Advanced Environmental Pollution Monitoring & Control PDF

ENVS 525 Advanced Environmental Pollution TERM 241 Air Pollution: Monitoring & Control...

ENVS 525 Advanced Environmental Pollution TERM 241 Air Pollution: Monitoring & Control Dr. Bassam Tawabini Sep., 2024 1 Air Quality Air Quality can be affected in many ways by the pollution emitted from these sources. These pollution sources can also emit a wide variety of pollutants. The EPA has pollutants classified as the 6 principal pollutants: (CO, O3, NOx, SOx, PM, Pb) The Clean Air Act established two types of: ⚫ Primary standards are designed to establish limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. ⚫ Secondary standards set limits to protect public welfare, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings 2 1  US Ambient Air Quality Standards Pollutant Primary Stds. Averaging Times Secondary Stds. Carbon Monoxide 9 ppm (10 mg/m3) 8-hour None 35 ppm 1-hour None (40 mg/m3) Lead 1.5 µg/m3 Quarterly Average Same as Primary Nitrogen Dioxide 0.053 ppm Annual (Arithmetic Mean) Same as Primary (100 µg/m3) Particulate Matter (PM10) 50 µg/m3 Annual (Arith. Mean) Same as Primary 150 ug/m3 24-hour Particulate Matter (PM2.5) 15.0 µg/m3 Annual (Arith. Mean) Same as Primary 65 ug/m3 24-hour Ozone 0.08 ppm 8-hour Same as Primary Sulfur Oxides 0.03 ppm Annual (Arith. Mean) ------- 0.14 ppm 24-hour ------- ------- 3-hour 0.5 ppm (1300 ug/m3) 3 Air Quality Index 4 2  Estimating Air Emissions CO, Pb, NO2 , and SO2 are emitted directly from sources, while ground level O3 is formed when NOx and VOCs react in presence of sunlight. PMs can be directly emitted, or it can be formed indirectly when emissions of NOx, SOx, ammonia, organic compounds, and other gases react in the atmosphere. ⚫ Air concentrations based on actual measurements of pollutant concentrations in the ambient (outdoor) air at selected monitoring stations. ⚫ Air emissions based on engineering estimates of the total tons of pollutants released into the air each year (indirect) Air emission estimates are based on many factors : Actual measurements Levels of industrial activity Fuel consumption Vehicle miles traveled Other estimates of activities that cause pollution. 5 Air Quality Monitoring Methods of Monitoring ⚫ Industrial Stack Emission ⚫ Ambient Air Emission (Outdoor Air) ⚫ Indoor Air Pollution 6 3  The Need For Air Monitoring For Government ⚫ To provide data for determining appropriate emission limits. ⚫ To provide data for determining compliance. ⚫ To provide data for health risk assessments. ⚫ To provide data for dispersion modeling. For industry ⚫ To evaluate air pollution control equipment. ⚫ To provide information for design of new process and control equipment. ⚫ To provide information on process operations. 7 Stack Emission 8 4  Types of Stack Emission Monitoring Periodic Measurements: ⚫ A measurement is carried out at periodic intervals (i.e. every hour or day or week…etc.). ⚫ Samples are usually, withdrawn from the stack (extractive sampling). ⚫ Spot or “grab” samples are collected over a period of time. ⚫ Samples may be obtained over hours, or an instrumental / automated technique may be used, where the sampling and analysis of the substance is fed to an on-line analyzer (non-extractive). ⚫ Alternatively, a technique may be used where a sample is extracted on site and analyzed later in a laboratory. Continuous Emission Monitoring (CEM): ⚫ An instrument permanently located at or near the stack continuously mentoring the levels of hazards air pollutants (rack). 9 Representative Air Sampling in Stacks The principle behind any sampling activity is that a small amount of collected material should be representative of all the material being monitored. Number and location of samples that are needed to make up a representative sample depends on how homogeneous the material is. If very homogeneous, only a few samples required. otherwise, many more samples will be required. 