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  • 1.
    Lagerkvist, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pelkonen, Markku
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Wikström, Tommy
    Quick-start of full-scale anaerobic digestion (AD) using aeration2015In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 38, p. 102-104Article in journal (Refereed)
    Abstract [en]

    A conventional 1300 m3 continuously stirred anaerobic tank reactor at the city of Boden, north Sweden, which was receiving a feed of both sewage sludge and food waste, was put out of operation due to the build-up of a float phase. The reactor was emptied and cleaned. At start-up there was no methanogenic sludge available, so an unconventional start-up procedure was applied: The reactor was rapidly (8 days with 1200 kg of total solids (TS) added daily) filled with thickened, and slightly acidic sewage sludge, showing only slight methane generation, which was subsequently heated to 55 °C. Then compressed air was blown into the digester and within a month a fully functional methanogenic culture was established. The transfer from acidogenic to methanogenic conditions happened in about one week. As a start-up technique this is fast and cost efficient, it only requires the access of a compressor, electricity and a source of air. In total, about 16 tonnes of oxygen were used. It is proposed that this method may also be used as an operational amendment technique, should a reactor tend to acidify.

  • 2.
    Pelkonen, Markku
    Laboratory of Environmental Engineering, Helsinki University of Technology.
    Upgrading oxygen transfer in the activated sludge process1990In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 22, no 7-8, p. 253-260Article in journal (Refereed)
    Abstract [en]

    The objectives were to get some information on the variation of the alpha factor and to study factors affecting oxygen transfer efficiency in fine-bubble aeration. Results from a 5 week continuous operation of a batch aeration column process show that the variation of the alpha factor was considerable in the aeration basin, especially at the inlet end. The variation follows a diurnal rhythm and the weekly variation is much smaller. The off-gas method was used to examine factors affecting oxygen transfer in process conditions. Regression models were constructed to describe the transfer process both on a semitechnical scale and on a full scale. The most important factors are the specific air flow rate, the respiration rate and the DO concentration. The enhancement in OTE through the respiration rate and the DO concentration is due to a biological mechanism. To optimize the transfer process it is necessary to maintain a high respiration rate and a sufficiently high DO concentration.The objectives were to get some information on the variation of the alpha factor and to study factors affecting oxygen transfer efficiency in finebubble aeration. Results from a 5 week continuous operation of a batch aeration column process show that the variation of the alpha factor was considerable in the aeration basin, especially at the inlet end. The variation follows a diurnal rhythm and the weekly variation is much smaller. The off-gas method was used to examine factors affecting oxygen transfer in process conditions. Regression models were constructed to describe the transfer process both on a semitechnical scale and on a full scale. The most important factors are the specific air flow rate, the respiration rate and the DO concentration. The enhancement in OTE through the respiration rate and the DO concentration is due to a biological mechanism. To optimize the transfer process it is necessary to maintain a high respiration rate and a sufficiently high DO concentration.--------------------------------------------------------------------------------

  • 3.
    Pelkonen, Markku
    et al.
    Laboratory of Environmental Engineering, Helsinki University of Technology.
    Kotro, Mikko
    Nordic Envicon Oy, Helsinki University, Development Services.
    Rintala, Jukka A.
    University of Jyväskylä, Department of Biology and Environmental Science.
    Biological nitrogen removal from landfill leachate: A pilot-scale study1999In: Waste Management & Research, ISSN 0734-242X, E-ISSN 1096-3669, Vol. 17, no 6, p. 493-497Article in journal (Refereed)
    Abstract [en]

    A pilot-scale two-stage process including an anaerobic pretreatment (up-flow anaerobic sludge blanket, UASB) unit and a pre-denitrification activated sludge process was studied for treating leachates from a municipal landfill (waste aged 4 to 5 years, area 2.5 ha) and from a windrow composting area (1 ha). A single-stage pilot process was used for nitrification studies. The leachate characteristics were as follows: COD 740 to 2400 mg l-1 (chemical oxygen demand), BOD7 (biochemical oxygen demand) approximately 1000 mg l-1, N(tot) 40 to 120 mg l-1 and the temperature was between 2 and 21°C. The results show that 45 to 50 COD removal could be achieved in the UASB reactor even at temperatures below 10°C. The activated sludge process was operated with a 1.1 to 2.2 d hydraulic retention time and at between 8 and 21°C. The removal efficiencies were 80 to 90 for COD, over 98 for BOD7, over 90 for NH4-N and over 70 for N(tot). The dependence of denitrification efficiency on leachate biodegradable COD fraction and COD to N ratio was evaluated. Overall treatment efficiencies were good and applicable for design purposes. The total costs were estimated for a full scale pre-denitrification process at FIM 10 to 20 m-3 and FIM 50 to 90 (kg N removed)-1 (3.5 to 7 DM m-3 and 17 to 30 DM [kg N removed]-1) for a landfill representing circumstances in Southern Finland with an annual average flow of 50 m3 d-1.

  • 4.
    Pelkonen, Markku
    et al.
    Helsinki University of Technology.
    Tenno, Robert A.
    Laboratory of Environmental Engineering, Helsinki University of Technology, Helsinki University of Technology.
    New control parameters and measurement techniques for the activated sludge process1993In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 27, no 5-6, p. 287-295Article in journal (Refereed)
    Abstract [en]

    An on-line oxygen uptake and CO2-production rate measurement system was used to analyse the biomass activity. CO2-production rate corresponded well with oxygen uptake rate in the carbon oxidation process. In the nitrification process the ratio CO2-prod./O2-consumed (r(q)) had a larger variation, but CO2-production had a good correlation with utilized COD; variation of the r(q)-value indicate differences in the auto-/heterotrophic oxidation balance. From this basis the oxygen uptake rate for carbon oxidation and nitrification can be separated. The comparison with two biomass determination methods based on ATP-analysis shows that for heterotrophic biomass the methods indicate clearly different changes of ATP, for nitrification process the results were more compatible. By combining the biomass and on-line measurements with biomass growth model based on IAWPRC-model equations reasonably good estimates were obtained. Best fit of model was in the nitrification process; by using VSS as the measure of biomass the fit was poor. The differences in the ATP-measurement results affect also the model coefficients.An on-line oxygen uptake and CO2-production rate measurement system was used to analyze the biomass activity. CO2-production rate corresponded well with oxygen uptake rate in the carbon oxidation process. In the nitrification process the ratio CO2-prod./O2-consumed (rg) had a larger variation, but CO2-production had a good correlation with utilized COD; variation of rg-value indicate differences in auto-heterotrophic oxidation and nitrification can be separated. The comparison with two biomass determination methods based on ATP-analysis shows that for heterophil biomass the methods indicate clearly different changes of ATP, for nitrification process the results were more compatible. By combining the biomass and on-line measurements with biomass growth model based on IAWPRC-model equations reasonably good estimated were obtained. Best fit of model was in the nitrification process; by using VSS as the measure of biomass the fit was poor. The differences in the ATP-measurement results affect also the model coefficients

  • 5.
    Pelkonen, Markku
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Wang, Yu
    School of Engineering, Aalto University, Espoo, Lahti Center, School of Science and Technology, Aalto University.
    Leachate direct-discharge limits and incentives related to landfill aftercare costs2017In: Journal of Material Cycles and Waste Management, ISSN 1438-4957, E-ISSN 1611-8227, Vol. 19, no 1, p. 413-422Article in journal (Refereed)
    Abstract [en]

    Society needs sustainable methods for landfilling from an environmental perspective, but they have to be cost effective and affordable. Aftercare represents considerable costs within waste management system and costs can be expected to accrue over a long period of time showing the need to compare different management options. Direct-discharge limits for leachate COD and nitrogen are different in various (European) countries. When leachate COD or nitrogen has decreased at the latter part of the aftercare period, effluent limits 50 or 200 mg/l for COD and 10 or 70 mg/l for nitrogen have a considerable impact on period length. The objective of this paper is to discuss the effects of leachate discharge limits on landfill aftercare and leachate management costs in various conditions. Landfill simulator results and modelling are used to estimate leachate concentrations in three different scenarios. It is suggested that stricter discharge limits (shown before) impact on the costs of activated carbon filtration (1.4-fold) and biological treatment (1.1–1.24-fold). Stricter limits also extend the aftercare period length considerably, but with substantial water circulation the differences are clearly smaller. These results support the recent suggestion of aftercare incentives, and some details of applying these incentives in different conditions are discussed.

