Swedish Plants Research Articles

Phosphorus speciation in sewage sludge and their ashes after incineration as a function of treatment processes.

Phosphorus (P) is a key component in agricultural fertilizers, but it is also a scarce resource, why its recycling has been thoroughly investigated and one promising resources is sewage sludge. Because of stricter regulations in terms of sludge disposal, thermal treatment (e.g. incineration) has become an attractive option. The incineration process alters the chemical speciation of P in favour to calcium-associated (apatite, apatite phosphorus (AP)) species, which is preferred for P recovery. In order to achieve qualitatively transformation, it is important to identify limiting or promoting factors. This study reports on the impact of iron, aluminium and calcium on the transformation of iron- and aluminium-phosphate (NAIP) to AP species, assessed by studying sludge and ash from 10 municipal wastewater treatment plants in Sweden. The effect of iron and aluminium added in the treatment processes was also evaluated. The obtained results show that high calcium concentration favours formation of AP species in both sludge and ashes, whereas high concentration of iron and aluminium favours formation of NAIP species in the sludge. The transformation from NAIP to AP species is hampered by aluminium, irrespectively of its origin, whereas no such correlations could be seen for iron. Therefore, in order to enable efficient P recovery from sewage sludge ash, the amount of aluminium added in the treatment process, as well as its concentration in influent streams to the treatment plants, must be limited.

Pilot scale removal of organic micropollutants by combining ozonation with powdered activated carbon

ABSTRACT Pilot experiments were conducted to assess the removal of organic micropollutants from biologically treated wastewater at a municipal wastewater treatment plant in Sweden. Powdered activated carbon (PAC) was combined with a low dose of ozone added directly before the PAC contact tank, enabling ozone to react simultaneously with the PAC and the wastewater contaminants. This combination of ozone and PAC was compared to PAC or ozone alone. The process, which included coagulation/flocculation and ballasted high-rate lamella sedimentation, proved to be both robust and efficient for the removal of micropollutants. The addition of 1.3 mg PAC/mg DOC resulted in a 73% average reduction of micropollutants. With the addition of 0.13 mg O3/mg DOC, the reduction increased to 83%, which was similar to the outcome with the addition of 26 mg PAC/mg DOC without ozone. The process configuration and operating conditions did not lead to any detectable bromate formation despite relatively high influent bromide levels. The estimated operating costs for combining PAC with a low dose of ozone were significantly lower than for applying a higher PAC dose. Thus, this way of combining PAC with ozone seems to have several advantages with respect to treatment efficiency and operation.

Unveiling the Potential of Mixed Reality: Enhancing Time Measurement and Operator Support in Manual Assembly Processes

This study investigates the potential of Mixed Reality (MR) in the manual assembly processes and conducts a case study at a pump manufacturing plant in Sweden. An MR solution is developed to assist operators through visual instructions and guiding aides. The solution also captures the operator's motions using advanced hand and eye tracking features for real-time guidance and accurate time measurement. The proposed MR solution uses the build feature of HoLolens and a workstation editor, which facilitates the use of the solution in diverse assembly environments. The results of the experiments show that the developed MR solution can improve operator support, reduce errors, and enhance the overall efficiency of manual assembly processes. Moreover, it is shown to be an efficient tool for time measurement of the manual assembly process that has promising potential to replace sophisticated and time-consuming traditional time study methods.

Application of REPAS to analyze the sump clogging issue following a LOCA and its impact on the reliability of the ECCS long-term core cooling function

Sump clogging has been identified as a relevant issue after an accident occurred in the Barsebäck-2 nuclear power plant in Sweden (1992). Following a steam line Loss of Coolant Accident (LOCA) due to the inadvertent opening of a safety relief valve, the jet stripped some insulation material from nearby pipes. The insulation debris were transported to the inlet of the strainers for the drywell spray system, thus clogging the intake. The accident was not serious but showed that the Emergency Core Cooling System (ECCS) could have failed. As a consequence, several actions have been undertaken by international organizations, regulatory bodies and nuclear power plant owners to characterize this issue, and propose solutions and improvements. In the present paper, the Reliability Evaluation of Passive Safety Systems (REPAS) methodology is applied to analyze the sump clogging issue and its effect on the long-term core cooling function. Originally developed to evaluate the reliability of passive systems, REPAS is here applied for the first time to an active system. The application is performed using the TRAC/RELAP Advanced Computational Engine (TRACE) code, developed by the USNRC, to simulate a generic three-loop PWR, with an active decay heat removal system.

