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At least 721 records · Page 40Linked to original sources
PubMed2004

Digestion of sludge and organic waste in the sustainability concept for Malmö, Sweden.

Anaerobic digestion of sludge has been part of the treatment plant in Malmö for many years and several projects on optimisation of the digestion process have been undertaken in full scale as well as in pilot scale. In order to facilitate a more sustainable solution in the future for waste management, solid waste organic waste is sorted out from households for anaerobic treatment in a newly built city district. The system for treatment of the waste is integrated in a centralised solution located at the existing wastewater treatment plant. A new extension of the digester capacity enables separate as well as co-digestion of sludge together with urban organic waste from households, industry, restaurants, big kitchens, food stores, supermarkets, green markets etc. for biogas production and production of fertiliser. Collection and pre-treatment of different types of waste are in progress together with examination of biogas potential for different types of organic waste. Collection of household waste as well as anaerobic digestion in laboratory and pilot scale has been performed during the last year. It is demonstrated that organic household waste can be digested separately or in combination with sludge. In the latter case a higher biogas yield is found than should be expected from digestion of the two materials separately. Household waste from a system based on collection of organic waste from grinders could be digested at mesophilic conditions whereas digestion failed at thermophilic conditions.

Anaerobiosis↗
PubMed2004

[Studies on the anaerobic phased solid digester system for municipal solid waste (MSW) treatment].

Through analyzing and detecting the leaching pollutant (COD) in two bioreactors, anaerobic phased solid digester system and leachate direct-recirculating landfill, the changing rule of municipal solid waste and the characteristics of methanogenesis were studied. The results showed that anaerobic phased solid digester system accelerated the process of degrading municipal solid waste and stabilizing landfill site. The relationship between the leaching pollutant (COD) and refuse age was logarithmic linear correlation. More than 80% of biogas in volume occured in the methanogenisis bioreactor, the methane content in which was 55%-69%. The preferable volumetric COD loading rate of the methanogenisis bioreactor was 6.5-7.5 g/(L x d).

Bacteria, Anaerobic↗
PubMed2004

Anaerobic co-digestion of sewage sludge and food waste using temperature-phased anaerobic digestion process.

This study was performed to overcome the low efficiency of anaerobic digestion of sewage sludge and food waste by combining temperature-phased digestion, sequencing batch operation, and co-digestion technology. It was demonstrated that the temperature-phased anaerobic sequencing batch reactor (TPASBR) system for the co-digestion of sewage sludge and food waste resulted in enhanced volatile solids (VS) reduction and methane production rate. At the organic loading rate (OLR) of 2.7 g VS/l/d, the TPASBR system showed the higher VS reduction (61.3%), CH4 yield (0.28 l/g VS(added)) and CH4 production rate (0.41 l CH4/l/d) than those (0.29 l CH4/l/d) of the mesophilic two-stage ASBR (MTSASBR). In the specific methanogenic activity (SMA) tests on thermophilic biomass of the TPASBR system, the average SMA of acetate (93 ml CH4/gVSS/d) was much higher than those of propionate (46 ml CH4/g VSS/d) and butyrate (76 ml CH4/g VSS/d). Also, higher specific hydrolytic activity (SHA, 217 mg COD/g VSS/d) of the biomass supported fast hydrolysis under thermophilic conditions. The track study revealed that the most active period of the 24 h cycle was between 6 and 12 h. The enhanced performance of the TPASBR system could be attributed to longer solids retention time, fast hydrolysis, higher CH4 conversion rate, and balanced nutrient condition of co-substrate. It was verified that this combination could be a promising and practical alternative for the simultaneous recycling of two types of organic fraction of municipal solid waste (OFMSW) with high stability.

Anaerobiosis↗
PubMed2005

[Influence of different sorbents on adsorption effect of ammonia and compost property in aerobic composting].

The three kinds of sorbents of 0.18% KH2PO4, 0.06% KH2PO4 + 15% sawdust mixture and 30% sawdust are added separately into composting to investigate their adsorption effect on ammonia. The experiment results exhibite that all the sorbents can restrain ammonia volatilizing. But sorption of 0.18% KH2PO4 sorbnet was best of all, one of 0.06% KH2PO4 + 15% sawdust mixture sorbent was secondly, one of 30% sawdust sorbent was thirdly. The total nitrogen loss ratios were separately reduced 25%, 23% and 17% after adding the three kinds of sorbents into composting. However, excessive KH2PO4 would produce negative influence on compost property, such as pH value being lessened, microorganism activity being reduced, and finally resulting in the reduction of biodegradation ratio of organic matter also. Comparing with it, there were not these problems as 0.06% KH2PO4 + 15% sawdust mixture being sorbent. The mixture sorbent not only produced finer adsorption effect on ammonia, but also made biodegradation ratio of organic matter to be promoted 7%.

Adsorption↗
PubMed2005

Pilot-scale two-stage process: a combination of acidogenic hydrogenesis and methanogenesis.

