Evaluation of Laminaria digitata and Phragmites australis for biogas production and nutrient recycling

Eutrophication and climate change are major global problems. The sea weed Laminaria digitata and the reed Phragmites australis have the potential to absorb nutrients and CO2 during growth, as well as being a source of renewable energy in the form of biogas. The aim of this study was to evaluate Laminaria digitata and Phragmites australis concerning biogas production and nutrient recycling using a two-stage pilot scale process. The plant has a total volume of 430 L and consists of a hydrolysis bed and an up-flow anaerobic sludge blanket reactor (UASB). Two experiments were performed; one with Laminaria digitata as the sole substrate and one with a mixture of Laminaria digitata and Phragmites australis. Frozen substrates were placed in the hydrolysis bed and digestion was performed at 305 K during 70 days for Laminaria digitata and 100 days for the mixture of Laminaria digitata and Phragmites australis. The methane yield achieved was approximately 170 L kg−1 volatile substances (273.15 K, 101.3 kPa) in both experiments. These results suggest that Laminaria digitata can be efficiently digested in larger scale and has the potential to contribute to a future sustainable energy mix, considering its relatively high methane yield when anaerobically digested as the sole substrate. Digestion of Phragmites australis needs further development to make use of its full potential

Associations between depressive symptoms and disease progression in older patients with chronic kidney disease: results of the EQUAL study

Background Depressive symptoms are associated with adverse clinical outcomes in patients with end-stage kidney disease; however, few small studies have examined this association in patients with earlier phases of chronic kidney disease (CKD). We studied associations between baseline depressive symptoms and clinical outcomes in older patients with advanced CKD and examined whether these associations differed depending on sex. Methods CKD patients (>= 65 years; estimated glomerular filtration rate <= 20 mL/min/1.73 m(2)) were included from a European multicentre prospective cohort between 2012 and 2019. Depressive symptoms were measured by the five-item Mental Health Inventory (cut-off <= 70; 0-100 scale). Cox proportional hazard analysis was used to study associations between depressive symptoms and time to dialysis initiation, all-cause mortality and these outcomes combined. A joint model was used to study the association between depressive symptoms and kidney function over time. Analyses were adjusted for potential baseline confounders. Results Overall kidney function decline in 1326 patients was -0.12 mL/min/1.73 m(2)/month. A total of 515 patients showed depressive symptoms. No significant association was found between depressive symptoms and kidney function over time (P = 0.08). Unlike women, men with depressive symptoms had an increased mortality rate compared with those without symptoms [adjusted hazard ratio 1.41 (95% confidence interval 1.03-1.93)]. Depressive symptoms were not significantly associated with a higher hazard of dialysis initiation, or with the combined outcome (i.e. dialysis initiation and all-cause mortality). Conclusions There was no significant association between depressive symptoms at baseline and decline in kidney function over time in older patients with advanced CKD. Depressive symptoms at baseline were associated with a higher mortality rate in men

Characterization and treatment of municipal landfill leachates

Abstract The efficiency of different leachate treatment methods for the removal of refractory organic compounds and ammonium-nitrogen was investigated. The methods evaluated were nitrification, denitrification, adsorption onto activated carbon, precipitation by ferric chloride or aluminum sulphate and oxidation by ozone or Fenton´s reagent. Furthermore, analyses were performed on leachates from municipal landfills of different kinds (a biocell deposit, a conventional mixed landfill containing household and industrial waste, and an ash deposit) in order to study the leachate composition in regard to various hydrophobic organic compounds as a function of the type of waste deposited. The results suggested that, in order to achieve a satisfactory removal of both ammonium-nitrogen and organic substances, the treatment of methanogenic leachates should be performed through a process combining biological and physical or chemical stages. When the biological treatment was not combined with a physical or a chemical process a COD removal of only 20-30% was achieved, wheras the toxicity of the leachate was significantl reduced. In contrast, a combination of nitrification and either adsorption onto activated carbon or oxidation using Fenton´s reagent resulted in a COD removal of about 80%, although certain specific organic compounds, such as phthalates, were unaffected by the treatment. A combination of nitrification, precipitation by ferric chloride and adsorption onto activated carbon removed 96% of the TOC. The analyses of leachates from municipal landfills of different types showed the leachate from the ash deposit to contain more C4-substituted phenols than the other leachates and to likewise contain alkanes,which the others did not

Degradation of phenol and cresols at low temperatures using a suspended-carrier biofilm process

Degradation of phenol and o-, m- and p-cresol at a concentration of 150 mg; l(-1) of each compound was studied in a suspended-carrier biofilm process consisting of two aerobic stages. The fungus Mortierella sarnyensis Mil'ko dominated the microflora. in the first reactor, while bacteria dominated in the second reactor. The process was studied at 4, 7, 11 and 15 degreesC. The results from the experiments showed the process to be relatively efficient even at 4 degreesC. The degradation rate was 33% of that at 15 degreesC for o-cresol. Both phenol and the cresols were degraded in the first reactor and a new peak appeared in the HPLC-chromatograms indicating the formation of one or more intermediate compounds in the first stage. These compounds were however degraded to below the detection limit in the second reactor. Small new peaks appeared in the chromatograms of the outlet from the second reactor at the maximum loading rates. (C) 2003 Elsevier Ltd. All rights reserved

Provrötning av marina substrat i laboratorie- och pilotskala : Delstudie i projektet Biogas – Nya substrat från havet

Denna rapport omfattar delstudie 4 av projektet Biogas-Nya substrat från havet. Inom delstudien har ett antal provrötningar av substrat från havet (vass, musslor, alger och skrapsill) genomförts. Syftet med delstudien var att få fram metanpotentialen för de olika substraten och att öka kunskapen kring hur dessa substrat uppför sig i en biogasprocess. Projektet var ett samverkansprojekt delfinansierat av EU Regionala fonden för Småland och öarna. Projektledare var Regionförbundet i Kalmar län. Inledningsvis genomfördes ett antal satsvisa försök med samtliga substrat. Metanpotentialerna för vassen, musslorna, algerna respektive skarpsillen var 400, 270, ca 210 och 460 Ndm3/kg VS. Ymp hämtades från Kalmar Biogas ABs industriella rötkammare. Vassen samrötades också med industriellt avfall i ett kontinuerligt våtrötningsförsök. Försöket genomfördes i två total omrörda tankreaktorer med volymen 30 l/st. Tillsatsen av vass gav en utökad metanproduktion med 220 Ndm3/kgVS. Vassen och musslorna studerades också i torrötningsförsök. Försöken i laboratorieskala genomfördes vid Avdelningen för Bioteknik i Lund medan försöket med musslor i pilotskala genomfördes vid Avdelningen för Bioenergiteknik, Linnéuniversitet. Metanpotentialen för vassen var i torrötningsförsöket ca 220 Ndm3/kg VS vilket är lika med potentialen i våtrötningsförsöket. För musslorna erhölls en metanpotential på 330 Ndm3/kg VS i laboratorieskaleförsöket. Pilotskaleförsöket visade att hydrolysen etablerades på likartat sätt som i laboratorieskaleförsöket. Metanhalten var ca 70 %. En visuell inspektion av musslorna efter rötningen visade också att endast skalen återstod. Det är dock inte möjligt att ange en metanpotential från detta försök beroende på ett antal tekniska problem med processen. Processen byggdes inför detta försök och det fanns inte tid att testköra den samma före försökets start.Arbetet med de satsvisa försöken och det kontinuerliga våtrötningsförsöket av vass genomfördes i samarbete med Kalmar Biogas AB. Detta bland annat genom att Kalmar Biogas AB tillhandahöll sin försöksanläggning med satsvisa och kontinuerliga reaktorer till projektet

Denitrification at low temperatures using a suspended carrier biofilm process

The denitrification process was studied in a stirred lab-scale suspended carrier biofilm reactor at low temperatures (3–20°C). The reactor was filled to 50% with Kaldnes K1 carriers. The denitrification rate showed only a rather weak dependence on the temperature, the rate at 3°C being approximately 55% of that at 15°C. The maximum denitrification rate obtained at 15°C was 2.7 g NOx−-N m−2 carrier d−1. The maximum denitrification rate at 3°C during an 8-day period was found to be constant. During the 8 days, the hydraulic retention time was approximately 1.5 h and the inlet NO3−-N concentration was 30 mg l−1

Decolorization of a mixture of textile dyes using Bjerkandera sp. BOL-13.

