Biodegradation Of Municipal Solid Waste Research Articles

Decline in microbial activity does not necessarily indicate an end to biodegradation in MSW-biowaste: A case study

The aim of this study was to examine whether a decline in microbial activity (i.e., CO 2 output) during the biodegradation of municipal solid waste (MSW) indicated an end to biodegradation and the appearance of a stable, final product. As the organic fraction of MSW was biodegraded in an 8 clamp Cambridge Batch System composter, CO 2 output declined by 50% and moisture content at the end of the process was <20%. Levels of biodegradable material remaining in the product were determined by the dynamic respiration index (DRI) method but despite 151 days in the composting system biodegradable material was still present at levels (24130 mg O 2/kg dry matter (DM)) which exceeded draft EU biowaste directive (2001) guidelines (10,000 mg O 2/kg DM). Further laboratory based incubations demonstrated that microbial activity and hence biodegradation of organic material could be restarted if moisture levels were adjusted suggesting that dehydration limited microbial activity. Low levels of microbial activity alone did not therefore indicate and end to biodegradation, biodegradable material was not exhausted and the final product was not stable which has serious implications for its end-use.

Sources and factors controlling the disposal of biodegradable municipal solid waste in urban and rural areas of Cyprus

An inventory of sources of biodegradable municipal soil waste (BMSW) was constructed for urban and rural areas in the EU accession region of Cyprus. Composition analysis was performed on source-separated BMSW collected from households in the rural Ergates Community and an urban area within the Agglanjia Municipality. The data were statistically scrutinized to identify the main factors influencing the quantities of BMSW disposed by urban and rural communities in Cyprus. The results were extrapolated to predict the quantities and types of BMSW disposed by the entire communities. Significantly more BMSW was disposed in the urban area compared to the rural community due to lower diversion rates for green waste and the disposal of food waste from commercial sources. The quantity of food waste collected from households was influenced by socio-economic (household size, income, percentage of children) and behavioural (feeding of food waste to domestic animals, consuming processed 'ready' food) factors, whereas garden size, the type of vegetation, the reuse of trimmings and home composting were the main factors controlling the disposal of green waste.

The Physical, Chemical and Microbial Characteristics of Biodegradable Municipal Waste Derived Composts

A comparative study of the physical, chemical and microbial properties of 12 composts sourced from United Kingdom commercial composting plants was carried out. The aim was to ascertain whether these composts could be used as growing media or for application to agricultural land. The composts were produced from either source segregated biodegradable municipal waste (BMW) or mixed municipal solid waste (MSW). Ten composts contained 100% source segregated BMW including green, fruit, vegetable, meat and kitchen waste, paper and cardboard. One compost was 72% mixed MSW plus 18% source segregated BMW, and one compost was 100% mixed MSW. Composts were analyzed for pH, electrical conductivity, carbohydrates, nutrients and contaminants. The composts sourced from mixed MSW contained higher levels of physical contaminants (glass, plastic and metal) than the source segregated BMW composts. Nitrogen concentrations (as % dry weight) were 1.7-2.2% where kitchen or meat waste was included and 1.0-1.6% otherwise. Phosphorus concentration ranged from 23 to 247 mg kg−1, and K from 1851 to 6615 mg kg−1. Total salts were higher in mixed waste composts (15-23 g kg−1), predominantly due to high concentrations of K, Ca, S and Na. Electrical conductivity varied from 670 μ cm−1 to 3320 μS cm−1. The levels of the heavy metals examined in the 10 source segregated BMW composts were much lower than the limits for composts in the United Kingdom (PAS 100). However, the 100% mixed MSW compost exceeded the PAS 100 levels in four of the seven heavy metals tested (Cu, Ni, Pb and Zn) which may have implications for repeated applications to agriculture. Salmonella was absent from all twelve composts, however, five composts contained levels of E. coli which exceeded the UK PAS 100 limits. Five composts produced from source segregated BMW could be applied to agricultural land, however, high levels of E. coli would exclude the other five. Moreover, high levels of heavy metals and physical contaminants would render the two mixed MSW composts unsuitable.