  • 6.
    Pelkonen, Markku
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Yu, Wang
    Aalto University.
    Long term leachate management based on anaerobic/aerobic landfill simulator studies2012In: Abstract proceedings of 7th Intercontinental Landfill Research Symposium: Södra Sunderbyn, June 25th to 27th, 2012 / [ed] Anders Lagerkvist, Luleå: Luleå tekniska universitet, 2012, p. 103-104Conference paper (Refereed)
  • 7.
    Tenno, Robert A.
    et al.
    Laboratory of Environmental Engineering, Helsinki University of Technology.
    Pelkonen, Markku
    Laboratory of Environmental Engineering, Helsinki University of Technology.
    Activated sludge concentration dynamics1994In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 28, no 2, p. 491-493Article in journal (Refereed)
    Abstract [en]

    The relationship between activated sludge concentration in the aeration and settling tank is determined on the basis of settling process characteristics. The relationship is used for description of the activated sludge concentration and stock dynamics in the aeration and settling tank. A limit value for maximization of activated sludge concentration is determined

  • 8.
    Tenno, Robert A.
    et al.
    Laboratory of Environmental Engineering, Helsinki University of Technology.
    Renko, Esa K.
    Laboratory of Environmental Engineering, Helsinki University of Technology.
    Pelkonen, Markku
    Laboratory of Environmental Engineering, Helsinki University of Technology.
    Online identification of activated sludge settling properties1995In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 29, no 11, p. 2587-2590Article in journal (Refereed)
    Abstract [en]

    Activated sludge settling properties can be characterised with two time-varying parameters. A simple method is presented for online identification of these parameters. The method is obtained as an exact solution of the filtration problem; it is obtained on the basis of the settling process description and the parameters variation process description. The method is suitable for practical application. It is a more exact solution of the identification problem than the alternative regression analysis method. An easily implementable system is proposed for automatic characterisation of the sludge settling properties

  • 9.
    Wang, Y.
    et al.
    Lahti Center, School of Science and Technology, Aalto University.
    Pelkonen, Markku
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Kaila, J.
    Lahti Center, School of Science and Technology, Aalto University.
    Strategies to enhance the biological nitrogen removal of high-strength ammonium and low C/N landfill leachate with the SBR process2012In: Environmental technology, ISSN 0959-3330, E-ISSN 1479-487X, Vol. 33, no 5, p. 579-588Article in journal (Refereed)
    Abstract [en]

    The treatment of high ammonium-nitrogen concentration landfill leachate has become an increasing problem because of the requirements to reduce nutrient emissions. A laboratory-scale sequential batch reactor (SBR) was operated and tested in order to optimize the operational strategies of a cost-saving method to enhance the removal of ammonium-nitrogen from a real landfill leachate. Two sequence schemes were tested, one with long non-aerated/aerated sequences and another with short sequences. The air supply levels with low to intermediate dissolved oxygen (DO) and external carbon addition were altered. With both schemes a high ammonium reduction (>99%) and a reasonable total nitrogen (TN) reduction (around 60%) could be achieved with strong carbon limitation (BOD 7/N=1.1). Chemical oxygen demand (COD) removal was lower with longer sequences. Denitrification via nitrite seemed to be an important part of TN removal, controlled with the low DO. With increasing nitrite accumulation COD/N removed decreased in both schemes indicating clearly a more efficient use of COD. The scheme with short sequences indicated advantages to save the air supply preventing nitrite oxidation under low air supply conditions and better TN and COD removal efficiencies. The results show that an applicable operational strategy can be found resulting in a reasonable pre-treatment option in landfills, requiring less carbon and aeration energy.

