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  • 1.
    Johansson, Lena
    Royal Institute of Technology, Sweden.
    The use of LECA (Light Expanded Clay Aggregates) for the removal of phosphorus from wastewater1997In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Water, Science and Technology, ISSN 0273-1223, Vol. 35, no 5, p. 87-93Article in journal (Refereed)
    Abstract [en]

    Increasing attention is being focused on the phosphorus retention capacity of wetlands. Several attempts have been made to improve the reduction of phosphorus in wastewater by the use of constructed wetlands. One way of improving the phosphorus reduction capacity is to use efficient filter materials in the wetland. Leca(R) (Light Expanded Clay Aggregates) has been tested in Norway, where laboratory and field investigations gave promising results. To further study the chemical removal mechanism of Leca, an experiment utilising five columns was performed. A phosphate solution was applied to the columns intermittently and samples were taken twice a week. Parallel to this study, a P-fractionation experiment was conducted to find out how the phosphate was sorbed to various components of the material. Both experiments showed that only a small amount of the applied phosphate was sorbed by the Leca. The amount sorbed was primarily attached to Al-complexes. In a second column experiment Opoka, a reactive medium rich in CaCO3, was added to Leca and sand to investigate the P-sorption capacity. The results from this investigation showed a higher P-uptake than in the previous column experiment. The lime additive clearly increased the P-sorption and, in this study, Leca in its pure form could be considered as chemically non-reactive. 

  • 2.
    Kanders, Linda
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Purac AB, Box 1146, Lund, SE-221 05, Sweden.
    Beier, M.
    Institute for Sanitary Engineering and Waste Management (ISAH), Leibniz Universitaet Hannover, Germany.
    Nogueira, R.
    Institute for Sanitary Engineering and Waste Management (ISAH), Leibniz Universitaet Hannover, Welfengarten 1, Hannover, 30167, Germany.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Sinks and sources of anammox bacteria in a wastewater treatment plant - screening with qPCR2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 78, no 2, p. 441-451Article in journal (Refereed)
    Abstract [en]

    The deammonification process, which includes nitritation and anammox bacteria, is an energyefficient nitrogen removal process. Starting up an anammox process in a wastewater treatment plant (WWTP) is still widely believed to require external seeding of anammox bacteria. To demonstrate the principle of a non-seeded anammox start-up, anammox bacteria in potential sources must be quantified. In this study, seven digesters, their substrates and reject water were sampled and quantitative polymerase chain reaction (qPCR) was used to quantify both total and viable anammox bacteria. The results show that mesophilic digesters fed with nitrifying sludge (with high sludge ages) can be classified as a reliable source of anammox bacteria. Sludge hygienization and dewatering of digestate reduce the amount of anammox bacteria by one to two orders of magnitude and can be considered as a sink. The sampled reject waters contained on average >4.0 × 104 copies mL1 and the majority of these cells (>87%) were viable cells. Furthermore, plants with side-stream anammox treatment appear to have higher overall quantities of anammox bacteria than those without such treatment. The present study contributes to the development of sustainable strategies for both startup of anammox reactors and the possibility of improving microbial management in WWTPs.

  • 3.
    Kanders, Linda
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Purac AB, Sweden.
    Yang, Jing-jing
    IVL Swedish Environmental Research Institute, Sweden.
    Baresel, Christian
    IVL Swedish Environmental Research Institute, Sweden.
    Zambrano, Jesus
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Full-scale comparison of N2O emissions from SBR N/DN operation versus one-stage deammonification MBBR treating reject water: - and optimization with pHset-point2019In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 79, no 8, p. 1616-1625Article in journal (Refereed)
    Abstract [en]

    To be able to fulfill the Paris agreement regarding anthropogenic greenhouse gases, all potential 12 emissions must be mitigated. Wastewater treatment plants should aim to eliminate emissions of the 13 most potent greenhouse gas, nitrous oxide. In this study, these emissions were measured at a full-scale 14 reject water treatment tank during two different operation modes: nitrification/denitrification (N/DN) 15 operating as a sequencing batch reactor (SBR), and deammonification (nitritation/anammox) as a moving 16 bed biofilm reactor (MBBR). Nitrous oxide was measured both in the water phase and in the off-gas. The 17 treatment process emitted significantly less nitrous oxide in deammonification mode 0.14-0.7 %, 18 compared to 10 % of Total Nitrogen in N/DN mode. The decrease can be linked to the change feeding 19 strategy, concentration in nitrite, load of ammonia oxidized, shorter aeration time, no ethanol dosage 20 and the introduction of biofilm. Further, evaluation was done how the operational pH set point 21 influenced the emissions in deammonification mode. Lower concentrations of nitrous oxide was 22 measured in water phase at higher pH (7.5-7.6) than at lower pH (6.6-7.1). This is believed to be mainly 23 because of the lower aeration ratio and increased complete denitrification at the higher pH set point.