10 5  Representative Air Sampling in Stacks.. A) Measurement of concentrations of gaseous species alone Easier than sampling gas & PM stream. Approach is to choose a sampling location where the gases are well mixed. Sampling can often be from a single sampling point in the sampling plane. If the mass emission rate is to be calculated, the gas volumetric flowrate will need to be measured; this will require temp. and velocity measurements to be made at several points across the sampling plane. It is important that each of these is chosen to be suitable for the application in question. ◆ A safe means of access to the sampling position ◆ A means of entry for sampling equipment into the stack ◆ Adequate space for the equipment and personnel ◆ Provision of essential services, such as electricity 11 Representative Air Sampling in Stacks B) Representative sampling of particulates & gases: ⚫ Gases can become non-homogeneous due to differences in chemical composition, or temp. and velocity, which may lead to stratification. ⚫ Where gas is also carrying particulates (PMs) along the duct, there is likely to be even less homogeneity. So, special measures must be taken to ensure samples are representative. ⚫ Inertial effects (gravity and duct geometry) lead to the particles being unevenly distributed in the duct. ⚫ Samples must be obtained from multiple sample points across the sampling plane to give an overall average of the particulate emission. ⚫ Isokinetic sampling is carried out using a recognized international standard such as US EPA Method 5 sampling train. The collected sample is analyzed to determine the pollutant concentrations. 12 6  Isokinetic Sampling For extractive methods of PM, the sample must be collected isokinetically. This means velocity and direction of gas/PM at the nozzle should match that of the approaching gas stream travelling in the stack. ⚫ It is not a quick, simple exercise – It is fairly involved and complex ⚫ Time consuming - setting up equipment, preliminary checks etc. ⚫ Specifically used for determining flue gas particulate concentrations in a duct or stack ⚫ Equipment specifically designed for Isokinetic Sampling 13 Number of Sampling Points 14 7  Range of Stack Gas Measurements Particulate Matter (PM) Acid Gases Metals Dioxins and Furans Amino acids and proteins Combustion products Full gas suite including; ⚫ VOC’s, CO, NOx, SO2, CO2 and O2 15 Stack Gas-Measurement Manual Gas Sampling 1: heated suction tube 2: gas sampling bottle 3: high vacuum pump 4: vacuum gauge 5: special orifice 8 Measurement of Particulate Matter from Stack Continuous Emission Monitoring CEM – Stack Monitoring 18 9  Ambient (outdoor) Air monitoring 19 Ambient Air Quality Monitoring Stations The objectives for ambient (outdoor) air quality measurements are : Provide air pollution data to the general public in a timely manner Support compliance with national and international air quality standards and emission strategy development Support for air pollution research studies in exposure and health assessment and sources identification. 20 10  Ambient Air Quality Monitoring Stations Air Quality Monitoring Stations are usually equipped with rack-mounted analyzers for measuring gases and PM as well as sophisticated data logging equipment, including GSM modem links to allow remote data retrieval, calibration and system performance checks. Air quality monitoring stations also record meteorological information such as, wind speed, wind direction, air temperature, atmospheric pressure, temperature, relative humidity, rainfall etc. Windrose-Graphical presentation of the frequency of occurrence of wind direction and wind speed categories. This information is used in the modeling and interpretation of the data Windrose 21 Mobile Analyzer / Laboratory Vans 22 11  Ambient Air Quality Monitoring Stations Gas Analysis ⚫ Colorimetric Method ⚫ Chemical-Sensing Electrodes and Electrochemical Cells. ⚫ Non-dispersive Infrared (NDIR) ⚫ Gas Chromatography (GC) Flame Ionization Detector (FID) Thermal Conductivity Detector (TCD) Chemiluminescence Mass Detector (MS) Gas Analyzers ⚫ Sulphur dioxide (SO2) using UV/fluorescence analyzers ⚫ Hydrogen Sulfide (H2S) analyzer, utilizing catalytic conversion to SO2. ⚫ Carbon monoxide (CO) using GFC-IR analyzer. ⚫ Ozone by U/V analyzer. 23 Measurements of Particulate Matter (PMs) - High-vol: >1 m3/min - Medium-vol: 0.1 m3/min - Low-vol: