STUDIES AND RESEARCH REGARDING THE EVALUATION OF TECHNOLOGICAL ASPECTS FOR THE POST-CLOSURE ACTIVITY OF LANDFILLS FOR MUNICIPAL SOLID WASTE / STUDII ŞI CERCETĂRI CU PRIVIRE LA EVALUAREA ASPECTELOR TEHNOLOGICE PENTRU PERIOADA DE POST-ÎNCHIDERE A DEPOZITELOR DE DEŞEURI MUNICIPALE SOLIDE.

The theoretical and experimental research on the evaluation of the technological aspects of the post-closure activity of the municipal solid waste landfills presented in this study constitutes an attempt to describe, by means of a detailed analysis, the relations of interdependence that exist between the management operations and the aspects having a significant impact on the environment in the municipal solid waste landfills areas . The results obtained by means of theoretical and experimental investigation lead us to the following conclusions: A. Concerning the timeliness of the topic/theme In base of studying specialised literature on waste, it can be stated that: - The waste quantity generated has an upward trend. The necessary options to reduce the amount of generated waste refer to [57, 80]: • reduction at source; • reducing the amount of waste streams; • waste valorisation: reuse, recycling and energy recovery; • waste disposal. - Municipal Solid Waste consists of household and similar waste collected by or on behalf of the municipal authorities. The structure of the municipal solid waste is composed of the following fractions [60, 62]: • paper, cardboard and paper products; • plastic materials; • glass; • metals; • food waste; • garden waste and textiles. - The modalities of waste collection are [98, 99, 111]: • traditional door to door collection; • differentiated collection by fractions for recovery operations. - Landfills present a number of factors which should be studied carefully in order to monitor the manufactured products, which can have a significant impact on the environment and can have harmful effects on the environment or on the population. - The sources of the environmental pollution are: • soil pollution (by disposing waste on the soil); • water pollution (by waterproofing systems and by the leachate collection; • air pollution (by the biogas collection system). - By implementing management systems and adequate monitoring, new jobs can be created – to perform different activities specific to landfills. - Large amounts of material can be recycled, especially non-hazardous materials. B. Aspects regarding the theoretical foundation of technological aspects of the post-closure activity of the landfills for municipal solid waste 1. From a legislative point of view, there are European regulations and norms that the operators and landfills managers must obey. Both Italy and Romania have their own legislation whose implementation is mandatory to ensure the landfill adequate operation. 2. Each landfill is specific to the category of waste that can be accepted for storage. The waste to be deposited in landfills can be classified into three categories [99]: - residential waste; - commercial waste; - industrial waste. 3. The properties of the analysed waste in the research can be classified as follows [24, 99]: - physical properties of waste: • waste moisture; • waste granulometry; • waste density; • waste permeability; • waste temperature; - chemical properties of waste; - biological properties of waste. 4. According to the type of waste deposited in the landfill, landfills can be classified into three categories [55-57, 99]: - landfills for inert waste; - landfills for non-hazardous waste: • landfills for inorganic waste; • landfills for organic waste: o landfills - bio-reactor; o landfills for pre-treated waste. • landfills for waste mixture; - landfills for hazardous waste. 5. The life cycle of the landfill is divided into four clearly defined stages (design and construction, active management, closure and passive management), but in the theoretical and experimental analysis, the active period (in which waste is deposited in the landfill) and the post-closure phase (minimum of 30 years after the landfill has been covered by vegetation) are considered to be important.. 6. The leachate is the result of the bacterial decomposition the organic substance, and of the extraction of the organic contaminants from waste by means of the solvent effect of water. This product is very aggressive and can have a serious environmental impact in case of mismanagement. 7. The biogas is a gas that is produced by the decomposition of the organic waste during the methanogenic phase. This decomposition produces a „micelle” composed of methane and carbon dioxide, and also containing low amounts of nitrogen, oxygen, sulphur, hydrogen, and carbon monoxide. 8. The post-closure period of the landfills is considered to be one of the most important periods of their life cycle. During this period, a permanent monitoring of the parameters having a significant environmental impact is necessary. The collection of generated products is also necessary to ensure the landfill safety. 