Performance and Cost Comparison of a FWS and a VSF Constructed Wetland System

The biodegradation of municipal solid waste (MSW) was investigated in simulated bioreactor landfills under aerobic conditions. The bioreactors were operated to determine Two constructed wetland systems, treating domestic wastewater, are compared in terms of performance and costs. One is a free water surface (FWS) wetland system located in Pompia, Crete, south Greece, and the other one is a vertical subsurface flow (VSF) wetland system located in Gomati, Chalkidiki, north Greece. The FWS system is designed for 1200 p.e. Its construction cost was €305,000, and the capital, operation and maintenance cost was €22.07 p.e.−1 yr−1 or €0.50 m−3 of influent. The VSF system is designed for 1000 p.e. Its construction cost was €410,850, and the capital, operation and maintenance cost was €36.81 p.e.−1 yr−1 or €0.56 m−3 of influent. Both systems achieved high removal rates for BOD5, COD, TSS, TKN, phosphorus, TC, and FC, which makes them ideal for small communities in the Mediterranean region.

Degradation of Municipal Solid Waste in Aerobic Bioreactor Landfills

The biodegradation of municipal solid waste (MSW) was investigated in simulated bioreactor landfills under aerobic conditions. The bioreactors were operated to determine the amount of leachate recirculation and municipal wastewater sludge addition required to optimize waste degradation. The leachate generated was recycled over 47 weeks, leachate samples were collected on a weekly basis and analyzed for pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), Total Kjeldahl Nitrogen (TKN), and ammonia nitrogen (NH3-N). The temperature of the MSW in the bioreactors was measured on a daily basis. Leachate and sludge were added at the rates of 5 l wk−1 to 15 l wk−1 and 0.5 l wk−1 to 1.5 l wk−1, respectively. Within 27 weeks enhanced MSW degradation was observed at a leachate recirculation rate of 15 l wk−1 (855 mg l−1 of MSW d−1) and sludge addition rate of 1.5 l wk−1 (85 mg l−1 of MSW d−1). During this period, the COD concentration in the leachate dropped significantly. A reduction in the leachate recirculation and sludge addition rate increased the waste stabilization period up to 45 weeks.

The impact of the European Landfill Directive on waste management strategy and current legislation in Turkey's Specially Protected Areas

The European Landfill Directive (ELD) 99/31/EC has become the most influential piece of waste management legislation to have been produced for some time and calls for reduction of the amount of biodegradable municipal solid waste disposed of to landfill. Moreover, national solid waste strategies need to be changed to achieve increased waste recycling and recovery rates will have to be modified ultimately to meet the targets set in the ELD. This paper outlines the waste management strategy implemented in the Specially Protected Areas (SPAs) in Turkey and gives the key requirements of ELD. On the other hand, it also outlines the adaptation of the Turkish Solid Waste Legislation (TSWL) to ELD and gives comments on the improvement of the TSWL. This study showed that although the TSWL shares the broad objectives of the ELD and includes corresponding requirements of landfill of waste, it is less detailed; there are fewer specific targets and many of the requirements of the ELD are missing in the TSWL. There is no specific target set for the reduction in biodegradable municipal waste going to landfills. On the other hand deposit schemes and recovery rates are being applied on packaging waste without including strategy with long term targets. TSWL states that 45% of the total amount (by weight) of packaging waste produced should be recovered in 1995. However, Control of Packaging and Packaging Waste Legislation specifies the recovery rates between 2005 and 2014 and prohibits the packaging waste made of paper and carton to be landfilled. The Authority for the Protection of Special Areas (APSA) is responsible for the implementation of solid waste management strategies produced by Ministry of Environment and Forest. Implementation of the landfill directive must remain a long-term goal, to be achieved through a succession of incremental steps, in line with economic and institutional development. The improvement in waste management standards can therefore only progress by small incremental steps made in pace with economic development. A quick step change towards the EU standards cannot be achieved. In the short term, the policy should allow to keep a small number of larger landfill sites in operation, and use the resources available to upgrade them with leachate management and other environmental protection systems. As per the realities of Turkey's economy, the construction of new landfill sites, composting or incineration plants should be planned in the long term.

