Search Results (31)

While horizontal roughing filters (HRFs) remain widely acclaimed for their exceptional efficiency in water treatment, especially in developing countries, they are inherently susceptible to clogging, which necessitates timely maintenance interventions. Conventional methods for managing clogging in HRFs typically involve evaluating filter head loss coefficients against established water quality standards. This study utilizes artificial neural network (ANN) for the prediction of clogging duration and effluent turbidity in HRF equipment. The ANN was configured with two outputs, the clogging duration and effluent turbidity, which were predicted concurrently. Effluent turbidity was modeled to enhance the network’s learning process and improve the accuracy of clogging prediction. The network steps of the iterative training process of ANN used different types of input parameters, such as influent turbidity, filtration rate, pH, conductivity, and effluent turbidity. The training, in addition, optimized network parameters such as learning rate, momentum, and calibration of neurons in the hidden layer. The quantities of the dataset accounted for up to 70% for training and 30% for testing and validation. The optimized structure of ANN configured in a 4-8-2 topology and trained using the Levenberg–Marquardt (LM) algorithm achieved a mean square error (MSE) of less than 0.001 and R-coefficients exceeding 0.999 across training, validation, testing, and the entire dataset. This ANN surpassed models of scaled conjugate gradient (SCG) and obtained a percentage of average absolute deviation (%AAD) of 9.5. This optimal structure of ANN proved to be a robust tool for tracking the filter clogging duration in HRF equipment. This approach supports proactive maintenance and operational planning in HRFs, including data-driven scheduling of backwashing based on predicted clogging trends. Full article

This study presents the development of a textile-based cascade filter for the removal of microplastics from an industrial laundry effluent. The cascade microfilter consists of three stages of 3D textile sandwich composite filter media, which have successively finer pores and are aimed at filtering microplastic particles down to 1.5 µm. Polypropylene fabrics with pore sizes of 100, 50 and 20 µm and 3D warp-knitted fabrics with high porosity (96%) were used. Filtration tests were carried out with polyethylene model microplastic particles at a concentration of 167 mg/L. To regenerate the filter and restore its filtration performance, backwashing with filtered water and compressed air was applied. Field trials at an industrial laundry facility and a municipal wastewater treatment plant confirmed high removal efficiencies. The 3D textile sandwich structure promotes filter cake formation, allowing extended backwash intervals and the effective recovery of filtration capacity between 89.7% and 98.5%. The innovative use of 3D textile composites enables a high level of microplastic removal while extending the filter media lifetime. This makes a significant contribution to the reduction in microplastic emissions in the aquatic environment. The system is scalable, space and cost efficient and adaptable to various industrial applications and is thus a promising solution for advanced wastewater treatment. Full article

A core tertiary wastewater reactive filtration technology, where continuously renewed hydrous ferric oxide coated sand is created in an upflow continuous backwash filter, has been adopted in about 100 water resource recovery facilities in several countries. Primarily focused on ultralow phosphorus discharge requirements to address nutrient pollution impacts and harmful algae blooms, the technology has also demonstrated the capacity to address high-efficiency removals of Hg, As, Zn, N, and other pollutants of concern, in addition to water quality needs met by common sand filtration, including total suspended solids. Recent work has demonstrated the capability of an additive iron–ozone catalytic oxidation process to the core reactive filtration technology platform to address micropollutants such as pharmaceuticals. Most recently, direct injection of frangible biochar into the reactive sand filter bed as a consumable reagent demonstrates a novel biochar water treatment technology in a platform that yields dose-dependent carbon negativity. In this work, the reactive filtration technology performance is reviewed from field pilot-scale to full-scale installation scenarios for nutrient removal and recovery applications. We also review the potential of the technology for nutrient recovery with the addition of biochar and micropollutant destructive removal with catalytic oxidation. Research exploration of this reactive filtration technology includes life cycle assessment (LCA) and techno-economic assessment to evaluate the environmental and economic impacts of this advanced water treatment technology. A recent LCA study of a pilot-scale field research and full-scale municipal system with over 2200 inventory elements shows a dose-dependent carbon negativity when biochar is injected into the process stream of reactive filtration. In this study, LCA demonstrates that reactive filtration has the potential as a negative emissions technology with −1.21 kg CO₂e/m³, where the negative contribution from the dosed biochar is −1.53 kg CO₂e/m³. In this biochar water treatment configuration, the system not only effectively removes pollutants from wastewater but also contributes to carbon sequestration and nutrient recovery for agriculture, making it a potentially valuable approach for sustainable water treatment. Full article

