DETERMINATION OF ODOR SOURCES FOR CONTROL
The successful solution of odor pollution problems first requires an assessment of the nature and extent of the problems. A plant or facility that emits odor from a single source (such as ii stack or vent) requires less effort than a plant with a variety of odor sources that may number in the hundreds. In the latter case, there is a need to assess the problem in such terms as to achieve maximum reduction in odor at a minimal control cost. Quantitative and accurate measurements of the various emission sources and their contribution to the odor in the ambient air must be determined in order to identify and rank the various sources that should receive priority for control. Accurate measurements of odor strength relative to concentration are also useful for defining the degree of control necessary for the single-source situation. Attempts to relate source odor measurements with ambient odors by the use of diffusion equations have met with varying degrees of success.1.2 Wohlers,l utilizing an evacuated bulb technique for sampling stack gases from a petroleum coking plant, a kralt paper mill, an anion-garlic dehydrating plant, and a rotogravure printing plant, found that odor measurements at the stacks did not agree in all cases with the calculated dilutions at the distances in the field where the odors were noted. Hogstrom2 demonstrated that a fluctuating plume dispersion model can be used to give realistic estimates of odor frequencies around a point source when the odor thresholds of the chimney gases (sulphate pulp factory) are determined by sampling and sensory methods described by Lindvall.3 Our experience in sampling and evaluating odors has indicated that existing sampling techniques such as ASTM syringe method have seriously underestimated the magnitude of odors emitted by a factor in the range of 2OO-2O,OOO.4 We believe that inadequate sampling and evaluation techniques are the major reasons for reported “failures” of dispersion estimates in predicting ambient odors. In our technique, we use trained odor chemists to carry out odor surveys of the surrounding areas to define the odor types and intensities perceived off-site and to conduct in-plant surveys to identify all significant odor sources. T o supplement this, we have developed a source-sampling detailed laboratory odor-evaluation technique to allow comparison of the various odor sources and to make use of predictions based on dispersion equations. We have observed reasonably good correlation between predicted odor intensities from the source analyses determined in the laboratory and those observed by our analysts in the field. OFF-SITE SURVEY
Theory and methods for odor evaluation
The typical study of the sense of smell is concerned with the effects of a single odor substance. Most of our knowledge therefore applies to pure substances and not complex gas mixtures 27,42,66. In real life, however, most odors are complex mixtures of various components in rather low concentrations. Although much is still unknown about the functioning of the olfactory system, the knowledge available gives an impressive picture of its capacity 22. For example, the ability to discriminate among odorous compounds is enormous even in the ever present odorous environment zs. Further, the sense can handle a wide range of stimulus concentrations and can often detect odor substances at the ppb level ~. On the other hand, the sense of smell is easily fatigued by continuous and constant odor exposure, though it recovers fast on the termination of exposure 38,42. The development of optimal methods for sensory odor evaluation using human observers presents both a challenge and a promise, regardless of whether the odor system is used as a measurement tool or as an indicator of environmental pollution. In the following, theories and methods for odor evaluation are discussed. Examples are given from laboratory as well as field research. Needless to say there is not much difference in the methodological requirements of basic and applied research.
Assessment of Ground Regeneration around Borehole Heat Exchangers between Heating Seasons in Cold Climates: A Case Study in Bialystok (NE, Poland)
Based on the experimental studies, the process of ground regeneration around the borehole loaded with brine-water heat pumps working exclusively for heating purposes in the period of four consecutive heating seasons in a cold climate was presented. The research was conducted in north-eastern Poland. The aim of the work is to verify the phenomenon of thermal ground regeneration in the period between heating seasons on the basis of the recorded data and to check whether the ground is able to regenerate itself and at what rate. It was noticed that the ground does not fully regenerate, especially during heating seasons with lower temperatures. In the analyzed period, from 22 September 2016 to 12 October 2020, the ground probably cooled irreversibly by 1.5 °C. In order to illustrate and evaluate the speed of changes in the ground, the one’s profile with an undisturbed temperature field was presented for each month of the year. The presented results can be a very important source of information for the analysis of geothermal conditions occurring in the ground. They can be used to verify mathematical models and conduct long-term simulations that allow us to see the complexity of the processes taking place in the ground.