Phosphorus (P) is a fundamental element for plant and animal growth; however, an excessive amount of phosphorus can cause a threat to ecological environmental safety and human health. Therefore, this study aims to synthesize an adsorbent based on calcium silicate hydrates using mixture of polonite and calcium oxide and to determine its adsorption capacity for phosphorus ions. Additionally, pseudo-first- and pseudo-second- order kinetic models were employed to understand the adsorption process. The adsorbent based on calcium silicate hydrate was synthesized in a mixture of CaO and Polonite (CaO/SiO2 molar ratio 1.5) under hydrothermal conditions (16 h, 200 degrees C). It was determined that during hydrothermal treatment two crystalline (tobermorite and alpha-C2SH) and semicrystalline type calcium silicates hydrates were formed. Batch adsorption experiments were carried out at temperatures of 25, 35, and 45 degrees C in a thermostatic absorber by stirring 10 g of synthetic adsorbent in 1 l of KH2PO4 solution containing 0.2 g of P5+/L (20 mg of P5+ per gram of adsorbent) of phosphate ions. The duration of adsorption lasted up to 168 h. It was determined that adsorption capacity of synthetic adsorbent for phosphorus ions depends on the reaction duration and adsorption temperature. Synthetic adsorbent showed an extremely high adsorption capacity (>18 mg P5+/g) for phosphorus ions under all adsorption conditions. The most intensive adsorption occurred at a temperature of 35 degrees C as within 1 h 1 g of adsorbent adsorbed 16.6 mg of phosphorus. The equilibrium was reached after 48 h, when adsorption capacity reached 18.7 mg P5+/g. The kinetic calculations and the results of X-ray diffraction showed that chemisorption occurred during the experiments.

Paint in road markings contains microplastics (MP) which can be released by wear from traffic. High emissions of road MPs have been theoretically estimated in Sweden which has placed the road network as the worst MP polluter. Data from field measurements are scarce so if that gap could be filled it would shed light on previous assumptions. Two road run-off treatment systems along the E4 road through Stockholm city were studied for over three years. The primary aim was to cast light on selected mineral filters' capacity to remove dissolved pollutants, e.g. metals. The sediments collected in the two systems' reservoirs were later in focus for a study of MPs. Superficial water in the Lilla Essingen pond and the Gröndal sedimentation reservoir were removed by pumping until the bottom sediment was available for sampling. The pond and the reservoir are outdoor and indoor systems and the first-mentioned receives some stormwater from a housing area. Both systems receive road runoff from the Essinge route of the E4 road by gutters hanging under bridges. Ten sediment samples from each system were investigated for physical parameters and microplastic content. The Lilla Essingen pond stored less sediment than Gröndal due to its smaller catchment area, however, calculated per m2 runoff area it was the opposite 1.32 kg and 1.09 kg dry weight, respectively. This difference is caused by the pond receiving organic material from lawns within the catchment area. The microplastic analysis included 13 polymers and rubber of which only three connected to road marking paint (RMP). The pattern of microplastics found was consistent for both sediments. The microplastic mass varied generally between 25 and 42,000 μg/kg dry substance. The highest measured amount was styrene-butadiene rubber with 82,200 μg/kg dry substance. The RMP polymers detected were polystyrene (PS), polymethylmethacrylate (PMMA) and polyamide 6 (PA6). In Gröndal sediment, PS and PA6 were found in six of ten and one of ten samples, respectively. In Lilla Essingen sediments, PS and PMMA were found in five of ten and one of ten samples, respectively. The release of polymeric RMP was calculated based on the Gröndal sediment as kg/hectare road marking area and year. The estimated value was 3.83 kg for the road with a traffic intensity of 165,000 annual average daily traffic (AADT). The wear of road markings from state roads has been estimated to vary between 1,500‒9,900 tons per year (entire particles) of which the polymer part is 30‒396 tons/year. Assume that 30 tons are released from the state roads and the total road marking area is 2,310 hectares; the release is 30 000 kg/23100000 m2 = 1.30 g/m2/year. A polymer release of 396 tons/year yields 17.14 g/m2/year. The fate of microplastics in that release is unknown other than possible destinies such as transport by road runoff, splash, snow removal, wind, and road sweeping. Difficulties in interpreting these different results depend on a lack of knowledge of how much microplastics leave the road other than through runoff. Field trials must therefore be carried out at a site where runoff, sludge collection, wind dispersion including splash from the road surface, and road maintenance can be measured and controlled. Limitations to the calculations are that some thermoplastic polymers usually found in RMP were not included in the analysis and that part of the analysis method with decantation may have caused losses of microplastics. Although the calculated value in this report is somewhat underestimated, the results indicate low microplastic RMP waterborne emissions from heavily trafficked roads. Sediments and sludge collected over time constitute historical archives that can reflect real conditions, however, more development work needs to be done regarding sampling and, above all, analytical methodology of microplastics in sediments.

