances and conventional adsorbents towards removing pharmaceutical compounds from wastewater. Polymer flocculants alone will have a limited ability in pharmaceuticals removal. The flocculation process combination with adsorption on natural components and particles is always necessary. Interaction of polymers with adsorbents in the wastewater could also play an important role in their removal by polymer flocculants due to its proven implementation. An understanding of the changes in processes and mechanisms involving the polymers is essential for achieving effective removal rate. Combination of polymer flocculants with conventional adsorbents such as carbon and clays during the treatment process could lead to a new effective and economic approach in removal of the pharmaceutical compound.
[Show abstract][Hide abstract] ABSTRACT: Pipe bursts in a drinking water distribution system lead to water losses, interruption of supply, and damage to streets and houses due to the uncontrolled water flow. To minimize the negative consequences of pipe bursts, an early detection is necessary. This paper describes a heuristic burst detection method, which continuously compares measured and expected values of water demands and pressures. The expected values of the water demand are generated by an adaptive water demand forecasting model, and the expected values of the pressures are generated by a dynamic pressure drop - demand relation estimator. The method was tested off-line on a historic dataset of 5 years of water flow and pressure data in three supply areas (with 650, 11,180 and 130,920 connections) in the western part of the Netherlands. In the period 274 bursts were reported of which, based on the definition we propose in this paper, 38 were considered as relatively larger bursts. The method was able to detect 50, 25.9 and 7.8% in the considered areas related to all bursts, and around 80% in all three areas related to the subset of relatively larger bursts. The method generated false alarms on 3% of the evaluated days on average.
Journal of Hydroinformatics 09/2014; 16(5):1194. DOI:10.2166/hydro.2014.120 · 1.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper reports on the direct ability of two positively charged organic polyelectrolytes (natural-based and synthetic) to reduce the atrazine concentration in water. The adsorption study was set up using multiple glass vessels with different polymer dosing levels followed by ultrafiltration with a 1 kDa membrane. The addition of polymers exhibited a capability in reducing the atrazine concentration up to a maximum of 60% in surface-to-volume ratio experiments. In the beginning, the theoretical L-type of the isotherm of Giles' classification was expected with an increase in the dosage of the polymer. However, in this study, the conventional type of isotherm was not observed. It was found that the adsorption of the cationic polymer on the negatively charged glass surface was necessary and influential for the removal of atrazine. Surface-to-volume ratio adsorption experiments were performed to elucidate the mechanisms and the polymer configuration. The glass surface area was determined to be a limiting parameter in the adsorption mechanism.
[Show abstract][Hide abstract] ABSTRACT: Reverse osmosis (RO) systems for secondary effluent water reuse frequently encounter severe biofouling due to the high nutrient concentration in the RO feed water. Deployment of negatively charged tight ceramic ultrafiltration (UF) may restrict biofouling in RO by phosphate limitation, since the tight ceramic UF can reject dissolved phosphate by electrostatic interactions. However, the organic matter and cations can potentially impact phosphate rejection by tight ceramic UF. In this study, the effects of organic matter and Ca2+ on phosphate rejection by the 3 kDa tight ceramic UF membrane were investigated, using synthetic water containing natural organic matter (NOM) and effluent organic matter (EfOM), as well as secondary effluent water. Phosphate rejection was found to be linearly correlated to the zeta potential of the organics in the membrane feed water when the membrane was fouled by NOM. Furthermore, the EfOM-fouled membrane yielded higher phosphate rejection than the membrane fouled by the NOM due to additional adsorption of phosphate by the biopolymers. A preferential phosphate rejection was observed during effluent water filtration by the 3 kDa tight ceramic UF membrane.