  • 4.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Diaz, J G
    Faculty of Science, Universidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco, Madrid, Spain.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Algae biomass cultivation in nitrogen rich biogas digestate.2015In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 72, no 10, p. 1723-1729Article in journal (Refereed)
    Abstract [en]

    Because microalgae are known for quick biomass growth and nutrient uptake, there has been much interest in their use in research on wastewater treatment methods. While many studies have concentrated on the algal treatment of wastewaters with low to medium ammonium concentrations, there are several liquid waste streams with high ammonium concentrations that microalgae could potentially treat. The aim of this paper was to test ammonium tolerance of the indigenous algae community of Lake Malaren and to use this mixed consortia of algae to remove nutrients from biogas digestate. Algae from Lake Malaren were cultivated in Jaworski's Medium containing a range of ammonium concentrations and the resulting algal growth was determined. The algae were able to grow at NH4-N concentrations of up to 200 mg L(-1) after which there was significant inhibition. To test the effectiveness of the lake water algae on the treatment of biogas digestate, different pre-cultivation set-ups and biogas digestate concentrations were tested. It was determined that mixing pre-cultivated suspension algae with 25% of biogas digestate by volume, resulting in an ammonium concentration of around 300 mg L(-1), produced the highest algal growth. The algae were effective in removing 72.8 ± 2.2% of NH4-N and 41.4 ± 41.4% of PO4-P.

  • 5.
    Nehrenheim, Emma
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Odlare, Monica
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Allard, Bert
    Örebro Univ.
    Retention of 2,4,6-trinitrotoluene and heavy metals from industrial waste water by using the low cost adsorbent pine bark in a batch experiment2011In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 64, no 10, p. 2052-2058Article in journal (Refereed)
    Abstract [en]

    Pine bark is a low cost sorbent originating from the forest industry. In recent years, it has been found to show promise as an adsorbent for metals and organic substances in contaminated water, especially landfill leachates and storm water. This study aims to investigate if pine bark can replace commercial adsorbents such as active carbon. An industrial effluent, collected from a treatment plant of a demilitarization factory, was diluted to form concentration ranges of contaminants and shaken with pine bark for 24 hours. Metals (e.g. Pb, Zn, Cd, As and Ni) and explosives, e. g., 2,4,6-trinitrotoluene (TNT), were analysed before and after treatment. The aim of the experiment was twofold; firstly, it was to investigate whether metals are efficiently removed in the presence of explosives and secondly, if adsorption of explosive substances to pine bark was possible. Langmuir and Freundlich isotherms were used to describe the adsorption process where this was possible. It was found that metal uptake was possible in the presence of TNT and other explosive contaminants. The uptake of TNT was satisfactory with up to 80% of the TNT adsorbed by pine bark.

  • 6.
    Olsson, Jesper
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Forkman, T.
    Swedish University of Agricultural Sciences, Sweden.
    Gentili, F.G.
    Swedish University of Agricultural Sciences, Sweden.
    Zambrano, Jesús
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Anaerobic co-digestion of sludge and microalgae grown inmunicipal wastewater: A feasibility study2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 77, no 3, p. 682-694Article in journal (Refereed)
    Abstract [en]

    In this study a natural mix of microalgae grown in wastewater of municipal character was co-digested with sewage sludge in mesophilic conditions, in both batch and semi-continuous modes. The semicontinuous experiment was divided into two periods with OLR 1 (Organic Loading Rate) of 2.4 kg VS m3 d-1 and HRT1 (Hydraulic Retention Time) of 15 days, and OLR2 of 3.5 kg VS m3 d-1 and HRT2 of 10 days respectively. Results showed stable conditions during both periods. The methane yield was reduced when adding microalgae (from 200 ± 25 NmL CH4 g VSin-1 , to 168±22 NmL CH4 g VSin-1). VS reduction was also decreased by 51%. This low digestability was confirmed in the anaerobic batch test. However, adding microalgae improved the dewaterability of the digested sludge. The high heavy metals content in the microalgae resulted in a high heavy metals content in the digestate, making it more difficult to reuse the digestate as fertilizer on arable land. The heavy metals are thought to originate from the flue gas used as a CO2 source during the microalgae cultivation. Therefore the implementation of CO2 mitigation via algal cultivation requires careful consideration regarding thesource of the CO2-rich gas.