An Overview of Phytophthora Species on Woody Plants in Sweden and Other Nordic Countries.

The genus Phytophthora, with 326 species in 12 phylogenetic clades currently known, includes many economically important pathogens of woody plants. Different Phytophthora species often possess a hemibiotrophic or necrotrophic lifestyle, have either a broad or narrow host range, can cause a variety of disease symptoms (root rot, damping-off, bleeding stem cankers, or blight of foliage), and occur in different growing environments (nurseries, urban and agricultural areas, or forests). Here, we summarize the available knowledge on the occurrence, host range, symptoms of damage, and aggressiveness of different Phytophthora species associated with woody plants in Nordic countries with a special emphasis on Sweden. We evaluate the potential risks of Phytophthora species to different woody plants in this geographical area and emphasize the increasing threats associated with continued introduction of invasive Phytophthora species.

Dissemination of carbapenemase-producing Enterobacterales through wastewater and gulls at a wastewater treatment plant in Sweden

Here we report the detection of carbapenemase-producing Enterobacterales (CPE) isolated from Swedish wastewater and gull faeces. CPE have not been detected in samples from animals in Sweden preceding this report. Sampling of wastewater treatment plant (WWTP) inlet and outlet, sedimentation basins, surface seawater from key aquatic bird habitats and freshly deposited gull faeces was done on six separate occasions during May to September 2021. Following broth enrichment, selective screening of putative CPE was performed on mSuperCarba™ (CHROMagar). Species identification was done with MALDI-TOF. Antimicrobial susceptibility testing was performed according to EUCAST. In total, seventeen CPE were verified by genome sequencing carrying blaGES-5, blaIMI-3, blaOXA-181 or blaOXA-244. The blaGES-5 was carried on IncP plasmids in four different species; Escherichia coli ST10 isolated from WWTP outlet, Raoultella ornithinolytica isolated from WWTP inlet, outlet and sedimentation basins as well as gull faeces collected at the WWTP and Klebsiella spp. isolates from WWTP inlet and outlet. The genetic environment surrounding blaGES-5 was similar in two Citrobacter freundii causing human infections. The blaIMI-3 was carried on IncFII(Yp) plasmids in four Enterobacter ludwigii, isolated from WWTP outlet and gull faeces collected at a recreational city park 2 km from the WWTP. The blaOXA-181 was located on a COLKP3 plasmid found in an E. coli, while blaOXA-244 was chromosomally located in an E. coli ST10, both isolated from WWTP inlet. Phylogenetic analysis of R. ornithinolytica and E. ludwigii isolates indicate that the gulls carried strains related to those identified in the WWTP samples. The results thus add to the increasing evidence of WWTPs as anthropogenic reservoirs for mobile genetic elements with antibiotic-resistance functionality. Such environments could profoundly impact the dissemination and spread of such genetic elements via for example aquatic birds, thereby warranting further study and surveillance.

Key elements for proper development and implementation of severe accident management guidance/guidelines – SAMG

Severe Accident Management Guidelines (SAMG) have been developed to support a nuclear power plant (NPP) in case of a severe accident, i.e. an (unlikely) accident where the core and/or the fuel in the Spent Fuel Pool (SFP) have been damaged and there is risk for radioactive releases. Various approaches exist, such as the SAMG developed by the PWR and BWR Owners Groups (PWROG, BWROG), by Electricité de France (EdF) for its fleet of plants, the Candu Owners Group (COG) and by several individual NPPs. Often, the developers of SAMG develop a generic type of SAMG, applicable for a certain type of NPP, and leave it to the individual plants to adapt these to their configuration and Emergency Response Organisation (ERO). That means, that quite some burden remains for the individual plants to finally implement the SAMG. This implementation includes not only technical items, such as defining proper strategies, but also many organisational issues, as handling a severe accident needs an effective ERO, in which the SAMG must be well embedded.Various plants have been reviewed, both the ways they have constructed their plant-specific SAMG, implemented them in their ERO and tested the performance in drills and exercises. Most recently, a review of SAMG at Swedish plants has been performed, after which it was decided to pull the various experiences together and summarize them in one compendium. Some of these also include aspects of the development of the generic SAMG.The result is a number of recommendations (∼30), both on the technical field as well as regarding the ERO. We could also define a number of good practices that deserve wider attention.A few words have been devoted to international support for a stricken plant (Epilogue).

