Any technological study focused to reduce the odour impact must be based in several steps:  from an effective diagnosis, followed by modeling different treatment scenarios, and afterwards doing the Technical – Economic Evaluation (CAPEX / OPEX) of different corrective tecnologies.

   In the present paper, it is explained the different steps of the study for two real cases.

Silvia Nadal ¹*, Marisa Latorre ¹, Rubén Cerdá ² and J.M. Juarez-Galan ²

1. Sistemas y Tecnologías Ambientales S.A. C/Còrsega 112, local 1. 08029 Barcelona, Spain
2. Labaqua S.A. C/Dracma 16-18, Polígono Industrial Las Atalayas. 03114 Alicante, Spain.
* E-mail: snadal@sta-at.com
Tel.: +34 932 53 07 40

   Competing interests: The author has declared that no competing interests exist.

   Academic editor: Carlos N Díaz.

   Content quality: This paper has been peer reviewed by at least two reviewers. See scientific committee here

   Citation: Silvia Nadal, Marisa Latorre, Rubén Cerdá and J.M. Juarez-Galan, 2015, Case study: selection of the best odour reduction technologies for industrial and environmental emissions, taking into consideration: odour removal efficiency, CAPEX and OPEX, III International Conference of Odours in the Environment, Bilbao, Spain, www.olores.org

   Copyright: 2016 olores.org. Open Content Creative Commons license. It is allowed to download, reuse, reprint, modify, distribute, and/or copy articles in olores.org website, as long as the original authors and source are cited. No permission is required from the authors or the publishers.

   ISBN: 978-84-608-2262-2.

   Keyword: High Eficiency Biofilters, Biofiltration, Thermal Oxidation, Supplementary Pneumatical Propulsion.

Abstract

   Studies aimed at resolving episodes of environmental impact by odours are often complex and can involve undertaking various stages: effective diagnosis of the emissions, modeling the impact of the odours, and finally selecting and implementing the best corrective solution with a technical and economic evaluation (CAPEX / OPEX) of different remediation technologies. Such as improving the dispersion of emissions, or the application of technologies such as end of line biofiltration, Advanced High Performance biofiltration, chemical scrubbing, thermal oxidation or adsorption. The decision taken between one option or another will depend on factors such as process characteristics and emissions to be treated, the associated legal or environmental restrictions, proximity to population centers, the environment of the installation, and the investments involved in short to medium term. This paper presents details of this process as applied to two real-life cases.

1. Introduction

   Although there is already a great deal of experience currently available at national level in the treatment of odour emissions, still, in many cases, treatment technologies are installed by analogy, without considering that it is essential to study and carefully characterize the emission or emissions in each particular case before deciding what treatment system should be applied. Although various industrial activities such as the paper industry, the meat processing of wastes, or the chemical industry, can generate odour problems, the hedonic tone emission of each of these activities is different, due to the presence of various contaminants in those emissions. Some of these contaminants in odorous emissions, such as, for example H₂S, NH₃, some mercaptans and some aldehydes, are soluble in water or chemical solutions and may be washed out by scrubber systems; but other pollutants such as thioethers present in emissions from sewage treatment plants, the terpenes present in emissions from solid waste treatment plants, volatile fatty acids and some aldehydes present in plants for degradation of animal waste products, and ethyl acrylate in plants manufacturing resins and polymers, are not, and consequently another technology must be found, such as an activated carbon adsorption, or a biological purification process, or a thermal oxidation system, according to the compounds present, the concentrations thereof, and the purification efficiency required.
   The following presentations are cases where, after in-depth characterization of the emission to be purified, the nature of best treatment system is discussed and decided upon.

2. Case studies

 Case 1: Treatment of odour emissions from the waste water treatment plant of a food industry company - juice manufacturing

   The treatment plant has a treatment capacity of 5000 inhabitants equivalent and consists of the following stages: prior homogenisation, followed by sedimentation, and a biological process involving moving beds. Since the factory production, and therefore also the wastewater, increases very considerably during the spring and summer, the operation of the treatment plant is not constant. Although it works best for water purification, it does generate significant odour emissions. To reduce the impact of this activity on the environment, as there are residential areas less than 20 m away, the owners decided to confine all the treatment plant ponds and remove the air and treat it properly to reduce the odour impact.

   Once the emissions were confined, several campaigns were conducted to determine the composition of gases to be treated. Significant variations of both the composition and concentrations were observed depending on the raw material used in the process. It was also surprising to find that, apart from H₂S and sulphurous VOCs, there were significant levels of terpenes (a-pinene, limonene, myrcene, carene, .. ), ketones, alcohols, as well as aldehydes. Table 1 shows a very brief summary of the pollutants and concentrations analyzed - in average values - in the total emissions from the treatment plant.

Table 1- Compounds and concentrations of pollutants in the emissions from the waste water treatment plant

   The extent of the odour emission in the initial situation was modeled, and the extent of the emission was modeled if a scrubbing system that would allow a greater deodorization efficiency of 90% were to be installed, and in a second option a system with an efficiency of over 95%. It was observed that the latter option would be necessary for the emissions to remain within the limits of the plot of the manufacturing plant. (See Figure 1)

   Figure 1- Extent of the odour emissions of the treatment plant of a factory at baseline situation, and after implementation of deodorization technology with 95% efficiency.

