Physicochemical analysis of hospital liquid effluents: a case in Belo Horizonte, Brazil

Hospital wastewater is composed of different types of chemical substances with scarce information about its biodegradability and environmental toxicity. This study characterized hospital effluents generated in the city of Belo Horizonte (Brazil) through data compilation provided by the local sanitation company and statistical analysis associated with parameters established by a technical rule which proposes the regulation and monitoring of liquid effluents discharge from industrial and commercial activities in the public sewer systems. Data covered a total of 78 small, medium-sized, and large establishments, presenting 395,586 results of monitored parameters from 10/09/2007 to 01/30/2019. Statistical analysis included normality test, Principal Components Analysis and variance comparison using software R. The analysis of correlograms showed a positive correlation between the parameters chemical oxygen demand (COD) and biochemical oxygen demand (BOD) in the analyzed hospitals, which also showed a strong correlation with the surfactants agents. Regarding the biodegradability effluent, 13.21% of samples obtained a BOD/COD ratio lower than 0.3. Among the nonconformities, 73% of records were found for total suspended solids, 25% for BTEX (benzene, toluene, ethylbenzene, xylenes), and for metals, the values were close to zero. The metals parameter showed less relevance. The analyzes also indicated that there was no seasonality evidence of nonconformities over the years. At last, the multiple comparisons indicated significant differences between the profiles of liquid emission effluents depending on the hospital's classification. Small size hospitals had the least impact.