Rapid Sand Filtration Research Articles

Optimization and technical parametric assessment of a novel triple media rapid sand filter: The effect of height of beds and size of particles

Turbidity is critically important in the drinking water treatment process and optimal performance of a sand filter can reduce it significantly. In this research, the optimization of a rapid sand filter was investigated in COMSOL Multiphysics® to decline the output turbidity. The conventional filter changed to a triple-bed filter. For validation of the large-scale model, an experimental model was used. According to 35 experimental data for surface load rate of 120 and 240 m3/m2.day, the average absolute deviation of outlet turbidity was calculated by nearly 7%. Moreover, 243 experiments were considered based on the different height of beds and dimeter of particles. The optimization results showed that the proposed model could remove the turbidity of 10 NTU in the inlet stream to 0.341 NTU in outlet one. Also, when the bed's porosity reaches about 0.2, the bed undergoes a pressure drop, and modeling calculations get slow, which indicates that the bed becomes filled. Therefore, it could be implemented as an index to estimate the filter's valuable working hours or backwash time.

Evaluation of Chitosans as Coagulants-Flocculants to Improve Sand Filtration for Drinking Water Treatment.

The World Health Organization (WHO) reports that two billion people worldwide lack access to safely managed water sources, including 1.2 billion who already have access to improved water sources. In many countries, household point-of-use (POU) water-treatment options are used to remove or deactivate microorganisms in water, but not all POU technologies meet WHO performance requirements to achieve safe drinking water. To improve the effectiveness of POU technologies, the use of multiple treatment barriers should be used as a way to increase overall treatment performance. The focus of this research is to evaluate multiple barrier treatment using chitosan, an organic coagulant-flocculant, to improve microbial and turbidity reductions in combination with sand filtration. Bench-scale intermittently operated sand filters with 16 cm layers of sands of two different grain sizes representing slow and rapid sand filters were dosed daily over 57 days with microbially spiked surface water volumes corresponding to household use. E. coli bacteria and MS2 coliphage virus reductions were quantified biweekly (N = 17) using culture methods. Bacteria and virus removals were significantly improved over sand filtration without chitosan pretreatment (Wilcoxon Rank-Sum, p < 0.05). When water was pretreated at an optimal chitosan dose of 10 mg/L followed by sand filtration, log10 reductions in bacteria and viruses met the two-star WHO performance level of effectiveness. Microbial and turbidity reductions generally improved over the filter operating period but showed no trends with filtration rates.

Assessment of the Performance of a Water Treatment Plant in Ecuador: Hydraulic Resizing of the Treatment Units

Granting access to drinking water has been a challenge because 47% of the worldwide population is not connected to a drinking water distribution network in rural settlements. This study aimed to evaluate the contaminant removal efficiency in a conventional water treatment facility in the Austro region of Ecuador, Paute, to identify the treatment units requiring hydraulic resizing. Water samples were collected from each treatment unit to characterize the physical-chemical and microbiological parameters, and the dimensions of the treatment ponds for hydraulic evaluation purposes. Water hardness, electrical conductivity, SO42−, and Fe2+ were the main issues found in the water, which failed to comply with Ecuadorian technical guidelines. The treatment units, such as the flocculator, rapid sand filter, and storage tank, were resized to meet the demand of the future population. In addition, the residual free chlorine was measured as insufficient in the community’s tap water, showing an unprotected water distribution system to microbiological contamination. No disinfection by-products were found despite the existence of biodegradable organic matter. The findings of this research propose improvements in the deployed treatment practices to provide the community with drinking water in accordance with the Sustainable Development Objectives (SDG 3 and SDG 6).

Acceleration of sand filtration start-up for manganese-containing groundwater treatment: microbial-mediated autocatalytic oxidation of manganese oxides

Mn removal performance in biotic and abiotic accelerated rapid sand filters.