9. The method used in this thesis to identify the amounts of leachate and biogas, and the characteristics of the products generated by the landfill is the estimative mathematical modelling. 10. For the analysis of the impact on the technological aspects of the post-closure phase of the municipal solid waste landfills, there have been carried out different estimations and comparative analyses that can represent the leachate and biogas quantities that can be collected in different periods of the landfill life-cycle. It has been identified the influence of the weather and climatological parameters on the amounts of landfill products, and there have established different mathematical relations and the factors that may have influence on the technological processes. 11. For the comparative analyses there were considered case studies from Italy and Romania, for which there were defined and specified the following: - the description, the construction and the management of landfills from Italy and from Romania; - the structure of landfills considered in case studies; - categories of waste stored in each landfill; - leachate collection in active phase and the estimation of its quantity in the post-closure phase; - biogas collection in active phase and the estimation of its quantity in the post-closure phase. 12. This theoretical and experimental analysis allows the possibility to estimate and identify the correlation between waste amounts, time, and leachate and biogas production capacity of each analysed landfill. C. Aspects concerning the experimental testing of the theory 1. To study the impact of the technological aspects of the post-closure phase of the municipal solid waste landfills, there were identified the following: - characteristics and parameters of the Italian and Romanian landfills: • Turin landfill, Italy; • Potenza landfill, Italy; • Enna landfill, Italy; • Bacău landfill, Romania; • Bihor landfill, Romania; • Piatra Neamț landfill, Romania; • Timiș landfill, Romania; - estimations of the leachate and biogas amounts generated by the landfills. 2. In Romania, the activity of waste depositing in ecological landfills, built according to the current legislation, is in its early stage – it began in the 2000s, when Municipalities or County councils built and developed specific areas and used them to create modern landfills funded through European projects. 3. As for the design, the Italian landfills have a greater number of cells, each of them being equipped with independent systems to collect leachate and biogas, restricted to municipal solid waste. 4. There is a characteristic of the Romanian landfills concerning the composition of the deposited waste: pre-sorting operations are carried out before depositing, but there are also deposited industrial and construction waste. 5. There were described estimative mathematical models for the identification of various parameters. Some models cannot be applied to certain landfills due to scarce data. 6. In order to calibrate and verify models accuracy two mathematical models for each product were implemented. Thus, for the leachate production, where there were sufficient data, there were used: - Hydrological Mass Balance Model for: • Turin landfill, Italy; • Potenza landfill, Italy; • Piatra Neamț landfill, Romania; • Bihor landfill, Romania; - Serial Water Balance Model for Turin landfill, Italy. For the calculation of biogas production, there were used: - Stoichiometric model for: • Turin landfill, Italy; • Bihor landfill, Romania; - LandGEM model for: • Turin landfill, Italy; • Bihor landfill, Romania. For the other landfills, it was impossible to carry out the calibration of the available mathematical models due to the lack of data about the actual waste quantities, or about the leachate and biogas production that was collected from each landfill. 7. A description of the main features was carried out for each landfill, the difference between the analysed cases being noticed even from the landfills structure. The main characteristics of each landfill are presented below: a. Turin landfill: - surface: 79.9·104 m2; - volume occupied: 18.628·106 m3; - number of cells: 9; - active phase between: 1984-2009; b. Potenza landfill: - surface:10·104 m2; - volume occupied: 0.579·106 m3; - number of cells: 7; - active phase between: 1989-2004; c. Enna landfill: - surface:4.5·104 m2; - volume occupied: 0.560·106 m3; - number of cells: 6; - active phase between: 2007-2013; d. Bacău landfill: - surface:22.1·104 m2; - volume occupied: 4.123·106 m3; - number of cells: 4; - active phase between: 2011 - present; e. Bihor landfill: - surface: 7.6·104 m2; - volume occupied: 0.864·106 m3; - number of cells: 2; - active phase between: 2005 - 2014; f. Piatra Neamț landfill: - surface: 4·104 m2; - volume occupied: 1.229·106 m3; - number of cells: 2; - active phase between: 2004 - 2013; g. Timiș landfill: - surface: 35.14·104 m2; - volume occupied: 5.131·106 m3; - number of cells: 5; - active phase between: 2011 – 2014; 