Färg i vägmarkeringar innehåller mikroplast (MP) som kan frigöras vid slitage från trafiken. Exempel på vägmarkeringar är körfältslinjer och trappflexlinjer. Höga utsläpp av mikroplast från vägmarkeringar har teoretiskt uppskattats i Sverige vilket har placerat vägnätet som den värsta MP-förorenaren. Data från fältmätningar är knappa så om det gapet kunde fyllas skulle det kunna verifiera eller förkasta tidigare antaganden. Två reningssystem för vägavrinning längs E4:an genom Stockholms stad studerades i över tre år i ett projekt som drevs av Trafikverket i samarbete med KTH. Det primära syftet var att belysa utvalda mineralfilters förmåga att avlägsna lösta föroreningar, t.ex. metaller. Sedimenten som samlades in i de två systemens reservoarer var senare i fokus för en studie av MP. Vattnet i Lilla Essingen-dammen och Gröndal sedimenteringsmagasin togs bort genom pumpning tills bottensedimentet var tillgängligt för provtagning. Dammen ligger under Essinge-bron som på så sätt bildar ett tak och magasinet ligger i ett bergrum. Båda systemen tar emot vägavrinning från Essingesträckningen på E4:an till hängrännor som för dagvattnet till anläggningarna.Tio sedimentprover från varje system undersöktes med avseende på fysikaliska parametrar och innehåll av mikroplast. Lilla Essingen dammen lagrade mindre sediment än Gröndal på grund av dess mindre avrinningsområde, men räknat per m2 avrinningsområde var det motsatt förhållande; 1,32 kg/m2 respektive 1,09 kg/m2 torrvikt. Denna skillnad orsakas av att dammen tar emot organiskt material från gräsmattor inom avrinningsområdet. Mikroplastanalysen, utförd av det certifierade laboratoriet Eurofins, omfattade 13 mikroplaster varav endast tre anses vara kopplade till vägmarkeringsfärg (RMP). Mönstret av mikroplast som hittades var konsekvent för de båda undersökta sedimenten. Massan av mikroplast varierade generellt mellan 25 och 42 000 μg/kg torrsubstans. Den högsta uppmätta mängden var styren-butadiengummi med 82 200 μg/kg torrsubstans. De RMP som detekterades var polystyren (PS), polymetylmetakrylat (PMMA) och polyamid 6 (PA6). I Gröndals sediment hittades PS och PA6 i sex av tio, respektive ett av tio prover. I Lilla Essingens sediment hittades PS och PMMA i fem av tio respektive ett av tio prover.Utsläpp av polymerisk RMP beräknades utifrån Gröndalsedimentet som kg/hektar vägmarkeringsyta och år. Utsläppet uppgick till 3,83 kg för vägsträckan med en trafikintensitet på 165 000 årlig genomsnittlig daglig trafik (ÅDT). Beräkningen per fordon och år är då 3 830 000 mg/165 000 = 23,2 mg. Järlskog et al. (2024) publicerade en rapport om mikroplastutsläpp från slitage av vägmarkeringar. De uppskattade att slitaget av vägmarkeringar från statliga vägar varierar mellan 1 500‒9 900 ton per år (hela partiklar) och att polymerdelen är 30‒396 ton/år. Antag att 30 ton släpps ut från de statliga vägarna och den totala ytan för vägmarkeringar är ca 2 310 hektar; utsläppet är då 30 000 kg/23100000 m2 = 1,30 g/m2/år. En polymerfrisättning beräknat på 396 ton/år ger 17,14 g/m2/år. Mikroplasternas öde i det släppet är okänt annat än möjliga öden som transport med avrinning på väg, stänk, snöröjning, vind och vägsopning. Svårigheter att tolka dessa olika resultat beror på att vi inte vet hur mycket mikroplaster som lämnar vägen på annat sätt än genom avrinning. Fältförsök måste därför utföras på en sådan plats där avrinning, slamuppsamling, vindspridning inklusive stänk/snöplogning från vägytan samt vägskötsel kan mätas och kontrolleras. Begränsningar för beräkningarna är att vissa termoplastiska polymerer inte ingick i analysen och att en del av analysmetoden med densitetssortering och dekantering kan ha orsakat förluster av mikroplaster. Resultaten tyder på att de teoretiska beräkningar som tidigare gjorts i andra undersökningar kan vara överdrivna. Även om det beräknade värdet i denna rapport till viss del är underskattat p g a nämnda metodfel, indikerar resultaten relativt låga RMP-utsläpp av mikroplast via avrinning från hårt trafikerade vägar. Sediment och slam som samlats in över tid utgör historiska arkiv som kan spegla verkliga förhållanden, dock behöver mer utvecklingsarbete göras gällande provtagning och framför allt metodik vid analyser av mikroplast i sediment.Denna studie bör följas upp av fler undersökningar av de insamlade sedimentproverna. Exempelvis bör de glasmikrokulor som observerats i mikroskop studeras i detalj och deras totala vikt bestämmas i Gröndal och Lilla Essingen sedimenten. En sådan analys skulle kunna kasta ljus på mikropärlorna som proxy för vägmarkeringsfärger enligt en nyligen publicerad vetenskaplig artikel. Gröndalsmagasinet och Lilla Essingen är genomströmningssystem med olika skötsel. I Gröndal samlas vägavrinning upp vid varje regn, flockningsmedel tilsätts och partiklar i vattnet sjunker snabbt till botten av magasinet. När magasinet fyllts sker avtappning av klarfasen. Bräddning är sällsynt förekommande. Lilla Essingen dammen har en ständig vattenmassa vars nivå pendlar inom ett intervall beroende på regn. Bräddning förekommer vid extrema flöden. Tillsatsen av ett flockningsmedel i Gröndal ger högst sannolikt förbättrad MP-avskiljning än den traditionella sedimenteringen i Lilla Essingen. Utflödet av MP från dessa system studerades inte noggrant i ett tidigare projekt men analys av några vattenprover visade på mycket låga koncentrationer av MP-partiklar (Agnieszka Renman, opublicerade data). En kompletterande studie på de undersökta platserna bör innefatta provtagning av inkommande och utgående3vägdagvatten för undersökning av sedimenteringens effektivitet. Liknande system med olika och lägre trafikbelastningar till de två studerade bör inkluderas och flödesövervakas från tillståndet av tömda sedimentbassänger till fyllda under en period av minst 2-3 år. Resultaten bör generera kunskap om hur man konstruerar och hanterar nuvarande och kommande dagvattenreningssystem för att minska mikroplast- och gummiföroreningar från vägar och tätorter.