Bioconversion of municipal solid waste to glucose for bio-ethanol production

Selected biodegradable municipal solid waste fractions were subjected to fifteen different pre-hydrolysis treatments to obtain the highest glucose yield for bio-ethanol production. Pre-hydrolysis treatments consisted of dilute acid (H(2)SO(4), HNO(3) or HCl, 1 and 4%, 180 min, 60 degrees C), steam treatment (121 and 134 degrees C, 15 min), microwave treatment (700 W, 2 min) or a combination of two of them. Enzymatic hydrolysis was carried out with Trichoderma reesei and Trichoderma viride (10 and 60 FPU g(-1) substrate). Glucose yields were compared using a factorial experimental design. The highest glucose yield (72.80%) was obtained with a pre-hydrolysis treatment consisting of H(2)SO(4) at 1% concentration, followed by steam treatment at 121 degrees C, and enzymatic hydrolysis with Trichoderma viride at 60 FPU g(-1) substrate. The contribution of enzyme loading and acid concentration was significantly higher (49.39 and 47.70%, respectively), than the contribution of temperature during steam treatment (0.13%) to the glucose yield.

Biodegradable municipal solid waste: biotreatment options

The context under which the UK Government plans to divert biodegradable municipal solid waste from landfill is described and the role that bioprocessing may play is presented. The concepts developed from different types of anaerobic processes and the differing possible process configurations are considered. The most commonly used options are then appraised on the basis of technical engineering operation and microbiological functionality. Some practical examples of system types are given, although these are not based on case studies. The long history of waste composting (aerobic bioprocessing) has meant that there are a large number of process systems on offer. The fundamentals behind the different types of process are considered, focusing on their overall aim of achieving sanitisation and stabilisation. The interrelationships between the key factors of particle size, aeration, nutrients and moisture content are considered together with how each of the generic systems seeks to manage them.

Nitrate and nitrite injection during municipal solid waste anaerobic biodegradation

Nitrified leachate recirculation has been proposed as a promising strategy for sustainable landfill management. In four test reactors, nitrate or nitrite was added ( 250 mg N - NO x - L - 1 ) during municipal solid waste biodegradation. Nitrogen-oxides reduction reactions were monitored. Denitrification was the main nitrogen reducing reaction observed. On one hand, during the acidogenic waste degradation phase, as high amounts of volatile fatty acids (VFA) were present, nitrogen-oxides reductions were interpreted as heterotrophic denitrifications. On the other hand, denitrification reactions occurring during the late methanogenic phase were accompanied by sulphate productions and, as VFA were not detected, it was probably an autotrophic reaction. Denitrification inhibition was observed once. Ammonium concentration increased suggesting the occurrence of a dissimilatory nitrate reduction to ammonium (DNRA). Statistical treatment of analytical data revealed that only H 2S concentration had a significant negative effect on N 2 production in our system. NO production was observed once when nitrite was injected during the acidogenic phase resulting in a total waste degradation inhibition. These results indicate that the consequences of nitrified leachate recirculation in full-scale landfills need to be carefully examined especially during the acidogenic phase or in the presence of waste containing high quantities of sulphur.

A Technical, Economic and Environmental Comparison of Composting and Anaerobic Digestion of Biodegradable Municipal Waste

Ireland produces two million tonnes per annum of biodegradable municipal solid waste. The implementation of the Landfill Directive (1999/31/EC) will lead to the construction of centralised biological facilities; these facilities may be either composting facilities or anaerobic digestion facilities. A technical, economic and environmental analysis of composting and anaerobic digestion is undertaken in this paper. The results of the analysis suggest that composting is economically preferable to anaerobic digestion at scales at or below 50 kt/a of biowaste treated. However when CH4-enriched biogas is produced for use as a transport fuel and excise duty is reduced, as allowed by the Biofuels Directive (2003/30/EC), then the economics of anaerobic digestion improve greatly. If 100% of excise duty is removed then anaerobic digestion is economically preferable to composting above 20 kt/a of biowaste treated. From an environment perspective anaerobic digestion saves more greenhouse gas due to displacement of fossil fuel powered energy. Anaerobic digestion with CH4-enriched biogas has the potential to save 1,451 kgCO2/t of biowaste treated as opposed to composting, which has the potential to save 1,190 kgCO2/t.

