Rapid Filtration Research Articles

Experimental studies on the hydrodynamic properties of a deposit in rapid filters during physicochemical removal of iron from groundwater

Abstract This article presents the results of experimental studies for information support of the hydraulic compartment of the mathematical model of physicochemical iron removal from groundwater. It is experimentally established that the bound water in the deposit significantly exceeds the mineral component (chemical iron) for any waters with the different levels of iron oxidation. The deposit dehydration takes place at its boundary with the liquid phase. As a result, ferrous iron is gradually oxidized and ferric iron transforms from hydroxide forms to oxide forms, which leads to a decrease in the deposit volume and a increase in its density and strength. Further, the coefficient of the deposit hydrodynamic stability is proposed to use to take into account changes in the properties of the deposit that accumulates in the granular medium. It is experimentally determined that the iron amount remaining in the medium after backwashing increases simultaneously with the deposit's age. It will lead to a gradual reduction of the operational dirt capacity of the granular medium and a need to have measures of the filtration properties restoration or to replace the filter medium entirely.

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.

Electrical resistivity tomography applied for monitoring backwash efficiency in drinking water filters

Abstract Sustainable production of drinking water requires safe and efficient production, operation, and maintenance of the entire production line. Rapid gravity granular filters in water production require periodic backwash to ensure water quantity and quality. Therefore, an efficient backwash strategy plays a key role in ensuring a sustainable operation of the filters. In this study, a real-time monitoring method based on electrical resistivity tomography has been developed and tested at full scale for a period of six months in a rapid gravity granular filter during drinking water production. It provides proof of concept for a developed equipment and monitoring strategy within the given production environment. The time series of collected data, with different depth sensitivities of the upper 40 cm filter bed, demonstrates the temporal and spatial resolution capability of the method. Results show temporal development related to dynamic operation and backwash which in this study is combined with snapshot diagnostic tools and operational parameters to increase the spatial understanding of the active processes within the filter. These results suggest electrical resistivity tomography to be a suitable method for monitoring backwash efficiency.

D-VITylation: Harnessing the biology of vitamin D to improve the pharmacokinetic properties of peptides and small proteins

Peptides have great potential to be potent and specific therapeutics, yet their small size leads to rapid glomerular filtration, which severely limits therapeutic applications. Although conjugation of small proteins to large polymers typically results in longer residence times, these conjugates often have a significant loss of biological activity due to steric hindrance. Here, we improve the pharmacokinetics (PK) of peptide therapeutics by harnessing the biology of vitamin D. Attachment of a small vitamin D-based molecule (D-VITylation) protects the conjugated peptide or protein from renal clearance by virtue of reversible binding to the serum-circulating vitamin D binding protein (DBP), without compromising bioactivity. Varying the conjugation site on vitamin D affects the binding to DBP, with higher affinity corresponding to a longer plasma half-life. We also demonstrate the important contribution of the peptide to the overall PK, likely due to alternative clearance mechanisms such as protease degradation and receptor-mediated cellular uptake. With a Fab antibody fragment, for which these alternate clearance mechanisms are not significant, D-VITylation increases the half-life of elimination from 14 to 61 h in rats. The PK profile in minipigs and projected lifetime in humans suggest that D-VITylation is a viable strategy to achieve once-weekly dosing of peptide therapeutics in humans.

Granular activated carbon caps - A potential treatment barrier for drinking water cyanotoxins

Incorporation of granular activated carbon (GAC) in rapid media filtration has been shown to serve as an effective means to mitigate cyanotoxin exposure via extracellular adsorption. Control of organics, including dissolved organic carbon (DOC), may also improve via adsorption followed by biological treatment. Although beneficial, complete replacement of filter media with GAC is often associated with high capital costs. A seven-month pilot study conducted at a water treatment facility located in Eugene, Oregon examined the benefits of replacing the top 15 cm of anthracite media with GAC “caps” to enhance control of a cyanotoxin as well as DOC, disinfection by-product formation potential (DBP FP), and chlorine demand. Removal of cylindrospermopsin by GAC cap adsorption was assessed via simulated cyanotoxin events utilizing orange II dye as a surrogate over a 4-month period. A pilot-scale filter incorporating a GAC cap demonstrated up to 40% higher reduction throughout the study when compared to a control. This reduction however decreased to 9% as operation time increased. While installation of a GAC cap increased biomass density (ATP concentration), it did not improve DOC or DBP FP removal or chlorine demand at this facility, likely due to the low EBCT (1.2 min) in the GAC layer. This study presents evidence that incorporation of GAC caps may provide a cost-efficient, albeit low capacity, barrier for cylindrospermopsin exposure following several months of continuous operation.

