Mechanical-biological Treatment Plants Research Articles

Analysis of MSW full-scale facilities based on anaerobic digestion and/or composting using respiration indices as performance indicators

The Landfill Directive (1999/31/EC) forces European States to reduce the amount of biodegradable municipal waste landfilled to 35% of 1995 levels. Mechanical-Biological Treatment (MBT) plants are the main alternative to waste incineration and landfilling. In this work, the waste treatment efficiency of six full-scale MBT facilities has been analysed using respiration indices (Dynamic Respiration Index and Cumulative Oxygen Consumption) to monitor plant performance. MBTs relying on anaerobic digestion plus composting achieved a high grade of stability on final compost (0.24±0.09mgO2g−1DMh−1 and 20±9mgO2g−1DM for dynamic respiration and cumulative consumption, respectively). On the contrary, MBTs relying only on composting showed a poor performance (1.3±0.2mgO2g−1DMh−1 and 104±18mgO2g−1DM for dynamic respiration and cumulative consumption, respectively). These results highlight the usefulness of respirometric balances to assess the performance of MBT full-scale plants.

Life Cycle Assessment of Mechanical–Biological Treatment of Mixed Municipal Waste

Abstract The aim of this study is to quantify the environmental exchanges associated with the mechanical–biological treatment (MBT) of mixed municipal waste, for a specific MBT plant, based on the annual operation data for the year 2015. Modeling of environmental performance of the MBT technology is done on actual, real data of the operating plant, taking into account particular, explicit outputs and efficiencies of the plant. Results contribute to quantitative understanding of MBT technology and its environmental impact, including the impacts from individual unit processes within MBT. The study is based on Life Cycle Assessment methodology, employing the EASETECH model. One megagram of mixed municipal waste entering the MBT plant is adopted as the functional unit. The system boundaries cover the whole value chain from collection and transport of mixed municipal waste through mechanical and biological operations until final treatment of end-waste generated in the MBT plant. Results of modeling show the MB...

Performance of mechanical biological treatment of residual municipal waste in Poland

The number and capacity of mechanical-biological treatment (MBT) plants in Europe increased significantly in the past two decades as a response to the legal obligation to limit the landfilling of biodegradable waste in landfills and to increase recycling and energy recovery from waste. The aim of these plants is to prepare residual municipal waste for recovery and disposal operations, including especially separation and stabilization of the easily biodegradable fraction (the biofraction). The final products of MBP technology are recyclables, stabilate, high calorific fraction which is used for the production of refuse derived fuel (RDF) and the remaining residual fraction. The shares of the output fractions, especially of the recyclables and RDF determine the overall efficiency of MBT technology in diverting waste from landfills. In this paper results of an assessment of one exemplary MBT plant are provided. The analysis was performed within a comparative study in which 20 selected MBT plants in Poland were subject to a detailed analysis, focusing, both at the design parameters as well as operational ones. The selected plant showed relatively higher overall materials recovery efficiency. With the view to circular economy targets, increased automation of the mechanical waste treatment will be required to support achieving high level diversion from landfills. The study reviled that stabilisation of biofraction should be improved by a better control of process conditions, especially moisture content.

Flexibility of mechanical biological treatment plants

Flexibility of mechanical biological treatment plants

The effect of purified sewage discharge from a sewage treatment plant on the physicochemical state of water in the receiver

Abstract The paper presents changes in the contents of physicochemical indices of the Sudół stream water caused by a discharge of purified municipal sewage from a small mechanical-biological treatment plant with throughput of 300 m3·d−1 and a population equivalent (p.e.) – 1,250 people. The discharge of purified sewage caused a worsening of the stream water quality. Most of the studied indices values increased in water below the treatment plant. Almost a 100-fold increase in ammonium nitrogen, 17-fold increase in phosphate concentrations and 12-fold raise in BOD5 concentrations were registered. Due to high values of these indices, the water physicochemical state was below good. Statistical analysis revealed a considerable effect of the purified sewage discharge on the stream water physicochemical state. A statistically significant increase in 10 indices values (BOD5, COD-Mn, EC, TDS, Cl−, Na+, K+, PO43−, N-NH4+ and N-NO2) as well as significant decline in the degree of water saturation with oxygen were noted below the sewage treatment plant. On the other hand, no statistically significant differences between the water indices values were registered between the measurement points localised 150 and 1,000 m below the purified sewage discharge. It evidences a slow process of the stream water self-purification caused by an excessive loading with pollutants originating from the purified sewage discharge.

