Frank Persson | Chalmers University of Technology (original) (raw)

Papers by Frank Persson

Resources, environment and sustainability, Mar 1, 2024

In biological wastewater treatment, the sorption process is an important removal pathway of organ... more In biological wastewater treatment, the sorption process is an important removal pathway of organic micropollutants from the aqueous phase. Beyond the conventional sorption to biomass and particulate matter, organic molecules can also partition to gas bubbles commonly present in aerated biological processes. This study investigated the partitioning behavior of 21 selected pharmaceuticals to two types of aerobic granular sludge, and the foam generated by aeration. Batch sorption experiments were performed with biologically inactive granules of controlled diameters (0.5-1, 1-2, and >2 mm). Removal during sorption tests was observed for four positively charged micropollutants (sertraline, citalopram, clarithromycin, and erythromycin), four neutral compounds (levonorgestrel, estradiol, ethinylestradiol, and ketoconazole), and one negatively charged pharmaceutical (losartan). This highlights the importance of electrostatic interactions and lipophilic affinity with the solids. For some compounds, the removal increased with time, suggesting that sorption in thick biofilm is limited by molecular diffusion into the biofilm matrix. Furthermore, partitioning of pharmaceuticals to aeration-induced foam was confirmed in separate batch tests. Clarithromycin, erythromycin, ketoconazole, losartan, levonorgestrel, and ethinylestradiol exhibited concentrations in the foam 1.0-5.3 times higher than the initial test values, indicating potential adsorption at the liquid/gas interface for these compounds.

Aerobic granular sludge is a compact and efficient biofilm process used for wastewater treatment ... more Aerobic granular sludge is a compact and efficient biofilm process used for wastewater treatment which has received much attention and is currently being implemented worldwide. The microbial associations and their ecological implications occurring during granule development, especially those involving inter-kingdom interactions, are poorly understood. In this work, we monitored the prokaryote and eukaryote community composition and structure during the granulation of activated sludge for 343 days in a sequencing batch reactor (SBR), and investigated the influence of abiotic and biotic factors on the granule development. Sludge granulation was accomplished with low-wash out dynamics at long settling times, allowing for the microbial communities to adapt to the SBR environmental conditions. The sludge .

Research Square (Research Square), Aug 20, 2020

Environmental Technology, 2007

ABSTRACT Geosmin and 2-methylisoborneol (MIB) are two substances causing earthy/musty odours that... more ABSTRACT Geosmin and 2-methylisoborneol (MIB) are two substances causing earthy/musty odours that are difficult to remove by conventional chemical drinking water treatment. In this study removal of geosmin and MIB by biofiltration of untreated surface water was investigated using granular activated carbon (GAC) and crushed expanded clay (EC) as filter media. Biofiltration through both GAC and EC removed geosmin and MIB present at low (20 ng l(-1)) concentrations by at least 97% at an empty bed contact time of 30 minutes and a temperature of 15 degrees C. At lower temperature (6-12 degrees C) and simultaneously lower biomass concentrations, removal efficiency was similar in the GAC but considerably lower in the EC biofilter, pointing to a second mechanism different from biodegradation. Consequently, microbial activity was suppressed with azide to enable discrimination between biodegradation and adsorption. During azide dosage, the GAC biofilters still removed geosmin and MIB nearly unaffectedly. In the EC biofilter, however, removal of both odorants ceased completely. Methylene blue adsorption confirmed that the GAC, even after almost four years of operation receiving surface water, had capacity to remove geosmin and MIB by adsorption. Since odour episodes commonly occur during the warm season when microbiological activity is high, EC constitutes a viable option as carrier medium for direct biological filtration of surface water. The additional GAC adsorption capacity however adds robustness to the removal process.

Fems Microbiology Letters, 2023

The Oslofjord subsea road tunnel is a unique environment in which the typically anoxic marine dee... more The Oslofjord subsea road tunnel is a unique environment in which the typically anoxic marine deep subsurface is exposed to oxygen. Concrete biodeterioration and steel corrosion in the tunnel have been linked to the growth of iron-and manganese-oxidizing biofilms in areas of saline w ater see pa ge. Surprisingl y, pr evious 16S rRNA gene surveys of biofilm samples r ev ealed micr obial communities dominated by sequences affiliated with nitrogen-cycling microor ganisms. This stud y aimed to identify microbial genomes with metabolic potential for novel nitrogen-and metal-cycling r eactions, r e pr esenting biofilm micr oorganisms that could link these cycles and play a role in concrete biodeterioration. We reconstructed 33 abundant, novel metagenome-assembled genomes (MAGs) affiliated with the phylum Planctomycetota and the candidate phylum KSB1. We identified novel and unusual genes and gene clusters in these MAGs related to anaerobic ammonium oxidation, nitrite oxidation, and other nitr ogen-cycling r eactions. Additionall y, 26 of 33 MAGs also had the potential for iron, manganese, and arsenite cycling, suggesting that bacteria r e pr esented by these genomes might couple these reactions. Our results expand the diversity of microorganisms putatively involved in nitrogen and metal cycling, and contribute to our understanding of potential biofilm impacts on built infr astructure .