Comparison Performances of Microfiltration and Rapid Sand Filter Operated in Water Treatment Plant

Water treatment of river water is generally carried out conventionally, a rapid sand filter consisting of a coagulation unit, flocculation, sedimentation, and sand filtration. One of the disadvantages of sand filters is that it requires a large volume of water for washing, inconsistent quality, and escape of microorganisms less than 0.01 mm in size. Membrane technology can solve this problem with the advantages of including a more compact unit with a larger surface area per volume. The immersed membrane has another advantage that it is possible to integrate with sedimentation units so that it can save the land. This paper will study a comparison of the performance of the microfiltration membrane with sand filters in two drinking water treatment plants. The comparison method is based on technical specification, capacity, and quality performance. The results show that the quality of the microfiltration membrane filtrate is better than the sand filter. Overall immersed membrane microfiltration with pore size 0.05 µm had removal efficiency of E. Coli was 100%, turbidity 93 %, TSS 100%. Organic permanganate value 37%, and Microplastics 81.5%, whereas pore size 0.07 µm removal E. Coli was 99.8%, turbidity 52.9 %, Organic permanganate value 17.6%, and Microplastics 37.1%. The productivity of microfiltration membranes is more significant than rapid sand filters. The removal efficiency of WWTP Ngagel was better than Siwalan Panji.

NaClO-based rapid sand filter in treating manganese-containing surface water: Fast ripening and mechanism

Recently, seasonal manganese contamination in the surface water is capturing ever-increasing attention and has posed significant challenges to the safety of water supply in the conventional drinking water treatment plants. This study aimed to develop new strategies to enhance the manganese removal by the sand filter. The synergistic effects of filter material type, filter layer thickness, filtration rate, and NaClO addition on the manganese removal performance, were systematically investigated. The results indicated that modified zeolite exerted the highest adsorption capacity (5.200 mg/g) for manganese. Introducing the NaClO oxidation would effectively improve the manganese removal efficiency (from 32 % to 97 %) by the modified zeolite filter compared to the control system at the filtration rate of 8 m/h, owing to the fast formation of catalytic oxidation capability. Accordingly, the effective layer thickness of modified zeolite can be shortened from 100 cm to 10–20 cm to engineer a double-layer filter consisting of both a thin modified zeolite layer and a thick natural quartz sand layer. Besides, NaClO involvement would neutralize the adverse effects of manganese removal caused by the filtration rate increase, and facilitate the formation of auto-catalytic manganese oxides (MnOx) with rough, heterogeneous, and porous surface morphology, as well as numerous tremella-like and sponge-type structures, which was related to the fast removal of manganese. These findings are full of significance in developing simple, practical, and cost-effective strategies for seasonal manganese contamination.

Granular limestone amended sand filters for enhanced removal of nanoplastics from water: Performance and mechanisms

Effluent from wastewater treatment plants (WWTPs) has been regarded as one of the major contributors of nanoplastics (NPs) in the environment. Improving the performance of rapid sand filter (RSF) systems in WWTPs is thus in urgent need. In this study, granular limestone, a low-cost and abundant natural material, was integrated into RSF systems to enhance NP removal from water. Laboratory filtration columns packed with pure sand and limestone-amended sand were applied to remove polystyrene nanospheres (100 nm) from deionized water (DIW) and artificial wastewater (AWW) under different grain size and flow velocity conditions. Pure sand filter showed neglectable NP removal from DIW but much higher NP removal from AWW, especially when fine sand was employed. Limestone amended RSF had a significant improvement in the removal of NPs for all the tested conditions and the removal efficiency of NPs became greater with increasing amount of limestone in columns. The sensitivity of NP immobilization to flow velocity changed significantly with different combinations of filter and background solutions. Coupled effects of physical straining, electrostatic interaction, cation screening and bridging, and surface roughness controlled the retention behaviors of NPs in the columns. The higher removal efficiency of NPs by limestone can be mainly attributed to its chemical composition as well as its surface heterogeneity and roughness. Results of this study demonstrate that limestone can offer extensive application potential for enhancing the performance of RSF systems in WWTPs to remove NPs from wastewater.

Nitrogen-metabolising microorganism analysis in rapid sand filters from drinking water treatment plant.