Drip irrigation is a widely spreading technology, mainly due to its high water-use efficiency. This technique requires a filtration process that exhibits cyclical behavior where both filtration and backwashing modes repeat. In filtration, pressure increases with time due to the particle retention up to a preset value. In backwashing, the flow is reversed to clean the filter. Different design strategies to reduce energy and water consumption have been proposed, but their practical effects are not yet clear. Here, a global analysis method based on the classification of the time evolution of the pressure curve in filtration mode was developed. Energy and water use efficiency indices were defined and evaluated under different scenarios. More design options can be undertaken to reduce the consumption of energy than of water. The decrease in the pressure drop for clean filter conditions arose as the best option to increase energy efficiency (in a realistic scenario, a reduction of 20% in the pressure drop with tap water resulted in a reduction of 7.6% in the energy consumption per volume of filtered water). Precise backwashing times and flow rates were essential to improve water use efficiency (e.g., doubling the backwashing time led to a 4.5% decrease in water use efficiency). Full article

Microplastics are plastic particles ranging in size from 1 μm to 5 mm, emitted at the source or resulting from the degradation of larger objects. Today, their global distribution is one of the major environmental problems recognized by the United Nations Sustainable Development Goals, polluting aquatic, terrestrial and atmospheric systems and requiring avant-garde solutions. Solid–liquid filtration is widely used in both industrial and biological systems, where some aquatic species are examined using very specialized filter-feeding apparatus, and when applied to industrial processes, microparticles can be separated from the water while minimizing maintenance costs, as they require less backwashing or additional energy consumption. The REMOURE project uses the Mediterranean species Mobula mobular (Bonnaterre, 1788) as a reference for the testing and optimization of low-cost microplastic filters applied to wastewater. For this purpose, a hydrodynamic test rig was designed and constructed by considering the hydraulic feeding conditions of the marine species, with a scale factor of 6. This paper presents the design conditions and the evaluation of the test results for the combination of three different variables: (1) flap disposition (two different models were considered); (2) inclination with respect to the flow direction; and (3) flow velocity. The models were printed in polyamide and videos were recorded to evaluate the behaviour of dye injection through the lobes. The videos were processed, and the results were statistically treated and used to calibrate a CFD model to optimize the filter design to be studied in a prototype wastewater treatment plant. Full article

Sand media filters are especially recommended to prevent emitter clogging with loaded irrigation waters, but their performances rely on backwashing. Despite backwashing being a basic procedure needed to restore the initial filtration capacity, there is a lack of information about the solid removal efficiency along the media bed depth. An experimental filter with a 200 mm silica sand bed height was used to assess the effect of two operation velocities (30/45 and 60/75 (filtration/backwashing) m h⁻¹) and two clogging particles (inorganic sand dust and organic from a reclaimed effluent) on the efficiency of backwashing for removing the total suspended solids retained in different media bed slices. The average solid removal backwashing efficiency was greater with organic particles (78%) than with inorganic ones (64%), reaching its maximum at a 5–15 mm bed depth. A higher operation velocity increased the solid removal efficiency by 16%, using organic particles, but no significant differences were observed with inorganic particles. The removal efficiencies across the media bed were more uniform with organic particles (63–89%) than with inorganic (40–85%), which makes it not advisable to reduce the media height when reclaimed effluents are used. This study may contribute to future improvements in sand media filter design and management. Full article

As emerging pollutants, pharmaceuticals and personal care products (PPCPs) in water have attracted more and more attention because of their harmfulness to the ecosystem and human health. Due to the perpetual input from sewage/wastewater effluents, landfill leachates, urban/agricultural runoff, etc., PPCPs in the aquatic environment are generally “pseudo-persistent”. Conventional filtration in the water treatment process cannot effectively remove PPCPs, while biofiltration, a synergistic combination of adsorption and biodegradation, is an effective upgrade method that has received great attention and application in recent years. This paper systematically reviewed the principle of biofiltration and its efficiency in the removal of PPCPs. The important operational parameters influencing biofiltration performance such as filter media, temperature, backwash conditions, empty bed contact time, etc. were summarized. In addition, the limitations and prospects of the current research on biofiltration were also pointed out. Full article