Impact of paper and cardboard suppression on OFMSW anaerobic digestion

Mechanical-biological treatment plants treat municipal solid waste to recover recyclable materials, nutrients and energy. Waste paper and cardboard (WP), the second main compound in municipal solid waste (∼30% in weight basis), is typically used for biogas generation. However, its recovery is gaining attention as it can be used to produce add-value products like bioethanol and residual derived fuel. Nevertheless, WP suppression or replacement will impact anaerobic digestion in terms of biogas production, process stability and digestate management. Two lab-scale reactors were used to assess the impact of WP in anaerobic digestion performance. A control reactor was only fed with biowaste (BioW), while a second reactor was fed with two different mixtures of BioW and WP, i.e. 85/15% and 70/30% (weight basis). Results indicate that either replacing half of the WP by BioW or removing half of the WP has little impact on the methane production. When removing half of the WP, methane production could be sustained by a larger waste biodegradability. The replacement of all WP by BioW increased the reactor methane production (∼37%), while removing all WP would have reduced the methane production about 15%. Finally, replacing WP loading rate by BioW led to a system less tolerant to instability periods and with poorer digestate quality.

Economic and life cycle analysis of municipal solid waste management for small islands: On-site management scenarios versus off-site transportation

<div> <p>A comparative economic and life cycle based analysis of five management scenarios for the solid waste generated in the island of Syros was conducted. The LCA part was performed with the LCA – IWM software. The four on-site waste management scenarios were: i) source separation of recyclable materials in combination with landfill disposal of the residuals (existing situation), ii) aerobic, windrow type, biological treatment (composting) with landfilling of residues, iii) anaerobic biological treatment (digestion) with landfilling of residues iv) aerobic mechanical biological treatment (MBT) and landfilling of residues. The off-site management scenario examined the transportation of the whole commingled wastes off the island for processing and disposal to the main mechanical and biological pretreatment plant in Athens. The results of analysis showed that the optimum waste management scenario in terms of environmental burdens (based on six environmental impact categories) and economics was off-site transportation, even when the specific landfill tax is included in calculations. The second best scenario in terms of environmental performance included the on-site aerobic MBT plant while the worst scenario was direct landfilling with mixed dry recyclables’ recycling. On-site anaerobic digestion had less environmental burdens and was more expensive than open windrow composting. Threshold distances were calculated below which the transportation of municipal solid wastes from a small island is financially and environmentally beneficial.</p> </div> <p> </p>

Analysis of the environmental performance of life-cycle building waste management strategies in tertiary buildings

At urban level, the generation Municipal Solid Waste and Construction and Demolition Waste is mostly related to the life-cycle of buildings. An evaluation method based on Life Cycle Assessment methodology is presented in this paper to make an analysis of the environmental performance of different life-cycle building waste management strategies in tertiary buildings. As a case study, several waste management strategies considering a tertiary building located in the city of Zaragoza in Spain, are studied. The aim of the case study is to compare the environmental impacts, in terms of Global Warming Potential, of the scenarios proposed focussing on the waste minimisation and avoidance of landfilling of at least 10% for the Municipal Solid Waste generation during a building's use stage, and Construction and Demolition Waste generated during its construction and end-of-life. In case of Municipal Solid Waste, the results show that when a recovery scenario includes energy recovery from the residual fraction of the mechanical-biological treatment plant in the form of Refuse Derived Fuel, greater benefits in terms of the Global Warming Potential are obtained than with current scenarios of landfill deposition of the residual fraction. On the other hand, in case of Construction and Demolition Waste, a similar situation can be observed in case of an increase of the recovery rates of metals.