Research Square (Research Square), Feb 24, 2020

Background: High-throughput amplicon sequencing of marker genes, such as the 16S rRNA gene in Bac... more Background: High-throughput amplicon sequencing of marker genes, such as the 16S rRNA gene in Bacteria and Archaea, provides a wealth of information about the composition of microbial communities. To quantify differences between samples and draw conclusions about factors affecting community assembly, dissimilarity indices are typically used. However, results are subject to several biases and data interpretation can be challenging. The Jaccard and Bray-Curtis indices, which are often used to quantify taxonomic dissimilarity, are not necessarily the most logical choices. Instead, we argue that Hill-based indices, which make it possible to systematically investigate the impact of relative abundance on dissimilarity, should be used for robust analysis of data. In combination with a null model, mechanisms of microbial community assembly can be analyzed. Here, we also introduce a new software, qdiv, which enables rapid calculations of Hill-based dissimilarity indices in combination with null models. Results: Using amplicon sequencing data from two experimental systems, aerobic granular sludge (AGS) reactors and microbial fuel cells (MFC), we show that the choices of bioinformatics pipeline and dissimilarity index can have considerable impacts on results and conclusions. Analysis of the AGS data set showed that results are sensitive to bioinformatics choices when dissimilarities between sample groups are compared with incidence-based indices. Analysis of the MFC data set with a combination of Hill-based indices and a null model revealed that random dispersal could explain the distribution of both rare and highly abundant taxa within a glucose-fed MFC whereas the distribution of taxa of intermediate relative abundance was governed by heterogeneous selection. Conclusions: Hill-based indices provides a rational framework for analysis of dissimilarity between microbial community samples. In combination with a null model, the effects of deterministic and stochastic factors on taxa of low-, intermediate-, and high relative abundance during microbial community assembly can be systematically investigated. Calculations of Hill-based dissimilarity indices in combination with a null model can be done in qdiv, which is freely available as a Python package (https://github.com/omvatten/qdiv).

Microbial biotechnology, Nov 14, 2016

Water Research, Nov 1, 2016

Suppression of nitrite oxidizing bacteria (NOB) is of vital importance to achieve successful, ene... more Suppression of nitrite oxidizing bacteria (NOB) is of vital importance to achieve successful, energy efficient, mainstream anammox processes for wastewater treatment. In this study, biofilm carriers from a fully nitrifying MBBR system, fed with mainstream wastewater, were temporarily exposed to reject water from sludge dewatering, to evaluate this as a possible strategy to inhibit NOB and achieve nitrite production under realistic conditions. Two different carrier types were compared, in which biofilm thickness was maintained at approximately 400 and 50 μm, respectively, and reject treatment was tested at different exposure time and loading rates. Reject exposure almost always resulted in an increased nitrite production in the thinner biofilm, and overall, nitrifiers growing in the thin biofilm were more sensitive than those grown in the thicker biofilm. The effect from reject exposure remained in the systems for four days after returning to mainstream operation, with nitrite production gradually increasing for three days. Increased concentrations of free ammonia correlated with reject exposure and may be the cause of inhibition, although other factors cannot be excluded.

Waterworks in Sweden that apply conventional surface water treatment are facing several challenge... more Waterworks in Sweden that apply conventional surface water treatment are facing several challenges, including changes in raw water quality and demands for improved particle removal. Studies were conducted to evaluate conventional treatment and alternative process combinations with ultrafiltration, nanofiltration, and biological pre-filtration. In pilot-scale experiments, the removal of natural organic matter (NOM), particles, taste and odour compounds, were studied; so were the biofilm formation potential and the microbial barrier function. In this publication, we attempt to briefly summarise the results, relate them to current knowledge, and discuss possible implications for surface water treatment in Sweden. Conventional treatment was a mediocre barrier for biological particles in bacterial and protozoan size, and did not sufficiently remove dissolved taste and odour compounds. Ultrafiltration may replace or complement rapid media filters and was a powerful and robust barrier for suspended particles and microorganisms, including viruses; it had no effect on NOM. Nanofilters removed most of the NOM, but require either relatively pure feed water to avoid fouling problems, or need to be operated at a low hydraulic load. Biofiltration equalized peak loads of particles, removed taste and odour compounds and decreased NF fouling by reducing biofilm formation, and the concentrations of organic and inorganic compounds

