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"Port Townsend Paper Corporation created an Odor Survey Team during the summer of 1993. The purpose of the team was to determine the mill emission sources causing odors offensive to community residents."
Port Townsend Paper Corporation ODOR SURVEY REPORT September 8, 1993 Authored by the Odor Survey Team Marco Youngberg and Ross Zimmerman PDF created with pdfFactory Pro trial version www.pdffactory.com ABSTRACT Port Townsend Paper Corporation created an Odor Survey Team during the summer of 1993. The purpose of the team was to determine the mill emission sources causing odors offensive to community residents. Local newspapers published information on the project and a hot line was set up to take odor reports and complaints. The team met with the callers to fill out an informational survey and ask them to take an odor sample test. Five emission odors captured in Tedlar bags were compared to the perceived odors experienced by the caller. The compiled information will allow the mill to concentrate future efforts on the emission sources that have the greatest impact in the community. Page 2 PDF created with pdfFactory Pro trial version www.pdffactory.com INTRODUCTION Port Townsend Paper Corporation is a kraft mill and like other kraft mills is characterized by malodorous organic sulfide gases. Over the years, numerous complaints have been directed toward the mill concerning the mill odor. In 1992 the Washington Department of Ecology held a series of public meetings and concluded that most townspeople are concerned with the odors caused by local pulp and paper mills. It was evident that few people knew what was causing the aroma or its impact on the community. A survey team was organized to: 1. Identify odors 2. Identify odor sources 3. Register complaints and concerns The identified odor sources could then be examined more closely and possible remedies could be determined. The P.T.P.C. project was modeled after the ITT Rayonier P.A. survey concluded in 1992. Emission Sources Eight major odor emission sources were found. These odors were observed and investigated by the Odor Survey Team It was found that four of the eight odors were similar to each other so all four were grouped into one category. This distinct odor was synonymous with the M&D digester. The M&D digester Esco valve vents are the largest and most pungent of the four sources with similar odors. The remaining four distinct mill odor sources are: the power boiler, the recovery furnace, the lime kiln, and the aeration stabilization basin (ASB). The emission sources from which samples were taken for the survey are described in the following paragraphs. M&D Digester The M&D digester is a continuous digester used to produce pulp. The digester is operated under pressure while a rotating Esco valve is used to feed the sawdust into the digester. As the valve rotates, some vapors from inside the digester are forced out through the valve and escape to the atmosphere. Included in this odor category is the brown stock washer vent, smelt dissolving tank vent and the digester fill vent. Each of these sources smell similar to a very dilute sample from the M&D digester vents. Page 3 PDF created with pdfFactory Pro trial version www.pdffactory.com Power Boiler The power boiler uses hog fuel (bark and wood scraps not used in the pulping process) as its primary fuel source to produce heat and steam for the mill. It also bums oil and primary treatment sludge as supplementary fuel. The combustion products from the firing chamber are directed through a wet scrubber to remove the particulate and ash from the air. The extremely hot air passing through this wet scrubber produces a large visible steam plume coming from the stack. Recovery Furnace 95% of the pulping chemicals used to make kraft paper are recyc1ed within the recovery furnace. Most of the sulfur containing compounds which enter the furnace are fully oxidized and recovered for reuse in the process. A trace of S02 is produced by this combustion process but the concentration of 10 to 50 ppm is well below the limit of 200 ppm set by the Washington Department of Ecology. The new electrostatic precipitator, completed in May, 1993, charges and removes fine particulate matter from the recovery furnace emissions at over 98% efficiency. Total Reduced Sulfur (TRS) gases exiting the furnace are generally below 10 ppm Lime Kiln The lime kiln serves two functions for the mill. Its main purpose is to convert calcium carbonate precipitate (obtained from the white liquor c1arifier) into calcium oxide using high temperatures (2200° to 2400°F). The calcium oxide is then used to produce white liquor. The lime kiln also serves as an incinerator for odor gases that the mill collects from other processes. Odor gas compounds are broken down and oxidized to form compounds that can be scrubbed form the exhaust using a Venturi scrubber system. Aeration Stabilization Basin (ASB) The ASB is a series of treatment channels that clean the water used in the pulp and paper making process. This secondary or biological treatment is nothing more than a duplication of nature's own purification process, except that it is carried out under contained and controlled conditions at accelerated rates. Under aerobic conditions, micro-organisms (mostly bacteria and fungi) consume oxygen to convert wastes into the ultimate end