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.

Predictive modelling of a rapid stratified bed filter for turbidity removal from surface water

The objective of the present work was to evaluate the hydrodynamic behaviour of a stratified bed filtration column consisting of 4 cm of sand and 2 cm of limestone to remove turbidity and measuring the head loss through the filter in several runs. In this study, two types of sand were used as filtering bed material, one fine and one medium. Crushed limestone was also available. These materials were characterized to determine the average particle diameter, porosity, and permeability coefficient. These were respectively 1.7∙10 –4 m, 336.96 and 0.68 m∙day –1 for fine sand, 3.3∙10 –4 m, 654.24 and 2.59 m∙day –1 for the medium sand and 1.26∙10–3 m, 388.8 and 8.64 m∙day–1 for crushed limestone. Using these materials, hydrodynamic analyses were carried out using clean water under rapid filtration conditions. In these analyses, different filtration rates were determined to be used in each experiment. Once the filtration rates were determined, the filtration analysis was performed with synthetic turbid water prepared at 8 NTU using tap water and bentonite. From the results obtained, a predictive model was developed based on total head losses for the evaluated filter, maintaining the rapid filtration condition. As a result, a turbidity removal efficiency of 97.7% was obtained with a total head loss of 17.8 cm at a filtration rate of 153 m·day –1. The developed model predicted head loss as a function of operating time, filtration rate, and filter depth to maximise turbidity removal. The model showed excellent prediction accuracy with R2 of 0.9999, which indicates that the model predictions are not biased. It was concluded that, due to the porosity of these materials, a stratified bed of sedimentary rocks has a great potential to be used in surface water filtration processes, which implies that it could be used at the rural community level as a form of water treatment, since the

Rapid and inexpensive nylon-66-filter solid-phase extraction followed by gas chromatography tandem mass spectrometry for analyzing perfluorinated carboxylic acids in milk

In this study, a new rapid and inexpensive filter solid-phase extraction method (FSPE) was developed for the extraction and separation of five perfluorinated carboxylic acids (PFCAs) (namely, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, and perfluorododecanic acid) from milk samples. Commercial nylon 66 syringe filters were used as adsorbents without additional modification. The proposed method could achieve the fast adsorption of analytes by benefitting from the advantages of using the nylon 66 filter membrane on PFCAs with multiple adsorption interactions, namely, hydrophobic interactions and hydrogen bonds. The FSPE was designed to achieve the rapid isolation of analytes based on the rapid solid-liquid separation while using the solid-phase extraction disk. PFCAs residues in milk were extracted by first flowing the samples through a nylon 66 syringe filter from top to bottom. Double contact desorption with methanol was then accomplished by pulling and pushing the syringe, followed by derivatization with acetyl chloride-methanol. Finally, the extracted PFCAs residues were monitored using gas chromatography-tandem mass spectrometry (GC-MS/MS) quantification. Under optimal conditions, the established method presented good linearity (correlation coefficient ≥ 0.9996), precision (relative standard deviation ≤ 13%), accuracy (81–105%), sensitivity (limits of quantification: 4–18 ng kg−1) and extraction performance (10 min).

Aptamer-immobilized bone-targeting nanoparticles in situ reduce sclerostin for osteoporosis treatment