  • 7.
    Olsson, Jesper
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Mesophilic and thermophilic co-digestion of microalgal-based activated sludge and primary sludgeIn: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732Article in journal (Refereed)
  • 8.
    Olsson, Jesper
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Microalgae as biological treatment for municipal wastewater - Effects on the sludge handling in a treatment plant2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, ISSN 0273-1223, Vol. 78, no 3, p. 644-654Article in journal (Refereed)
    Abstract [en]

    A mix of microalgae and bacteria was cultivated on pre-sedimented municipal wastewater in a continuous operated microalgae-activated sludge process. The excess material from the process was co-digested with primary sludge in mesophilic and thermophilic conditions in semi-continuous mode (5 L digesters). Two reference digesters (5 L digesters) fed with waste-activated sludge (WAS) and primary sludge were operated in parallel. The methane yield was slightly reduced (≈10%) when the microalgal-bacterial substrate was used in place of the WAS in thermophilic conditions, but remained approximately similar in mesophilic conditions. The uptake of heavy metals was higher with the microalgal-bacterial substrate in comparison to the WAS, which resulted in higher levels of heavy metals in the digestates. The addition of microalgal-bacterial substrate enhanced the dewaterability in thermophilic conditions. Finally, excess heat can be recovered in both mesophilic and thermophilic conditions. 

  • 9.
    Rodriguez Caballero, Adrian
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Hallin, S
    Swedish Univ Agr Sci.
    Påhlson, Carl
    Uppsala Univ.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering.
    Ammonia oxidizing bacterial community composition relates to process performance in wastewater treatment plants under low temperature conditions2012In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 65, no 2, p. 197-204Article in journal (Other academic)
    Abstract [en]

    Nitrification can be difficult to maintain at wastewater treatment plants (WWTPs) during cold periods resulting in disrupted nitrogen removal. The aim of this study was to relate nitrification process performance to abundance and composition of the ammonia oxidizer communities in two closely located municipal WWTPs in Sweden during an eight month period covering seasonal changes and low temperature conditions. Both facilities showed lower NH4+-N removal efficiency and nitrification rates as temperature decreased. However, one of the plants had a more stable nitrification rate and higher ammonia removal efficiency throughout the entire period. The differences in performance was related to a shift in the composition of the bacterial ammonia oxidizing community from a Nitrosomonas oligotropha-dominated community to a mixed community including also Nitrosomonas ureae-like ammonia oxidizers. This was likely a response to differences in NH4+-N and organic loading.

  • 10.
    Samuelsson, Oscar
    et al.
    Uppsala University, Sweden.
    Anders, Björk
    IVL Swedish Environmental Research Institute, Sweden.
    Zambrano, Jesús
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Carlsson, Bengt
    Uppsala University, Sweden.
    Gaussian process regression for monitoring and fault detection of wastewater treatment processes2017In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 75, no 12, p. 2952-2963Article in journal (Refereed)
    Abstract [en]

    Monitoring and fault detection methods are increasingly important to achieve a robust and resource efficient operation of wastewater treatment plants (WWTPs). The purpose of this paper was to evaluate a promising machine learning method, Gaussian process regression (GPR), at WWTP monitoring applications. We evaluated GPR at two WWTP monitoring problems: estimate missing data in a flow rate signal (simulated data), and detect a drift in an ammonium sensor (real data). We showed that GPR with the standard estimation method, maximum likelihood estimation (GPR-MLE), suffered from local optima during estimation of kernel parameters, and did not give satisfactory results in a simulated case study. However, GPR with a state-of-the-art estimation method based on sequential Monte Carlo estimation (GPR-SMC) gave good predictions and did not suffer from local optima. Comparisons with simple standard methods revealed that GPR-SMC performed better than linear interpolation in estimating missing data in a noisy flow rate signal. We conclude that GPR-SMC is both a general and powerful method for monitoring full-scale WWTPs. However, this paper also shows that it does not always pay off to use more sophisticated methods. New methods should be critically compared against simpler methods, which might be good enough for some scenarios.

  • 11.
    Samuelsson, Oscar
    et al.
    Uppsala University, Sweden.
    Björk, Anders
    IVL Swedish Environmental Research Institute, Sweden..
    Zambrano, Jesus
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Carlsson, Bengt
    Uppsala University, Sweden.
    Fault signatures and bias progression in dissolved oxygen sensors2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 78, no 5, p. 1034-1044Article in journal (Refereed)
    Abstract [en]

    Biofilm fouling is known to impact the data quality of sensors, but little is known about the exact effects. We studied the effects of artificial and real biofilm fouling on dissolved oxygen (DO) sensors in full-scale water resource recovery facilities, and how this can automatically be detected. Biofilm fouling resulted in different drift direction and bias magnitudes for optical (OPT) and electrochemical (MEC) DO sensors. The OPT-sensor was more affected by biofilm fouling compared to the MEC sensor, especially during summer conditions. A bias of 1 mg/L was detected by analysing the impulse response (IR) of the automatic air cleaning system in the DO sensor. The IR is an effect of a temporal increase in DO concentration during the automatic air cleaning. The IRs received distinct pattern changes that were matched with faults including: biofilm fouling, disturbances in the air supply to the cleaning system, and damaged sensor membrane, which can be used for fault diagnosis. The results highlight the importance of a condition based sensor maintenance schedule in contrast to fixed cleaning intervals. Further, the results stress the importance of understanding and detecting bias due to biofilm fouling, in order to maintain a robust and resource efficient process control.

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