Advanced Oxidation Processes at Laboratory Scale: Environmental

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Advanced Oxidation Processes at laboratory scale: Environmental and Economic Impacts Jaime Gimenez, Bernardí Bayarri, Óscar González, Sixto Malato, José Peral, and Santiago Esplugas ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.5b00778 • Publication Date (Web): 30 Oct 2015 Downloaded from http://pubs.acs.org on November 10, 2015

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ACS Sustainable Chemistry & Engineering

Advanced Oxidation Processes at laboratory scale: Environmental and Economic Impacts Jaime Giméneza*, Bernardí Bayarria, Óscar Gonzáleza, Sixto Malatob, José Peralc, Santiago Esplugasa.

(a) Departament d’Enginyeria Química, Universitat de Barcelona, C/ Martí i Franquès 1, 08028 Barcelona, Spain. (b) Plataforma Solar de Almería (CIEMAT), Carretera de Senes, km 4, 04200 Tabernas, Almería, Spain. (c) Departament de Química, Edifici Cn, Universitat Autònoma de Barcelona, 08193 Bellaterra, Cerdanyola del Vallès, Spain.

Abstract Advanced Oxidation Processes (AOPs) are widely used at laboratory in the treatment of different pollutants and many references appear in the literature on this subject. However, there are not many works devoted to the study of the impact of these laboratory works from an environmental and economic point of view. For these reasons, this study is focused on the environmental impact evaluation, by LCA, of two AOPs (photocatalysis and pho-Fenton) in two different experimental setups (solarbox and CPCs), for the treatment of metoprolol. LCA has proved to be useful to compare the AOPs and the tested devices. In the same way, an economic assessment was made for the same AOPs and installations. Conclusions are very meaningful, pointing out that the cost of such experiments at laboratory level is not negligible and has to be seriously considered. As a consequence, laboratory work has to be accurately planned and analysis techniques and proves to be used must be carefully selected to avoid excessive increases in the costs of laboratory experiments.

Keywords: AOPs economics, AOPs environmental impact, AOPs LCA, AOPs costs, laboratory costs

*Corresponding author: Jaime Giménez, Departament d’Enginyeria Química, Universitat de Barcelona, C/ Martí i Franquès 1, 08028 Barcelona, Spain. Tel. +3493402123, E-mail: [email protected] 1

ACS Paragon Plus Environment


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ABSTRACT ART

Synopsis LCA and economic assessment techniques are useful tools in showing the environmental and economic impacts of AOPs at lab level.

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Introduction.

The use of Advanced Oxidation Processes (AOPs) has shown vigorous growth in recent years and represents today an important field of research concerning pollutants treatment. This interest is proved by the large number of research works published in the last years. A look to the literature, only in the period 2005-2014 (see Table 1), and in the field of photocatalysis, shows 56059 publications (according to SCOPUS data) or 17206 (according to the Web of Science data). In any case, this represents an enormous amount of publications and indicates the efforts devoted to the research in this field.

Table 1. Photocatalysis works cited in Scopus and Web of Knowledge databases. SC: Data obtained from Scopus, all fields, document type: all, February 2015. WS: Data obtained from Web of Science, by Topic, February 2015. Year

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 TOTAL

Photocatalysis SC 2254 2538 3131 3535 4611 4982 6740 8011 9485 10772 56059

WS 752 829 1135 1263 1556 1508 1981 2420 2719 3043 17206

Photocatalysis AND life cycle assessment SC WS 5 1 5 2 6 1 15 34 1 29 2 37 2 41 0 70 2 73 1 315 12

Photocatalysis AND costs estimation SC WS 8 4 14 12 23 18 22 33 43 1 52 229 1

Photocatalysis AND costs evaluation SC WS 30 1 40 45 1 54 2 92 96 4 180 2 173 4 290 3 313 3 1313 20

Of course, research plays an irreplaceable role in the testing of new methodologies and techniques before the implementation at pilot plant and/or industrial scale. In this way, the cited works on photocatalysis are undoubtedly an important tool. However, the cost of laboratory experiments should not be forgotten, even less in crisis times and when many research works are funded with public money. For this reason, economic evaluation of the laboratory work is gaining importance. AOP economic assessment methodologies could be based on different parameters. The typical engineering cost estimations will be used for the economic assessment in this paper. There is growing public concern for environmental issues, as reflected inter alia in an increasingly restrictive environmental legislation. Even though AOPs have been shown to be 3