Sand filters (SFs) are common treatment processes for nitrogen pollutant removal in drinking water treatment plants (DWTPs). However, the mechanisms on the nitrogen-cycling role of SFs are still unclear. In this study, 16S rRNA gene amplicon sequencing was used to characterise the diversity and composition of the bacterial community in SFs from DWTPs. Additionally, metagenomics approach was used to determine the functional microorganisms involved in nitrogen cycle in SFs. Our results showed that Pseudomonadota, Acidobacteria, Nitrospirae and Chloroflexi dominated in SFs. Subsequently, 85 high-quality metagenome-assembled genomes (MAGs) were retrieved from metagenome datasets of selected SFs involving nitrification, assimilatory nitrogen reduction, denitrification and anaerobic ammonia oxidation (anammox) processes. Read mapping to reference genomes of Nitrospira and the phylogenetic tree of the ammonia monooxygenase subunit A gene, amoA, suggested that Nitrospira is abundantly found in SFs. Furthermore, according to their genetic content, a nitrogen metabolic model in SFs was proposed using representative MAGs and pure culture isolate. Quantitative real-time polymerase chain reaction (qPCR) showed that ammonia-oxidising bacteria (AOB) and archaea (AOA), and complete ammonia oxidisers (comammox) were ubiquitous in the SFs, with the abundance of comammox being higher than that of AOA and AOB. Moreover, we identified a bacterial strain with a high NO3-N removal rate as Pseudomonas sp. DW-5, which could be applied in the bioremediation of micro-polluted drinking water sources. Our study provides insights into functional nitrogen-metabolising microbes in SFs of DWTPs.

Physiochemical Treatment of Wastewater Utilizing Polyaluminum Chloride for Khartoum North Wastewater Effluent

This paper focuses on the possibility of applying physiochemical treatment for industrial wastewater combined with domestic wastewater that are currently treated by the conventional activated sludge process in Khartoum North Treatment plant at Haj Yousif (Wad Dafeah). A lab-scale experiment was carried out utilizing Poly aluminum chloride (PAC) as a coagulant for determining the optimum dose to reduce the turbidity of the wastewater sample to the lowest level. The results of the lab-scale model showed that a dose of 0.8 ml/l of the PAC achieved significant removal of turbidity (from turbidity >1000 NTU of raw sewage to turbidity level of 18 NTU of the treated effluent). This dose of 0.8ml/l obtained from the lab-scale experiment was applied in a pilot plant of capacity 30 m3/d erected at the site of the treatment plant (Wad Dafeah). The process units utilized in the pilot plant were of minimum or negligible electrical power consumption. They include an inverted hydro cyclone for flash mixing of the coagulant, pipes arrangement to achieve hydraulic gentle mixing as flocculation process, vertical sedimentation tank to enhance efficient settling of particles and tertiary treatment using a rapid sand filter. Raw sewage of BOD5 = 5000 mg/l was introduced into the pilot plant and excellent quality of treated effluent was obtained. Removal efficiencies of both BOD5 and SS were high (97 % & 98% respectively).Treated effluent had BOD5 = 23 mg/l & SS = 22 mg/l. The high dose of PAC utilized for the treatment (0.8 ml/l= 1040 mg/l) can be reduced significantly if raw wastewater of lower BOD content such as domestic wastewater is treated. In a parallel study with the domestic sewage of BOD5 =350 mg/l, the PAC dose required was 0.1 ml/l (130 mg/l). Recycling of residual PAC in the sludge is recommended to decrease the cost of treatment. The approach & methodology followed in this study can be further adopted using other coagulant material such as ferric salts or other similar local product which can achieve high efficiency in reducing the load of organic substances in the wastewater with minimum cost.Keywords: Physiochemical; Poly aluminum chloride; inverted hydro cyclone

A Coagulation Process Combined with a Multi-Stage Filtration System for Drinking Water Treatment: An Alternative for Small Communities

