Urban Solid Residues Research Articles

Determination of total and soluble chromium(VI) in compost by ion chromatography–inductively coupled plasma mass spectrometry

Ion chromatography coupled to inductively coupled plasma quadrupole mass spectrometry (IC-ICP-MS) was used for the specific determination of Cr(VI) in compost samples. Potential interferences from humic substances, carbon and chlorine species were avoided by chromatographic separation. Solution detection limits below 150 ng L−1 were obtained for injection volumes of 100 µL. Total Cr(VI) was determined by the previous alkaline digestion of the sample, following the method EPA3060A. Recoveries of pre- and post-digestion spikes (2.5 µg and 50 µg L−1 of Cr(VI) as potassium chromate, respectively) were better than 90%, indicating that the combined method can provide accurate results in spite of the high content of organic matter. Detection limits of 6 ng g−1 were obtained for the total Cr(VI) determination, the repeatability was better than 2% (at 30 µg L−1), and the reproducibility between extractions was around 6%. Soluble Cr(VI) was determined by the leaching of compost samples with water (liquid-to-solid ratio 10 : 1). A total Cr(VI) content of 1.2 µg g−1 was obtained for a compost from urban solid residues, whereas the soluble Cr(VI) in the pH range 4–10 was below the detection limit of the leaching method (1 ng g−1).

Lixões inativos na região carbonífera de Santa Catarina: análise dos riscos à saúde pública e ao meio ambiente

The existence of inactive dumps considerably increases the so-called "environmental liability"; so much so that the final destination of urban solid residues takes a prominent place on the list of environmental issues of societies(1). In the state of Santa Catarina, it can be said that, currently, the real conditions of the "final destination deposits", or simply the inactive dumps, is officially unknown. This is maybe most evident in the carboniferous area of the state that already suffers from the environmental impact of coal mining. This study attempts to make a survey of the inactive dumps in the carboniferous area of Santa Catarina, analysing the risks they represent to public health and to the environment. The results gathered show that, of the eleven municipal districts in the carboniferous area, nine have inactive dumps. In these nine districts, there are eleven inactive dumps that, according to the this evaluation, represent a large risk to public health and the environment when the parameters analysed are taken into acount.

Efeito do composto de resíduo sólido urbano no teor de metais pesados em solo e goiabeira

O trabalho foi realizado no município de Cachoeiras de Macacu (RJ) com o objetivo de avaliar as várias formas dos metais Cu, Cr, Mn, Ni, Pb e Zn em solo Gleissolo pouco húmico tratado com composto de resíduos urbanos, e as concentrações desses metais nas folhas e nos frutos de goiabeira (Psidium guajava L.). Foram utilizadas três áreas com históricos distintos: área que recebeu doses de 40 t.ha¹ de composto de resíduo sólido urbano (CRSU) na superfície por onze anos consecutivos; área com uma única aplicação de CRSU na cova; e área-controle que não utilizou CRSU e sem goiabeiras. As amostras de solo foram tomadas dentro de cada área, nas camadas de 05; 515 e 1530 cm. A extração seqüencial dos metais contidos nas amostras (05 cm) de terra demonstrou uma tendência de redução das formas móveis ou mais biodisponíveis de metais pesados no solo com uso do CRSU. Houve aumento nos teores de metais pesados em folhas e frutos de goiabeira cultivadas em áreas que receberam CRSU; porém os teores obtidos estavam dentro da faixa considerada normal. Há necessidade de monitoramento dos teores totais de metais no solo e nas plantas, devido ao incremento dos teores de metais pesados em solos tratados com CRSU.