   After determining the efficiency of deodorization necessary, as shown very briefly in Table 2, an evaluation of different purification technologies on the market was undertaken, and as selection criteria the following aspects were evaluated:

- Deodorization efficiency expected for the emission under study.
- Occupied space (since it is an existing plant with limited space available).
- The costs associated CAPEX and OPEX.

   As can be seen from Table 2, the only technologies that give the necessary purification efficiency in this case are the activated carbon adsorption and Advanced High Performance Biofilter (HPB). A comparison was made of costs CAPEX and OPEX of all the technologies, and it was noted that, although the investment cost of the HPB is the highest of all the technologies evaluated, due to the low operating costs, because there is no consumption of chemical products, their operational costs loss is low. The replacement of the biomedia should only be required every 8-10 years in this type of Installation. HPB gives the lowest overall costs, along with pine splinter biofilter, at the end of operational life of the plant.

Table 2- Comparison of costs associated with the different deodorizing technologies evaluated.

   It is worth noting that the HPB was installed in the summer of 2012 and since then the system is operating at full capacity, and that no complaints have been registered in relation to the odour impact of the treatment plant. Due to space problems, it was assembled on a metal structure over a truck route-way, as shown in Figure 2.

Figure 2: Photo images of Advanced High Performance Biofilter (HPB) installed for deodorization of emissions from the treatment plant in the food industry installations

 Case 2 : Plastics incineration process

   This activity emitted gases resulting from a drying process of plastics through a chimney. Although the drying oven may be considered to be a treatment system, since the drying temperature was only 300C, it was not high enough to achieve complete purification, and so it was affecting the environment, especially when drying Type A plastics.

   A thorough characterization of the emission of the focus was made for when the problematic plastic Type "A" was being dried, and the parameters listed in Table 3 were determined. Also the possible presence of dioxins and other potentially toxic VOCs was able to be discarded.

Table 3- Characteristic parameters of the emission of Type A plastic drying process.

(*) Because the plastic materials are non-chlorinated, the presence of precursors of PCDD and PCDF was not observed. Sulphur compounds present and some aromatic compounds contributed to the emission's odoriferous load.

   In making the assessment of treatment technologies, it was noted that the emissions met the limits requested by the administration for VOCs. So the study focused on reducing the odour impact:

- Biological based technologies as Biotrickling and biofiltration processes were discarded because the emission temperature exceeds 40°C, which is the maximum operating temperature for these technologies, and because the pollutants analyzed are hardly biodegradable.

- Adsorption systems were also rejected because at temperatures above 100°C desorption takes place rather than adsorption and consequently purification of the emissions is not possible at such elevated temperatures. Given the high rate of emission, the possibility of prior cooling would lead to a very high energy cost, so the cooling process was also dismissed.

- Chemical scrubbing systems were also discarded because the pollutants in the emissions are not soluble.

   So, comparative studies and evaluations were made between 1) thermal oxidation systems, which would purify the emissions, and 2) the EOLAGE system that improves the dispersion, reducing emissions and odour impact on the surroundings. This was a possible candidate because the emissions already complied with the limits required by the Administration for VOCs.

   Figure 3 shows the range of the odour impact of the emissions at baseline, and the modeling of the impact if emissions were treated by thermal oxidation, or by installation of the EOLAGE system.

Figure 3- Range of odoriferous impact of plastics drying plant.

   As can be seen in the models, only with thermal oxidation was it possible to achieve a reduction of the odour impact acceptably. However, since the drying process for plastic "A" happens only occasionally, a comparison of the overall costs associated with both technologies was made. The results are shown in Table 4.

Table 4- Comparison of the characteristics and the costs associated with the two proposed treatment scenarios.

   Although the costs of the thermal oxidation system are considerably higher than those associated with the EOLAGE system, ultimately, the client decided to install the thermal oxidation. However, this installation failed to materialise because the customer finally decided not to treat more plastic Type "A" making the investment unnecessary.

Figure 4: Photo images of an EOLAGE system, and a thermal oxidation system.

CONCLUSIONS

   It is essential to characterize emissions well before evaluating which deodorization technology to apply. Depending on the treatment flow, the temperature of the emission pollutants and purification efficiency required, these should be evaluated to find the most efficient technology for each specific case, taking into consideration that often, advanced technologies are those which present a higher CAPEX and a lower OPEX. This often turns out to be, eventually, comparatively less expensive than other technologies over medium term, with the added advantage of offering much higher purification efficiencies.

REFERENCES

Almarcha D., Almarcha M., Nadal S. y Caixach J. (2012), Comparison of the depuration efficiency for VOC and other odoriferous compounds in conventional and Advanced Biofilters in the abatement of odour emissions from urban waste treatment plants, Chemical Engineering Transactions, volume 29, 2012 (In press).

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