As set out in the Sustainable Development Goals, it is necessary to achieve universal and equitable access to safe drinking water services for all the world’s population. Appropriate water treatment alternatives for rural areas should be prioritised to achieve this goal. In this work, a simplified drinking water treatment system (SDWTS), which has great potential for application in small communities and rural areas, was evaluated on a pilot scale for turbidity and apparent colour removal using synthetic raw water. The SDWTS integrates Upflow Gravel Filter in Layers (UGFL) and Rapid Sand Filter (RSF) with previous coagulation. This evaluation was carried out using a 23 factorial experiment, with the factors: type of water, type of coagulant and flow. The factorial design showed that the SDWTS had the highest turbidity removal efficiencies (>98.7%) with type II (20 NTU) water and PACl coagulant, while flow rate had no significant effect on turbidity removal. Under optimal operating conditions (type II water, PACl and 1.0 m3/d), the SDWTS produces treated water that meets the standards required by Colombian regulations and World Health Organisation recommendations for drinking water, concerning the variables: turbidity, apparent colour, total coliforms, E. coli, pH, electrical conductivity and Al. The SDWTS maintained its capacity to produce potable water when evaluated with the increased operating flow (up to 3.0 m3/d) and raw water turbidity (up to 50 NTU). The SDWTS can be an efficient and innovative alternative for water treatment, and its implementation in small communities can contribute to equitable access to drinking water.

Selection of Unit Design for Teluk Buyung 4 Water Treatment Plant (WTP), Bekasi City, West Java, Indonesia

The city of Bekasi is experiencing rapid development so the demand for water is increasing. To increase service coverage and meet the drinking water needs of the people of Bekasi City with a quality that meets the Minister of Health Regulation No. 492 of 2010, it is planned to up rate the capacity that the Teluk Buyung 4 WTP has a capacity of 300 L/second with a raw water source, namely the West Tarum Secondary Channel. The Teluk Buyung 4 WTP is planned to use the design criteria from the Equivalent WTP evaluation, namely Teluk Buyung 3 WTP and literature studies. Teluk Buyung 4 WTP uses processing units, intake unit, hydraulic coagulation, hydraulic flocculation, plate settler sedimentation, rapid sand filtration, disinfection, and reservoir. The data used in the planning process is divided into two, namely primary data and secondary data. The intake unit has several components, namely a barscreen, sluice gate, carrier channel, and collecting well. The pre-sedimentation unit consists of 2 tanks and is channeled to a collection well and then pumped to the WTP. The coagulation unit uses hydraulic coagulation with a plunge of 1 tub. The coagulant used was PAC at a dose of 25 mg/L. The flocculation unit uses hydraulic flocculation with up and down flow with 2 tubs. The sedimentation unit uses a plate settler with 2 tanks. The filtration unit uses a rapid sand filter with dual media, namely anthracite media and sand media and has 7 tubs. Disinfection process uses NaOCl with a dose of 41.67 mg/L. The reservoir unit uses 1 tub with a ground reservoir type.

Evaluation of water consumption in rapid sand filters backwashed under varied physical conditions

Egypt suffers from water scarcity. In water treatment plants using sand filters, a significant amount of treated water is consumed, estimated at 10%–15% of the filtered water during backwashing. The objective of this study is to determine the most effective way to reduce the amount of treated water used for backwashing. The methodology of this study was to evaluate the effects of air and water rates, treated water turbidity of 1.6 NTU or slightly higher synthetic turbidity of 4.0 NTU, and media type with single or dual media on reducing treated water consumption during rapid sand filter backwashing procedures. The experimental set up was a bench-scale filter operated at a filtration rate of 189 m3/m2/day. Backwashing with the right water and air rates reduce water usage by 18%, enhanced process performance, and reduced the ripening period. Backwashing using synthetic turbid water recovered 100% of the treated water and improved the ripening duration without affecting backwashing efficiency. This study concluded that backwashing the dual media filter with silica sand and activated carbon achieved the highest treated backwash water consumption by approximately 60%. While anthracite coal was utilized as a dual-media filter, the least reduction in treated water consumption was discovered.

