A Screening Evaluation of Glutaraldehyde Deposition from Cooling Tower Drift

摘要

A screening technique is presented for evaluating ambient concentrations and deposition from cooling tower air emissions. A wet cooling tower provides direct contact between the cooling water and the air passing through the tower. It will have air emissions when "drift" (liquid water entrained in air) is carried out of the tower in the draft. The drift droplets usually have the same chemical composition as the water circulating through the cooling tower. Cooling water contains chemicals to inhibit corrosion and microbial growth. This paper presents methods to evaluate the environmental impact of chemical emissions as responsible product stewardship. Drift deposition is more complex than particle deposition, because water droplets can shrink due to evaporation. Use of the EPA ISCST3 air dispersion model and its limitations are discussed. An example study is presented to calculate glutaraldehyde drift deposition. Three results of this study are: 1. Guidance is provided on selecting parameters that influence drift deposition; such as cooling tower operating characteristics, drift rate, chemical emission rate, and droplet size. 2. A meteorological data set was developed that reflects a range of meteorological conditions, for use when monitored hourly data are unavailable. 3. A correlation to 1-hour dry deposition was developed for annual and 24-hour averaging times.