Biodegradable municipal solid waste: Characterization and potential use as animal feedstuffs

Five different fractions of the biodegradable municipal solid waste (BMSW) were evaluated as potential animal feedstuffs. For each source of waste (meat waste (MW), fish waste (FW), fruit and vegetables waste (FVW), restaurant waste (RW), household waste (HW)), samples were obtained from small shops (butchers, fishmongers, fruit and vegetable shops), restaurants and a MSW treatment plant (household waste). The chemical composition, microbiological characterization, dioxins, furans, PCB’s and mineral content were determined for every type of waste fraction. The analysed biodegradable waste presented high moisture content (from 60% to 90%). Some fractions were dense in one nutrient: meat waste in ether extract, fish waste in crude protein, fruit and vegetable waste in nitrogen free extract. The other studied fractions (restaurant fraction and household fraction) presented a more balanced composition, but the presence of toxic concentrations of contaminants such as metals was higher than European legislation permitted values in animal feeding. From a microbiological standpoint, a heat treatment at 65 °C for 20 min was sufficient to ensure microbiological quality of the samples. This treatment was also advisable to reduce the moisture content: a lower moisture content facilitates the waste handling and processing and, therefore, the inclusion of these waste fractions in commercial animal diets. This paper presents a potential alternative for the recovery of organic matter content in municipal solid waste. The results obtained in this research and the feedstuffs legislation in force related to animal feed, indicated that some of the studied biodegradable waste fractions (meat waste, fruit and vegetable waste and fish waste) could be considered as alternatives to typical raw materials used in animal feeds.

Evaluation of Decomposition Effect on Long-Term Settlement Prediction for Fresh Municipal Solid Waste Landfills

A considerable amount of settlement occurs due to the decomposition of municipal solid waste (MSW) in landfills over a period of years. Therefore, the effect of biological decomposition governs the long-term settlement characteristics of municipal solid waste landfills. In this study, we investigated the long-term settlement characteristics by applying a number of prediction methods to fresh MSW sites and predicting the settlement curves. Most proposed methods, excluding the power creep law, successfully predicted long-term settlement only if accelerated logarithmic compression due to decomposition of biodegradable MSW was included in the settlement prediction.

Bioreactor landfills: experimental and field results

Bioreactor landfills allow a more active landfill management that recognizes the biological, chemical and physical processes involved in a landfill environment. This paper presents the results of an experimental study carried out to determine the effect of solid waste size, leachate recirculation and nutrient balance on the rate of municipal solid waste (MSW) biodegradation. Higher rates of MSW biodegradation eventually cause a reduction of the contaminant life span of the landfill and decrease in the cost of long term monitoring. The study indicated that the smaller the size of the MSW the faster the biodegradation rate of the waste. In addition, the paper presents the results of leachate recirculation on solid waste biodegradation in a full-scale landfill site, which is located in Nepean, Ontario, Canada. The leachate was recirculated into the landfilled solid waste for 8 years through infiltration lagoons. Similar results to those obtained in the laboratory scale experiments were noted. The average pH of the leachate in the early stages of recirculation was on the acidic range of the pH scale, however, the pH value was in the range of 7–8 after 2 years of leachate recirculation. The concentration of chloride remained fairly constant at about 1000 mg/l during the leachate recirculation period. A decreasing trend of the organic load, measured as biological oxygen demand and chemical oxygen demand, was observed. Recovery of landfill air space was also noted because of the enhanced subsidence and decomposition of the solid waste.