products of carbon dioxide and water. The anaerobic bacteria take over and continue biological action producing methane and hydrogen sulfide. Pulp and paper mill wastes are essentially non-toxic following this biological treatment. There are two components for the peculiar ASB odor. For one, sulfur gases produced from biological action is highly noticeable in low concentrations. Secondly, foul vapors condensed in the mill get dissolved in the mill effluent. This condensate is transported to the ASB where the mechanical aeration devices free the dissolved odor gases into the atmosphere. Page 4 PDF created with pdfFactory Pro trial version www.pdffactory.com ODOR SURVEY Purpose The primary purpose of the survey was to identify the odorous emission sources and their relative contributions as perceived by the community. The secondary goals of the survey were: 1. To determine people's major concerns about the mill's emissions. 2. To determine the time of day which people tend to notice the mill odor. 3. To determine the frequency and intensity of odors. 4. To determine what areas and relative distances the odors are noticed. 5. To educate and inform the community and answer general questions. Odor Sampling Samples were collected at five emission points using a portable sampling device. A stainless steel sample rod was connected with Tygon tubing to a unidirectional hand pump. The sample bag was then connected to the pump. Each sample point required specific methods to reduce chances of contamination. The ASB pond required air bubbled through the effluent to acquire the characteristic odor (Figure 1). A 50% dilution was necessary to balance odor intensities. The M&D digester emissions were cooled and filtered through a cold water flask (Figure II). Dilution required 6 parts M&D and 94 parts ambient air. Separate tubing and pumps were designated for this sample point due to the strength of the odor at the source. Dilutions remained 50% for the power boiler, lime kiln, and the recovery furnace odor samples. Numbered bags always contained the same source during each refilling and were flushed with nitrogen every three days to prevent change in odor. Pump and tubing were also flushed after each use to prevent contamination. Page 5 PDF created with pdfFactory Pro trial version www.pdffactory.com Data Collection The mill's odor survey program was designed, planned, and implemented beginning June 18th and lasted until September 3rd. There were two types of data collected during the survey. One type was personal data received from the people who smell the odors in the community. The other type was routine data taken by the Odor Survey Team. Personal Data Collection Articles in local papers and weekly advertisements publicized the project and a survey hot line was set up to facilitate odor complaints. People were encouraged to call when they detected any odor believed to be emanating from the mill or had any questions or comments about these odors. An answering machine would take any calls that occurred after business hours. In response to a call, the survey was described and the caller was encouraged to participate in a personal interview and odor sample test. The written survey included these questions: When is the odor smelled most often? How many times per month, on average, is the odor noticed? Is it always the same odor? If not, how many? How long have you lived in the area? In this time, has the odor intensity changed? How does the odor affect your lifestyle? What are your major concerns? Health? Comfort? Environment? This information coupled with their location and general comments and concerns allowed the Odor Survey Team to determine the impact the odors had on the community. Page 6 PDF created with pdfFactory Pro trial version www.pdffactory.com The bag sample test consisted of sampling six Tedlar bags containing odors from each of the major odor sources. The residents were asked to compare these samples with the odors they smelled at home. Routine Data Collection A daily route was developed to determine the noticeable odors in the community. The route extended to a 2 mile radius from the mill site covering the land portion of the area. Odors at or near 15 specific locations were rated from 1 to 10. An odor rating of 1 was barely noticeable and a rating of 10 would be similar to the intensity at the source. If an odor was discernible, the source was noted by the corresponding rating number. Fires, road construction projects, and other strange odors were noted for reference. Weather, wind speed and direction, barometric pressure, temperature and unusual mill operations were also recorded. Frequencies and intensities were charted versus check point locations for general hot spots and flow patterns. Due to the variables related to weather conditions and fluctuations, odor patterns would change throughout the day. Page 7 PDF created with pdfFactory Pro trial version www.pdffactory.com RESULTS Personal Data The Odor Survey Team received 117 calls between June 30th and September 3, 1993. Some callers preferred not to be visited by the team but information from the phone call was registered. The team was able to visit 66 people and give them the odor sample bag survey. Odor responses as far as eight miles away reported smelling the mill. Odor Survey Team observations of mill odor occurred at 10 of the interview locations so survey information