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- Hagelqvist, Alina, 1980-, et al.
(author)
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Anaerobic self-degradation of pig and dairy manure using co-digestion with grass silage and pulp and paper mill sludge to shorten the start-up time
- 2013
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Other publication (other academic/artistic)abstract
- The aim of this study was to find a way to shorten the start-up time of a pig and dairy manure based anaerobic digester without addition of external inoculum. Self-degradation was tested to simulate the setting of many sites where the use of external seed culture is not feasible because of the large distance to a nearest location where appropriate material can be collected. In this case study, co-digestion of pig and dairy manure with grass silage and pulp and paper mill sludge was tested using different compositions. The results showed that one tertiary mixture of 17 per cent of piggery manure, 17 per cent of dairy manure and 66 per cent of pulp and paper mill sludge resulted in a considerably shorter start-up time (about 15 days) as well as in a higher methane yield (120 ml CH4/g VS added after 44 days of batch operation) as compared to other mixtures tested. This mixture composition is recommended to start-up the full-scale process. Concentrations of ammonium of 0.4 g/l combined with slowly degradable material favoured a rapid start and efficient digestion.
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- Hagelqvist, Alina, 1980-
(author)
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Batchwise mesophilic anaerobic co-digestion of secondary sludge from pulp and paper industry and municipal sewage sludge
- 2013
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In: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 33:4, s. 820-824
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Journal article (peer-reviewed)abstract
- Residues from forest-industry wastewater-treatment systems are treated as waste at many pulp and paper mills. These organic substances have previously been shown to have potential for production of large quantities of biogas. There is concern, however, that the process would require expensive equipment because of the slow degradation of these substances. Pure non-fibrous sludge from forest industry showed lower specific methane production during mesophilic digestion for 19 days, 53 ± 26 Nml/g of volatile solids as compared to municipal sewage sludge, 84 ± 24 Nml/g of volatile solids. This paper explores the possibility of using anaerobic co-digestion with municipal sewage sludge to enhance the potential of methane production from secondary sludge from a pulp and paper mill. It was seen in a batch anaerobicdigestion operation of 19 days that the specific methane production remained largely the same for municipal sewage sludge when up to 50% of the volatile solids were replaced with forest-industry secondary sludge. It was also shown that the solid residue from anaerobic digestion of the forest-industry sludge should be of suitable quality to use for improving soil quality on lands that are not used for food production.
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- Hagelqvist, Alina, 1980-, et al.
(author)
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Co-digestion of manure with grass silage and pulp and paper mill sludge using nutrient additions
- 2016
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In: Environmental technology. - : Taylor & Francis Group. - 0959-3330 .- 1479-487X. ; 37:16, s. 2113-2123
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Journal article (peer-reviewed)abstract
- The purpose of this research is to evaluate how methane production is affected by the co-digestion of pig and dairy manure with grass silage and pulp and paper mill sludge at mesophilic conditions, and to assess whether methane production is affected by other factors than the now known ones, i.e., nutrient deficiency, low buffering capacity, inadequate dilution, and an insufficient activity and amount of microorganism culture. The season of grass silage and manure collection proved to be an important, previously unreported, factor affecting short-term (20 days) methane production.
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- Hagelqvist, Alina, 1980-
(author)
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Forest industry sludge as a resource for energy recovery
- 2009
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Licentiate thesis (other academic/artistic)abstract
- Forest industries produce large amounts of carbon rich sludges as by-products in their processes. Presently sludge is treated as a poor quality biofuel for co-incineration, some mills treat it solely as a disposal problem. This thesis provides an introduction to production, composition and disposal issues of sludge. It also includes a presentation of strategies for sludge handling.The main concern with energy recovery from sludge is connected to high content of water (50-80%). Mechanical dewatering is an energy efficient method of decreasing the water content. However, there are limitations to how far sludge can be dewatered mechanically. Thermal dewatering is sometimes required to dewater the sludge beyond these limits, in order to obtain a high quality biofuel for incineration and/or thermal gasification. It is often inefficient, from an energy point of view, to incorporate thermal dewatering in the sludge handling strategy.An interesting alternative to thermal processes is anaerobic digestion, which is a biological process used for energy recovery. Advantages with anaerobic digestion include biogas production, efficient treatment of sludge with high content of water and potential for nutrients recovery. The process and the kinetics of anaerobic digestion are presented.The aim of this thesis is to present a method for evaluating different sludge handling strategies from an energy perspective, and to further develop anaerobic digestion as a process for energy recovery from sludge. The thesis is based on two papers. Paper I presents an inclusive approach with focus on energy use and energy recovery in wastewater management, including wastewater treatment and sludge handling. Paper II explores the possibility to enhance biogas production by anaerobic co-digestion of pulp mill sludge with municipal sewage sludge.
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- Hagelqvist, Alina, 1980-, et al.
(author)
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Improving the biogas potential of pulp and paper mills while decreasing the electricity demand for wastewater treatment
- 2013
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Conference paper (peer-reviewed)abstract
- Sludge formed during the necessary wastewater treatment in forest industry is currently considered to be a waste stream; rich in organic substances and poor in macronutrients, especially phosphorus and nitrogen. Previous work has shown that excessive use of electricity for aeration in wastewater treatment counteracts the potential for energy recovery in the subsequent sludge handling system, as prolonged aeration is used to degrade organic matter. This work shows that chemical oxygen demand of wastewater was not reduced further when the solids retention time was increased in aerated wastewater treatment from 2 days to 10 and 20 days respectively. The results presented here strengthen the previous conclusion that energy should only be used for sufficient effluent treatment, not for sludge reduction. A decreased need for aeration can be achieved by shortening the sludge retention time both by a decreased oxygen requirement and increased aeration efficiency. Shortened sludge retention time was shown here to increase production of biosludge as well as to increase the specific methane potential of biosludge. The results show that sludge with shorter solids retention time in the aerated treatment step gives more production of methane gas compared to sludge with longer solids retention time.
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| 8. |
- Hagelqvist, Alina
(author)
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Sludge from pulp and paper mills for biogas production : Strategies to improve energy performance in wastewater treatment and sludge management
- 2013
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Doctoral thesis (other academic/artistic)abstract
- The production of pulp and paper is associated with the generation of large quantities of wastewater that has to be purified to avoid severe pollution of the environment. Wastewater purification in pulp and paper mills combines sedimentation, biological treatment, chemical precipitation, flotation and anaerobic treatment, and the specific combination of techniques is determined by the local conditions. Wastewater treatment generates large volumes of sludge that after dewatering can be incinerated and thus used for bio-energy production. Sludge is currently viewed as biofuel of poor quality due to its high water content, and some mills treat it solely as a disposal problem.Two strategies have been identified as feasible options to improve the energy efficiency of sludge management. One is drying using multi-effect evaporation followed by incineration. The other is anaerobic digestion of the wet sludge to produce methane.This thesis explores the energy balances of sludge management strategies in pulp and paper mills with special focus on anaerobic digestion. The first part consists of a system analysis, used to evaluate some wastewater treatment processes and sludge management, and the second part of empirical studies of anaerobic digestion of pulp and paper mill sludge. It was shown that the use of energy for aeration in aerobic biological treatment should be kept to the minimum required for acceptable quality of the processed water. Additional aeration for reduction of the generated sludge will only result in reduced energy generation in a subsequent methane generation stage. In the second part of the thesis, it is shown that anaerobic digestion is a feasible option for sludge management as it leads to production of high value biogas. Co-digestion with grass silage, cow/pig manure or municipal sewage sludge should then be used to counteract the low nitrogen content of pulp and paper mill sludge.
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