Sediments contaminated with hazardous metals pose risks to humans and wildlife, yet viable management options are scarce. In a series of laboratory experiments, we characterized Polonite® – an activated calcium-silicate – as a novel sorbent for thin-layer capping of metal-contaminated sediments. We tested a fine-grained by-product from the Polonite production as a cheap and sustainable sorbent. First, Polonite was reacted with solutions of Cu, Pb, and Zn, and the surface chemistry of the Polonite was examined using, e.g., scanning electron microscopy to investigate metal sorption mechanisms. Batch experiments were conducted by adding Polonite to industrially contaminated harbor sediment to determine sorption kinetics and isotherms. Importantly, we measured if the Polonite could reduce metal bioavailability to sediment fauna by performing digestive fluid extraction (DFE). Finally, a cap placement technique was studied by applying a Polonite slurry in sedimentation columns. The results showed rapid metal sorption to Polonite via several mechanisms, including hydroxide and carbonate precipitation, and complexation with metal oxides on the Polonite surface. Isotherm data revealed that the sediment uptake capacity (Kf) for Cu, Pb, and Zn increased by a factor of 25, 21, and 14, respectively, after addition of 5% Polonite. The bioavailability of Cu, Pb, and Zn was reduced by 70%, 65%, and 54%, respectively, after a 25% Polonite addition. In conclusion, we propose that sediment treatment with low doses of the Polonite by-product can be a cheap, sustainable, and effective remediation method compared to other more intrusive methods such as dredging or conventional isolation capping.

