Emissions of chemical compounds and bioaerosols during the secondary treatment of paper mill effluents

This study identified and quantified the main chemical compounds-the substa nces responsible for the disagreeable odors-and the bioaerosols emitted dur ing the biological treatment of paper mill effluents. It also identified th e characteristics of the process that effects the generation or diffusion o f these substances. All treatment stages were evaluated. Measuring sites we re located as closely as possible to the potential emission sources. Measur ements were taken in the summer in 11 paper mills during a 2- to 3-day peri od in each mill. Chemical compounds were evaluated by direct-reading instru ments; bioaerosols were sampled by impaction and counted. Sulfur compounds, emitted into the air when the effluent or the sludge is stirred, had the h ighest concentrations; their presence was attributable to such things as kr aft-type paper pulp. Next in concentration were the carbon and nitrogen oxi des, ammonia, and some organic acids, produced by the action of microorgani sms. These acids are found mainly in the sludge environment. Terpenes, whic h come from wood, are present at various locations in paper mills. Odor per ception thresholds for most of these substances are much lower than those e stablished to protect the health of workers. Significant concentrations of total bacteria, total molds, and endotoxins were measured at several sites. Gram-negative bacteria were high at only one site, whereas the mold Asperg illus fumigatus was occasionally present at low concentration. No actinomyc etes bacteria were detected. The highest concentrations were measured where there was water or dust aerosolization. Emissions are therefore controlled by controlling the operations that lead to the dispersion of water and par ticles into the air.