  • 10.
    Wang, Yu
    et al.
    School of Engineering, Aalto University, Espoo, Lahti Center, School of Science and Technology, Aalto University, Laboratory of Environmental Engineering, Helsinki University of Technology.
    Pelkonen, Markku
    Laboratory of Environmental Engineering, Helsinki University of Technology.
    Impacts of temperature and liquid/solid ratio on anaerobic degradation of municipal solid waste: An emission investigation of landfill simulation reactors2009In: Journal of Material Cycles and Waste Management, ISSN 1438-4957, E-ISSN 1611-8227, Vol. 11, no 4, p. 312-320Article in journal (Refereed)
    Abstract [en]

    Management of landfill emissions, i. e., landfill gas (LFG) and landfill leachate, is an important and resource-intensive task. A long-term demonstration pilot, consisting of landfill simulation reactors (LSRs), was used to study the impact of temperature and the applied liquid/solid ratio (L/S ratio) on landfill emissions, characteristics, and trends. This pilot has already run for more than 1000 days since the end of 2004 and will continue to run for some time. The degradation of waste at different temperatures has impacts on the overall degradation degree and on the length of post-closure care required. Higher temperatures accelerated the degradation, but also resulted in higher leachate chemical oxygen demand (COD) and ammonia concentrations, which prolong the aftercare period. Meanwhile, at a given stabilization degree [e. g., 70 l gas/kg waste (dry)], the total leached nitrogen under psychrophilic conditions was 3. 5 times that under mesophilic/thermophilic conditions, which resulted in a higher required effort for leachate treatment. The impact of L/S ratio or simulated annual L/S rates was also evaluated. The results show the significance of efficiently obtaining the targeted L/S ratio in order to achieve low landfill emission potential

  • 11.
    Wang, Yu
    et al.
    Lahti Center, School of Science and Technology, Aalto University.
    Pelkonen, Markku
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Kaila, J.
    Lahti Center, School of Science and Technology, Aalto University.
    Cost-saving biological nitrogen removal from strong ammonia landfill leachate2011In: Waste Management & Research, ISSN 0734-242X, E-ISSN 1096-3669, Vol. 29, no 8, p. 797-806Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to develop an improved management mode in Ammassuo landfill (Finland) for leachate ammonium-nitrogen removal, to minimize the leachate management costs and secure compliance with the uptrend requirements of regulations for on-site leachate management. With a single sequential batch simulation reactor, the minimum C/N ratio was detected as 1.7 (adjusted by external carbon addition), to achieve the acceptable removal efficiency of 99, 62 and 74% in NH(4)-N, total nitrogen and chemical oxygen demand, respectively. Both total nitrogen removal and efficiency of carbon use were correlated with an increasing NO(2)(-)/NO(x)(-) ratio indicating higher performance with denitrification via nitrite. It was estimated that the leachate management cost could be reduced by 28 to 38%.

  • 12.
    Wang, Yu
    et al.
    School of Engineering, Aalto University, Espoo.
    Pelkonen, Markku
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Kaila, Juha
    School of Engineering, Aalto University, Espoo.
    Are there carbon and nitrogen sinks in the landfills?2014In: Sustainable Environment Research, ISSN 1022-7636, Vol. 24, no 6, p. 423-429Article in journal (Refereed)
    Abstract [en]

    The management of sanitary landfills after closure is an important engineering, economic and sustainability issue. The society needs sustainable methods for landfilling from an environmental perspective but it has to be cost-effective and affordable for a society as well. Compared with inorganics, carbon and nitrogen are more reactive. It is important to identify the time needed for them to achieve the limit values of leachate emission (i.e., the length of aftercare period). However, does it mean that the environmental impacts have been minimized after the active aftercare period? Especially at low temperature, the decomposition rate and release rate of carbon and nitrogen are lower; so the leachate emission concentrations are lower and it is easier to achieve the emission limit values. In these conditions the residual carbon and nitrogen remaining in the landfill are higher, but according to the results this is not a practical problem. In the degradation of stable humic compounds, carbon and nitrogen sinks are formed. Their fraction in the organics seems to be comparable with waste treated in mechanical-biological way and has impact as a sink. The humification process seems to be affected by temperature, but more knowledge is still needed like total balances of humic substances. It is necessary to discuss the performance of carbon and nitrogen within aftercare (active aftercare) and after aftercare (passive aftercare). The solutions should be designed accordingly from both environmental and economic considerations.