The impact of the European landfill directive on waste management in the United Kingdom

The European Union Landfill Directive calls on member states to reduce the amount of biodegradable municipal solid waste disposed of to landfill. In addition, national waste strategies will require the constituent parts of the United Kingdom to achieve increased household waste recycling and recovery rates. Both these measures will require the development of the infrastructure to support national high-intensity recycling and composting schemes and the construction of at least 35 new municipal waste to energy incinerators. Before plans can be developed for meeting the targets several areas relating to municipal solid waste need to be clarified. Depending on the definition of municipal solid waste, its composition and likely future growth rates the number of incinerators required could be up to 170.

Effect of Leachate Recirculation on Municipal Solid Waste Biodegradation

Abstract Biological processes are known to reduce the organic fraction of municipal solid waste, but current landfilling practices have not been altered to reflect this knowledge. The advantages of enhancing degradation of solid waste include reduced period of leachate treatment, increased methane production, expedited landfill site reclamation through stabilized waste mining, and accelerated subsidence permitting recovery of valuable landfill air space. The techniques that can be used to enhance biological degradation include leachate recirculation, addition of nutrients, shredding, sludge and buffer solutions addition, lift design, temperature, and moisture content management. Manipulation of these variables promotes a more conducive environment for microbial activity. This paper presents the results of a leachate recirculation experiment into three pilots scale solid waste cells. A computer-operated pumping system controlled the rate of recirculated leachate into the solid waste cells. The leachate was recirculated over a period of 65 weeks, and effluent samples were obtained on a weekly basis and analyzed for pH, BOD, COD, TOC and heavy metal concentrations. The experimental results indicated that addition of supplemental materials to the leachate during recirculation has a positive effect on the rate of biological degradation of solid waste. The addition of primary sludge and supplemental nutrients resulted on a rapid increase in BOD and COD concentrations in the effluent samples. This rapid increase in BOD and COD concentrations suggests that following a lag phase prior to the methano-jenesis phase, a rapid decrease in the organic load in the leachate will be ichieved within a reasonable time frame. In addition, the results of this investigation indicates that the primary sludge is an excellent source of microbial inoculum. The addition of supplemental nutrients (nitrogen and phosphorus) with buffer also increases the concentration of the BOD and COD in the effluent samples, proving that a balance of pH and an increase in the available nutrients increases biological activities in the solid waste cells compared to the control cell.

Fuel gas enhancement by controlled landfilling of municipal solid waste

The controllable processing options available for maximum and accelerated fuel gas production from municipal solid waste (MSW) were studied in the laboratory in “controlled” landfill test cells. Fuel gas production was enhanced substantially compared to conventional “uncontrolled” sanitary landfills. Up to 0.142 m 3 CH 4/dry kg MSW (4600 ft 3 CH 4/dry ton) was obtained in just 3 months under the simulated landfill conditions, equivalent to a conversion of more than 50% of the biodegradable MSW fraction to fuel gas. Twenty-six controlled landfill experiments were performed in up to 200-litre (55 gallon) capacity test cells for periods of up to 410 days. Compaction to 712 kg/m 3 (1200 pounds/cubic yard) was used in all tests. Of the enhancement parameters investigated, the following significantly increased the fuel gas yield and production rate: (1) increasing the moisture content of the MSW; (2) controlling the pH with CaCO, buffer; (3) increasing the population of anaerobic microorganisms; (4) increasing the nutrients (mainly nitrogen and phosphorus); and (5) increasing overall distribution of the materials added throughout the MSW. Digested sewage effluent supplied the nutrients, the inoculum of microorganisms, and the moisture. Both static and leachate recirculation modes were also studied; recycle resulted in slightly higher fuel gas yields. Further, experiments were run at compactions from 593 to 949 kg/m 3 (1000 to 1600 pounds/cubic yard); percent MSW conversions to fuel gas were constant, but higher fuel gas production per unit volume was observed with increasing compaction.