Semi-crystalline microplastics in wastewater plant effluents and removal efficiencies of post-treatment filtration systems

Microplastics (MPs) are ubiquitous in the environment and have been found in every environmental compartment. Wastewater and wastewater treatment plants (WWTPs) have been identified as possible point sources contributing to the emission of microplastic particles (MPP) into the aquatic environment. So far, MPP in wastewater effluents have mainly been analyzed by spectroscopic methods resulting in concentrations as number per volume. In this study, we present mass concentrations in the secondary effluents of four German municipal WWTPs, removal efficiencies of seven post-treatment systems and the resulting load emissions. Differential Scanning Calorimetry (DSC) was used for the analysis of semi-crystalline MPs. The concentrations of secondary effluents ranged from 0.1 to 19.6 µg L-1. Removal efficiencies > 94% were found for a microfiltration membrane (MF), two cloth types of a pile cloth media filter (PCMF), a micro strainer, a discontinuous downflow granulated activated carbon filter (GAC) and a powdered activated carbon (PAC) stage with clarifier and rapid sand filtration. A rapid sand filter (RSF) at WWTP B showed a removal efficiency of 82.38%. Only a continuous upflow GAC filter at WWTP C proved to be unsuitable for MP removal with an average removal efficiency of 1.9%.

The Effect of Filter Media Size and Loading Rate to Filter Performance of Removing Microplastics using Rapid Sand Filter

Microplastics (MP) can pose a serious threat to the environment and human health because of their tiny size and ability to spread easily in water. One of the alternative treatments to remove MP from water is the rapid sand filter (RSF). The objective of this study was to analyze the effects of filter media size and loading rate on RSF performance in removing MP. The applied filter media was silica sand with effective sizes (ES) of 0.39 and 0.68 mm. The loading rates of filtration were 4; 6; 8 and 10 m3/m2-h. The MP samples were made from plastic bags and torn tires (artificial samples: 10 to 800 µm). This study showed that the MP removal percentage was up to 96.6% (MP size larger than 200 µm). The head loss increment for loading rates 4; 6; 8; 10 m3/m2-h was 0.16; 0.35; 0.34; 0.25 m (ES 0.39 m) and 0.10; 0.18; 0.18; 0.19 m (ES 0.68 m)), respectively. Meanwhile, the filtration cycle for loading rates 4; 6; 8; and 10 m3/m2-h was 5, 2, 2, and 1 days (ES 0.39 mm) and 9, 4, 3, and 3 days (ES 0.68 mm), respectively. The result of this study showed that the smaller the filter media size, the higher the head loss of the filter media bed. Furthermore, there is an increased head loss of the filter media bed when the loading rate is greater.

Innovative polymeric inorganic coagulant-flocculant for wastewater purification with simultaneous microbial reduction in treated effluent and sludge

The current work introduces polymeric inorganic coagulant-flocculants; poly-ferric chloride (POFC) which prepared using iron-containing waste. Different POFCs were produced according to Fe/basicity ratio. Likewise, the efficiency of POFC for purification and microbial decontamination of domestic wastewater was evaluated using various doses of POFC coagulant-flocculants. The solid content of the prepared POFCs was ranged from 11.1 to 29.9%, and density was varied from 1.13 to 1.24 kg/L with the varying iron/basicity ratios. Analyses results of XRD, FTIR and SEM confirm formation of a new inorganic polymeric ferric chloride that it is not assumed simple mixture of components. Moreover, the prepared POFCs showed coagulant-flocculant characteristics; therefore it is employed for treating wastewater without introducing organic polymer. Both POFCs coagulant-flocculants showed removal efficiencies of 99, 99 and 91% for total suspended solids (TSS), turbidity and chemical oxygen demand (COD) from domestic wastewater. Also, a complete deactivation of the tested waterborne species in wastewater was achieved at 100 ppm dose of POFCs. At POFC dose of 150 ppm, it was found that the anaerobic microbes and sulfate-reducing bacteria in sludge were reduced by 99.9 and 98%, respectively. The deactivation anaerobic micobes and sulfate-reducing bacteria in the produced sludge by using POFC will result in odor reduction generated from sludge. Moreover, the integration between POFC-based coagulation and rapid sand filtration (RSF) lowers POFC dose use and showed a good efficiency for domestic wastewater purification and microbial decontamination. Finally, POFC-based treatment aids in the decrease organic and bacterial load that results in reducing disinfection use and declining disinfection by-products levels. Moreover, POFC-based treatment/rapid sand filtration is considered a well-located cost-effective train for purification of domestic wastewater and microbial decontamination in treated effluent and sludge and which can be reused for safe agricultural purpose.

