Mid Sweden University

Background

Wastewater discharges from the old pulp and paper industry led to the accumulation of contaminated wood pulping fbers and debris—referred to as fberbanks (FB)—in the Baltic Sea and freshwater bodies across Sweden and other pulp-producing countries. These anthropogenic sediments are polluted with toxic metal(oid)s and persistent organic pollutants, and their decomposition releases greenhouse gases. Phytoremediation ofers a nature-based solution for the ex-situ treatment of these fbrous sediments, but they present unique challenges due to the abundant and unstable organic matter and aged pollution. This study aims to identify potential plant candidates and to address the limitations of fberbanks as a plants growing media for phytoremediation.In a greenhouse experiment, we assessed the performance of fve plant species (Brassica juncea, Brassica napus, Helianthus annuus, Hordeum vulgare, and Poa annua) grown in substrates formulated with fberbank. The evaluation included plant growth parameters, bioconcentration and uptake efciency of metal(oid)s (V, Cr, Co, Ni, Cu, Zn, As, Cd, and Pb), and the degradation of polycyclic and linear hydrocarbons.

Results

Despite initial concerns, fberbanks displayed favorable physical characteristics and a degree of fertility conducive to plant growth. Even though all tested species seeds could cope with fberbanks acute toxicity, H. vulgare and P. annua showed better tolerance to the fberbanks substrates and superior aerial biomass development, which promoted a highest toxic metal(oid)s uptake efciency, regardless of lower bioconcentration factors for most of the target elements. Zn (17.16–23.25 mg/kg of FB), Cu (4.18–6.48 mg/kg of FB) and Cr (1.05–1.36 mg/kg of FB) were most efectively taken up by these plants. The uptake of Co (0.04–0.18 mg/kg of FB) and Ni (0.05–0.17 mg/kg of FB) was lower. As (0.01–0.02 mg/kg of FB), Cd (0.02–0.06 mg/kg of FB), Pb (0.02–0.04 mg/kg of FB) and V (0.02–0.03 mg/kg of FB) phytoextraction was not signifcant. None of the species exhibited a signifcant removal of targeted organic pollutants.

Conclusions

Phytoremediation, either on its own or in combination with other strategies, shows promise for the remediation of fberbanks. However, further research is needed to understand how the organic matrix and long-term underwater aging of fberbanks afect pollutants bioavailability.

Aquatic ecosystems in mountainous regions are crucial for fulfilling natural and anthropogenic water demands around the world. This study integrates Escherichia coli (E. coli) enumeration, microbial source tracking (MST), and environmental DNA (eDNA) analysis to identify sources of fecal contamination in oligotrophic mountain waters. Conducted in an area with intense tourism and traditional reindeer herding, this research addresses the urgent need to identify fecal pollution sources to safeguard the water quality of these vital ecosystems. Our study reveals that E. coli levels vary significantly across different locations and times, suggesting varied sources of contamination from humans, wildlife, and livestock animals. MST techniques, alongside eDNA analysis, provided insights into the complex patterns of fecal pollution, allowing for the distinction between human and animal contributions to water contamination. Our findings highlight the importance of combining various analytical methods to track fecal pollution sources effectively, and to develop targeted strategies for water quality management.

Microbial source tracking leverages a wide range of approaches designed to trace the origins of fecal contamination in aquatic environments. Although source tracking methods are typically employed within the laboratory setting, computational techniques can be leveraged to advance microbial source tracking methodology. Herein, we present a logic regression-based supervised learning approach for the discovery of source-informative genetic markers within intergenic regions across the Escherichia coli genome that can be used for source tracking. With just single intergenic loci, logic regression was able to identify highly source-specific (i.e., exceeding 97.00%) biomarkers for a wide range of host and niche sources, with sensitivities reaching as high as 30.00%–50.00% for certain source categories, including pig, sheep, mouse, and wastewater, depending on the specific intergenic locus analyzed. Restricting the source range to reflect the most prominent zoonotic sources of E. coli transmission (i.e., bovine, chicken, human, and pig) allowed for the generation of informative biomarkers for all host categories, with specificities of at least 90.00% and sensitivities between 12.50% and 70.00%, using the sequence data from key intergenic regions, including emrKY–evgAS, ibsB–(mdtABCD-baeSR), ompC–rcsDB, and yedS–yedR, that appear to be involved in antibiotic resistance. Remarkably, we were able to use this approach to classify 48 out of 113 river water E. coli isolates collected in Northwestern Sweden as either beaver, human, or reindeer in origin with a high degree of consensus—thus highlighting the potential of logic regression modeling as a novel approach for augmenting current source tracking efforts.

