Thermal post-treatment of digestate in order to increase biogas production with simultaneous pasteurization.

Biogas production by anaerobic digestion (AD) of organic wastes is important for the transition to fossil free fuels in both the transport sector, industries and shipping. The aim of this study was to target the residual organic matter in the outgoing residue from the AD process, so called digestate, with different thermal treatment methods in order to improve digestate degradability and biogas potential upon post-digestion. The thermal treatment was performed at 55 °C in 24 h, 70 °C in 1 h and by thermal hydrolysis process (THP; 165 °C, 8 bar in 0.33 h), and were carefully selected to offer a simultaneous possibility for pasteurization of the digestate according to the regulations in Sweden. Digestates from ten full-scale biogas plants were collected, with different substrate profiles including wastewater treatment plant (WWTP), food waste digestion, agriculture digestion and manure digestion. The results showed that all thermal treatment methods caused increased dissolved organic carbon concentration (DOC). Four of the thermal treated digestates with the highest increase in DOC were subsequently tested for the bio-methane potential. Thermal treatments at 70 °C and THP, respectively, resulted in the highest increase in bio-methane potentials, with an increase of 15-39% for one WWTP, 38 - 40% for digestate from an agriculture digestion plant and 20 - 22% for digestate from a co-digestion plant treating food waste. Interestingly, the bio-methane potential from digestate treated with the energy-intense THP method, did not show any significant difference compared to thermal treatment at 70 °C for 1 h. The outcomes of this study suggest that placing a pasteurization unit between a main digester and a post digester, when applying two-step digestion allows for a combined pasteurization and increased biogas production.

Post-treatment of dewatered digested sewage sludge by thermophilic high-solid digestion for pasteurization with positive energy output.

This study investigated the possibility to use thermophilic anaerobic high solid digestion of dewatered digested sewage sludge (DDS) at a wastewater treatment plant (WWTP) as a measure to increase total methane yield, achieve pasteurization and reduce risk for methane emissions during storage of the digestate. A pilot-scale plug-flow reactor was used to mimic thermophilic post-treatment of DDS from a WWTP in Linköping, Sweden. Process operation was evaluated with respect to biogas process performance, using both chemical and microbiological parameters. Initially, the process showed disturbance, with low methane yields and high volatile fatty acid (VFA) accumulation. However, after initiation of digestate recirculation performance improved and the specific methane production reached 46 mL CH4/g VS. Plug flow conditions were assessed with lithium chloride and the hydraulic retention time (HRT) was determined to be 19-29 days, sufficient to reach successful pasteurization. Degradation rate of raw protein was high and resulted in ammonia-nitrogen levels of up to 2.0 g/L and a 30% lower protein content in the digestate as compared to DDS. Microbial analysis suggested a shift in the methane producing pathway, with dominance of syntrophic acetate oxidation and the candidate methanogen family WSA2 by the end of the experiment. Energy balance calculations based on annual DDS production of 10000 ton/year showed that introduction of high-solid digestion as a post-treatment and pasteurization method would result in a positive energy output of 340 MWh/year. Post-digestion of DDS also decreased residual methane potential (RMP) by>96% compared with fresh DDS.

Life weariness and suicidal thoughts in late life: a national study in Sweden.

OBJECTIVES: This study aimed at investigating the point prevalence of life weariness and suicidal thoughts and their relationship with socio-demographic characteristics in a population of older adults in Sweden. METHOD: Data from 7913 individuals aged 60 years and older were drawn from the Swedish National Study on Aging and Care, a collaborative study in Sweden. Life weariness and suicidal thoughts were measured by one item derived from the Montgomery-Åsberg Depression Rating Scale. A multinomial regression model was used to investigate the relationships of socio-demographic characteristics with life weariness and suicidal thoughts. RESULTS: Living in urban and semi-urban areas, being of advanced age, being divorced and having lower educational levels were related to life weariness. Living in a residential care facility, being widowed or unmarried, being born in a non-Nordic European country and experiencing financial difficulties were related to both life weariness and suicidal thoughts. Sex was found to be unrelated to either life weariness or suicidal thoughts. CONCLUSION: This study found that several socio-demographic variables were associated with life weariness and suicidal thoughts among older adults. Specific attention to older individuals with these characteristics may be warranted as they might be more vulnerable to life weariness and suicidal thoughts.

The effect of different mesophilic temperatures during anaerobic digestion of sludge on the overall performance of a WWTP in Sweden.

This project was initiated to evaluate the effect of alternative process temperatures to 38 °C at the anaerobic digestion step in a Swedish wastewater treatment plant (WWTP) treating mixed sludge. The efficiency of the different temperatures was evaluated with respect to biogas production, volume of sludge produced and nutrient content in the reject water to find the optimum temperature for the WWTP as a whole. Three temperatures, 34 °C, 38 °C and 42 °C, were compared in laboratory scale. Increasing the process temperature to 42 °C resulted in process instability, reduced methane yield, accumulation of volatile fatty acids and higher treatment costs of the reject water. By decreasing the temperature to 34 °C, slightly higher sludge mass was observed and a lower gas production rate, while the specific methane produced remained unchanged compared to 38 °C but foaming was observed at several occasions. In summary 38 °C was proved to be the most favourable temperature for the anaerobic digestion process treating mixed sludge when the evaluation included effects such as foaming, sludge mass and quality of the reject water.