The next revolution in biological nutrient removal at municipal wastewater treatment plants (WWTP... more The next revolution in biological nutrient removal at municipal wastewater treatment plants (WWTPs) is fully autotrophic nitrogen removal. Extensive pilot tests at Sjolunda WWTP in Malmo, Sweden, are ongoing for implementing Manammox (mainstream anammox) in the existing plant, which already today separates COD and nitrogen removal. The Manammox concept is based on a combined process where nitritation-anammox is operated in moving-bed biofilm reactors for sludge liquor treatment and treatment of mainstream wastewater with exchange of biofilm carriers between the two systems. Almost complete ammonium oxidation and more than 80% nitrogen reduction was reached in the sludge liquor system and up to 60% in the main stream process. Quantitative PCR showed almost the same composition of the bacterial population with high abundance of anammox bacteria and ammonia-oxidising bacteria in all reactors and that the exchange of carriers did not effectively suppress the nitrite-oxidising bacteria in the system. Optimal choice of the oxygen supply for the process seems to be crucial for further increase of the nitrogen reduction in the mainstream.

Water Research, Nov 1, 2020

Bacteria capable of anaerobic ammonium oxidation (anammox) enable autotrophic nitrogen removal. O... more Bacteria capable of anaerobic ammonium oxidation (anammox) enable autotrophic nitrogen removal. Organic carbon in wastewater can instead be utilized for energy production. However, anammox-based processes are not yet used at any extent for treatment of the main stream at wastewater treatment plants. One of the reasons for this is the challenge for the slow growing autotrophic bacteria to work at low temperatures. Here we investigate one-stage nitritationanammox at temperatures of 13-16°C in a pilot moving bed biofilm reactor (MBBR) receiving reject water from anaerobic sludge digestion. At a target nitrogen loading rate of 1 g NH 4 +-N m-2 d-1 the average nitrogen removal rate was 0.81 g NH 4 +-N m-2 d-1 and 0.55 g NH 4 +-N m-2 d-1 at 16°C and 13°C respectively. At low temperatures oxygen control is important to avoid oxygen penetration to the deeper parts of the biofilm, which causes inhibition of the anammox bacteria and as a result nitrite accumulation. Hence, the process was operated at conditions to limit the activity of the aerobic ammonium oxidizing bacteria (AOB) by oxygen availability. The biofilm biomass was dominated by anammox bacteria, with 1.0 × 10 14 copies m-2 (16S rRNA), with considerably fewer AOB of 2.1 × 10 12 copies m-2 (amoA), as measured by quantitative PCR. Cell specific conversion rates of anammox bacteria and AOB were estimated at 0.3-0.5 fmol N cell-1 d-1 and 7-9 fmol N cell-1 d-1 , respectively. The study shows the applicability of one-stage nitritation-anammox in MBBRs at low temperatures and highlights the importance of quantification of AOB and anammox bacteria for understanding process performance.

Science of The Total Environment

In a microbial electrolysis cell (MEC), the oxidization of organic compounds is facilitated by an... more In a microbial electrolysis cell (MEC), the oxidization of organic compounds is facilitated by an electrogenic biofilm on the anode surface. The biofilm community composition determines the function of the system. Both deterministic and stochastic factors affect the community, but the relative importance of different factors is poorly understood. Anode material is a deterministic factor as materials with different properties may select for different microorganisms. Ecological drift is a stochastic factor, which is amplified by dispersal limitation between communities. Here, we compared the effects of three anode materials (graphene, carbon cloth, and nickel) with the effect of dispersal limitation on the function and biofilm community assembly. Twelve MECs were operated for 56 days in four hydraulically connected loops and shotgun metagenomic sequencing was used to analyse the microbial community composition on the anode surfaces at the end of the experiment. The anode material was the most important factor affecting the performance of the MECs, explaining 54-80 % of the variance observed in peak current density, total electric charge generation, and start-up lag time, while dispersal limitation explained 10-16 % of the variance. Carbon cloth anodes had the highest current generation and shortest lag time. However, dispersal limitation was the most important factor affecting microbial community structure, explaining 61-98 % of the variance in community diversity, evenness, and the relative abundance of the most abundant taxa, while anode material explained 0-20 % of the variance. The biofilms contained nine Desulfobacterota metagenome-assembled genomes (MAGs), which made up 64-89 % of the communities and were likely responsible for electricity generation in the MECs. Different MAGs dominated in different MECs. Particularly two different genotypes related to Geobacter benzoatilyticus competed for dominance on the anodes and reached relative abundances up to 83 %. The winning genotype was the same in all MECs that were hydraulically connected irrespective of anode material used.

Water Environment Research

This study demonstrates a comparison of energy usage, land footprint and volumetric requirements ... more This study demonstrates a comparison of energy usage, land footprint and volumetric requirements of municipal wastewater treatment with aerobic granular sludge (AGS) and conventional activated sludge (CAS) at a full‐scale wastewater treatment plant characterized by large fluctuations in nutrient loadings and temperature. The concentration of organic matter in the influent to the AGS was increased by means of hydrolysis and bypassing the pre‐settler. Both treatment lines produced effluent concentrations below 5 mg BOD7 L‐1, 10 mg TN L‐1, and 1 mg TP L‐1, by enhanced biological nitrogen‐ and phosphorus removal. In this case study, the averages of volumetric energy usage over one year were 0.22 ± 0.08 and 0.26 ± 0.07 kWh m‐3 for the AGS and CAS, respectively. A larger difference was observed for the energy usage per reduced P.E., which was on average 0.19 ± 0.08 kWh P.E.‐1 for the AGS and 0.30 ± 0.08 kWh P.E.‐1 for the CAS. However, both processes had the potential for decreased energy...

IOP Conference Series: Materials Science and Engineering

The present study investigates the presence and removal of target organic micropollutants in a la... more The present study investigates the presence and removal of target organic micropollutants in a large Swedish wastewater treatment plant designed for nutrient removal including activated sludge, trickling filters, nitrifying moving bed biofilm reactors (MBBRs) and post-denitrifying MBBRs. A total of 28 organic micropollutants were analysed, at concentrations ranging from few ng/L to µg/L, in the influent and effluent of the different biological reactors in two sampling campaigns. The observed micropollutant removal efficiencies of the wastewater treatment plant varied from insignificant (< 20%) to high (> 90%) between compounds. The activated sludge reactor, being the first in line, contributed to most of the removal from the water phase. Additional removal of a few compounds was observed in the biofilm units, but most of the persistent compounds remained stable through all biological treatments.

Frontiers in Microbiology

In single-chamber microbial electrolysis cells (MECs), organic compounds are oxidized at the anod... more In single-chamber microbial electrolysis cells (MECs), organic compounds are oxidized at the anode, liberating electrons that are used for hydrogen evolution at the cathode. Microbial communities on the anode and cathode surfaces and in the bulk liquid determine the function of the MEC. The communities are complex, and their assembly processes are poorly understood. We investigated MEC performance and community composition in nine MECs with a carbon cloth anode and a cathode of carbon nanoparticles, titanium, or stainless steel. Differences in lag time during the startup of replicate MECs suggested that the initial colonization by electrogenic bacteria was stochastic. A network analysis revealed negative correlations between different putatively electrogenic Deltaproteobacteria on the anode. Proximity to the conductive anode surface is important for electrogens, so the competition for space could explain the observed negative correlations. The cathode communities were dominated by h...

FEMS Microbiology Letters

The Oslofjord subsea road tunnel is a unique environment in which the typically anoxic marine dee... more The Oslofjord subsea road tunnel is a unique environment in which the typically anoxic marine deep subsurface is exposed to oxygen. Concrete biodeterioration and steel corrosion in the tunnel have been linked to the growth of iron- and manganese-oxidizing biofilms in areas of saline water seepage. Surprisingly, previous 16S rRNA gene surveys of biofilm samples revealed microbial communities dominated by sequences affiliated with nitrogen-cycling microorganisms. This study aimed to identify microbial genomes with metabolic potential for novel nitrogen- and metal-cycling reactions, representing biofilm microorganisms that could link these cycles and play a role in concrete biodeterioration. We reconstructed 33 abundant, novel metagenome-assembled genomes (MAGs) affiliated with the phylum Planctomycetota and the candidate phylum KSB1. We identified novel and unusual genes and gene clusters in these MAGs related to anaerobic ammonium oxidation, nitrite oxidation, and other nitrogen-cycl...