PCDD/Fs environmental impact from an anaerobic digestion treatment

The presence of mechanical-biological treatment (MBT) plants for municipal solid waste (MSW) in a territory could result in significant contamination by dioxins and furans (PCDD/Fs). This study points out the importance of carrying out a preliminary environmental impact assessment for MBT plants. A preliminary investigation was carried out with reference to the anaerobic digestion (AD) of MSW. A dispersion model was applied to an MBT plant. The AD process was analysed as a treatment of the filtrate, i.e., the putrescible fraction (undersieve), of screened residual MSW, before a post-biostabilisation (BS) step. A comparison with the BS of the oversieve alone, i.e., the coarse fraction of residual MSW, was made too. A conventional biofilter and a regenerative thermal oxidiser (RTO) were also compared to emission control solutions. Thanks to the increased dilution by the RTO, lower impacts are expected on the surroundings. In addition, coupling AD with post-BS results considerably lower PCDD/Fs emissions with respect to BS alone.

Effect of tourism-generated wastewater on biogenic ions concentrations in stream water in Tatra National Park (Poland)

The purpose of the research conducted in the years 2008–2009 was to determine the effect of wastewater generated by several tourist lodges in Tatra National Park (an alpine environment) on the concentration of biogenic ions (NH4 +, NO2 −, NO3 − and PO4 3−) in local streams into which the wastewater was being discharged. Wastewater discharged from mechanical biological wastewater treatment plants operated by tourist lodges usually has high concentrations of NH4 + and PO4 3−. The largest loads of biogenic ions were discharged into streams during the tourist season from May until September. Although the dilution conditions were good, the concentrations of some forms of biogenic ions in streams were significantly higher at points tens of metres downstream from the point of discharge than at points located upstream from the point of discharge. The concentrations of NH4 + and PO4 3− ions increased significantly in streams into which wastewater was being discharged from wastewater treatment plants in Tatra National Park (NP). Concentrations of NO3 − increased in the case of a stream into which untreated wastewater was being discharged after flowing down a mountain couloir for several hundred metres in the Tatras. The water and sewer management situation in Tatra NP has improved significantly since the time when this research was conducted. Poland’s entry into the European Union in 2005 made additional EU funding available to be invested in various environmental projects. Most existing wastewater treatment plants were fully modernized in the years 2010–2011, and new plants were built where none had been. Even so, it seems that transporting wastewater to treatment plants outside the national park is the most effective and reliable method of protecting the oligotrophic mountain waters of the Tatras from pollution.

Multi-criteria selection of municipal waste treatment system using VIKOR method

The main goal is determination of municipal waste treatment system. System alternatives include recycling, composting, incineration, and landfilling. Criteria are derived from environmental protection, efficiency, financial, and social effects. This decision problem is characterised by non-commensurable and competing (conflicting) criteria, with no solution satisfying all criteria simultaneously. The multi-criteria decision making method VIKOR is applied for ranking alternatives of waste treatment and selecting compromise solution from the set of feasible alternatives. The method compromises conflicting criteria, and group utility with individual regret. Multi-criteria decision making for municipal solid waste management in the region of Novi Sad, Serbia, is presented as an example, illustrating alternatives generation, formulation of criteria functions, evaluation of alternatives in terms of criteria, application of the VIKOR method and the proposition of final solution. Selected treatment system consists of mechanical-biological treatment (MBT) plant, incineration in cement kiln, sanitary landfill, and market for recycling material.

