To ensure stability of a construction the physical properties of its components have tobe well known. In a landfill, waste presents the largest structural element and controlsboth the stability and integrity of the lining system. In spite of this critical role there is adearth of knowledge on behaviour of waste as an engineering material. Wastevariability and changes in waste stream aggravate the assessment of wastemechanical properties.In a literature review the main influences on shear behaviour of municipal solid waste(MSW) were identified. Design values and recommendation for shear parameter weresummarised. To assess mechanical behaviour in a systematic way the use of aclassification system was deemed crucial for a comparison of different findings fromliterature and a categorisation of waste in regard to its composition. A framework for aclassification system was introduced. Main elements of a comprehensive classificationsystem were identified in a literature review and discussed, and data from literaturewas applied to the classification framework. For the validation of a classificationsystem, municipal solid waste was examined in an in-situ waste sorting analysis andalso applied to the framework.The findings from the waste sorting and the classification system were also used todevelop a family of synthetic waste to gradually examine the influencing factors onwaste mechanical behaviour. For this, the materials, size ranges and shapes of wastecomponents identified in the waste sorting analysis were reduced to a minimum butstill representative amount. A range of synthetic waste compositions was engineeredand tested in a large-scale shear device. Compression tests were also conducted in alarge compression cell. The results from the laboratory testing were compared tovalues from the literature and MSW mechanical behaviour was subsequentlydiscussed in view to potential changes from changing waste streams.The results from shear and compression tests (constrained and shear modulus) onsynthetic waste were linked to the classification system and trends of the mechanicalbehaviour in relation to the tested synthetic waste compositions were identified.A framework for classifying MSW and comparing waste mechanical behaviour waspresented and demonstrated. A family of synthetic wastes was engineered and testedin shear and compression tests. The results were comparable to values from theliterature. Further research is recommended to refine the synthetic waste and theclassification.

A stable mixed culture, deposited as ATCC 55644, previously shown to degrade petroleum hydrocarbons at relatively high concentrations was used as the source of inoculum. This culture was grown in Stanier’s minimal media, either in the presence of different concentrations of naphthalene, nitrobenzene and toluene (NNT) or naphthalene and toluene (NT) as the sole source of C and/or N. Results showed that the majority of the strains isolated from the mixed culture were able to grow in the presence of NNT or NT. A total of 20 different isolates were isolated from the mixed culture. Individual isolates were grown in Stanier’s minimal medium containing a single hydrocarbon as the source of carbon or carbon and nitrogen. Only one strain was found to grow solely in the presence of nitrobenzene as the source of C and N. Most of the other isolates were able to grow in the presence of naphthalene, toluene, acenaphthene, anthracene, fluoranthene and phenanthrene, n-dodecane, hexadecane, n-pentadecane, n-tetradecane, and n-octadecane. Planktonic and immobilized cells of the controlled mixed culture (ATCC 55644) were grown in separate Sequential Batch Reactors (SBR) using Stanier's media, to which naphthalene, nitrobenzene and toluene were added as the sole source of C and/or N. Biodegradation was determined by measuring the residual hydrocarbon in the SBR and the amount of trapped volatile organic carbon (VOC) and the evolved CO2. Gas chromatography data showed that immobilized cells were able to degrade NNT faster than the planktonic cells. This observation was confirmed by CO2 evolution. Over time the loading of hydrocarbon was significantly increased from a starting level of 400 ppm (Naphthalene), 100 ppm (Nitrobenzene), and 500 ppm (toluene), to a final level of 3000 ppm (Naphthalene), 400 ppm (Nitrobenzene), and 1600 ppm (toluene). While increasing nutrient loading, the frequency of re-feeding with hydrocarbons was changed from an initial re-feeding every 60 hrs to a final re-feeding frequency of 18 hrs. The experiments clearly showed that the attached, mixed microbial community was able to effectively and rapidly degrade high concentrations of hydrocarbons. This demonstrated the practical advantages of employing attached, mixed microbial cultures in a SBR.