Resources, environment and sustainability, Mar 1, 2024

In biological wastewater treatment, the sorption process is an important removal pathway of organ... more In biological wastewater treatment, the sorption process is an important removal pathway of organic micropollutants from the aqueous phase. Beyond the conventional sorption to biomass and particulate matter, organic molecules can also partition to gas bubbles commonly present in aerated biological processes. This study investigated the partitioning behavior of 21 selected pharmaceuticals to two types of aerobic granular sludge, and the foam generated by aeration. Batch sorption experiments were performed with biologically inactive granules of controlled diameters (0.5-1, 1-2, and &gt;2 mm). Removal during sorption tests was observed for four positively charged micropollutants (sertraline, citalopram, clarithromycin, and erythromycin), four neutral compounds (levonorgestrel, estradiol, ethinylestradiol, and ketoconazole), and one negatively charged pharmaceutical (losartan). This highlights the importance of electrostatic interactions and lipophilic affinity with the solids. For some compounds, the removal increased with time, suggesting that sorption in thick biofilm is limited by molecular diffusion into the biofilm matrix. Furthermore, partitioning of pharmaceuticals to aeration-induced foam was confirmed in separate batch tests. Clarithromycin, erythromycin, ketoconazole, losartan, levonorgestrel, and ethinylestradiol exhibited concentrations in the foam 1.0-5.3 times higher than the initial test values, indicating potential adsorption at the liquid/gas interface for these compounds.

Aerobic granular sludge is a compact and efficient biofilm process used for wastewater treatment ... more Aerobic granular sludge is a compact and efficient biofilm process used for wastewater treatment which has received much attention and is currently being implemented worldwide. The microbial associations and their ecological implications occurring during granule development, especially those involving inter-kingdom interactions, are poorly understood. In this work, we monitored the prokaryote and eukaryote community composition and structure during the granulation of activated sludge for 343 days in a sequencing batch reactor (SBR), and investigated the influence of abiotic and biotic factors on the granule development. Sludge granulation was accomplished with low-wash out dynamics at long settling times, allowing for the microbial communities to adapt to the SBR environmental conditions. The sludge .

Research Square (Research Square), Aug 20, 2020

Environmental Technology, 2007

ABSTRACT Geosmin and 2-methylisoborneol (MIB) are two substances causing earthy/musty odours that... more ABSTRACT Geosmin and 2-methylisoborneol (MIB) are two substances causing earthy/musty odours that are difficult to remove by conventional chemical drinking water treatment. In this study removal of geosmin and MIB by biofiltration of untreated surface water was investigated using granular activated carbon (GAC) and crushed expanded clay (EC) as filter media. Biofiltration through both GAC and EC removed geosmin and MIB present at low (20 ng l(-1)) concentrations by at least 97% at an empty bed contact time of 30 minutes and a temperature of 15 degrees C. At lower temperature (6-12 degrees C) and simultaneously lower biomass concentrations, removal efficiency was similar in the GAC but considerably lower in the EC biofilter, pointing to a second mechanism different from biodegradation. Consequently, microbial activity was suppressed with azide to enable discrimination between biodegradation and adsorption. During azide dosage, the GAC biofilters still removed geosmin and MIB nearly unaffectedly. In the EC biofilter, however, removal of both odorants ceased completely. Methylene blue adsorption confirmed that the GAC, even after almost four years of operation receiving surface water, had capacity to remove geosmin and MIB by adsorption. Since odour episodes commonly occur during the warm season when microbiological activity is high, EC constitutes a viable option as carrier medium for direct biological filtration of surface water. The additional GAC adsorption capacity however adds robustness to the removal process.

Fems Microbiology Letters, 2023

The Oslofjord subsea road tunnel is a unique environment in which the typically anoxic marine dee... more The Oslofjord subsea road tunnel is a unique environment in which the typically anoxic marine deep subsurface is exposed to oxygen. Concrete biodeterioration and steel corrosion in the tunnel have been linked to the growth of iron-and manganese-oxidizing biofilms in areas of saline w ater see pa ge. Surprisingl y, pr evious 16S rRNA gene surveys of biofilm samples r ev ealed micr obial communities dominated by sequences affiliated with nitrogen-cycling microor ganisms. This stud y aimed to identify microbial genomes with metabolic potential for novel nitrogen-and metal-cycling r eactions, r e pr esenting biofilm micr oorganisms that could link these cycles and play a role in concrete biodeterioration. We reconstructed 33 abundant, novel metagenome-assembled genomes (MAGs) affiliated with the phylum Planctomycetota and the candidate phylum KSB1. We identified novel and unusual genes and gene clusters in these MAGs related to anaerobic ammonium oxidation, nitrite oxidation, and other nitr ogen-cycling r eactions. Additionall y, 26 of 33 MAGs also had the potential for iron, manganese, and arsenite cycling, suggesting that bacteria r e pr esented by these genomes might couple these reactions. Our results expand the diversity of microorganisms putatively involved in nitrogen and metal cycling, and contribute to our understanding of potential biofilm impacts on built infr astructure .

