Application of a methodology for categorizing and differentiating urban soundscapes using acoustical descriptors and semantic-differential attributes.

A subjective and physical categorization of an ambient sound is the first step to evaluate the soundscape and provides a basis for designing or adapting this ambient sound to match people's expectations. For this reason, the main goal of this work is to develop a categorization and differentiation analysis of soundscapes on the basis of acoustical and perceptual variables. A hierarchical cluster analysis, using 15 semantic-differential attributes and acoustical descriptors to include an equivalent sound-pressure level, maximum-minimum sound-pressure level, impulsiveness of the sound-pressure level, sound-pressure level time course, and spectral composition, was conducted to classify soundscapes into different typologies. This analysis identified 15 different soundscape typologies. Furthermore, based on a discriminant analysis the acoustical descriptors, the crest factor (impulsiveness of the sound-pressure level), and the sound level at 125 Hz were found to be the acoustical variables with the highest impact in the differentiation of the recognized types of soundscapes. Finally, to determine how the different soundscape typologies differed from each other, both subjectively and acoustically, a study was performed.

Efficiency of a biological aerated filter for the treatment of leachate produced at a landfill receiving non-recyclable waste.

The feasibility of a biological aerated filter for the treatment of a partially stabilized leachate from a landfill receiving non-recyclable wastes was assessed in laboratory-scale experiments. Maximum COD, BOD(5) and TSS removal efficiencies achievable by the biofilter as well as the optimal hydraulic and organic loading rates were determined by laboratory-scale tests in batch and continuous mode. Experiments in batch mode which lasted for 7 days showed that COD and BOD(5) removal efficiencies were stabilized after the second day of operation and kept at around 56-60% and 83-97%, respectively, for the rest of the period studied. The remaining fraction (approximately 40% of the COD) was found to be composed of recalcitrant or not easily biodegradable compounds. The COD and BOD(5) removal efficiencies decreased with increasing hydraulic loading rates. The plant worked under optimal conditions at hydraulic loading rates of 0.71 and 1.41 m(3)/m(2)d (hydraulic retention times of 15.95 and 7.97 h, respectively) and at COD loading rates below 14 kg COD/m(3), where COD removal efficiencies were around 60%. TSS removal efficiencies were not significantly influenced by the hydraulic loading rate. The results obtained demonstrated the feasibility of a biological aerated filter for the removal of the biodegradable fraction of the organic matter contained in the leachate. However, a physicochemical process was found to be necessary as pre- or post-treatment for the removal of the recalcitrant fraction.

Evaluation of the quality and treatability of leachate produced at a landfill connected to an urban waste composting and recovery plant at Alhendin (Granada, Spain).

The leachate produced at a landfill adjoining an urban waste composting and recovery plant at Alhendin (Granada, Spain) was sampled for a period of more than 3 years from February 2003 until July 2006. The main pollutant parameters (COD, BOD(5), solids, nitrogen, main anions and cations, pH, Eh and conductivity) were analysed with the aim of selecting the most effective treatment for the leachate. The results obtained showed high concentrations of different pollutants with COD and BOD(5) values up to 74,133 mg/L and 39,000 mg/L respectively. Seasonal changes in leachate composition were mainly attributed to differences in rainfall, temperatures, and evaporation rates. Our study classified the Alhendin landfill leachate as a partially stabilized leachate because of: (i) its management strategies (storage at artificial ponds and recirculation); (ii) the coexistence in the landfill of active and closed cells with wastes of different ages and at different decomposition phases. The leachate quality data obtained was statistically evaluated using various statistical tools. A good correlation was found between many of the parameters analysed, some of which also showed good linear regressions. Principal component analysis allowed the reduction of most of the parameters analysed to four components: Component 1 (K(+), Mg(2 +), FTS, VDS, VTS, Na(+) and Cl(-)), component 2 (BOD(5)), component 3 (TDS, TS, FDS and conductivity) and component 4 (pH, FSS, Eh and VSS). The results obtained are valuable for the selection of the best leachate treatment option. A combination of a physicochemical treatment and a fixed film biological system is recommended for this leachate.

Stability and efficiency of biofilms for landfill leachate treatment.

The objective of this work was to assess the feasibility of a fixed-film biological aerated filtration process for the treatment of the leachate produced at Harnhill landfill site (South Gloucestershire, UK). The laboratory scale plant consisted of four identical biological aerated filters (a triplicate and a "control" column) packed with small brick fragments. Biofilm formed within 24h of immersion of the support material in the reactor, and had a high resistance to antibiotics and other toxic agents. The plant maintained a stable operation in the 20-45 degrees C temperature range, showing the best results (35.4+/-6.6% COD removal and 73.9+/-5.5% BOD(5) reduction) at 40 degrees C. The lowest COD and BOD(5) values obtained at the outlet of the columns were 7067 mg/L and 1050 mg/L, respectively.