Case study of an MBT plant producing SRF for cement kiln co-combustion, coupled with a bioreactor landfill for process residues

The paper describes the performances of the energy recovery pathway from the residual waste based on the production of a Solid Recovered Fuel (SRF) to be exploited via co-combustion in a cement kiln. The SRF is produced in a single stream Mechanical–Biological Treatment plant, where bio-drying of the waste is followed by mechanical refining in order to fulfil the quality requirements by the cement kilns. Peculiar of this MBT is the fact that sorting residues are disposed in a nearby landfill, managed according to a bioreactor approach, where landfill gas is collected for electric energy recovery. A detailed mass and energy balance of the system is presented based on one year operational data, followed by its Life Cycle Assessment. Results show that the system is energetically and environmentally effective, with most of the impacts being more than compensated by the savings of materials and energy. Major role in determining such outcome is the displacement of petcoke in the cement kiln, both in terms of its fossil CO2 emissions and of its life cycle impacts, including the trans-oceanic transport. To check the robustness of the results, two sensitivity analyses are performed on the landfill gas collection efficiency and on the avoided electric energy mix.

The use of multi-criteria analysis for selection of technology for a household WWTP compatible with sustainable development / Zastosowanie analizy wielokryterialnej do wyboru rozwiązania technologicznego przydomowej oczyszczalni ścieków zgodnego z ideą zrównoważonego rozwoju

Abstract This paper presents the use of multi-criteria analysis as a tool that helps choosing an adequate technology for a household wastewater treatment plant. In the process of selection the criteria of sustainable development were taken into account. Five municipal mechanical-biological treatment plants were chosen for the comparative multi-criteria analysis. Different treatment technologies, such as sand filter, activated sludge, trickling filter, a hybrid system - activated sludge/trickling filter and a hybrid constructed wetland system VF-HF type (vertical and horizontal fl ow) were taken into account. The plants’ capacities were 1 m3∙d-1 (PE=8) and they all meet the environmental regulations. Additionally, a solution with a drainage system was included into the analysis. On the basis of multi-criteria analysis it was found that the preferred wastewater treatment technologies, consistent with the principles of sustainable development, were a sand filter and a hybrid constructed wetland type VF-HF. A drainage system was chosen as the best solution due to the economic criteria, however, taking into consideration the primary (ecological) criterion, employment of such systems on a larger scale disagree with the principles of sustainable development. It was found that activated sludge is the least favourable technology. The analysis showed that this technology is not compatible with the principles of sustainable development, due to a lack of proper technological stability and low reliability.

Chemical Evaluation of Compost Produced at a Large Greek Mechanical Biological Treatment Plant: Metal Availability and Phytotoxicity

ABSTRACTThe present work investigates the impact of municipal solid waste mechanical separation and industrial composting on the metal content of composts and assesses the availability of Cu, Cd, Cr, Pb, and Zn at different maturation stages of compost produced at the largest mechanical biological treatment plant in Greece. Substantial metal contamination of composts was found to take place within the industrial facility, attributed to segmentation and sorption mechanisms during composting. In fresh compost, Zn is present in mobile fractions (41%), Cu is mostly held on the less mobile organic phases (57%), Cd is mostly present in bioavailable forms (51%), whereas Pb and Cr are associated with less mobile phases, such as Fe-Mn oxides and organic molecules. Cd, Cu, and Zn migrate to more inert phases during compost maturation, paralleled by the decrease of overall metal leachability. Cu and Pb concentrations (mg kg−1) exceeded the permissible limits in both composts (Fresh: Cu: 213 ± 48, Pb: 128 ± 69; Mature: Cu: 263 ± 1, Pb: 158 ± 29) and water leachates (Fresh: Cu: 106 ± 4, Zn: 126 ± 13; Mature: Cu: 50 ± 0.50, Zn: 118 ± 20). Nevertheless, toxic effects were not observed in monocot, dicot, or aquatic biosensor plants as indicated by radicle and shoot growth and visual quality ratings. Since metal availability in composts is related to their leaching potential, metal speciation studies should be conducted in leachates for the appropriate characterization of industrial composts.