Effects of trace element addition on process stability during anaerobic co-digestion of OFMSW and slaughterhouse waste.

This study used semi-continuous laboratory scale biogas reactors to simulate the effects of trace-element addition in different combinations, while degrading the organic fraction of municipal solid waste and slaughterhouse waste. The results show that the combined addition of Fe, Co and Ni was superior to the addition of only Fe, Fe and Co or Fe and Ni. However, the addition of only Fe resulted in a more stable process than the combined addition of Fe and Co, perhaps indicating a too efficient acidogenesis and/or homoacetogenesis in relation to a Ni-deprived methanogenic population. The results were observed in terms of higher biogas production (+9%), biogas production rates (+35%) and reduced VFA concentration for combined addition compared to only Fe and Ni. The higher stability was supported by observations of differences in viscosity, intraday VFA- and biogas kinetics as well as by the 16S rRNA gene and 16S rRNA of the methanogens.

Observation of vestibular asymmetry in a majority of patients over 50 years with fall-related wrist fractures.

Previously [The abstract has been shortened somewhat, and the headings removed, in order to conform to journal style], we have observed vestibular asymmetry in about one-third of healthy senior citizens and in about two-thirds of subjects with previous hip fractures and no other significant ailments. Wrist fractures are considered a harbinger of hip fractures. If vestibular asymmetry is correlated with falls and fractures among the elderly then it should also be reflected among subjects with wrist fractures. Sixty-six consecutive patients (mean age 67.8 years) who had sustained a fall-related wrist fracture during a 10-month period were included in the study. The frequency of head shake nystagmus among the patients was compared to that found among 49 healthy senior citizens (mean age 74.9 years). Nystagmus after head shaking, indicating asymmetric vestibular function, was found in 50 participants (76%) (p <0.001). Thirty-eight of these were graded with distinct or prominent nystagmus responses. Sixty percent of the subjects with horizontal nystagmus had a wrist fracture coinciding with the slow phase of nystagmus. Twenty-three subjects reported 30 previous fall-related fractures during the previous 10 years. Subjects with nystagmus after head shaking sustained 26 of these fractures. The frequency of signs of vestibular asymmetry was significantly higher (p < 0.001) among the subjects than among healthy senior citizens. These findings suggest that an asymmetric vestibular function could be an epidemiologically important contributory factor to falls and wrist fractures among the elderly population.

Accidental falls and related fractures in 65-74 year olds: a retrospective study of 332 patients.

We investigated, by studying medical records, background factors and consequences of accidental falls of patients 65-74 years who attended the Department of Orthopedics' emergency clinic in Lund. We also assessed possible prevention measures. Fractures occurred in three quarters of the registered falls. Women were more prone to sustain fractures than men. Forearm fractures were commonest among women while hip fractures were commonest among men. One third of the patients were admitted to an orthopedic ward because of the fall. The patients who were less healthy had sustained fractures oftener and also needed more hospital care. Information regarding risk factors for falls and fractures were often missing in the patients' medical records. Impaired walking and balance, and medication increased the risk of falls. Such patients constitute a high risk group for future falls and fractures. A newly developed instrument is suggested as a routine in the emergency department to increase the awareness of risk factors for falls in the elderly. Satisfactory documentation is a prerequisite for further treatment and referrals to prevent falls and fractures.

Outcome after hip fracture in different health care districts. Rehabilitation of 837 consecutive patients in primary care 1986-88.

The social and functional outcome for 837 consecutive hip fracture patients rehabilitated in primary care was studied during 1986-1988. Of patients coming from their own home (59%) the majority (76%) were back at home four months after fracture and had a good functional status, while 9% were dead. Predictors of managing ADL (dressing/personal hygiene) four months after hip fracture were age, type of fracture, sex, and having regular social contacts outside the home before fracture. Health care districts differed in the incidence of hip fractures, the patients hospital stay, housing, type of fracture, and age. These differences had consequences on costs. Total costs per patient were lowest in districts where most of the patients were discharged to their own homes. No significant differences in fracture incidence were seen between rural and urban primary health care districts.

Hip fractures in primary health care. Evaluation of a rehabilitation programme.

The routine follow-up of hip fracture patients was transferred from the Orthopaedic Department, Lund University Hospital, to the primary health care districts in 1985. The medical state and social functions of all 298 patients during the first 12 months of the follow-up rehabilitation programme were registered. Before fracture, 61% lived in their own homes, 22% in old people's homes, and 14% in geriatric hospitals or nursing homes. Four months after fracture, 13% were dead, 47% were living in their own homes, 14% were in old people's homes, 25% in geriatric hospitals or nursing homes, while the rest were in other types of institutional residence. Of patients coming from their own homes, 75% were back at home four months after fracture and their social and functional status were as good as before fracture. The study has shown that routine check-ups at the orthopaedic department can be omitted. Follow-up in primary health care without radiography and orthopaedic expertise gives equally good functional results as in previous studies, provided that patients with pain and walking problems from the hip are guaranteed rapid specialist treatment.