relied heavily on the caller to make positive odor identifications. The majority of the 66 people surveyed identified two of the samples as the odor they encounter at their homes. Figure III shows that 89% chose the ASB and 88% chose the M&D digester. It should be noted, there are three additional sources having the same characteristic odor (though not as strong) as the M&D digester vent. These sources are: the brown stock washer vent, the smelt dissolving tank vent, and the digester fill vent. Figure III also shows 35% of the people surveyed identified the recovery furnace as a possible contributor to the mill odor. This implies that the recovery furnace might have a small community impact. The lime kiln and power boiler each had 11% of the people chose them while 10% chose the bag with plain air in it. One question on the survey form asked people to identify their major concerns about the mill odor. Figure IV shows that 66% of the 64 people who took the survey are concerned about the odors on their health, 66% are concerned about their general comfort, and 58% of the people are concerned about the environment. Page 8 PDF created with pdfFactory Pro trial version www.pdffactory.com Another question on the survey asked people to identify the time of day that the mill odor was most prevalent. Figure V shows that the mill odor was experienced primarily at night and in the mornings. There are two explanations. Air temperatures are cooler in the mornings and at night resulting in calm winds. In addition, sulfur odors are heavier than air and tend to settle near the ground. When the sun comes up and warms the land, the winds pick up and the odors are carried away. Long term residents noticed odors more in the winter months for the same reasons. The second explanation relies on the fact that more people are at home and inactive at night and in the mornings and are more apt to notice any changes in the ambient odors. Page 9 PDF created with pdfFactory Pro trial version www.pdffactory.com Figure VI shows that the majority of the calls were localized in two major areas: the uptown district of Port Townsend and the hill west of Kah-Tai Lagoon. Routine Data Figure VII is a map of the immediate area surrounding the mill. Dark lines trace the daily route driven by the Odor Survey Team. Circles indicate check points where the odor observations took place. The numbers next to each dot represents the number of times (out of 87 total observations) that the mill odor was encountered. The color represents the average intensity rating at that observation point. From Figure VII, it can be seen that the mill odor was encountered more frequently west of the mill on Mill Road and tended to carry up the valley directly west. It was found that the direction and intensity of the mill odor was largely dependent on the weather conditions. Cool days with high humidity and calm winds were most conducive for the odors to be noticeable in the community. Page 10 PDF created with pdfFactory Pro trial version www.pdffactory.com Page 11 PDF created with pdfFactory Pro trial version www.pdffactory.com Page 12 PDF created with pdfFactory Pro trial version www.pdffactory.com CONCLUSIONS The Odor Survey which took place during the summer of 1993 was a successful way to gain valuable information about the odors emanating from the Port Townsend Paper Corporation mill in Port Townsend, Washington. The success of the program was largely dependent on community participation. Thanks to this participation, the Odor Survey Team was able to identify the emission sources perceived by the community to be the most offensive. The mill can now concentrate their odor reduction efforts on these sources. The major conclusions determined by this survey are: 1. The M&D digester (with related odors) and the ASB are major contributors of offensive odors experienced in the community. The recovery furnace, lime kiln, and power boiler are minor in comparison. 2. People are concerned with and uninformed about mill emissions. 3. The mill odor is noticed by the community primarily at night and in the early morning due to weather patterns, not changes in mill operations. 4. Most complaints occurred in the Uptown District and on the hill west of Kah- Tai Lagoon. The farthest registered complaint was eight miles away. 5. The mill odor is strongest and encountered most often in the valley west of the mill. Odors were more noticeable in low lying areas. Page 11 PDF created with pdfFactory Pro trial version www.pdffactory.com REFERENCES 1. Henllnen, M., Winges, K; "Community Participation in a Mill Sponsored Odor Survey", TAPPI Environmental Conference; 1993. 2. Kerger, B. D., Barfield, L.; "Current Understanding of Hydrogen Sulfide Toxicity With Specific Reference to Regulatory Policies and Pulp and Paper Mill Emissions", McLaren/Hart Environmental Engineering; July, 1992. 3. Sjostrorn, E.; Wood Chemistry Fundamentals and Applications, Academic Press Inc.; 1981. 4. Smook, G. A.; Handbook for Pulp & Paper Technologists, Joint Textbook Committee of the Paper Industry; 1982. 5. Williams, J.; "1989-1990 Annual Report, Air Quality Program", Washington State. Department of Ecology; July, 1991. 6. Workers Compensation Board of British Columbia; "Mercaptans in Industry", pamphlet; 1991. Page 12 PDF created with pdfFactory Pro trial version www.pdffactory.com
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