The white-rot fungus Bjerkandera sp. BOL-13 was evaluated regarding decolorization of four textile dyes Reactive blue 21, Reactive black 5, Reactive orange 13 and Reactive yellow 206. Experiments were performed in batch and continuous modes. The total dye concentration in all experiments was 100 mg l(-1). The results of the batch experiments showed that the fungus decolorized all dyes but at different rates. There was, however, an increase in the ultraviolet (UV) absorbance when a medium with a low concentration of nitrogen was used. No increase in UV range was observed when the nitrogen concentration was increased. A continuous experiment was performed to study the decolorization of a mixture of three of the dyes Reactive blue 21, Reactive black 5 and Reactive orange 13. Scanning of inlet and outlet samples showed that the absorbance at the peaks in the visible range decreased by 60-66%. The UV absorbance of the outlet increased during the first days of operation after which it decreased again to reach the same level as the inlet. The hydraulic retention time in the reactor was 3 days. The medium containing the higher nitrogen concentration was used in the continuous experiment

Degradation of acetonitrile through a sequence of microbial reactors

Degradation of nitrogen containing organic compounds often leads to formation of ammonium and some low molecular weight organic compounds. The study is focused on degradation of acetonitrile in a sequence of stirred biofilm reactors, where the degradation of acetonitrile into acetic acid and ammonia takes place in the first two reactors. A large fraction of the acetic acid is also degraded in these reactors. The subsequent two reactors were introduced in order to take care of the ammonia, while a fifth reactor was a polishing step before the water was released to the recipient. From earlier studies it is known that the rate of acetonitrile degradation is approximately 80 g acetonitrile/(m(3) reactor h). In the present study nitrification proceeded with 10g NH4+-N/(m(3) reactor h) and the denitrification by 35g NOx--N/ (m(3) reactor h). This means that the reactors involved in removal of the nitrogen component needs to be far larger than those dealing with degradation of the more complex molecules. (C) 2004 Elsevier Ltd. All rights reserved

Precipitation of heavy metals from landfill leachates by microbially-produced sulphide

Four leachates from two landfills in Sweden were treated for the removal of heavy metals with the aid of sulphate-reducing bacteria (SRB). Both continuous and batch experiments were performed. A packed-bed process was used for sulphide production. The metals studied were As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. The continuous experiments showed that Cd and Cu were most efficiently removed and that Cr was the most difficult to precipitate. In a continuous experiment with one of the leachates, the removal of Cd, Cu and Zn depended upon the retention time in the system. In the batch experiments, precipitation of the metals was a relatively fast process. No significant differences in metal concentrations were found between experiments terminated after a day and those terminated after a week. In a batch experiment involving one of the leachates, the precipitation of Cd and Cu was shown to be dependent upon the metal:sulphide ratio. Removal of the metals increased with an increase in the sulphide:metal ratio up to 45:1. The process with SRB showed an interesting potential for removal of heavy metals from leachates. One of the two leachates for which the highest metal removals were obtained came from a landfill for hazardous waste

Effects of irrigation and water content of packings on

The main objective of this investigation is to determine the effect of different physical parameters on the performance of biofilters, treating hydrophobic compounds. In this respect, the effects of irrigation and water content of packings on the removal efficiency of bed in different pollutant loading rates, and gas phase flow rates, is studied. Alpha-pinene, which is produced from variety of industrial wood products, pulp and paper industries, and fragrance production units, has been selected as a model compound. Since the effectiveness of biofiltration depends strongly upon water solubility of compounds, in the case of alpha-pinene (2.5 ppm, at 25 ◦C), the process of waste gas treatment is faced with difficulties. In this paper, it is shown that performance of biofilters, treating hydrophobic contaminants, declines due to irrigation. This reduction is detected by an increase in the outlet concentration from 11% up to 22.5%. Its magnitude depends on the gas velocity inside the biofilter and outlet concentration of the bed. The result indicated that pore blocking along the bed has less effect on the performance reduction than diffusion coefficient. Also the inhibitory effects of velocity on biodegradation are considerably higher than the effects of concentration. In addition, this compost-based biofilter shows noteworthy higher elimination capacities in comparison with previous studied biofiltration systems. In this study, a maximum elimination capacity of 227 gm−3 of packing h−1 is achieved by 95% of removal efficiency. The maximum concentration in the inlet gas was 650 mgm−3. © 2005 Elsevier B.V. All rights reserved