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Microplastics (MPs) cannot be completely removed from water/wastewater in conventional wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). According to the literature analysis, membrane technologies, one of the advanced treatment technologies, are the most effective and promising technologies for MP removal from water and wastewater. In this paper, firstly, the properties of MPs commonly present in WWTPs/DWTPs and the MP removal efficiency of WWTPs/DWTPs are briefly reviewed. In addition, research studies on MP removal from water/wastewater by microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and membrane bioreactors (MBRs) are reviewed. In the next section, membrane filtration is compared with other methods used for MP removal from water/wastewater, and the advantages/disadvantages of the removal methods are discussed. Moreover, the problem of membrane fouling with MPs during filtration and the potential for MP release from polymeric membrane structure to water/wastewater are discussed. Finally, based on the studies in the literature, the current status and research deficiencies of MP removal by membrane technologies are identified, and recommendations are made for further studies. HIGHLIGHTS The removal efficiency of MPs by pressure-driven membrane technologies and MBRs are presented and discussed separately.; The advantages of MP removal by membrane technologies compared to other removal methods are discussed.; Studies investigating membrane fouling with MPs and the possibility of MP release from polymeric membranes to water/wastewater are discussed.;

Polyaluminium chloride (PAC) with different basicity is used as a coagulant in most drinking water treatment plants (WTP). The aluminium concentration in PAC and its hydrolysis mechanism varied with the basicity of PAC. Incremental addition of PAC changes various physico-chemical properties and turbidity removal mechanisms in water. Water treatment plants use the PAC concentration beyond its optimum dose without considering other aspects, including residual aluminium concentration. In the present work, the effect of high and medium basicity of PAC on different physico-chemical properties like pH, zeta potential, and residual aluminium concentration of water was investigated. The pH of treated water decreases with the incremental addition of PAC, and an increase in zeta potential and residual aluminium concentration in treated water was evidenced. The change in pH after PAC addition is responsible for deciding the coagulation mechanism and efficiency of the coagulation process. pH reduction is comparatively more in high basicity PAC than medium basicity. PAC hydrolysis mechanism is controlled by the zeta potential of water and can be used as an alternative method to decide the optimum coagulant dose. The performance of clariflocculator and pulsator-based WTP was also evaluated for raw water from the same source. To reduce down the turbidity below the acceptable level, the coagulant requirement for clariflocculator based WTP is comparatively less than pulsator based WTP. The floc blanket in the pulsator gets disturbed with a slight change in the coagulant chemistry and quantity. HIGHLIGHTS Performance of clariflocculator and pulsator-based WTP was studied for the same raw water source.; Clariflocculator based WTP required comparatively less coagulant than pulsator based WTP to remove turbidity below 1 NTU.; Incremental coagulant addition decreases pH and enhances zeta potential and residual Al in treated water.; Floc blanket in the pulsator gets disturbed with a small change in the coagulant chemistry and quantity.;

This article aims to study the hydrodynamic conditions of the parameters that influence the removal of dirt particles and aggregates by the drainage of wash water into filter materials for better regeneration efficiency. The water treatment plant with a nominal capacity of 600 m3·h−1 is located in the city of Parakou in Benin. It appears that one of the causes of the poor performance of the methods used for water treatment is the insufficient value of the shear stresses of the movement created by the flow of washing water in the filter bed. The use of hydro-elevators and hydrocyclones for the removal of particles from the surface of the grains of the filtering material under hydraulic load makes it possible to reduce the quantity of remaining pollution respectively by 1.5 to 2.5 times compared with the combined washing of water and air. To this end, the performance of grain washing in the hydrocyclone is explained by the presence of centrifugal field, self-separation and the friction of the particles between themselves and on the wall of the apparatus. The regeneration of the filter material under the action of ultrasonic waves reduces the remainder of particles compared to washing with water and air about 6 times. HIGHLIGHTS Study of the hydrodynamic conditions for dirt particles and aggregates removal.; Regeneration efficiency of the granular filtering material.; Calculation of the value of the shear stresses of the movement created by the flow of washing water in the filter bed.; Regeneration of the filter material under the action of ultrasonic waves.;