Tests of microfiltration efficiency used for the pretreatment of backwash water from sand filters were conducted at two water treatment plants treating surface water and infiltration water. Microfiltration efficiency was evaluated for three membrane modules: two with polymeric membranes and one with a ceramic membrane. This study showed that the contaminants that limit the reuse of backwash water from both plants by returning them to the water treatment line are mostly microorganisms, including pathogenic species (Clostridium perfringens). Additionally, in the case of backwash water from infiltration water treatment, iron and manganese compounds also had to be removed before its recirculation to the water treatment system. Unexpectedly, organic carbon concentrations in both types of backwash water were similar to those present in intake waters. Microfiltration provided for the removal of organic matter, ranging from 19.9% to 44.5% and from 7.2% to 53.9% for backwash water from the treatments of surface water and infiltration water, respectively. Furthermore, the efficiency of the iron removal from backwash water from infiltration water treatment was sufficient to ensure good intake water quality. On the other hand, manganese concentrations in the backwash water, from infiltration water treatment, pretreated using the microfiltration process exceeded the levels found in the intake water and were, therefore, an additional limiting factor for the reuse of the backwash water. In both types of backwash water, the number of microorganisms, including Clostridium perfringens (a pathogenic one), was a limiting parameter for backwash water reuse without pretreatment. The results of the present study showed the possibility for using microfiltration for the pretreatment of backwash water, regardless of its origin but not as the sole process. More complex technological systems are needed before recirculating backwash water into the water treatment system. The polyvinylidene fluoride (PVDF) membrane proved to be the most effective for DOC and microorganism removal from backwash water. Full article

This paper presents research on the mass dispersion and adsorption of organics present in tap water on powdered activated carbon (PAC) in a two-layer filter column. The adsorption rate depends on the difference between the concentration of organics and the equilibrium concentration. In homogeneous flocculators with simultaneous adsorption on PAC, the concentration difference is lower than in a filter column with PAC. Therefore, the utilization of the PAC’s adsorption capacity in filters is higher than in homogeneous flocculators. PAC is introduced into the upper anthracite layer of a filter bed, while the bottom layer is a sand layer, which protects the underdrain system from becoming clogged with PAC particles. The sorbent wis introduced into the bed in the final phase of filter backwashing. The authors present a model of adsorption on PAC in a filter column. Both experiments and calculations confirmed a better utilization of PAC’s adsorption capacity in the filter column compared to its utilization in a homogeneous flocculator. Three criterion equations were developed using dimensionless numbers, Re, Pe and Nu, as well as two similarity moduli related to a sorbent apparent density and an adsorption coefficient. Additionally, a relationship between the Peclet number (Pe) and the Reynolds number (Re) as well as the similarity modulus for the sorbent apparent density were determined for the mass dispersion process. The relationship between the diffusive Nuselt number (Nu) and the Re number as well as the similarity modulus for the sorbent apparent density were determined for the parameter describing an adsorbate permeation rate across a water–sorbent interface. The impact of the Re number and the similarity modulus for the sorbent apparent density on the Henry constant was also investigated. The criterion equations can be used to determine the adsorption model parameters; they may be helpful in designing a filtration system supplemented with PAC. In the capillary velocity range $V_x^{*}$ ∈ ⟨0.15·10⁻²; 0.72·10⁻²⟩ m/s and with a change in the apparent density of the sorbent ${\rho }_{p,sorb}$ from 3000 to 12,000 g PAC/m³ of the bed, as a result of the experimental tests carried out, it was established that the actual coefficient of longitudinal dispersion $D_x^{*}$ varied in the range of 0.16·10⁻⁴ to 2.03·10⁻⁴ m²/s, the product of the constant mass transfer rate and the specific outer surface of sorbent $k\cdot a_m$ varied in the range of 2.23·10⁻⁷ to 1.70·10⁻⁶ (m/s)·(m²/g PAC), while the Henry constant Γ* varied in the range of 7.24 to 44.20 1/m³ of sorbent and the Henry constant Γ varied in the range of 0.0012 to 0.0019 m³ of water/g PAC. Full article