The Intergovernmental Panel on Climate Change (IPCC) points out alpine regions worldwide as climate change hotspots. Expanding and diversifying summer tourism in northern Scandinavian mountains exerts additional severe pressure to these areas and their oligotrophic and sensitive aquatic ecosystems. Previous research at Mid Sweden University has shown that fecal contamination of mountain rivers, indicated by the enumeration of E. coli, is frequent in areas that are intensively being used for tourism and reindeer herding. According to the IPCC, climate change is projected to reduce raw water quality, posing risks to drinking water quality even with conventional treatment. Therefore, there is an urgent need for improved monitoring of water quality in such areas to be able to protect the ecosystem as well as the rights of indigenous people, human and animal health and to provide support for water management decision. To be able to monitor the water quality is of great importance for the sustainability of mountain regions and water sources in general. The inaccessibility of the watercourses in remote mountain areas makes it difficult to establish sufficient monitoring programs.

In this research, the use of airborne monitoring systems to assess water quality in remote regions is investigated. Remote monitoring systems based on e.g. drones and satellites have the potential to replace less climate friendly options making use of terrain vehicles, snow mobiles and helicopters. The drones can be equipped with various sensors or sampling equipment, can overcome long transportations as well as time-consuming and expensive field samplings. Drones have great potential to be employed in everyday practices as an essential part of decision support systems for monitoring, evaluation and remediation of contaminated sites. The goal is to use drones to establish water quality monitoring programs in remote regions such as the mountain areas of Northern Sweden. In this research we intend to cover the catchment area of upper parts of river Indalsälven situated in the mountain region on the Swedish/Norwegian border, including the catchment areas of the tributaries Handölan and Enan covering approximately 777km².

One approach in this research is to image large areas of interest by the use of a multispectral camera on a drone and to identify spectral bands or band ratio´s which correlate to physicochemical parameters that are related to water quality. Another approach is to further explore the use of dronebased water sampling for laboratory or in-field analysis of microbial and chemical parameters.

Both approaches should eventually lead to the development of a drone-based monitoring program for oligotrophic rivers that can image or measure water pollution with sufficient spatial coverage and time resolution to enable early warning of outbreaks of fecal pollution. Results of this research will contribute to SDG 6, targets 3 and 6 and SDG 14. 

This study evaluates the use of fermentation to increase nutrient availability in pulp and paper bio-sludge (PPBS) as feed for black soldier fly larvae (BSFL). Rearing of BSFL on fermented PPBS was carried out in a climate chamber in order to assess nutrient availability and larvae survival and growth. The PPBS used came from a chemo-thermomechanical pulp/groundwood pulp mill. The PPBS was fermented at 35 °C and 55 °C, respectively, at initial pH of 10. The effects of sediment and liquid from fermented PPBS on larvae dry weight, survival rate until the prepupae stage, bioconversion, and reduction rate of PPBS were measured. The bioconversion of the liquids (4.1–6.6%) was substantially higher than for both the sediments and untreated PPBS (≤ 0.4%). The survival rate, on the other hand, was substantially lower (26.3–30.9 %) than for the sediments and untreated PPBS (49.5–52.6%). Neither the sediments nor the liquids had significant effects on the larvae weight or on the PPBS reduction rate. The sediments had no significant effect on the survival rate or the bioconversion. This study demonstrates that fermentation dissolves a part of the PPBS and that dissolved substances in the fermentation liquid readily convert to larvae biomass. However, the bulk of the lignocellulose is not dissolved, and most of PPBS nutrients remain unavailable for growth of the larvae. Further research should focus on improved pretreatment of PPBS to increase availability of nutrients and thereby improve the feasibility of BSFL as a recycling method for PPBS.

Soil pollution is a threat to food security and ecological and human health. Cd is one of the most common pollutants in agricultural soil and, due its human toxicity, one of the most hazardous. Amaranth is a documented hyperaccumulator of Cd and other pollutants, and it is commonly grown in Asia and South America. A considerable amount of amaranth is grown in suboptimal conditions, including nutrient-poor acidic soils. The objective of this experimental study was to examine the capacity of Amaranthus hypochondriacus to extract Cd from a nutrient-poor, acidic substrate that was spiked with different concentrations of Cd (2 and 20 mg kg−1 dw) during a period of 180 days. The plants grown in the substrate that was spiked with 20 mg Cd kg−1 dw did not develop into mature plants, but the plants grown in substrate that was spiked with 2 mg Cd kg−1 dw extracted a significant amount of Cd from the substrate by accumulating it into the above-ground biomass. The Cd levels varied from 113 to 176 mg kg−1 in the stems at the four measuring points, and from 64 to 94 mg kg−1 in the leaves. The concentrations in the plants increased with time and reached a maximal concentration of 176 ± 45 mg kg−1 dw for stems and 94 ± 41 mg kg−1 dw for leaves after 180 days. The mean bioaccumulation factor in the plants was 86 ± 15 after 90 days, 72 ± 12 after 120 days, 105 ± 37 after 150 days, and 99 ± 31 after 180 days, which confirms the previously reported capacity of Amaranthus hypochondriacus to hyperaccumulate Cd. Amaranthus hypochondriacus may, thus, be used to improve ecological and human health by remediating moderately Cd-polluted soils, even in nutrient-poor acidic soils.