Bone-targeted drug delivery to reduce systemic complications and maintain sufficient doses in bone tissues is the main challenge for osteoporosis treatment. Here, we develop a novel, and simply synthesized bone-targeting nanomedicine (DNA-MSN, DNAM) containing a PEGylated dendritic mesoporous silica nanoparticle (MSN) core (~ 65 nm) and an anti-sclerostin aptamer (Aptscl56) layer, to treat osteoporosis. The nanoparticle core protects the immobilized Aptscl56 from rapid nuclease degradation and renal filtration, prolonging in vivo half-lives. The DNAM-immobilized Aptscl56 layer exhibits dual functions to direct bone-attachment of ovariectomized mice, due to the interaction between phosphate groups in DNA aptamer Aptscl56 and bone calcium in hydroxyapatites, and to in situ capture sclerostin with picomolar affinities. Moreover, we show DNAM significantly reverses the serum level of sclerostin and osteoporotic bone loss to a normal level, improving bone histomorphology parameters and mechanical properties in the femur, and recovering serum levels of bone turnover markers, without systemic toxicity. Notably, the therapeutic effect of DNAM is superior to the "gold standard" drug alendronate, and the systemic dose of DNAM-immobilized Aptscl56 is only 25% of free Aptscl56. The present study provides insights into the regulation of unwanted circulating biohazards and represents a promising approach to deliver nanomedicines to treat osteoporosis.

PEMBUATAN SARINGAN CEPAT (RAPID FILTER) (Penggunaan Pipa PVC Dengan Sistem Pencuci Balik (Backwash) Di SMAN 1 Jejawi OKI)

Water is the basic need of every living thing, especially humans, animals and plants. Without water, living things cannot be alive. Jejawi District is an area of ​​Ogan Komering Ilir (OKI) Regency, South Sumatra Province with a population of 38,098 people. The people of Jejawi District get water for their daily needs from the river and well. The use of water with low quality might potentially cause diarrhea. As such, it is regarded as a potential endemic disease and is an Extraordinary Events (KLB) causing death. The prevalence of diarrhea in children under five in OKI Regency reached 11.35% where Jejawi District was in the fifth place with the highest cases that are 1,328 cases of diarrhea. Given the importance function of water, as one of the study programs at PGRI Palembang University, the chemical engineering study program is committed to contributing to environmental management, especially in the area of ​​South Sumatra, one of which is about water. Some of the courses listed in the curriculum in chemical engineering study programs include water treatment equipment used in water management, such as water filters. A Water filters are tools that can be used to filter and eliminate impurities in the water, by means of a barrier, either by chemical, physical or biological processes. Water filters are widely useful in irrigation, drinking water, aquarium as well as swimming pool. One type of filter that is commonly used is a fast filter water filter (Rapid Filter) with a back wash system. Therefore as an application of the learning outcomes in the chemical engineering study program at the PGRI University of Palembang, As well as helping the problems in Jejawi disrict, particullarly for the academic community of sman 1 jejawi in water treatment, the training was held to make water rapid filter by back wash system.

Design of Water Supply Scheme for Bisur Village

Abstract: In order to meet the water demand of the continuously growing population of Bisur village and failure of current water supply system it is essential to provide the sufficient and uniform quantity of water through the design of various units of water treatment plant, so for design work we have collected information of proposed area like Main water source, Population, Demand of water, quality of water, distribution network and water tanks etc. from MJP (Maharashtra Jeevan Prabhakaran) and local authorities. After analysed above data we calculated (i) Future population (ii) Water characteristics (iii)Design Period (iv)Water demand [101 LPCD]. After conducting and analysis of survey data we proposed an efficient new alignment for water distribution system and we designed various units of water treatment plant like Aeration, Alum Tank, Tube settler, Rapid Gravity filter, rising main, Jack Well, Sump etc. This proposed design of the water supply scheme for proper supply of water is sufficient to meet the daily requirement of water in selected area. Keywords: RRWS, ESR, Water Demand, MJP, WTP, Population

13C-Isotope-Assisted Assessment of Metabolic Quenching During Sample Collection from Suspension Cell Cultures.

Metabolomics and fluxomics are core approaches to directly profile and interrogate cellular metabolism in response to various genetic or environmental perturbations. In order to accurately measure the abundance and isotope enrichment of intracellular metabolites, cell culture samples must be rapidly harvested and cold quenched to preserve the in vivo metabolic state of the cells at the time of sample collection. When dealing with suspension cultures, this process is complicated by the need to separate the liquid culture media from cellular biomass prior to metabolite extraction. Here, we examine the efficacy of several commonly used metabolic quenching methods, using the model cyanobacterium Synechocystis sp. PCC 6803 as an example. Multiple 13C-labeled compounds, including 13C-bicarbonate, 13C-glucose, and 13C-glutamine, were used as tracers during the sample collection and the cold-quenching process to assess the extent of metabolic turnover after cells were harvested from culture flasks. We show that the combination of rapid filtration followed by 100% cold (-80 °C) methanol quenching exhibits the highest quenching efficiency, while mixing cell samples with a partially frozen 30% methanol slurry (-24 °C) followed by centrifugation is slightly less effective at quenching metabolism but enables less laborious sample processing. By contrast, rapidly mixing the cells with a saline ice slurry (∼0 °C) is less effective, as indicated by high isotope-labeling rates after sample harvest, while mixing the cells with 60% cold methanol (-65 °C) prior to centrifugation causes significant metabolite loss. This study demonstrates a rigorous, quantitative, and broadly applicable method for assessing the metabolic quenching efficacy of protocols used for sample collection in metabolomics and fluxomics studies.