Research Square (Research Square), Feb 24, 2020

Background: High-throughput amplicon sequencing of marker genes, such as the 16S rRNA gene in Bac... more Background: High-throughput amplicon sequencing of marker genes, such as the 16S rRNA gene in Bacteria and Archaea, provides a wealth of information about the composition of microbial communities. To quantify differences between samples and draw conclusions about factors affecting community assembly, dissimilarity indices are typically used. However, results are subject to several biases and data interpretation can be challenging. The Jaccard and Bray-Curtis indices, which are often used to quantify taxonomic dissimilarity, are not necessarily the most logical choices. Instead, we argue that Hill-based indices, which make it possible to systematically investigate the impact of relative abundance on dissimilarity, should be used for robust analysis of data. In combination with a null model, mechanisms of microbial community assembly can be analyzed. Here, we also introduce a new software, qdiv, which enables rapid calculations of Hill-based dissimilarity indices in combination with null models. Results: Using amplicon sequencing data from two experimental systems, aerobic granular sludge (AGS) reactors and microbial fuel cells (MFC), we show that the choices of bioinformatics pipeline and dissimilarity index can have considerable impacts on results and conclusions. Analysis of the AGS data set showed that results are sensitive to bioinformatics choices when dissimilarities between sample groups are compared with incidence-based indices. Analysis of the MFC data set with a combination of Hill-based indices and a null model revealed that random dispersal could explain the distribution of both rare and highly abundant taxa within a glucose-fed MFC whereas the distribution of taxa of intermediate relative abundance was governed by heterogeneous selection. Conclusions: Hill-based indices provides a rational framework for analysis of dissimilarity between microbial community samples. In combination with a null model, the effects of deterministic and stochastic factors on taxa of low-, intermediate-, and high relative abundance during microbial community assembly can be systematically investigated. Calculations of Hill-based dissimilarity indices in combination with a null model can be done in qdiv, which is freely available as a Python package (https://github.com/omvatten/qdiv).

Microbial biotechnology, Nov 14, 2016

Water Research, Nov 1, 2016

Suppression of nitrite oxidizing bacteria (NOB) is of vital importance to achieve successful, ene... more Suppression of nitrite oxidizing bacteria (NOB) is of vital importance to achieve successful, energy efficient, mainstream anammox processes for wastewater treatment. In this study, biofilm carriers from a fully nitrifying MBBR system, fed with mainstream wastewater, were temporarily exposed to reject water from sludge dewatering, to evaluate this as a possible strategy to inhibit NOB and achieve nitrite production under realistic conditions. Two different carrier types were compared, in which biofilm thickness was maintained at approximately 400 and 50 μm, respectively, and reject treatment was tested at different exposure time and loading rates. Reject exposure almost always resulted in an increased nitrite production in the thinner biofilm, and overall, nitrifiers growing in the thin biofilm were more sensitive than those grown in the thicker biofilm. The effect from reject exposure remained in the systems for four days after returning to mainstream operation, with nitrite production gradually increasing for three days. Increased concentrations of free ammonia correlated with reject exposure and may be the cause of inhibition, although other factors cannot be excluded.

Waterworks in Sweden that apply conventional surface water treatment are facing several challenge... more Waterworks in Sweden that apply conventional surface water treatment are facing several challenges, including changes in raw water quality and demands for improved particle removal. Studies were conducted to evaluate conventional treatment and alternative process combinations with ultrafiltration, nanofiltration, and biological pre-filtration. In pilot-scale experiments, the removal of natural organic matter (NOM), particles, taste and odour compounds, were studied; so were the biofilm formation potential and the microbial barrier function. In this publication, we attempt to briefly summarise the results, relate them to current knowledge, and discuss possible implications for surface water treatment in Sweden. Conventional treatment was a mediocre barrier for biological particles in bacterial and protozoan size, and did not sufficiently remove dissolved taste and odour compounds. Ultrafiltration may replace or complement rapid media filters and was a powerful and robust barrier for suspended particles and microorganisms, including viruses; it had no effect on NOM. Nanofilters removed most of the NOM, but require either relatively pure feed water to avoid fouling problems, or need to be operated at a low hydraulic load. Biofiltration equalized peak loads of particles, removed taste and odour compounds and decreased NF fouling by reducing biofilm formation, and the concentrations of organic and inorganic compounds