Performance improvement and mechanism of composite PAC/PDMDAAC coagulant via enhanced coagulation coupled with rapid sand filtration in the treatment of micro-polluted surface water

The coagulation and filtration are widely used for surface water due to cost effectiveness therefore the need to study its’ improvements for safe drinking water that meet national standards. The performance of enhanced coagulation of composite coagulants (ECC) using poly aluminium chloride/poly di-methyl di-allyl ammonium chloride (PAC/PDMDAAC) coupled with rapid sand filtration (RSF) was studied. This was performed using jar testing, optimized, and operated at same dosage and supernatant turbidity (SDST) mode; also, the interception points for PAC and composites at baseline turbidity between 1.0 and 1.50 NTU with fixed RSF operating conditions while water parameters like turbidity, CODMn, NH3N, and zeta potentials were used as indicators for improved removal rates. Furthermore, the floc size and morphology analysis at optimum dosage combined with zeta potentials were used to explained the mechanism of ECC-RSF. The results showed that most composites out-performed PAC only, before and at the interception points; however, beyond this point, the superior performance disappears with the increasing PAC dosage above 3.0 mg/L. At the optimum dosage, composite PAC/PDMDAAC at 1.60 dL/g, 10:1 showed the best overall removal rate at SDST mode of 99.36%, 64.50%, and 66.18%, respectively for turbidity, NH3N, and CODMn. The dominant mechanism of composite coagulation is charge neutralization within the dosage range used and strengthened by adsorption-bridging due to the presence of PDMDAAC while the major mechanism during filtration is adsorption. It was concluded that depending on the raw water quality, the coagulation mode of SDST at baseline turbidity near 1.0 NTU can maximized the water quality removal for composite PAC/PDMDAAC. New operational insights about maximizing the performance of composite PAC/PDMDAAC coagulants have been put forward.

ANALISIS MULTI KRITERIA DALAM PEMILIHAN UNIT PENGOLAHAN AIR IPA CIAWI, KECAMATAN MEGAMENDUNG, KABUPATEN BOGOR

To increase service coverage and meet the increasing demand for drinking water, PDAM Tirta Kahuripan plans to build a Ciawi WTP in Megamendung District with a processing capacity of 165 L/second using the Sukabirus River as a raw water source. The purpose of this study was to determine the processing units in the design of the Ciawi WTP using multi-criteria analysis. Based on the results of the analysis of raw water quality, there were several parameters that do not meet the drinking water quality standards according to the Minister of Health Regulation No. 492 of 2010 and PPRI No. 82 of 2001, namely turbidity, Fecal coliform, total coliform, TSS, BOD, COD, and DO. There were three alternative processing circuits used. Alternative I consists of intake, hydraulic coagulation, up-down flow hydraulic flocculation, plate settler sedimentation, rapid sand filtration, disinfection, and reservoir. Alternative II consists of intake, hydraulic coagulation, vertical-shaft paddle wheel mechanical flocculation, tube settler sedimentation, rapid sand filtration, disinfection, and reservoir. Alternative III consists of intake, in-line static mixers coagulation, horizontal-shaft paddle wheel mechanical flocculation, plate settler sedimentation, rapid sand filtration, disinfection, and reservoir. There are other factors that must be considered in the selection of treatment units, namely contaminant removal, reliability, flexibility, construction, land requirements, ease of operation, maintenance, cost, and environmental compatibility. Based on multi-criteria analysis, the percentage of suitability for alternative I is 78%, Alternative II is 63%, and Alternative III is 48%. From this assessment, it can be said that alternative I is the best alternative.