Can 10× cheaper, lower-efficiency particulate air filters and box fans complement High-Efficiency Particulate Air (HEPA) purifiers to help control the COVID-19 pandemic?

Public health departments such as CDC and California Department of Public Health (CA-DPH) advise HEPA-purifiers to limit transmission of SARS-CoV-2 indoor spaces. CA-DPH recommends air exchanges per hour (ACH) of 4–6 air for rooms with marginal ventilation and 6–12 in classrooms often necessitating multiple HEPA-purifiers per room, unaffordable in under-resourced community settings. Pressure to seek cheap, rapid air filtration resulted in proliferation of lower-cost, Do-It-Yourself (DIY) air purifiers whose performance is not well characterized compared to HEPA-purifiers. Primary metrics are clean air delivery rate (CADR), noise generated (dBA), and affordability ($$). CADR measurement often requires hard-to-replicate laboratory experiments with generated aerosols. We use simplified, low-cost measurement tools of ambient aerosols enabling scalable evaluation of aerosol filtration efficiencies (0.3 to 10 μm), estimated CADR, and noise generation to compare 3 HEPA-purifiers and 9 DIY purifier designs. DIY purifiers consist of one or two box fans coupled to single MERV 13–16 filters (1″–5″ thick) or quad filters in a cube. Accounting for reduced filtration efficiency of MERV 13–16 filters (versus HEPA) at the most penetrating particle size of 0.3 μm, estimated CADR of DIY purifiers using 2″ (67%), 4″ (66%), and 5″ (85%) filters at lowest fan speed was 293 cfm ($35), 322 cfm ($58), and 405 cfm ($120) comparable to best-in-class, low-noise generating HEPA-purifier running at maximum speed with at 282 cfm ($549). Quad filter designs, popularly known Corsi-Rosenthal boxes, achieved gains in estimated CADR below 80% over single filter designs, less than the 100% gain by adding a second DIY purifier. Replacing one of the four filters with a second fan resulted in gains of 125%–150% in estimated CADR. Tested DIY alternatives using lower-efficiency, single filters compare favorably to tested HEPA-purifiers in estimated CADR, noise generated at five to ten times lower cost, enabling cheap, rapid aerosol removal indoors.

A novel CFD model to predict effluent solids concentration and pressure drop in deep bed granular filters for water treatment

Rapid sand filtration is a widely used technology to remove suspended solids in drinking water and wastewater treatment plants. One of the challenges of the rapid sand filtration is to reliably predict the removal efficiency of suspended solids and pressure drop as a function of filtration time. In this study we put forward a novel CFD model to simultaneously predict the solids concentration in the effluent and hydraulic resistence build-up in rapid sand filters. The CFD model is assessed against lab scale filtration data at different filter media grain sizes and filtration velocities. Our results show an overall satisfactory agreement with the observations. Finally, we highlight the complexity and need for further work in developing general CFD models for rapid sand filtration.