The next revolution in biological nutrient removal at municipal wastewater treatment plants (WWTP... more The next revolution in biological nutrient removal at municipal wastewater treatment plants (WWTPs) is fully autotrophic nitrogen removal. Extensive pilot tests at Sjolunda WWTP in Malmo, Sweden, are ongoing for implementing Manammox (mainstream anammox) in the existing plant, which already today separates COD and nitrogen removal. The Manammox concept is based on a combined process where nitritation-anammox is operated in moving-bed biofilm reactors for sludge liquor treatment and treatment of mainstream wastewater with exchange of biofilm carriers between the two systems. Almost complete ammonium oxidation and more than 80% nitrogen reduction was reached in the sludge liquor system and up to 60% in the main stream process. Quantitative PCR showed almost the same composition of the bacterial population with high abundance of anammox bacteria and ammonia-oxidising bacteria in all reactors and that the exchange of carriers did not effectively suppress the nitrite-oxidising bacteria in the system. Optimal choice of the oxygen supply for the process seems to be crucial for further increase of the nitrogen reduction in the mainstream.

Water Research, Nov 1, 2020

Bacteria capable of anaerobic ammonium oxidation (anammox) enable autotrophic nitrogen removal. O... more Bacteria capable of anaerobic ammonium oxidation (anammox) enable autotrophic nitrogen removal. Organic carbon in wastewater can instead be utilized for energy production. However, anammox-based processes are not yet used at any extent for treatment of the main stream at wastewater treatment plants. One of the reasons for this is the challenge for the slow growing autotrophic bacteria to work at low temperatures. Here we investigate one-stage nitritationanammox at temperatures of 13-16°C in a pilot moving bed biofilm reactor (MBBR) receiving reject water from anaerobic sludge digestion. At a target nitrogen loading rate of 1 g NH 4 +-N m-2 d-1 the average nitrogen removal rate was 0.81 g NH 4 +-N m-2 d-1 and 0.55 g NH 4 +-N m-2 d-1 at 16°C and 13°C respectively. At low temperatures oxygen control is important to avoid oxygen penetration to the deeper parts of the biofilm, which causes inhibition of the anammox bacteria and as a result nitrite accumulation. Hence, the process was operated at conditions to limit the activity of the aerobic ammonium oxidizing bacteria (AOB) by oxygen availability. The biofilm biomass was dominated by anammox bacteria, with 1.0 × 10 14 copies m-2 (16S rRNA), with considerably fewer AOB of 2.1 × 10 12 copies m-2 (amoA), as measured by quantitative PCR. Cell specific conversion rates of anammox bacteria and AOB were estimated at 0.3-0.5 fmol N cell-1 d-1 and 7-9 fmol N cell-1 d-1 , respectively. The study shows the applicability of one-stage nitritation-anammox in MBBRs at low temperatures and highlights the importance of quantification of AOB and anammox bacteria for understanding process performance.

Science of The Total Environment

In a microbial electrolysis cell (MEC), the oxidization of organic compounds is facilitated by an... more In a microbial electrolysis cell (MEC), the oxidization of organic compounds is facilitated by an electrogenic biofilm on the anode surface. The biofilm community composition determines the function of the system. Both deterministic and stochastic factors affect the community, but the relative importance of different factors is poorly understood. Anode material is a deterministic factor as materials with different properties may select for different microorganisms. Ecological drift is a stochastic factor, which is amplified by dispersal limitation between communities. Here, we compared the effects of three anode materials (graphene, carbon cloth, and nickel) with the effect of dispersal limitation on the function and biofilm community assembly. Twelve MECs were operated for 56 days in four hydraulically connected loops and shotgun metagenomic sequencing was used to analyse the microbial community composition on the anode surfaces at the end of the experiment. The anode material was the most important factor affecting the performance of the MECs, explaining 54-80 % of the variance observed in peak current density, total electric charge generation, and start-up lag time, while dispersal limitation explained 10-16 % of the variance. Carbon cloth anodes had the highest current generation and shortest lag time. However, dispersal limitation was the most important factor affecting microbial community structure, explaining 61-98 % of the variance in community diversity, evenness, and the relative abundance of the most abundant taxa, while anode material explained 0-20 % of the variance. The biofilms contained nine Desulfobacterota metagenome-assembled genomes (MAGs), which made up 64-89 % of the communities and were likely responsible for electricity generation in the MECs. Different MAGs dominated in different MECs. Particularly two different genotypes related to Geobacter benzoatilyticus competed for dominance on the anodes and reached relative abundances up to 83 %. The winning genotype was the same in all MECs that were hydraulically connected irrespective of anode material used.

