Air Pollution Emission Factors for Medical Waste Incinerators

Abstract

This paper presents the results of an extensive literature survey and data analysis conducted to determine uncontrolled and controlled pollutant emission factors (mass pollutant emitted per mass waste incinerated) for medical waste incinerators (MWI). Pollutant emission factors were calculated separately by type of medical waste (red bag, general hospital, and pathological waste), and add-on air pollution control (APC) equipment (wet scrubber systems, or dry scrubber/baghouse combinations). Pollutants for which emission factors were determined are particulate matter, carbon monoxide, hydrogen chloride, sulfur dioxide, nitrogen oxides, various metals, dioxins/furans, and selected volatile organic compounds (VOCs). In addition, the combustion gas produced per mass of waste incinerated was determined in order to compute expected pollutant concentrations in the exhaust gases based on the pollutant emission factors.

Data from 40 MWIs burning various forms of medical waste and equipped with or without add-on air pollution control equipment were used to develop pollutant emission factors. Technical reports of emission tests were reviewed in detail, and calculations were made to convert reported outlet stack gas concentrations (before and after APC equipment) to pollutant emission rates. Reported waste feed rates were combined with the pollutant emission rates to produce emission factors. The emission factors were then grouped and averaged within appropriate groups to give best-estimate emission factors for various pollutants. Also, air pollution control equipment efficiencies were determined for each pollutant.

Wide variations were observed for many of the pollutant emission factors, both controlled and uncontrolled. These variations are most likely a result of different operating conditions of APC equipment (e.g., caustic feed rates, water feed rates, and inlet temperatures), variable waste compositions, and differing incinerator operations among the reported MWI facilities. Based on the data examined, it appears that control of dioxins/furans by wet scrubber systems is, on the average, twice as good as that by dry scrubber/baghouse combinations. However, control of metals by dry scrubber/ baghouse combinations appears to be far superior to that of wet scrubber systems.