7. The graphical representations and the response function mathematical formulae have highlighted the technological aspects of the post-closure period of municipal solid waste landfills, as well as the leachate and biogas production capacities: - it was carried out the estimation of the total quantity of liquid that can be generated from the moisture content of each fraction of different types of waste (municipal solid waste, analogous municipal solid waste, and sewage sludge) and from the liquid amount that can be produced due to weather and climatological conditions, specific to each landfill; - from the total liquid quantity, it was realised an estimation of the leachate production for each landfill, for a period of active phase and for a period of at least 30 years of post-closure phase. 8. For Turin landfill, Italy, the data was presented as follows: - the total amount of waste deposited in the period of activity consist of three types of waste: • municipal solid waste - 73%; • analogous municipal solid waste -14%; • sewage sludge – 13%; - it was presented the composition of municipal solid waste for the period 2000-2009; - the average percentage composition of the fractions of the municipal solid waste stored in the landfill, which was used to calculate the deposited waste. The fractions contained in the waste composition are:: • paper and cardboard waste; • leather and textile waste; • wood waste; • glass and inert waste; • metal waste; • plastic waste; • organic waste; • fine particles of waste; • other types of waste; - the actual monthly average variations of precipitations, temperature, and solar radiation, and the calculated monthly average variations of runoff and evapotranspiration; - the moisture content of each fraction of municipal solid waste, and of analogous municipal solid waste; - the moisture content of sewage sludge deposited in the landfill; - a comparative analysis of the calculated leachate quantity and the estimated leachate quantity – using the estimative mathematical model for the leachate production capacity. The estimation of the leachate amount was determined for 30 years of post-closure phase. The correlation coefficient used in the equation on was 0.91155; - an estimation of the biogas amount using an estimative mathematical model, to work out the biogas production capacity, which was compared to the real quantity of biogas collected from the landfill. The estimation of the biogas quantity was calculated for a period of 31 years of post-closure phase. 9. For Potenza landfill, Italy, the data was presented as follows: - the total quantity of waste deposited in landfill in active phase is composed from two types of waste: • municipal solid waste - 90%; • sewage sludge – 10%; - it was represented the average percentage of municipal solid waste composition, which it was utilised in mathematical calculations for deposited waste. The fractions from municipal solid waste are: • paper and cardboard waste; • leather and textile waste; • wood waste; • glass and inert waste; • organic waste; • fine particles of waste; • other types of waste; - the actual monthly average variations of precipitations, temperature and the calculated monthly average variations of runoff and evapotranspiration; - the moisture content for each fraction of municipal solid waste and of sewage sludge; - a comparative analysis of the calculated and estimated amounts of leachate – for the estimation, the estimative mathematical model was used (to determine the leachate production capacity). The total quantity of liquid that could be produced by the landfill was 168,162.3 m3. The estimation of the leachate quantity for the post-closure phase was worked out for a period of 30 years. The correlation coefficient used for estimation was 0.92003; - an estimation of the biogas quantity using an estimative mathematical model to calculate the biogas production capacity, which was compared to the real quantity collected from the landfill. The estimation of the biogas quantity for the post-closure phase was carried out for a period of 32 years. 10. For Enna landfill, Italy, the data was presented as follows: - the total amount of waste deposited during the active phase is composed of municipal solid waste. - There is no public information about the waste structure of the landfill. That was why it was represented the average percentage of the composition of the municipal solid waste deposited in the landfill, which was used to calculate the amount of the deposited waste. The fractions used in calculations are the following: • paper and cardboard waste; • leather and textile waste; • wood waste; • glass and inert waste; • metal waste; • plastic waste; • organic waste; • fine particles of waste; • other types of waste; - there were represented the monthly average variations of precipitations and temperature, and the monthly average variations of runoff evapotranspiration. - it was estimated the moisture content of each fraction of municipal solid waste. - It was carried out a comparative analysis of the amounts of leachate calculated and estimated (using an estimative mathematical model to determine the production capacity for leachate). The total amount of leachate that can be generated by the landfill was 145,833.59 m3. The estimation of leachate quantity for the post closure phase was worked out for a period of 30 years. The correlation coefficient was 0.96841; - it was carried out an estimation of the biogas amount using an estimative mathematical model to determine the biogas production capacity , which was compared to the real quantity collected from the landfill. The estimation of the biogas quantity for the post-closure phase was realised for a period of 31 years. 