Water Environment Research

This study demonstrates a comparison of energy usage, land footprint and volumetric requirements ... more This study demonstrates a comparison of energy usage, land footprint and volumetric requirements of municipal wastewater treatment with aerobic granular sludge (AGS) and conventional activated sludge (CAS) at a full‐scale wastewater treatment plant characterized by large fluctuations in nutrient loadings and temperature. The concentration of organic matter in the influent to the AGS was increased by means of hydrolysis and bypassing the pre‐settler. Both treatment lines produced effluent concentrations below 5 mg BOD7 L‐1, 10 mg TN L‐1, and 1 mg TP L‐1, by enhanced biological nitrogen‐ and phosphorus removal. In this case study, the averages of volumetric energy usage over one year were 0.22 ± 0.08 and 0.26 ± 0.07 kWh m‐3 for the AGS and CAS, respectively. A larger difference was observed for the energy usage per reduced P.E., which was on average 0.19 ± 0.08 kWh P.E.‐1 for the AGS and 0.30 ± 0.08 kWh P.E.‐1 for the CAS. However, both processes had the potential for decreased energy...

IOP Conference Series: Materials Science and Engineering

The present study investigates the presence and removal of target organic micropollutants in a la... more The present study investigates the presence and removal of target organic micropollutants in a large Swedish wastewater treatment plant designed for nutrient removal including activated sludge, trickling filters, nitrifying moving bed biofilm reactors (MBBRs) and post-denitrifying MBBRs. A total of 28 organic micropollutants were analysed, at concentrations ranging from few ng/L to µg/L, in the influent and effluent of the different biological reactors in two sampling campaigns. The observed micropollutant removal efficiencies of the wastewater treatment plant varied from insignificant (< 20%) to high (> 90%) between compounds. The activated sludge reactor, being the first in line, contributed to most of the removal from the water phase. Additional removal of a few compounds was observed in the biofilm units, but most of the persistent compounds remained stable through all biological treatments.

Frontiers in Microbiology

In single-chamber microbial electrolysis cells (MECs), organic compounds are oxidized at the anod... more In single-chamber microbial electrolysis cells (MECs), organic compounds are oxidized at the anode, liberating electrons that are used for hydrogen evolution at the cathode. Microbial communities on the anode and cathode surfaces and in the bulk liquid determine the function of the MEC. The communities are complex, and their assembly processes are poorly understood. We investigated MEC performance and community composition in nine MECs with a carbon cloth anode and a cathode of carbon nanoparticles, titanium, or stainless steel. Differences in lag time during the startup of replicate MECs suggested that the initial colonization by electrogenic bacteria was stochastic. A network analysis revealed negative correlations between different putatively electrogenic Deltaproteobacteria on the anode. Proximity to the conductive anode surface is important for electrogens, so the competition for space could explain the observed negative correlations. The cathode communities were dominated by h...

FEMS Microbiology Letters

The Oslofjord subsea road tunnel is a unique environment in which the typically anoxic marine dee... more The Oslofjord subsea road tunnel is a unique environment in which the typically anoxic marine deep subsurface is exposed to oxygen. Concrete biodeterioration and steel corrosion in the tunnel have been linked to the growth of iron- and manganese-oxidizing biofilms in areas of saline water seepage. Surprisingly, previous 16S rRNA gene surveys of biofilm samples revealed microbial communities dominated by sequences affiliated with nitrogen-cycling microorganisms. This study aimed to identify microbial genomes with metabolic potential for novel nitrogen- and metal-cycling reactions, representing biofilm microorganisms that could link these cycles and play a role in concrete biodeterioration. We reconstructed 33 abundant, novel metagenome-assembled genomes (MAGs) affiliated with the phylum Planctomycetota and the candidate phylum KSB1. We identified novel and unusual genes and gene clusters in these MAGs related to anaerobic ammonium oxidation, nitrite oxidation, and other nitrogen-cycl...