A closed-loop on-site wastewater treatment system (OWT) was studied comprising steps of septic tank to remove organics (Biological Oxygen Demand (BOD)), biofiltration clarifier for biological removal of nitrogen (N), phosphorus (P) and BOD, reactive Polonite® filter for chemical adsorption and precipitation removal of dissolved P, and tidal flow constructed wetland (TFCW) sand filter for polishing the effluent to low P and N effluent Swedish standards. The field experimental data that have been used to optimize TFCW design in the numerical modelling using HYDRUS-2D coupled with and without PHREEQC indicated that the adsorption efficiency of the reactive Polonite® adsorbent was nearly double to that obtained in TFCW sand filters for PO4-P (95 %) and Total-P (85 %) removal in summer at a high temperature range (15.4–18.8 °C) and pH range (9.9–10.8). The weaker PO4-P (53 %) and Total-P (25 %) removal efficiency in winter was due to a low temperature (1.5–8.1 °C) and low pH (7.2–7.9). This decrease in pH was attributed to salinity in the domestic wastewater and dilution of rainwater. Modelling results revealed that the transport mechanisms and rate of P adsorption kinetics in the TFCW sand filters enhanced with calcium and iron flow from chemical dissolution in the preceding Polonite® adsorbent was increased with the increase in temperature. However, the P adsorption was less sensitive at high ferrihydrite (Fe(OH)3) dose, suggesting limited effects of cations dissolution and abundance of metal oxides and hydroxide ions at the mineral surface for anions exchange with phosphate for surface complexation. The strategy of combining field data and modelling provided valuable insights for assessing adaptability and optimizing TFCW design under variable fluxes and scenario effects of insulated/uninsulated and dilution by rainwater in cold-climate regions.

This study examined the adsorption capacity and treatment efficiency of sand filters in on-site treatment systems for cold climate regions. The effects of different operating conditions, porosity and kinetics parameters were investigated in column experiments and COMSOL Multiphysics® modelling, to comprehensively reveal the mechanisms and optimize treatment efficiency of nitrogen (N) and phosphorus (P) removal in a field tidal flow constructed wetland (TFCW), treating effluent from a package treatment plant with P filter material. The results from column experiments with sand showed that Total-P adsorption rate was dependent on feed water quality (Septic tank >0.77 ± 0.06 g kg−1; Biotreatment >0.41 ± 0.07 g kg−1; Reactive material Polonite® <0.18 ± 0.07 g kg−1). In the field TFCW trial, Total-P adsorption in the top layer (>1.42 ± 0.55 g kg−1) and middle layer (>1.06 ± 0.51 g kg−1) was twice that in laboratory columns, due to strong interaction with the air-water interface and use of fluctuated domestic wastewater solutions. The breakthrough curve (BTCs) of the coarse sand matched the physical behaviour of tracer electrical conductivity (EC) in effluent from the sand column experiments. The modelling results demonstrated that high filter porosity and low hydraulic load were significant factors for optimal removal of NH4–N, Total-N, PO4–P, Total- P in the top layer (>99.95 ± 0.03 %, 44.37 ± 28.75%, 70.89 ± 28.30%, 76.18 ± 20.3%), middle layer (>98.94 ± 1.77%, 18.23 ± 23.04%, 76.62 ± 28.73%, 65.40 ± 31.85%) and deep layer (>99.99 ± 0.02%, 65.50 ± 20.64%, 75.53 ± 23.16%, 41.54 ± 28.81%) in the TFCW system, respectively. The results show that on-site wastewater treatment in cold climate TFCW can be applied as a technology to polish effluent from a three-step pretreatment system. However, hydraulic optimization is an important factor for the design of the TFCW to receive a successful long-term operating system.

The effects of stormwater discharges on receiving aquatic environments and the need for their purification were highlighted by an EU court in May 2020. The ruling stated the need for removal of dissolved pollutants, which justifies field studies for development of far-reaching methods for runoff treatment. In this study, a standard sand was used as medium for road runoff filtration and removal of dissolved and particle-bound (<0.45 mu m) zinc (Zn) and copper (Cu). Data included 24 road runoff events, mimicking the flow variations and pollutant emissions over a seven-month period. The findings showed that sand can be used to remove Zn and Cu from road runoff in a gravity fed treatment system at a surface load ranging from 16.8 to 201 L m(-2) h(-1). The removal of total Zn and Cu was 93 and 67%, respectively. Dissolved Zn was efficiently removed by the sand (87%), however not Cu (19%). The sand efficiently removed total suspended solids (TSS) from the maximum occurring 443 mg L-1 to below 5 mg L-1. No head loss due to the TSS loadings was observed. The sand's potential to remove the investigated metals was shown, but in the longer term, effluent concentrations may exceed permitted values.