Lignocellulose-bearing sediments are legacies of the previously unregulated wastewater discharge from the pulp and paper industry, causing large quantities of toxic organic waste on the Baltic Sea floor and on the bottom of rivers and lakes. Several km2 are covered with deposits of lignocellulosic residues, typically heavily contaminated with complex mixtures of organic and inorganic pollutants, posing a serious threat to human and ecological health. The high toxicity and the large volume of the polluted material are challenges for remediation endeavours. The lignocellulosic material is also a considerable bioresource with a high energy density, and due to its quantity, it could appeal to commercialization as feedstock for various marketable goods. This study sets out to explore the potential of using this polluted material as a resource for industrial production at the same time as it is detoxified. Information about modern production methods for lignocellulosic material that can be adapted to a polluted feedstock is reviewed. Biochemical methods such as composting, anaerobic digestion, as well as, thermochemical methods, for instance, HTC, HTL, pyrolysis, gasification and torrefaction have been assessed. Potential products from lignocellulose-bearing sediment material include biochar, liquid and gaseous biofuels, growing substrate. The use of a contaminated feedstock may make the process more expensive, but the suggested methods should be seen as an alternative to remediation methods that only involve costs. Several experiments were highlighted that support the conception that combined remediation and generation of marketable goods may be an appropriate way to address polluted lignocellulose-bearing sediments. Graphic abstract: [Figure not available: see fulltext.] 

Pulp and paper production is one of the largest global industries producing annually 400 million metric tons of pulp and paper products and 6 million tons of pulp and paper biosludge (PPBS). From a resource efficiency and sustainability perspective, there is a need for improving PPBS management. This study assessed fermentation of PPBS as pretreatment to improve PPBS feasibility as feed for black soldier fly larvae. The impact of temperature, pH, and inoculum on the concentration of soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFA) was assessed. An initial pH of 10 and the addition of inoculum from an anaerobic digester substantially increased the concentration of sCOD. The obtained concentration of VFA was low compared to the VFA concentration needed to improve the growth of Black Soldier Fly Larvae (BSFL). The PPBS is recalcitrant to fermentation because of the high content of lignocellulose. Fermentation as done in this study does not convert PPBS to a feasible feed for black soldier fly larvae; thus, further research on improved fermentation is needed. However, fermentation at alkaline pH and addition of inoculum do increase the final pH of PPBS which improves its feasibility as feed for BSFL. Future studies should explore pH > 10 and temperatures > 55 °C to increase sCOD and improving generation of VFA by removal of inhibiting substances, testing other types of inoculum (rumen microorganisms) and co-fermentation.

Increasing pollution levels in waters from remote mountain areas in northern Sweden have been observed. To support a sustainable water quality management, it is necessary to know which environmental and antrophogenic factors influence the water quality. The purpose of this study was to map the Escherichia coli prevalence in the catchment area of the upper part of a large northern Scandinavian river and investigate the controlling factors of microbial contamination. A total of 112 water samples were collected from various locations in the research area between July 2020 and December 2020. These samples were analyzed for microbial and chemical characteristics, and information about tourism and reindeer herding was compiled. Additionally, microbial and physicochemical water characteristics collected by Indalsälven Water Conservation Association (IWCA, 1993–2020) and Swedish Meteorological and Hydrological Institute (SMHI, 2004–2020) were analyzed. The results showed that E. coli enumerations ranged between 0 and 500 CFU/100 ml. There was generally no obvious relation between suspected point sources, e.g., sewage treatment plants at mountain stations, and E. coli levels at downstream sampling points. Principal component analysis showed that E. coli was correlated to coliforms, total heterotrophic count, river discharge, CODMn and river color. Since microbial analyses are time-consuming, expensive and difficult to perform in remote areas, it is important to find more easily extracted water parameters that can serve as a proxy for E. coli. In particular, river color and discharge are promising parameters that may serve as an early indication of bacterial outbreak and fecal contamination in mountain waters.