Determinação do tamanho mínimo de amostra para análise física de resíduos sólidos e elaboração de método para avaliação qualitativa da coleta seletiva

Abstract

Solid waste management in universities presents a challenge due to the multiple activities carried out and the diversity of generating sources. Determining the gravimetric composition, per capita generation, and specific mass of solid waste is an essential step in improving waste management. For this, it is crucial that characterization is based on a representative sampling. NBR 10.007/2004 recommends quartering as a sampling technique but does not specify the minimum amount of waste required to ensure representativeness. This study aimed to test different fractions of solid waste to verify their adequacy in the physical characterization of solid waste and to assess the quality of source segregation in selective collection programs. Six weekly samplings of recyclable materials were carried out, analyzing fractions corresponding to 100% (all collected bags during the analysis period), 50%, 25%, and 12.5%. The values were recorded in spreadsheets and supported the results of physical waste parameters such as specific mass, per capita generation, and gravimetric composition. The results indicated that the median weight of the bags ranged between 1.75 kg and 1.81 kg for the different fractions analyzed. The total sampled mass was 4.5% and 5.6% lower than the theoretical value in the 50% and 25% fractions, respectively. For the 12.5% fraction, the difference was 18%, indicating that this proportion may underestimate parameters such as the specific mass of the waste. Regarding gravimetric composition, the variation in the number of sampled bags did not change the percentage of materials such as paper, plastic, and cardboard. The qualitative analysis of the waste resulted in a reasonable classification, with ratings of poor, reasonable, good, and excellent, with final values ranging between 4.25 and 5.95 on a scale from 0 to 10.