The sorption capacities of sand filters used for onsite wastewater treatment and their associated risks of phosphorus (P) leaching on contact with rainwater were investigated in column experiments and with modelling tool for over 300 days. Columns packed with sand were exposed to real domestic wastewater of different characteristics and hydraulic loading modes. The wastewater fed into the columns was effluent collected from three different treatment units in the field: a septic tank (ST), biofiltration tank (BF) and Polonite® filter bag (PO). The risk of P leaching to groundwater and surface water was also assessed, by exposing the same sand columns to natural rainwater. Overall results indicated that sand soils can exhibit different adsorption and desorption capacities for electrical conductivity (EC), Total-P, phosphate-P and total suspended solids, depending on the characteristics of influent wastewater, loading rate and total operation time. The removal efficiencies of the sand columns increased in the order ST (98.16 %) > PO (93.36%) > BF (81.57%) for PO4-P and slightly decreased ST (97.11 %) > PO (92.06%) > BF (76.76%) for Total-P columns. All sand columns loaded with actual wastewater solutions from septic tanks and biofiltration tank have demonstrated high risks of phosphorus leaching (> 99.99%) to the groundwater. The modelling was successful captured behavior of EC tracer and adsorption of PO₄-P with acceptable prediction uncertainty in the PO < 8% columns. The modelling results indicated that the decrease of loading rate from 83.3 mL d^-1 to 20.83 mL d^-1 led to an average increase of removal efficiency and prolong operational lifetime and mass of adsorbed Total-P in the sand soil. This study concludes that sand is a valuable filter medium at low loading rate for phosphorus removal in full-scale operations of onsite treatment systems, however very vulnerable for leaching P when in contact with rainwater.

The performance of a tidal flow constructed wetland (TFCW) following wastewater treatment in a package plant designed for two households was studied in a nine-month field trial and its design evaluated through process modelling and pumping tests. The TFCW is operated by filling and draining periods lasting five to nine days, depending on wastewater production by users. The effects of passive aeration, temperature, influent concentration of nutrients and bacteria as well as hydraulic loading on the treatment efficacy of the TFCW system were studied. Results showed that the TFCW system removed ammonium-nitrogen (NH4-N, 76%), phosphate -phosphorus (PO4-P, 56%), total inorganic nitrogen (TIN, 28%) and reduced water pH by15%. The removal efficiency of TIN was significantly improved in the summer (> 50%). The average influent concentration of total phosphorus (TP) was low after the preceding package plant treatment (1.12 mg L-1), but the TFCW showed ability to further reduce TP to the average concentration of 0.57 mg L-1. A coupled reactive transport model was developed in the COMSOL Multiphysics (R) 5.6 software to predict processes of water flow and was validated against the actual data from the field. The modelling exhibited a satisfactory prediction accuracy and capability to capture behavior of effluent PO4-P, NH4-N and dissolved oxygen concentration. Moreover, modelling processes helped to understand the defects of water flow and adsorption processes within the treatment wetland.

A toolbox of methods must be available for the remediation of lakes and water bodies suffering from eutrophication. One method suggested is hypolimnetic withdrawal based on a closed-circuit system. Prior to the start of a pilot-scale test at Lake Hönsan, Sweden, a laboratory trial with containers filled with water and bottom sediment from this lake was performed. A peristaltic pump distributed equal bottom water volume to four columns, two filled with glass beads and two with the filter material Polonite, and then back to the surface of the containers. The reactive filter medium (RFM) removed phosphate (PO₄-P) efficiently (98.6%), despite the relatively low influent concentration (390 µg L⁻¹). The control column filled with glass beads, removed 2.9% of the PO₄-P. The anoxic sediment, containing 2.47 mg P g⁻¹, released PO₄-P, which was indicated by the increased concentration in near-bottom water. The redirected water after RFM filtration had high pH (x¯=11.1); however, an equalization took place in the water mass to a lower but still increased pH value  (x¯=8.7) compared to the control  (x¯=7.02). This article reports the pros and cons of a full-scale system using the proposed method.

The predominant techniques used for road runoff treatment are sedimentation and filtration. In filtration systems, the ability of the media to adsorb the contaminants is a finite process. Consequently, construction, operation and maintenance managers of such systems should know in advance the service life, i.e., when the used medium should be replaced, and associated costs of operation and maintenance. A batch experiment followed by a packed bed reactor (PBR) experiment addressed the kinetics of the studied media argon oxygen decarburization slag (AOD) and Polonite, followed by the development of a 1D-model to describe the change of concentration of Cu and Zn within time. The batch test results showed that Cu and Zn adsorption followed the Freundlich isotherms for AOD and Polonite. Those results coupled with the linear driving force model and the developed model resulted in good agreement between the PBR results and the simulation. The model was capable to predict (i), the service life at the hydraulic load of 0.18 m/h for AOD (Cu: 395 d; Zn: 479 d) and Polonite (Cu: 445 d; Zn: 910 d), to show (ii) the profile concentration in the PBR within time and the gradient of the concentration along the height of the reactor.