The presence of invertebrates in drinking water distribution systems, particularly Chironomidae larvae, has raised concerns among the general public. This study aimed to comprehensively address the issue of larvae breakout in water filtration systems and provide potential solutions to prevent their escape into the water supply. The research investigated various factors contributing to larvae breakout, including the type of filtration column, sand depth, pretreatment methods, and the effective size and uniformity coefficient of sand media. Experimental results revealed that the GAC column, primarily utilized for adsorption, was ineffective in retaining Chironomidae larvae, leading to their escape within a short period. Similarly, the sand filter column, with a design that is currently widely used with sand specifications of an effective size of 0.7 mm and a uniformity coefficient of 1.7, failed to act as a barrier for larvae. Increasing the height of the sand media and applying a pretreatment method, which was expected to prevent larvae from entering the treated water, yielded unsatisfactory results. Our research results show that reducing the uniformity coefficient to 1.5 while maintaining an effective size of 0.7 mm proved to be important in preventing the release of larvae into treated water. The Sand/GAC and Sand/Anthracite systems, by maintaining adjusted media sand specifications, also succeeded in retaining larvae in the filtration system. Additionally, this study emphasized the importance of following the recommended backwash procedure, consisting of specific steps involving air flow, a combination of air and water flow, and final water flow. This sequence effectively removed contaminants, turbidity, and Chironomidae larvae from the filtration media, ensuring improved water quality and system performance. The findings of this study provide valuable insights and recommendations for water treatment plants to address the issue of larvae breakout and enhance water quality. Full article

The present study aimed to investigate the potential application of chitosan (CS) and its two derivatives, dialdehyde chitosan (DCT) and carboxymethyl chitosan (CMC), as new flocculants in the purification of filter backwash water. The main objective of the work was to remove the disadvantages and inconveniences associated with using synthetic flocculants, mainly based on polyacrylamide, by using biodegradable and non-toxic biopolymer flocculants. The chitosan derivatives were obtained in the process of the chemical modification of this polysaccharide. CS was oxidated with periodate in acetic acid solution to obtain DCT with a degree of substitution (DS) of 44.29%. For the CMC synthesis, after the alkaline activation of chitosan, the solution was treated with monochloroacetic acid (MCA) at 60 °C for 3 h, leading to carboxymethylated chitosan formation with a DS of 49.55%. Characterizations of the flocculants using Fourier transform infrared (FT-IR) spectroscopy, ¹³C nuclear magnetic resonance (¹³C NMR) spectroscopy, and an elementary analysis confirmed the successful modification of the chitosan. The morphology and thermal stability of the samples were investigated using scanning electron microscopy (SEM) and a thermogravimetric analysis (TGA), respectively. Moreover, the biopolymer materials were studied in a series of flocculation jar tests for filter backwash water samples collected at a water treatment plant (WTP) in Kutno, Poland. CMC turned out to be a particularly effective agent in an optimal amount of 0.2 mg/L, achieving nearly 99% iron removal and 98.26% turbidity removal efficiency rates, which indicates that chitosan–based materials can be ecological alternatives for polyacrylamide flocculants, effectively removing the impurities of iron ions. Full article

Due to the worldwide water crisis and diminishing water supplies, it is imperative to reduce water use and reuse it. One possible source of water is the washings created during the purification of drinking water. Backwashing constitutes 2–8% of the treated water used globally; it is more commonly used, primarily for irrigation or to expand surface/groundwater resources. Therefore, recirculating it at the beginning of the water treatment system is reasonable and justifiable, as it can lead to a decrease in the cost of the water that is being used. A study of variations in the content of washings in two water treatment plants revealed the requirement for pollutants to be removed before the water is reused. For the safety of consumers, the presence of microbes in backwashings from both facilities was essential. Variability in the amount and composition of backwashings was higher for surface water treatment in comparison to infiltration water treatment; however, the amount of backwashings was greater in infiltration water. The quantity of microorganisms, including indicator ones, was substantially higher in washings following surface water treatment. On the other hand, in the washings from the infiltration water treatment, large amounts of iron and manganese compounds were present, the recycling of which would reduce the effectiveness of infiltration water treatment. Pre-treatment backwashings from both facilities will be suitable for the suspension separation procedures and disinfection. It is essential to compare the costs connected with water use against the anticipated cost of washing. The potential to purify additional water in the event of a worsening water shortage, however, is the most significant advantage of water reuse. Recycling of the washings will allow to reduce the fees for the use of the environment, even to EUR 150,000 and EUR 250,000 per year for surface and infiltration WTP, respectively. Full article