The Effect of the Elemental Composition of Municipal Sewage Sludge on the Phosphorus Recycling during Pyrolysis, with a Focus on the Char Chemistry—Modeling and Experiments

The present study investigates how the original sewage sludge characteristics influence the composition of sewage sludge-based chars for land applications. Sewage sludge from two different wastewater treatment plants in Sweden was pyrolyzed at 500, 700, and 900 °C, and the resulting chars were analyzed. Thermodynamic equilibrium calculations (TEC), together with chemical fractionation, were implemented to simulate the char after the pyrolysis process at different temperatures. The results showed that, in general, for both the municipal sewage sludge (MSS), phosphorus (P) was significantly retained in the char at various temperatures. However, no specific correlation could be found between the pyrolysis temperature and the amount of P remaining. With regard to the heavy metals removed from the char after the pyrolysis reaction, the concentrations of copper, chromium, lead, nickel, zinc, and cadmium were below the limits of the Swedish regulations for farmland application.

Statistical analysis of fuel cycle data from Swedish Pressurized Water Reactors and the impact of simplifying assumptions on simulated nuclide inventories

When analyzing and assessing properties of spent nuclear fuel (SNF) such as radionuclide inventories, the power history of the fuel during its time spent inside the reactor core plays an important role. This information can be very useful in the field of nuclear safeguards wherein a safeguards inspector can use it to verify the fuel properties such as burnup, initial enrichment and cooling time (or collectively termed as the “BIC” set of variables). However, such information may often be unavailable to the safeguards inspector or the level of detail in the available information may be lacking. Therefore, when analyzing SNF for various purposes (such as for safety, safeguards and back-end purposes), the power history of the fuel is most often disregarded altogether and the inspectors only look at the fuel BIC. If the power history-level information is considered, it is not uncommon to make simplifying assumptions about how the fuel is burned in the reactor. In this work, we perform an exploratory analysis of fuel cycle data from two PWR units of the Ringhals nuclear power plant in Sweden. The said analysis describes the variation in the number of cycles, cycle lengths, downtimes et cetera in order to develop a simplified yet representative model of irradiation that may be used to construct synthetic data libraries. Furthermore, we look into impact of changes in the power history on the nuclide inventories of key gamma emitters and isotopes responsible for decay heat in the SNF of the fuel in three different irradiation scenarios. Our results show that in most cases with fuels that are considerably long-cooled, it is acceptable and even preferred to use a simplified power history over an idealized or a representative irradiation model obtained from exploratory analysis of the fuel cycle data. However, for short-cooled fuels, using a simplified or even an idealized history is less preferable over modeling the detailed power history of the fuel due to the presence of short-lived nuclides in the SNF which are more sensitive to variations in the power history.

Per- and polyfluoroalkyl substances (PFAS) in sludge from wastewater treatment plants in Sweden — First findings of novel fluorinated copolymers in Europe including temporal analysis