Diagnóstico sobre a disposição final dos resíduos sólidos urbanos da cidade de Maringá, Estado do Paraná, Brasil

This work is related to the diagnosis of the solid residue final disposal, identifying the most important factors responsible for the degradation and pollution of particular urban areas. The studied case was accomplished in the city of Maringá, State of Paraná, South of Brazil. Technical visits were accomplished "in loco", where the impacts of final solid residue disposal in the environment were appraised. The obtained data showed the urgent need of an adapted handling of the final disposal of the urban solid residue in the city. This fact was observed by the qualitative evaluation of the environmental impacts caused by inadequate final disposal and confirmed by means of the Embankments Index Quality (Índice de Qualidade de Aterros de Resíduos - IQR). The evaluation shows the degradation intensity of both environmental and human existence in that universe, considering that all the generated dejections in the city are indiscriminately thrown in a rubbish dump site. Results show that a final disposal site for the residue is urgently needed, so that such impacts are minimized. Thus, some parallel improving actions were taken in order to adapt the area, suggesting the interruption of the residue disposal in the site as well

Kinetic of thermal decomposition of residues from different kinds of composting

Non-isothermal kinetic parameters regarding to the thermal decomposition of the ligninocellulosic fraction present in compost from urban solid residues (USR) obtained through stack covered (SC) with composted material, comes from the usine in composing of Araraquara city, Săo Paulo state, Brazil, and from stack containing academic restaurant organic solid residues (SAR). The samples were periodically revolved round 132 days of composting. Results from TG, DTG and DSC curves obtained on inert atmosphere indicated that the lignocellulosic fraction present, despite the slow degradation during the composting process, is thermally less stable than other substances originated during that process. The lignocellulosic fraction decomposition, between 200 and 400°C, were kinetically evaluated through non-isothermal methods of analysis. By using the Flynn-Wall and Ozawa isoconversional method, the medium activation energy, Ea, and pre-exponential factor, lgA, were 283.0±14.6, 257.6±1.3 kJ mol-1 and 25.4±0.8, 23.2±0.2 min-1, to the SC and SAR, respectively, at 95% confidence level. From Ea and lgA values and DSC curves, Malek procedure could be applied, suggesting that the SB (Sestak-Berggren) kinetic model is suitable for the first thermal decomposition step.

The influence of pH in the hydrolytic stage of anaerobic digestion of the organic fraction of urban solid waste

The influence of the pH in the first stage, the hydrolytic stage, of the anaerobic digestion of the organic fraction of urban solid waste in a two phase anaerobic reactor was studied. The reactor was fed with a solution of the organic fraction of urban solid residues containing 5 to 7% solids. Four reactors with a working volume of 3 L were used, the experiments were done at three controlled pHs; 6, 7, and 8, and one with free pH, the temperature was keep at 37 degrees C in all the experiments. The higher degradation of TSS and VSS was obtained in the reactors operated at pH 7 and 8; 75% degradation of TSS and 85% degradation of VSS. The volatile fatty acids were determined at the different pH conditions, no significant differences were found, and as was expected, the acetic acid was found at the higher value among them (from 25 to 29 g/L). According to the results obtained it is possible to conclude that in the case of the hydrolytic stage of the anaerobic digestion of the organic fraction of urban solid waste it is not necessary to control the pH, the pH is kept stable by the buffer effect of the protein residues and other macromolecules present in the residue.

Modelo de gestão integrada de resíduos sólidos urbanos – estudo para o município de Maringá, Estado do Paraná

This work presents a model of integrated administration of the urban solid residues for Maringá city. Besides its modern technological character, with base in the results obtained in this research, it is constituted in an integration among the several phases, mainly in the differentiated collection, with several forms of final treatment/destination, that lead to a smaller environmental, social and economic impact, looking for the ransom of the citizenship, through the warranty of better life conditions for the less favored segments of society and better life quality. The model consists of an integrated management system, composed of: segregated collect, selective collect, screen units, composed unit and sanitary earthwork. The work presents a focus about the current situation in the matter of the urban solid residues in Maringá city, and it foresees a remediation action and the closing of the garbage place, beginning with the formulation of a technological model, implantation of the project and its management.

Influence of the addition of organic wastes on the metal contents of a soil

A 3-step sequential extraction scheme for soil metals was used to detect possible changes in the composition of metal species caused by several composted residues added to soils: urban solid residues (USR), waste from paper industry (WPI), and residues of olive oil industry (OI). In the first two fractions of the extraction process (soluble in weakly acid solutions and reducible) changes by USR and/or WPI can be observed, while the oxidisable fraction is much less affected. The data suggest a definite mobilisation of Zn by USR, but in general the increase is caused by the contribution of the metals originally present in the composts. OI is the least effective in altering metal species.