The global growth in demand for raw materials is leading to a continuous increase in the mining of ores and thus to an expanding volume of tailings to be stored. To ensure safer storage and an optimized recovery of process water, the tailings slurry is often thickened followed by filtration in filter presses and dry stacking. However, an increasing blinding effect during the time of operation requires cleaning or replacement of the filter media. Cloth washing using spray nozzles is a possible solution, but there is insufficient quantitative data published on the performance. For this reason, this article examines the cleaning of an iron ore cloth from tailings filtration by continuous water spraying. Water flux, spray time and direction (front- and back-wash) variation were investigated by evaluating cleaning performance using flow resistance measurement and comparison to the unused and industrially used state where blinding has occurred. Sufficient cleaning and achieving the flow rate of the unused cloth is possible. However, excessive spray cleaning should be avoided, as damage to the fibers may occur. Spray cleaning can be stated to be economically reasonable since a water demand of 2.5 m³ m⁻² and an energy consumption of 6.5 kWh m⁻² is necessary for a sufficient regeneration. Furthermore, the spray cleaning is assumed to cost USD 6 m⁻², which is approximately similar to replacing the fabric but reduces plastic waste. Full article

Swimming pools are examples of water-intensive facilities, where solutions for reducing economic and environmental costs are searched with increased frequency. One of the solutions supporting savings is the recovery of water from wastewater, including backwash water obtained while rinsing the filter bed. The study objective was the qualitative and quantitative assessment of post-coagulation sludges, the main pollutant found in the washings. During the analyses, assessment of the sedimentation capabilities of the sludges was performed (gravitationally), particle size distribution was assessed (particle size distribution analyser) and assessment of phytotoxicity with the use of plant indicators in short-term tests was performed (Lemna minor, Lepidium sativum, Sinapis alba, Raphanus sativus). The samples were collected from two independent circulations, which differed in terms of capacity and type of coagulant used. The tested post-coagulation sludges were characterized by high content of total suspended solids: in samples from Circuit 1 from 251 to 128 mg/L, in Circuit 2 from 489 to 228 mg/L. However, the sedimentation processes enabled significant separation of sludges. The hydrolyzed coagulant contributed to the improvement of sedimentation capabilities of the sludges. Despite the fact that in many samples low sludge concentrations favored stimulation of plant growth, the post-coagulation sludges can constitute a hazard to plant growth, particularly in the long-term perspective. Full article

Hybrid ceramic membranes (i.e., membranes with a layer-by-layer (LbL) coating) are an emerging technology to remove diverse kinds of micropollutants from water. Hybrid ceramic membranes were tested under laboratory conditions as single-channel (filter area = 0.00754 m²) and multi-channel (0.35 m²) variants for the removal of pharmaceuticals (sulfamethoxazole, diclofenac, clofibric acid, and ibuprofen) and typical wastewater pollutants (i.e., COD, TOC, PO₄-P, and TN) from drinking water and treated wastewater. The tests were conducted with two low transmembrane pressures (TMP) of 2 and 4 bar and constant temperatures and flow velocities, which showed rejections above 80% for all the tested pharmaceuticals as well for organic pollutants and phosphorous in the treated wastewater. Tests regarding sufficient cleaning regimes also showed that the LbL coating is stable and resistant to pHs between 2 and 10 with the use of typical cleaning agents (citric acid and NaOH) but not to higher pHs, a commercially available enzymatic solution, or backwashing. The hybrid membranes can contribute to the advanced treatment of water and wastewater with low operational costs, and their application at a larger scale is viable. However, the cleaning of the membranes must be further investigated to assure the stability and durability of the LbL coating. Full article