Thousands of per- and polyfluoroalkyl substances (PFAS) are on the global market, while only a minor proportion is monitored regularly in the environment. Wastewater treatment plants (WWTPs) have been suggested to be a point source for PFAS to the environment due to emission of effluent and sludge. In this study, 81 PFAS including two rarely studied perfluoroalkyl sulfonamide-based (FASA) copolymers were analyzed in sludge samples to understand the usage of PFAS in the society. Sludge samples (n = 28) were collected at four WWTPs in Sweden between 2004 and 2017. The total levels of 79 measured PFAS were between 50 and 1124 ng/g d.w. All sludge samples showed detectable levels of both C8- and C4-FASA-based copolymers. The concentrations of the FASA-based copolymers were proposed to be reported in fluorinated side-chain equivalents (FSC eq.), in order to compare the levels of the copolymers with the other neutral and anionic PFAS, as no authentic standards were available. The concentrations of the FASA-based copolymers in sludge were between 1.4 and 22 ng FSC eq./g d.w. A general predomination of precursor and intermediate compounds was observed. A lower contribution of perfluoroalkyl carboxylic acids was noted for the WWTPs more influenced by domestic emission when compared with more influenced by industrial emission. An overall declining trend in the total PFAS concentration was seen between the years 2004 and 2017. The present study observed a shift from the C8-based chemistry toward shorter chain lengths, included a declining trend for C8-FASA-based copolymer over the entire study period. These findings further demonstrate the occurrence of side-chain fluorinated copolymers in Sweden and that sludge is a useful matrix to reflect the usage of PFAS in society and the potential for environmental exposure.

Key factors for site-selection of biogas plants in Sweden

Biogas production through anaerobic digestion is an integral part of the transition toward a biobased and circular economy and its expansion is foreseen in many parts of the world as well as in Europe. In Sweden, a governmental inquiry suggested biogas production to be increased from about 2 TWh today to 7 TWh by 2030. This rapid expansion would require installation of several new biogas plants across the country. However, the location of biogas plants can greatly affect its business performance and there are several geographic and socio-political factors that would limit the choice of location. Through dialogue with existing biogas producing companies and a few other related actors, we identified 12 factors that are commonly considered in the site-selection of biogas plants in Sweden or are considered to be important in the years to come. These factors are grouped into those related to supply and demand (feedstock supply, biogas demand, digestate demand, and carbon dioxide demand), infrastructure and synergies (available infrastructure, adjacent existing industries), land-use and zoning (nearby housing, zoning, and historic preservation sites), and socio-political context (political strategies and goals, organizational capability, and local social acceptance). We discuss how these factors can be used under rapidly transforming conditions in Sweden through different site-selection logics and highlight the importance of spatially explicit analysis for individual or coordinated decision making in future. Our method of enquiry and analysis, and to a certain degree the factors, can be also relevant for other countries, particularly in Europe. This study paves the way for more in-depth investigation of the question of site-selection of biogas plants in Sweden; both in the direction of detailed analysis at the local level, or screening analysis on the regional or national level for improved coordinated actions.

Organic micropollutants, heavy metals and pathogens in anaerobic digestate based on food waste

Anaerobic digestate based on food waste is increasingly used as fertilizer in food production. This study examined the characteristics of anaerobic digestate based on food waste from three biogas plants in Sweden. The characterization included measurements of heavy metals (n = 7), chemicals of emerging concern (CECs), such as currently used drugs and pesticides (n = 133), and an extended range of food-borne pathogens, including two notable sporeformers and some widespread antibiotic-resistant bacteria. The amounts of Escherichia coli, enterococci, and Salmonella and the concentrations of the target heavy metals were all below the maximum accepted levels at all three locations studied. However, the spore-forming Bacillus cereus was found to be present at high levels in samples from all three biogas plants. Among the 133 CECs investigated, 48 were detected at least once, and the highest concentrations were found for pyroxidine, nicotine, caffeine, theobromine, and nicotine. The biofertilizers from the different biogas plants had similar CEC profiles, which indicate similarities in household waste composition and thorough mixing in the biogas plants. If this profile is found to be spatially and temporally consistent, it can help regulators to establish priority lists of CECs of top concern. Assuming increasing use of biofertilizers for food production in the future, it would be beneficial to have concentration limits for CECs Risk estimation based on risk quotients (RQs) indicated generally low environmental risks associated with application of biofertilizer to soils for food crop production. However, the toxicity of CEC mixtures needs to be considered when estimating the risks from application of biofertilizers on agricultural land or in other production systems.

Liquid Anaerobic Digestate as Sole Nutrient Source in Soilless Horticulture-Or Spiked With Mineral Nutrients for Improved Plant Growth.