Fine grain separation for the production of biomass fuel from mixed municipal solid waste

The main goal of the project MARSS (Material Advanced Sustainable Systems) is to build a demonstration plant in order to recover a renewable biomass fuel suitable for the use in biomass power plants out of mixed municipal solid waste (MMSW). The demonstration plant was constructed in Mertesdorf (Germany), working alongside an existing mechanical–biological treatment plant, where the MMSW is biological dried under aerobe conditions in rotting boxes. The focus of the presented sorting campaign was set on the processing of fine grain particles minor than 11.5mm which have the highest mass content and biogenic energy potential of the utilized grain size fractions. The objective was to produce a biomass fuel with a high calorific value and a low content of fossil (plastic, synthetic) materials while maximizing the mass recovery. Therefore, the biogenic components of the dried MMSW are separated from inert and fossil components through various classification and sifting processes. In three experimental process setups of different processing depths, the grain size fraction 4–11.5mm was sifted by the use of air sifters and air tables.

Life Cycle Assessment of Mixed Municipal Solid Waste: Multi-input versus multi-output perspective

This paper analyses four strategies for managing the Mixed Municipal Solid Waste (MMSW) in terms of their environmental impacts and potential advantages by means of Life Cycle Assessment (LCA) methodology. To this aim, both a multi-input and a multi-output approach are applied to evaluate the effect of these perspectives on selected impact categories. The analyzed management options include direct landfilling with energy recovery (S-1), Mechanical-Biological Treatment (MBT) followed by Waste-to-Energy (WtE) conversion (S-2), a combination of an innovative MBT/MARSS (Material Advanced Recovery Sustainable Systems) process and landfill disposal (S-3), and finally a combination of the MBT/MARSS process with WtE conversion (S-4). The MARSS technology, developed within an European LIFE PLUS framework and currently implemented at pilot plant scale, is an innovative MBT plant having the main goal to yield a Renewable Refined Biomass Fuel (RRBF) to be used for combined heat and power production (CHP) under the regulations enforced for biomass-based plants instead of Waste-to-Energy systems, for increased environmental performance. The four scenarios are characterized by different resource investment for plant and infrastructure construction and different quantities of matter, heat and electricity recovery and recycling. Results, calculated per unit mass of waste treated and per unit exergy delivered, under both multi-input and multi-output LCA perspectives, point out improved performance for scenarios characterized by increased matter and energy recovery. Although none of the investigated scenarios is capable to provide the best performance in all the analyzed impact categories, the scenario S-4 shows the best LCA results in the human toxicity and freshwater eutrophication categories, i.e. the ones with highest impacts in all waste management processes.

The application of SRF vs. RDF classification and specifications to the material flows of two mechanical-biological treatment plants of Rome: Comparison and implications

This work assessed the quality in terms of solid recovered fuel (SRF) definitions of the dry light flow (until now indicated as refuse derived fuel, RDF), heavy rejects and stabilisation rejects, produced by two mechanical biological treatment plants of Rome (Italy). SRF classification and specifications were evaluated first on the basis of RDF historical characterisation methods and data and then applying the sampling and analytical methods laid down by the recently issued SRF standards. The results showed that the dry light flow presented a worst SRF class in terms of net calorific value applying the new methods compared to that obtained from RDF historical data (4 instead of 3). This lead to incompliance with end of waste criteria established by Italian legislation for SRF use as co-fuel in cement kilns and power plants. Furthermore, the metal contents of the dry light flow obtained applying SRF current methods proved to be considerably higher (although still meeting SRF specifications) compared to those resulting from historical data retrieved with RDF standard methods. These differences were not related to a decrease in the quality of the dry light flow produced in the mechanical-biological treatment plants but rather to the different sampling procedures set by the former RDF and current SRF standards. In particular, the shredding of the sample before quartering established by the latter methods ensures that also the finest waste fractions, characterised by higher moisture and metal contents, are included in the sample to be analysed, therefore affecting the composition and net calorific value of the waste. As for the reject flows, on the basis of their SRF classification and specification parameters, it was found that combined with the dry light flow they may present similar if not the same class codes as the latter alone, thus indicating that these material flows could be also treated in combustion plants instead of landfilled. In conclusion, the introduction of SRF definitions, classification and specification procedures, while not necessarily leading to an upgrade of the waste as co-fuel in cement kilns and power plants, may anyhow provide new possibilities for energy recovery from waste by increasing the types of mechanically treated waste flows that may be thermally treated.