Study of Rapid Filtration of Cement Based Grouts by a Steel Model in the Field

Study of Rapid Filtration of Cement Based Grouts by a Steel Model in the Field

Endotoxin removal efficiency in conventional drinking water treatment plants, a case study in Egypt

The present study determines the endotoxin removal efficiency of drinking water treatment plants (DWTPs) in Egypt, as examples of conventional treatment methods used in developing countries. The total endotoxin in source water (Nile River) of these DWTPs ranged from 57 to 187 EU∙mL−1, depending on the location of treatment plants. Coagulation/ flocculation/sedimentation (C/F/S) after chlorine pre-oxidation removed bound endotoxins by 76.1–85.5%, but caused cell lysis and increased free endotoxins by 28.2–33.3% of those detected in raw waters. Rapid sand filtration had not significant effect on free endotoxins, but reduced bound endotoxins by 23–33.3%. Final chlorine disinfection also reduced bound endotoxins to levels around 1 EU/mL, accompanied by an increase in free endotoxins (37–112 EU∙mL−1) in finished waters. Simultaneously, final chlorine disinfection removed all heterotrophic bacteria, with low cyanobacterial cell numbers (348–2 450 cells∙mL−1) detected in finished waters. Overall, conventional treatment processes at these DWTPs could removal substantial amounts of bound endotoxins and bacterial cells, but increase free endotoxins through cell lysis induced by pre-oxidation and final chlorine disinfection. The study suggests that conventional processes at DWTPs should be optimized and upgraded to improve their performance in endotoxin removal and ensure safe distribution of treated water to consumers.

Nanoplastics removal during drinking water treatment: Laboratory- and pilot-scale experiments and modeling

Microplastics detected in potable water sources and tap water have led to concerns about the efficacy of current drinking water treatment processes to remove these contaminants. It is hypothesized that drinking water resources contain nanoplastics (NPs), but the detection of NPs is challenging. We, therefore, used palladium (Pd)-labeled NPs to investigate the behavior and removal of NPs during conventional drinking water treatment processes including ozonation, sand and activated carbon filtration. Ozone doses typically applied in drinking water treatment plants (DWTPs) hardly affect the NPs transport in the subsequent filtration systems. Amongst the different filtration media, NPs particles were most efficiently retained when aged (i.e. biofilm coated) sand was used with good agreements between laboratory and pilot scale systems. The removal of NPs through multiple filtration steps in a municipal full-scale DWTP was simulated using the MNMs software code. Removal efficiencies exceeding 3-log units were modeled for a combination of three consecutive filtration steps (rapid sand filtration, activated carbon filtration and slow sand filtration with 0.4-, 0.2- and 3.0-log-removal, respectively). According to the results from the model, the removal of NPs during slow sand filtration dominated the overall NPs removal which is also supported by the laboratory-scale and pilot-scale data. The results from this study can be used to estimate the NPs removal efficiency of typical DWTPs with similar water treatment chains.

Extracting phosphorus and other elements from lake water: Chemical processes in a hypolimnetic withdrawal and treatment system

Hypolimnetic withdrawal provides a way to remove phosphorus (P) from eutrophic lakes, but the method is still rarely combined with water treatment for capturing this P. Thus, little is known about the chemical interactions of P and other elements upon the treatment of hypolimnetic lake water. We investigated these chemical processes in a hypolimnetic withdrawal and treatment system (HWTS) in which hypolimnetic water is first led into a treatment unit for dissolved P (dP) precipitation and subsequently filtered before being circulated back into the lake. We studied three different field-scale treatment unit setups and water treatments (aeration only, aeration+calcium hydroxide (Ca(OH)2), aeration+biopolymer) to compare their effectiveness for dP removal and the geochemical properties of the resulting precipitate. In the aeration only treatment, most of the dissolved iron (dFe) (91-95%) and dP (71-91%) were removed when sand filters were used. The addition of Ca(OH)2 and biopolymer enhanced Fe flocculation, leading to more effective removal of dFe (d99-100%) and dP (88-95%) from the water. Regardless of the water treatment method, dP was always precipitated by amorphous Fe oxides formed in the hypolimnetic water upon aeration. The P content of the resulting precipitates was somewhat lower than expected (2439-4145 mg kg-1), which may be linked to chemical interactions between Fe and other components in the hypolimnetic water, such as organic matter. The precipitates also contained some heavy metals such as copper and zinc. We conclude that all the tested water treatments were effective in removing dP from hypolimnetic water, but the enhanced precipitation by the addition of treatment chemicals is beneficial when a mesh or other rapid filtration method is used, or when there is only negligible accumulation of dFe in the hypolimnion of the treated lake. Depending on the water treatment method and the water chemistry of the treated lake, the precipitate may have potential for nutrient recycling, although it may sometimes require preliminary processing to enhance bioavailability for plants and to reduce the concentration of heavy metals.