11. For Bacău landfill, Romania, the data was presented as follows: - There was no data concerning the quantity of deposited waste. . - There was represented the monthly average variations of precipitations and temperatures, and there were calculated the monthly average variations of runoff and evapotranspiration. - because there no data about the amount of waste deposited in the landfill, the estimation of the leachate and biogas production cannot be made. 12. For Bihor landfill, Romania, the data was presented as follows: - the total quantity of waste deposited during the active phase is composed only of municipal solid waste. There were also deposited fractions of industrial or construction waste, but they were neglected in calculations. - it was represented the average percentage of the municipal solid waste composition, which was used to calculate the amount of deposited waste. The municipal solid waste fractions are: • paper and cardboard waste; • leather and textile waste; • wood waste; • glass and inert waste; • metal waste; • plastic waste; • organic waste; • fine particles of waste; • other types of waste; - there were represented the monthly average variations of precipitations and temperature, and there were calculated the monthly average variations of runoff and evapotranspiration; - it was estimated the moisture content related to each fraction from municipal solid waste; - it was performed a comparative analysis of the calculated and estimated amounts of leachate (using an estimative mathematical model to determine the leachate production capacity). The total quantity of leachate that could be formed in the Bihor landfill was 458,485.6 m3. The estimation of the post-closure leachate quantity was made for a period of 30 years. The correlation coefficient was 0.95516; - it was made an estimation of the biogas amount using an estimative mathematical model to determine the biogas production capacity, which was compared to the real quantity collected from the Bihor landfill. The estimation of the post-closure biogas quantity was realised worked out for a period of 32 years. 13. For Piatra Neamț landfill, Romania, the data was presented as follows: - the total quantity of waste deposited during the active phase was composed only of municipal solid waste. The waste also contained fractions of industrial and/or construction waste, which were neglected in calculations; - it was represented the average percentage of municipal solid waste composition, which was used in mathematical calculations for the deposited waste. The fractions of municipal solid waste are: • paper and cardboard waste; • leather and textile waste; • wood waste; • organic waste; • fine particles of waste; - There were represented the monthly average variations of precipitations and temperature, and there were calculated the monthly average variations of runoff and evapotranspiration; - it was estimated the moisture content of each fraction of the municipal solid waste deposited in the Piatra Neamț landfill; - it was performed a comparative analysis of the amounts of leachate calculated and estimated (using an estimative mathematical model to determine the leachate production capacity. The total quantity of leachate that could be formed in the Piatra Neamț landfill was 214,702.12 m3. The estimation of the post-closure leachate quantity was made for a period of 30 years. The correlation coefficient was 0.96029; - it was made an estimation of the biogas quantity using an estimative mathematical model to determine the biogas production capacity, which was compared to the real quantity collected from the landfill. The estimation of the post-closure biogas quantity was calculated for a period of 30 years. 14. For Timiș landfill, Romania, the data was presented as follows: - There were no data concerning the amount of deposited waste. - there were presented the monthly average variations of precipitations and temperature, and there were calculated the monthly average variations of runoff and evapotranspiration. - As there was no information about the amount of waste deposited in the landfill, the estimation of the leachate and biogas productions was not possible. 