Potential SRF generation from a closed landfill in northern Italy

The aim of this work is to assess the possibility of producing solid recovered fuel (SRF) and “combustible SRF” from a landfill located in the north of Italy, where the waste is placed in cylindrical wrapped bales. Since the use of landfills for the disposal of municipal solid waste has many technical limitations and is subject to strict regulations and given that landfill post-closure care is very expensive, an interesting solution is to recover the bales that are stored in the landfill. The contents of the bales can then be used for energy recovery after specific treatments.Currently the landfill is closed and the local municipal council together with an environmental agency are considering constructing a mechanical biological treatment (MBT) plant for SRF production.The municipal solid waste that is stored in the landfill, the bio-dried material produced by the hypothetically treated waste in a plant for bio-drying, and the SRF obtained after the post-extraction of inert materials, metals and glass from the bio-dried material were characterized according to the quality and classification criteria of regulations in Italy.The analysis highlighted the need to treat the excavated waste in a bio-drying plant and later to remove the inert waste, metals and glass. Thus in compliance with Italian law, the material has a high enough LHV to be considered as “combustible SRF”, (i.e. an SRF with enhanced characteristics).

Thermophilic anaerobic co-digestion of organic fraction of municipal solid waste (OFMSW) with food waste (FW): Enhancement of bio-hydrogen production

Bio-hydrogen production from dry thermophilic anaerobic co-digestion (55°C and 20% total solids) of organic fraction of municipal solid waste (OFMSW) and food waste (FW) was studied. OFMSW coming from mechanical–biological treatment plants (MBT plants) presents a low organic matter concentration. However, FW has a high organic matter content but several problems by accumulation of volatile fatty acids (VFAs) and system acidification. Tests were conducted using a mixture ratio of 80:20 (OFSMW:FW), to avoid the aforementioned problems. Different solid retention times (SRTs) – 6.6, 4.4, 2.4 and 1.9days – were tested. It was noted that addition of food waste enhances the hydrogen production in all the SRTs tested. Best results were obtained at 1.9-day SRT. It was observed an increase from 0.64 to 2.51LH2/Lreactorday in hydrogen productivity when SRTs decrease from 6.6 to 1.9days. However, the hydrogen yield increases slightly from 33.7 to 38mLH2/gVSadded.

Studies on the Chemical Stabilisation of Digestate from Mechanically Recovered Organic Fraction of Municipal Solid Waste

This study aims to explore an innovative approach consisting of the Fenton’s process to stabilise organic wastes as an alternative to the traditional aerobic decomposition (composting). Digestate from the anaerobic digestion of the organic fraction of municipal solid wastes was taken from a mechanical–biological treatment plant and was thoroughly characterised regarding physical, chemical and biological properties. This sludge contained around 7.8 g Fe kg TS−1, which can be beneficial to the chemical oxidation. However, the use of zero-valent iron nanoparticles or iron(II) salt revealed treatment can be improved by adding extra iron into the system. The response surface methodology determined that the best peroxidation conditions were 35.6 g H2O2 kg TS−1 and 33.1 g Fe2+ kg TS−1, while maintaining constant pH 3, L/S 5 and room temperature. The chemical treatment enhanced the stability, reducing the oxygen uptake rate from 4.63 to 2.57 g O2 kg VS−1 h−1. Moreover, the germination index increased from 37 to 99.9 %, which means the treatment yielded a non-phytotoxic product. The outcomes of the present study are promising and open a new pathway for the Fenton peroxidation in semi-solid processes since this fast method can be very competitive when compared with the slow composting technology.