This study was performed to optimize both acidogenic hydrogenesis and methanogenesis, and then to develop a pilot-scale two-stage process producing not only CH4 but also H2. Firstly, acidogenic hydrogenesis of food waste was examined in pilot-scale leaching-bed reactors using dilution rate (D) as a tool to improve the environmental conditions. The maximum efficiency of 71.4% was obtained by adjusting D from 4.5 to 2.5 d(-1) depending on the state of degradation. Secondly, the wastewater from acidogenic hydrogenesis was converted to CH4 in a pilot-scale UASB reactor. The COD removal efficiency exceeded 95% up to the loading rates of 13.1 g COD/Ld, which corresponded to HRT of 0.25 d (6 h). Lastly, a pilot-scale two-stage process was devised based on a combination of acidogenic hydrogenesis and methanogenesis. Over 120 days, the pilot-scale process resulted in large VS reduction of 70.9% at the high loading rate of 12.5 kg VS/m3/d in a short SRT of 8 days.

Bacteria, Anaerobic↗
PubMed2005

Effect of pretreatment on acid fermentation of organic solid waste.

The effect of various pretreatment methods on acidogenesis of food waste from a cafeteria was investigated. Thermal, enzymatic, and combined thermal-enzymatic batch pretreatment were conducted. Solubilization of food waste in thermal or enzymatic pretreatment increased with either increasing thermal duration or enzyme dosage, respectively. An optimal condition in thermal or enzymatic pretreatment was 60 min of thermal processing or 0.1% (v/v) of enzyme dosage level, respectively, based on volatile suspended solids (VSS) reduction. In the combined pretreatment, increased thermal duration also increased VSS reduction and the solubilization efficiency was higher than that in only enzymatic or thermal pretreatment. The maximum volatile fatty acids (VFAs) production and the highest VFAs fraction in soluble COD in the acid fermentation were achieved with the food waste after 60 min of thermal processing followed by 0.1% (v/v) enzymatic treatment. Increase in VFAs production of the fermenter was over 380% compared to the control fermenter without any pretreatment.

Acids↗
PubMed2005

Co-digestion of energy crops and the source-sorted organic fraction of municipal solid waste.

The biological and technical performance during co-digestion of energy crops and the source-sorted organic fraction of municipal solid waste has been investigated at laboratory and pilot scale. A 50:50 (TS-based) mixture of energy crops and organic waste reached a loading rate of 6.0 gVS L(-1)d(-1) with a methane yield of 0.33-0.38 LgVS(-1), while a 80:20 mixture showed elevated levels of volatile fatty acids at 5.5 gVS L(-1)d(-1) The better performance of the 50:50 mixture can partly be explained by a better nutritional composition. Mincing the ley crop reduced viscosity and reduced problems with fibre floating and scum-blanket formation. The electricity consumed for mincing and stirring at a full-scale plant corresponds to ca 3% of the energy produced. Calculations of the costs for full-scale plants indicate that the price of the upgraded biogas has to be at least 0.078 Euro/kWh in order to balance the costs.

Agriculture↗
PubMed2005

A hybrid anaerobic solid-liquid system for food waste digestion.

A hybrid anaerobic solid - liquid (HASL) system was developed to enhance food waste bioconversion in comparison with the conventional two-phase anaerobic digester. The advantages of the HASL system were the higher efficiency of methane production and smaller volume of effluent from the system. The biogas, which was generated from the methanogenic phase, had an average methane content of 71-72%. Total removal of volatile solids consisted of 78-80%. The HASL system can be operated in both batch and semi-continuous modes with satisfactory performance. The addition of a submerged biofilter for ammonia removal to the HASL system further enhanced the performance of anaerobic digestion. Methane production in the enhanced HASL system was increased by 26% in comparison with the HASL system without submerged filter. This paper describes the development of the enhanced HASL system for anaerobic treatment of food waste.

Bacteria, Anaerobic↗
PubMed2005

Performance of UASB septic tank for treatment of concentrated black water within DESAR concept.

Separation of wastewater streams produced in households according to their origin, degree of pollution and affinity to a specific treatment constitutes a starting point in the DESAR concept (decentralised sanitation and reuse). Concentrated black water and kitchen waste carry the highest load of organic matter and nutrients from all waste(water)streams generated from different human activities. Anaerobic digestion of concentrated black water is a core technology in the DESAR concept. The applicability of the UASB septic tank for treatment of concentrated black water was investigated under two different temperatures, 15 and 25 degrees C. The removal of total COD was dependent on the operational temperature and attained 61 and 74% respectively. A high removal of the suspended COD of 88 and 94% respectively was measured. Effluent nutrients were mainly in the soluble form. Precipitation of phosphate was observed. Effective sludge/water separation, long HRT and higher operational temperature contributed to a reduction of E. coli. Based on standards there is little risk of contamination with heavy metals when treated effluent is to be applied in agriculture as fertiliser.

Bacteria, Anaerobic↗