The purpose of this study was to monitor the presence of Cryptosporidium spp. and Giardia duodenalis in a water treatment plant (WTP) using settling sludge and backwash water (BW) samples in previous and post the deflocculation of polyaluminium chloride (PAC) flacks. Eleven collections were performed. BW and settling sludge (SSF) were concentrated by calcium carbonate flocculation, and another aliquot of settling sludge (SSC) by centrifugation. The samples were divided as follows: Group A, containing 33 samples without degradation of PAC flakes, and Group B, with degradation by alkalinization with 10 M NaOH. Sample DNA was extracted with a commercial kit, and nested polymerase chain reaction (PCR) was used to detect Cryptosporidium and G. duodenalis. All samples from Group A were negative for Cryptosporidium spp., and 6.1% (2/33) were positive for G. duodenalis in SSC samples. While the absence of Cryptosporidium may be due to a low contamination level of the water resource, the presence of G. duodenalis indicates contamination of the raw water. The detection of G. duodenalis in SSC samples indicates that this detection method was the most effective. The 33 samples from Group B were negative for both protozoa, probably due to the presence of aluminium and humic substances. [ABSTRACT FROM AUTHOR]

Phenomenological models and hybrid phenomenological-chemometric models were developed to predicf natural organic matter (NOM) removal based on the real water treatment data from the city of Minneapolis over a 3 year period. The analysis of the modeling results showed that the phenomenological model was able to capture the major variations of NOM removal but it tended to over predict the NOM removal in independent data sets. These results could be significantly improved by the hybrid model, which was less biased and much more accurate than the phenomenological model. The phenomenological model parameters showed low statistical confidence because the available data, collected in real water treatment conditions, was not sufficiently informative to identify the complex model structure. By comparison, the hybrid modeling method enabled a more reliable discrimination of the most important factors affecting NOM removal. The final hybrid model was implemented in an Excel spreadsheet and can be easily used for NOM removal prediction and the control of chemical dosing. [ABSTRACT FROM AUTHOR]

Problematic algae, species that do not settle or are not easily removed by water treatment processes, are common in many water treatment plants (WTPs). We recorded algae in the water that overflowed from sedimentation basins (SBs) to filtration basins of WTPs in South Korea. Diatoms were common and other algae were not discernible in the floes. Our field observation indicated that long and needle-shaped algae were less likely to settle and more likely to be present in overflow water. Many diatom cells or colonies that were extremely deformed from spherical had high overflow rates. Another long alga, Phormidium sp. (Cyanobacteria), originated from periphytic biofilms attached to SB walls. Algae that form long cells or colonies are less compact and less likely to settle as poor floes, Species that overflowed the basin also clogged the sand filters, leading to a need for repeated backwashing, thus limiting the production of clean water. Species that clogged the sand filters included the needle-shaped diatom Synedra acus and the discoid diatom Stephanodiscus hantzschii f. tenuis. We also observed two cases where S. acus clogged WTP filters, requiring frequent backwashing that resulted in reduced production of drinking water and economic loss. [ABSTRACT FROM AUTHOR]

Perfluorinated compounds (PFCs) such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have been detected in the environment, in biota and in humans. The exposure pathways of these chemicals to humans are unclear. Tap water and bottled water are two possible pathways of PFCs occurrence in human blood. The major objectives of the study were to identify the occurrences of PFCs in tap and bottled water and to evaluate conventional water treatment processes performance on removal of PFCs. Solid phase extraction coupled with HPLC-ESI-MS/MS were used for the analysis of ten PFCs. PFCs were detected in all tap water samples and bottled water samples. The average PFOS and PFOA concentrations in tap water were 0.17 and 3.58 ng l-1, respectively. PFOS and PFOA were not similarly distributed in all areas in the city. PFCs concentrations were higher in bottled water than in tap water. Moreover, the current treatment processes were not effective in removing PFCs in aqueous phase. Nevertheless, PFCs in particulate phase were effectively removed by primary sedimentation and rapid sand filtration. Based on the guideline from the New Jersey Department of Environmental Protection, PFOA concentrations in tap water and bottled water found in Bangkok were not expected to cause any health risks. [ABSTRACT FROM AUTHOR]