15. With respect to management, it is necessary to emphasize the following: - leachate is collected and monitored in both Italian and Romanian landfills, and is treated using technical solutions specific to each case. In Romania, besides the fact that intermediate layers for landfill periodical covering are not used, there is no monitoring system for the collected leachate , and leachate recirculation is not performed; - As for the biogas, only some operators, who are on charge of the Romanian landfills, collect the biogas and use it for energy recovery (Bihor landfill). Biogas collection presents several advantages for operators, and has important consequences as far as the prevention of disasters is concerned. 16. The post-closure phase activities (performed for approximately 30 years after the final closure of the landfill - according to specialised literature) play a crucial role in the life cycle of a landfill. D. Concerning the originality of the thesis 1. On the basis of bibliographical study on the evaluation of the technological aspects related to the post-closure phase of the municipal solid waste landfills, in both Italy and Romania, the following aspects were highlighted: - description, design, construction and management of landfills from Italy and from Romania; - the structure of landfills considered in case studies; - categories of waste stored in each landfill; - leachate collection in active phase and the estimation of its quantity in the post-closure phase; - biogas collection in active phase and the estimation of its quantity in the post-closure phase. 2. In order to perform comparative analyses, there were chose three landfills from Italy and four from Romania, in various stages of activity, on the basis of the complexity of the technological processes, concerning leachate and biogas, that occur in the landfills. 3. Following estimations and comparative analyses, correlations were established between the amounts of leachate and biogas that could be collected. Mathematical modelling was used: one equation to estimate the quantity of leachate, and another one to identify the biogas production. 4. For the leachate calculation, the estimative equation for leachate production showed a degree of truth (r2) between 0.91 and 0.97. The maximum degree of truth was worked out for the Romanian landfill of Bihor, while the minimum degree was worked out for the Italian landfill of Turin. 5. For the biogas calculation it was used an estimative mathematical model that was influenced by the amount of waste deposited during the activity and the full life of the landfill (active and post-closure phases). 6. On the basis of the estimates obtained for the leachate and biogas production capacities of the analysed landfills, there were developed, using the TableCurve3D software, the following mathematical models: - for the leachate production capacity, the model obtained had a degree of correlation (r2) between 57 and 93%; - for the biogas production capacity, the model obtained had a degree of correlation (r2) between 87 and 96%. E. Concerning future developments of the research 1. Landfills represent the most commonly used method for storing waste in Romania. Two of the analysed landfills from Italy are in post-closure period, from 2004 and 2010 respectively, and another one is still in its active phase, while all analysed Romanian landfill in their active phase. In calculations, the closure of the landfills was considered to occur in the last year for which data about the amount of waste were available. 2. In Romania, waste storage in ecological landfills built in accordance to current legislation began relatively late, after 2000s, when Municipalities or County Councils built and developed special areas and used them to develop modern landfills funded through European projects. 3. The theoretical studies and comparative analyses presented in this can be a useful material for addressing similar issues in this area, to identify the various aspects concerning the processes that occur in landfills in different periods of their life cycle. 4. To clarify the correlations between the amount of deposited waste and the leachate and biogas production capacities, it is necessary that future studies and researches consider other parameters that may influence leachate and biogas production. 5. To eliminate the discrepancies between the actual land values and the values calculated using mathematical models, it is necessary to use mathematical models that involve a number of parameters specific to each landfill. In case differences occur in the composition of waste, or structural waterproofing was carried out in a different way, major differences may occur in the calculations. Other important factors that may have an important influence on leachate and biogas production are: - The degree of compaction of waste; - Regular coverage of waste; - Collection system for leachate and for biogas; - Leachate recirculation. 6. The present study has not considered the qualitative and/or chemical-biological parameters of waste. This may be the subject of future research papers.