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In Northern Europe, most lakes are characterized by extended periods of winter ice cover, high spring inflow from snow melt and brown water produced by the transport of dissolved organic carbon (DOC) from the surrounding catchments. In this chapter, the potential impact of climate change on the dynamics of these lakes is addressed by: (i) Describing the historical responses of the lakes to changes in the weather. (ii) Summarizing the results of modelling studies that quantify the impact of future changes in the climate on the lakes and the surrounding catchments. Many existing water quality problems could well be exacerbated by the effects of climatic change. It is therefore important to assess the holistic responses of the individual lakes to the combined effects of local changes in the catchment and regional changes in the weather (Hall et al., 1999; Anderson et al., 2005). Overall, the response of individual lakes to climate change can be very different (Blenckner et al., 2004). For example, mountain lake catchments are affected differently from those at lower altitudes. In addition, the landscape position of a particular lake influences hydrological flow regime (Kratz et al., 1997). Furthermore, the response of lakes to climatic variation is also modified by physical lake features such as morphometry and water clarity which, in turn, is also affected by the concentration of the dissolved organic carbon (see for example Fee et al., 1996). Also, the alignment of the lake in relation to the main wind direction is important for the timing of the ice break-up and mixing regime. Even, the environmental changes experienced by the lake in the past can affect the magnitude of the response to climatic variation. Lakes in a recovery phase from eutrophication, acidification, toxic components or any other strong human disturbance, might respond differently to climatic variability and change owing to their specific history and food web structure.

The potential of black water and a mixture of black water and kitchen waste as substrates for on-site dark fermentative hydrogen production was screened in upflow anaerobic sludge blanket reactors at 20 degrees C. Three different inocula were used with and without heat treatment. With glucose, the highest specific hydrogenogenic activity was 69 ml H2 g volatile solids(-1) d(-1) in batch assays and the highest hydrogen yield 0.44 mol H2 mol glucose(-1) in upflow anaerobic sludge bed reactor. The mixture of black water and kitchen waste degraded readily into volatile fatty acids in the reactors, thus showing potential for hydrogen production. In the conditions applied, however, the highest end product was propionate and no hydrogen was produced. Black water alone apparently contained too little readily soluble carbohydrates for hydrogen producing bacteria, and little VFA and no hydrogen was produced.

AbstractLakes are important habitats for biogeochemical cycling of carbon. The organization and structure of aquatic communities influences the biogeochemical interactions between lakes and the atmosphere. Understanding how trophic structure regulates ecosystem functions and influences greenhouse gas efflux from lakes is critical to understanding global carbon cycling and climate change. With a whole-lake experiment in which a previously fishless lake was divided into two treatment basins where fish abundance was manipulated, we show how a trophic cascade from fish to microbes affects methane efflux to the atmosphere. Here, fish exert high grazing pressure and remove nearly all zooplankton. This reduction in zooplankton density increases the abundance of methanotrophic bacteria, which in turn reduce CH4 efflux rates by roughly 10 times. Given that globally there are millions of lakes emitting methane, an important greenhouse gas, our findings that aquatic trophic interactions significantly influence the biogeochemical cycle of methane has important implications.

Energy efficient solutions for six farm biogas production was found by calculating mass and energy balance in different scenarios. Raw materials in biogas production were cow manure and grass silage that were produced in these farms. There were calculated mass and energy balances on average for one year biogas prouduction that consisted of grass silage production, raw material transportation and biogas production in the biogas plant. In addition, direct greenhouse gases from biogas production were estimated. The direct mass and energy flows were calculated. It turned out that one input energy unit can produce 5.0 to 5.5 energy units as heat and electricity. Biogas reactor consumed heat from 42 to 66 % of the produced electricity. The electricity consumption in the biogas plant was from 12 to 18 % of the produced electricity. Energy consumption in the raw material transportation was from 7 to 14 % of the produced electricity. Energy consumption in the grass silage production was from 11 to 16 % of the produced electricity. In the electricity production the heat is also produced that should be utilized to keep the total energy balance positive. If the heat utilizer would not considered, the direct carbon dioxide emissions and the energy consumption in transportation could be decreased by one third. The energy consumption in the grass silage production consisted of an energy consumption in the field and a transportation energy consumption between farms and their field blocks. It turned out that the transportation energy consumption can be even more than half of the energy consumption in the field. By replacing mineral fertilizers with digestate, it could be possible to half the need of mineral fertilizers from present situation.

Eutrophication (as an increase in total phosphorus [TP]) increases harmful algal blooms and reduces the proportion of high-quality phytoplankton in seston and the content of ω-3 long-chain polyunsaturated fatty acids (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) in fish. However, it is not well-known how eutrophication affects the overall nutritional value of phytoplankton. Therefore, we studied the impact of eutrophication on the production (as concentration; μg L-1) and content (μg mg C-1) of amino acids, EPA, DHA, and sterols, i.e., the nutritional value of phytoplankton in 107 boreal lakes. The lakes were categorized in seven TP concentration categories ranging from ultra-oligotrophic (50 μg L-1). Phytoplankton total biomass increased with TP as expected, but in contrast to previous studies, the contribution of high-quality phytoplankton did not decrease with TP. However, the high variation reflected instability in the phytoplankton community structure in eutrophic lakes. We found that the concentration of amino acids increased in the epilimnion whereas the concentration of sterols decreased with increasing TP. In terms of phytoplankton nutritional value, amino acids, EPA, DHA, and sterols showed a significant quadratic relationship with the lake trophic status. More specifically, the amino acid contents were the same in the oligo- and mesotrophic lakes, but substantially lower in the eutrophic lakes (TP > 35 μg L-1/1.13 μmol L-1). The highest EPA and DHA content in phytoplankton was found in the mesotrophic lakes, whereas the sterol content was highest in the oligotrophic lakes. Based on these results, the nutritional value of phytoplankton reduces with eutrophication, although the contribution of high-quality algae does not decrease. Therefore, the results emphasize that eutrophication, as excess TP, reduces the nutritional value of phytoplankton, which may have a significant impact on the nutritional value of zooplankton, fish, and other aquatic animals at higher food web levels.

A two-stage pilot-scale thermophilic aerobic suspended carrier biofilm process (SCBP) was set up for the on-site treatment of pulp and paper mill whitewater lining. The microbial diversity in this process was analyzed by length heterogeneity analysis of PCR-amplified 16S ribosomal DNA. The primer pair selected for PCR amplification was first evaluated by a computational analysis of fragment lengths in ten main phylogenetical eubacterial groups. The fragment contained the first third of the 16S rRNA gene, which was shown to vary naturally between 465 and 563 bp in length. The length heterogeneity analysis of polymerase chain reaction (LH-PCR) profile of the biomass attached to carrier elements was found to be diverse in both stages of the SCBP. During normal operating conditions, sequences belonging to beta-Proteobacteria, Cytophaga/Flexibacter/Bacteroides group and gamma-Proteobacteria were assigned to the most prominent LH-PCR peak. Samples from the suspended biomass consisted of completely different bacterial populations, which were, however, similar in the serial reactors. The pilot process experienced alkaline shocks, after which Bacillus-like sequences were detected in both the biofilm and suspended biomass. However, when the conditions were reversed, the normal microbial population in the biofilm recovered rapidly without further biomass inoculations. This study shows that LH-PCR is a valuable method for profiling microbial diversity and dynamics in industrial wastewater processes.

Abstract This paper investigates the trace compounds affecting energy utilisation in biogas that come from different production sites. With biogas being more widely used in different energy applications more interest has arisen for the specific composition of biogas. In traditional energy applications, methane and hydrogen sulphide contents have had the most influence when energy utilisation application has been considered. With more advanced processes also the quantity and quality of trace compounds is more important. In regards to trace compounds, it was found that the concentrations and the variations of volatile organic compounds (VOCs) can be high in different landfills, especially, with compounds originating from the biological degradation process (like aromatics and terpenes) as seasonal variations affect the biological degradation. Trace compounds produced by direct volatilisation (halogenated and silicon compounds) show a smaller seasonal variation. Halogenated compounds are rarely present in high concentrations in waste water treatment plant (WWTP) biogas, but the concentrations of organic silicon compounds and their variation is high. Organic silicon compounds are usually detected only in low concentrations in co-digestion plant biogas, when no WWTP sludge is used as a raw material.

Abstract A pilot-scale counter current absorption process for upgrading municipal solid waste (MSW) landfill gas to produce vehicle fuel was studied using absorption, desorption and drying units and water as an absorbent. Continuous water recycling was used without adding new water to the system. The process parameters were defined by a previous study made with this pilot system. The effect of pressure (20–25 bar), temperature (10–25 °C) and water flow speed (5.5–11 l/min) on the upgrading performance, trace compounds (siloxanes, halogenated compounds) and water quality were investigated. Raw landfill gas flow was kept constant at 7.41 Nm3/h. Methane (CH4) and carbon dioxide (CO2) contents in the product gas were 86–90% and 4.5–8.0% with all studied pressures and temperatures. The remaining fraction in product gas was nitrogen (N2) (from 1% to 7%). Organic silicon compounds (siloxanes) were reduced by 16.6% and halogenated compounds similarly by 90.1% by water absorption. From studied process parameters, only water flow speed affected the removal of siloxanes and halogen compounds. The absorbent water pH was between 4.4–4.9, sulphide concentration between 0.1–1.0 mg/l and carbonate concentration between 500–1000 mg/l. The product gas drying system reduced the siloxane concentration by 99.1% and halogenated compounds by 99.9% compared to the raw landfill gas. In conclusion, the pilot-scale gas upgrading process studied appears to be able to produce gas with high energy content (approx 86–90% methane) using a closed water circulation system. When using a standard gas drying system, all trace compounds can be removed by over 99% compared to raw landfill gas.