  • 13.
    Wang, Yu
    et al.
    School of Engineering, Aalto University, Espoo.
    Pelkonen, Markku
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Kaila, Juha
    School of Engineering, Aalto University, Espoo.
    Optimization of landfill leachate management in the aftercare period2012In: Waste Management & Research, ISSN 0734-242X, E-ISSN 1096-3669, Vol. 30, no 8, p. 789-799Article in journal (Refereed)
    Abstract [en]

    The management of sanitary landfills after closure is an important engineering, economic and sustainability issue and is referred to as the greatest unresolved landfill challenge. Most sanitary landfills are operated according to the dry tomb principle, resulting in aftercare periods of hundreds of years. To study landfill body behaviour, long-term leachate emissions were studied with anaerobic landfill simulators, and a forecast model was developed targeting the behaviour of NH4-N, COD and chlorides as a function of temperature and the L/S-ratio (liquid-to-solid). It was found that NH4-N is the decisive factor in leachate management, requiring the highest L/S-ratio (around 6) to meet the direct discharge limit values. Various scenarios were constructed to find optimal leachate management strategies both in large (waste height H = 25 m) and medium-sized landfills (H = 10 m) with corresponding temperature ranges. The results show that by minimizing the aftercare period length with leachate pre-treatment and recirculation, both sustainability and economic benefits can be achieved. The results provide new views on how to manage the long-term leachate aftercare problem. In the case of large landfills, further efforts are needed to reach stabilization within a reasonable time frame.

  • 14.
    Wang, Yu
    et al.
    School of Engineering, Aalto University, Espoo, Lahti Center, School of Science and Technology, Aalto University, Department of Civil and Environmental Engineering, Helsinki University of Technology.
    Pelkonen, Markku
    Department of Civil and Environmental Engineering, Helsinki University of Technology.
    Kotro, Mikko
    Nordic Envicon Oy.
    Treatment of high ammonium-nitrogen wastewater from composting facilities by air stripping and catalytic oxidation2010In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 208, no 1-4, p. 259-273Article in journal (Refereed)
    Abstract [en]

    Composting municipal wastewater sludge may generate composting wastewater (acid washer water and tunnel wastewater) with high ammonium-nitrogen (NH 4-N) concentration; this kind of wastewater is usually generated in a rather small daily amount. A procedure of air stripping with catalytic oxidation was developed and tested with pilot-scale and full-scale units for synthetic disposal of the high NH4-N wastewaters from composting facilities. In air stripping, around 90% NH4-N removal efficiency was reliably achieved with a maximum of 98%. A model to describe the stripping process efficiency was constructed, which can be used for process optimization. After catalytic oxidation, the concentrations in the outlet gas were acceptable for NH3, NOX, NO2, and N2O, but the NH3 and N2O concentrations limited the feasible loading range. The treatment costs were estimated in detail. The results indicate that air stripping with the catalytic oxidation process can be applied for wastewater treatment in composting facilities

  • 15.
    Wang, Zengzhang
    et al.
    Taiyuan University of Technology.
    Niu, Zhi Qing
    Taiyuan University of Technology.
    Pelkonen, Markku
    Helsinki University of Technology.
    Management of process performance at low water temperatures in respect of filamentous organisms2004In: Journal of Environmental Sciences(China), ISSN 1001-0742, E-ISSN 1878-7320, Vol. 16, no 1, p. 113-116Article in journal (Refereed)
    Abstract [en]

    The management of sludge-settling properties in Nordic conditions is of importance during the low temperature (spring) season because of the peak settler load. A survey was made in 10 Finnish waste water treatment plants(WWTP's) and the total extended filament length and DSVI in half of the plants exceeded the limits, which indicates sludge bulking(15 km/g SS and 150 ml/g respectively). The dominant organism was Microthrix parvicella, the abundance of which was 59.22% of total extended filament length on average. Chemicals were tested to control the filaments, and it was found that special attention has to be paid to maintaining the nitrification at low temperature. A dosage of(H2O2-based) oxidants controlled the growth of Microthrix parvicella effectively and rapidly, whereas with the use of aluminium hydroxidechloride a 2 to 5-week period was needed to decrease the filament length.

  • 16.
    Wikström, Tommy
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Nordmark, Desiree
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pelkonen, Markku
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Lagerkvist, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Fluorescent in situ hybridization technique in anaerobic process studies2012In: Abstract proceedings of 7th Intercontinental Landfill Research Symposium :: Södra Sunderbyn, June 25th to 27th, 2012 / [ed] Anders Lagerkvist, Luleå: Luleå tekniska universitet, 2012, p. 130-131Conference paper (Refereed)
1 - 16 of 16
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