Digestate from biogas production high in plant-available macro- and micro-nutrients could replace mineral fertilizer in protected (soilless) horticulture. Previous uses of digestate have shown that low concentrations of plant-available phosphorus (P) and sulfur (S) may be limiting factors for growth when using digestate as the sole fertilizer. In this study, digestate collected from a municipal biogas plant in Sweden was nitrified in a moving-bed biofilm reactor prior to its use as fertilizer. A greenhouse pot trial with pak choi grown in peat-based growing medium was established to assess the (i) macro- and micro-nutrient availability in the digestate, with particular focus on P and S and (ii) the effect of amending the digestate solution with nutrients considered to be lacking [P, S, magnesium (Mg), manganese (Mn), boron (B), and molybdenum (Mo)]. The results showed that plants fertilized with raw digestate suffered from S and B deficiency and early P deficiency. Supplementing the digestate with nutrients originating from mineral salts resulted in sufficient plant tissue concentrations of all elements except S. The marketable yield was similar to that achieved using standard mineral fertilizer and the dry matter yield was 17% higher. In the light of the present results, the use of nitrified digestate in soilless plant production seems like a fruitful way forward to recycle organic nutrients from waste streams. In the case where a strict organic protocol is not needed, amendment with inorganic nutrients may be a way to increase the utilization of organically derived nutrients.

Economic and Environmental Potential of Large-Scale Renewable Synthetic Jet Fuel Production through Integration into a Biomass CHP Plant in Sweden

The potential of bio-electro-jet fuel (BEJF) production with integration into an existing biomass-based combined heat and power (CHP) facility was investigated. The BEJF is produced via Fischer–Tropsch (F–T) synthesis from biogenic CO2 and H2 obtained by water electrolysis. Techno-economic (TEA)- and life. cycle (LCA)- assessments were performed to evaluate the production cost and environmental impact of the BEJF production route. The BEJF mass fraction reached 40% of the total F–T crude produced. A reduction of 78% in heating demands was achieved through energy integration, leading to an increase in the thermal efficiency by up to 39%, based on the F–T crude. The total production cost of BEJF was in the range of EUR 1.6–2.5/liter (EUR 169–250/MWh). The GWP of the BEJF was estimated to be 19 g CO2-eq per MJ BEJF. The reduction potential in GWP in contrast to the fossil jet baseline fuel varied from 44% to more than 86%. The findings of this study underline the potential of BEJF as a resource-efficient, cost-effective, and environmentally benign alternative for the aviation sector. The outcome is expected to be applicable to different geographical locations or industrial networks when the identified influencing factors are met.

Key Factors for Site-Selection of Biogas Plants in Sweden

Key Factors for Site-Selection of Biogas Plants in Sweden

Phosphorus speciation in sewage sludge from three municipal wastewater treatment plants in Sweden and their ashes after incineration.

Given the high efficiency in phosphorus removal at municipal wastewater treatment plants (MMWWTP), sewage sludge constitutes a promising resource for phosphorus (P) recovery. Sewage sludge is, however, a complex matrix and its direct use as fertiliser is limited by its content of metals/metalloids and organic pollutants. In order to increase its usability as a potential resource of P, there is a need for increased knowledge on phosphorus speciation in these matrices. The sludge composition is highly influenced by local conditions (i.e. wastewater composition and treatment method), and it is therefore important to study sludge from several MMWWTPs. In this study, three different protocols for sequential extraction were utilised to investigate the chemical speciation of phosphorus in sludge from three different MMWWTP sludges in Sweden, as well as in corresponding ashes following incineration. The results showed that the total amounts of phosphorus ranged from 26 to 32 mg g-1 sludge (dry weight), of which 79-94% was inorganically bound (IP). In the sludge, 21-30% of the IP was associated with calcium (Ca-P), which is the preferred species for fertiliser production. Following incineration, this fraction increased to 54-56%, mainly due to transformation of iron-associated phosphorus (Fe-P), while aluminium-associated species of phosphorus (Al-P) remained unaltered. The results from this study confirm that incineration is a suitable treatment for sewage sludge in terms of potential phosphorus recovery.