Much research has been performed into the science of aesthetic water quality, but utilities have had difficulty incorporating this science into their practices. A decision tree was developed that, for the first time, provides a resource that utility professionals can use to describe an off-flavor, determine the origin, quickly learn how to proceed with an investigation of the off-flavor event and identify potential solutions. Utility personnel can quickly learn how to be detectives for their systems without the training necessary to be experts. If the electronic decision tree does not lead to resolution of the taste and odor problem, then the utility professional, who was not previously knowledgeable in off-flavors, can have a productive discussion with an expert regarding tastes and odors. Communicating the lessons learned by the scientists of aesthetic water quality to the utility professionals in a quick and easy manner will lead to more resolved taste and odor events and better water quality. [ABSTRACT FROM AUTHOR]

Coagulant dosing is one of the major operation costs in water treatment plant, and conventional control of this process for most plants is generally determined by the jar test. However, this method can only provide periodic information and is difficult to apply to automatic control. This paper presents the feasibility of applying artificial neural network (ANN) to automatically control the coagulant dosing in water treatment plant. Five on-line monitoring variables including turbidity (NTUin), pH (pHin) and conductivity (Conin) in raw water, effluent turbidity (NTUout) of settling tank, and alum dosage (Dos) were used to build the coagulant dosing prediction model. Three methods including regression model, time series model and ANN models were used to predict alum dosage. According to the result of this study, the regression model performed a poor prediction on coagulant dosage. Both time-series and ANN models performed precise prediction results of dosage. The ANN model with ahead coagulant dosage performed the best prediction of alum dosage with a R² of 0.97 (RMS=0.016), very low average predicted error of 0.75 mg/L of alum were also found in the ANN model. Consequently, the application of ANN model to control the coagulant dosing is feasible in water treatment. [ABSTRACT FROM AUTHOR]

Performance of nanofiltration plants are described, for the two mainareas of application: The elimination of dissolved organic matter and the reduction in the salinity of a particular water and specifically that found in a divalent form. [ABSTRACT FROM AUTHOR]

This paper presents the methodology used for the rehabilitation of the pretreatment stage in a water treatment plant for a village located in Bolivia which has 3500 inhabitants. The treatment plant was initially composed by horizontal-flow roughing filters and slow sand filters, but due to the high contents of colloidal turbidity of the providing source, it did not work properly. A plan of rehabilitation was made which comprised laboratory tests, pilot tests and proposal of modifications based on the results of previous stages. The laboratory tests were made in order to find the optimum conditions to coagulate the raw water. It was found that horizontal flow roughing filters must be turned into up-flow roughing filters. so a pilot plant was built and was operated for three months in order to find suitable design parameters. The results obtained obtained during the operation of the pilot plant and the proposal of modifications at presented. The resultsof operation of the final plant which are also reported, demonstrated the advantages of the up-flow roughing filtration as a pretreatmentstage when it is necessary to add chemical products in small treatment plants. (c) 1998 IAWQ. Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]

A coagulation process for water purification plants mainly uses feedforward control based on raw water quality and empirical data and requires operator's help. We developed a new floc sensor for measuring floc size in a flush mixer to be used for floc control. A control system using model predictive control was developed on the floc size data. A series of experiments was performed to confirm controllability ofsettled water quality by controlling flush mixer floc size. An automatic control with feedback from the coagulation process was evaluatedas practical and reliable. Finally this new control method was applied for actual plant and evaluated as practical. [ABSTRACT FROM AUTHOR]

Coagulation and sedimentation occur naturally in all lakes and reservoirs and, by design, in water treatment plants using surface supplies. Important factors that affect water quality in lakes and reservoirs include nutrient loading, areal hydraulic loading, and detention time together with the concentrations of land-derived (pedogenic) natural organic matter entering the lake or reservoir. These, in turn, have important effects on the design and operation of potable water treatment systems. It is difficult and expensive to use the good physics to compensate for poor chemistry in water treatment plant design. There are many interesting and useful similarities among the physical and chemical characteristics of lakes, reservoirs and water treatment plants. [ABSTRACT FROM AUTHOR]

Abstract in French. [ABSTRACT FROM AUTHOR]

Abstract in French. [ABSTRACT FROM AUTHOR]