Exploring organic micropollutant biodegradation under dynamic substrate loading in rapid sand filters

Microbial removal of trace organic micropollutants (OMPs) from drinking water sources remains challenging. Nitrifying and heterotrophic bacteria in rapid sand filters (RSFs) are capable of biodegrading OMPs while growing on ammonia and dissolved organic matter (DOM). The loading patterns of ammonia and DOM may therefore affect microbial activities as well as OMP biodegradation. So far, there is very limited information on the effect of substrate loading on OMP biodegradation at environmentally relevant concentrations (∼ 1 µg/L) in RSFs. We investigated the biodegradation rates of 16 OMPs at various substrate loading rates and/or empty bed contact times (EBCT). The presence of DOM improved the biodegradation of paracetamol (41.8%) by functioning as supplementary carbon source for the heterotrophic degrader, while hindering the biodegradation of 2,4-D, mecoprop and benzotriazole due to substrate competition. Lower loading ratios of DOM/benzotriazole benefited benzotriazole biodegradation by reducing substrate competition. Higher ammonia loading rates enhanced benzotriazole removal by stimulating nitrification-based co-metabolism. However, stimulating nitrification inhibited heterotrophic activity, which in turn inhibited the biodegradation of paracetamol, 2,4-D and mecoprop. A longer EBCT promoted metformin biodegradation as it is a slowly biodegradable compound, but suppressed the biodegradation of paracetamol and benzotriazole due to limited substrate supply. Therefore, the optimal substrate loading pattern is contingent on the type of OMP, which can be chosen based on the priority compounds in practice. The overall results contribute to understanding OMP biodegradation mechanisms at trace concentrations and offer a step towards enhancing microbial removal of OMPs from drinking water by optimally using RSFs.

Filter media for basin infiltration: a case study

Abstract This study presents a viable filter media for infiltration basins used by managed aquifer recharge (MAR) plants. Filter media properties for sand filters, such as rapid and slow sand filters, are well established. This article investigates suitable filter media based on operational experience and filter media recommendations for sand filters, which is applied to the Vomb water treatment plant (WTP), a MAR plant in south Sweden. The results from this case study showed that a filter media with an effective grain size (d10) of 0.22–0.38 mm was likely viable based on the grain sizes of the natural glacifluvial deposits. The recommendation also included an optimal d10 range of 0.22–0.30 mm to increase the retention of particles in the filter media, rather than particles clogging and reducing the permeability of the aquifer. As a result of using filter media with lower d10-values than the glacifluvial deposits, unsaturated conditions under the infiltration basins will also likely improve. Furthermore, the recommendations presented in this study include limits for certain natural occurring contaminants (such as arsenic and mercury), other grain size grading characteristics and mineral composition.

Seasonal variation and spatial distribution of microplastics in tertiary wastewater treatment plant in South Korea

Wastewater treatment plant (WWTP) is proposed to be a point source of microplastics (MPs) that enter aquatic environments. Here, we quantified and characterized MPs down to 20 µm at a tertiary WWTP in Korea over a 1-year period. All wastewater contained MPs during the monitoring period, with concentrations ranging from 114 ± 17–216 ± 65 particles/L for influent and from 0.26 ± 0.29–0.48 ± 0.11 particles/L for effluent. MP abundance in the influents showed significant seasonal differences whereas a seasonal trend was not observed for the effluents, indicating a stable treatment performance (approx. 99.8%) of the WWTP. Spatial surveys of MP distribution in the WWTP showed that most MPs were removed by coagulation-sedimentation and rapid sand filtration, but some MPs still remained in the final effluent to generate the potential annual load of 2.9 × 109 particles and 0.54 kg into the rivers. These findings highlight the importance of long-term monitoring and MP mass quantification that would promote more accurate estimation of the MP load from WWTPs.