Combination of LCA and circularity index for assessment of environmental impact of recycled aggregate concrete

Multidisciplinary approach is used to evaluate concrete with recycled concrete aggregates (RCA) from technical, environmental impacts and product circularity perspectives. Two RCA replacements investigated, RAC50: fine aggregates; RAC100: both coarse, fine aggregates. Reference, recycled concretes have same cement content, similar workability and compressive strength requirement, proven experimentally. RCA is sourced from pre-fab element discards of a Swedish plant, the logistical alternatives requiring environmental impact analysis. Alternatives are RCA crushing at plant and crushing at a different location including transportation. LCA shows transportation is second largest contributor after cement in all impact categories. RAC alternatives show lower total impact than reference concrete due to RCA replacement. A circularity index for concrete based on economic value of recirculated aggregates; supplements LCA for sustainability reporting. Circularity index results: RAC100 > RAC50 > RC. Combining circularity index with LCA helps optimize recycling process with regard to amount of recycled material and logistics respectively.

Potential for the Integrated Production of Biojet Fuel in Swedish Plant Infrastructures

Replacing fossil jet fuel with biojet fuel is an important step towards reducing greenhouse gas (GHG) emissions from aviation. To this end, Sweden has adopted a GHG mandate on jet fuel, complementing those on petrol and diesel. The GHG mandate on jet fuel requires a gradual reduction in the fuel’s GHG emissions to up to 27% by 2030. This paper estimates the potential production of biojet fuel in Sweden for six integrated production pathways and analyzes what they entail with regard to net biomass input and the amount of hydrogen required for upgrading to fuel quality. Integrated production of biofuel intermediates from forestry residues and by-products at combined heat and power plants as well as at the forest industry, followed by upgrading to biojet fuel and other transportation fuels at a petroleum refinery, was assumed in all the pathways. The potential output of bio-based transportation fuels was estimated to 90 PJ/y, including 22 PJ/y of biojet fuel. The results indicate that it will be possible to meet the Swedish GHG mandate for jet fuel for 2030, although it will be difficult to simultaneously achieve the GHG mandates for road transportation fuels. This highlights the importance of pursuing complementary strategies for bio-based fuels.

Cleaning and disinfection of transport crates for poultry – comparison of four treatments at slaughter plant

Transport crates for poultry can contribute to the spread of pathogens, with those of public health interest, for example, Campylobacter, being of particular importance. A strict cleaning procedure and use of an effective disinfection method for transport equipment are thus important to avoid introduction of Campylobacter to chicken and poultry farms, particularly during flock thinning. This study evaluated the efficacy of the disinfection procedure currently in use at one of the largest slaughter plants in Sweden and compared the effects with those of other disinfection methods. The evaluation was based on treatment ability to reduce the presence and amount of indicator bacteria belonging to the family Enterobacteriaceae and total aerobic bacteria. In 4 trials, sodium hypochlorite, peracetic acid, and drying with hot air, with or without sodium hypochlorite for final disinfection, were compared. The analysis was based on 40 cotton swab samples taken in each treatment, 20 after the soaking stage and 20 after the final disinfection step.The results showed that use of a chemical disinfectant in combination with drying with hot air (dehumidifier) was the most effective treatment, with an average reduction of 3.4 log for total aerobic bacteria and 3.8 log for Enterobacteriaceae. Since all crates treated with hot air were dry, transport conditions for the birds also improved, particularly in cold weather. A disadvantage is that this treatment is energy-consuming and would require substantial technical changes to the current cleaning process, increasing operating costs at the slaughter plant. However, considering the contribution of improved crate cleaning to overall hygiene control within the poultry supply chain and the beneficial effect on animal welfare, the costs may be justified.

Market Power and Joint Ownership: Evidence from Nuclear Plants in Sweden*

I examine the anticompetitive effects of joint ownership by analyzing the operation of three Swedish nuclear plants. I formulate a model of optimal maintenance allocation given three behavioral assumptions: i) maximal collusion, where all owners’ profits on both nuclear and other output are jointly maximized; ii) Cournot competition, where the majority owners’ profits on both nuclear and other output are maximized; and iii) a divested solution, where all owners’ profits on nuclear output are maximized. Maximal collusion is only achieved during the summer, when regulatory oversight is less strict. During the winter, data is instead consistent with the divested solution.