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appropriate for the degradation of persistent organic compounds, chemicals or electricity consumption involved may be considerable. Cleaning up wastewater therefore comes at the price of consuming scarce resources and generating pollutant emissions and wastes associated with the chemicals and electricity needed1. It is thus increasingly important to understand the environmental impact of implementing a particular AOP. This concern has to be translated to the research work and we have to know the environmental impact associated to the laboratory work. Different methodologies are available for environmental impact assessment. In our case, Life Cycle Assessment (LCA) was chosen. Table 1 points out that studies related to economic and environmental impacts of AOPs are not usual. There are many works on photocatalysis but this number decreases dramatically when the boundaries of the search are restricted either with LCA or costs estimation or evaluation. Despite the differences observed in the number of works, according to the source used, at most, only a 2% of works include costs evaluation and only a 0.5% includes LCA (see Table 1). Thus, an important task can be made in this way. In addition, the works including environmental2-9 or economic10-16 aspects are normally devoted to studies related to a possible industrial implementation of AOPs. For these reasons, this work is centered on laboratory scale, because the cost of research task has to be also evaluated, both its environmental and economic impacts. Thousands of papers per year are related with laboratory work done by hundreds of research groups. Such a huge work is not trivial from the point of view of environmental impact and costs and it deserves to be studied.

Environmental impact evaluation.

The well-known LCA tool has been successfully used to assess the environmental impact of chemical processes17,18. This tool finds the potential impacts associated with the entire life cycle of a product or a process19. LCA application, following the standards ISO 14.040:2006 and ISO 14044:2006, is developed through four basic stages: goal and scope definition, inventory analysis, Life Cycle Impact Assessment (LCIA) and interpretation of results. The first step is to define the goal of the study (for instance, environmental impact related to each liter of wastewater treated by each AOP), along with the scope, main hypothesis, including system boundaries, and type and quality of data.

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The inventory analysis step involves data collection to quantify system inputs and outputs, that is, evaluation of raw materials, energy consumption, and pollutants production. In LCIA step, the inventory data are assigned to impact categories and characterized, using different factors. These impact categories depend on the LCA method used. Two types of methodologies can be defined: midpoint methods19, which define only the impact in certain categories, such as ozone depletion, climate change, etc., and endpoint methods20, which analyze the final impact on human health, environment or resource consumption. In the interpretation step, the results are examined in terms of critical sources of impact and the ways or opportunities for reducing these impacts. This methodology has been devised to study and compare processes at industrial level but can be perfectly used at the laboratory level, as is the case of this work.

Economic assessment.

There are several methods of estimating the costs of implementing each of the different AOPs. Of course, all methods have to end up with the right relationship between cost and amount of treated pollutant. In general, cost calculation is similar to any engineering project. Thus the following items are proposed21:

•

Facility Cost (CI): equipment, pumps, pipes, valves, gauges, instrumentation and control, transportation of equipment, civil engineering, etc. All items intrinsic to the facility, and facility operation, including external devices or services, such as electricity generation plants, boilers, cooling towers, storage tanks, laboratories, offices, maintenance, emergency services, etc.

•

Project Contingency (CC): During project design, it is often impossible the detailed knowledge of all final details, and thus there will always be a slight difference between the real final cost and the estimated cost, a difference that usually amounts 10 to 20% of the cost of facilities, depending on the design details that were collected.

•

Engineering Project (CG): Includes system design,

integration in existing

specifications, procurement of components, engineering fees, operator training, etc., usually estimated as 50% of facility costs plus contingencies. However, in this case, the methodology is applied to laboratory devices, so engineering costs are estimated as 20% of facility costs plus contingencies.

•

Replacement costs (CR): Usually estimated as 0.5% of facility costs plus project contingencies. 5



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The sum of these four concepts is the total installed cost (CTI), based on which the yearly economic impact is evaluated. This includes facility lifetime, depreciation period, interest, taxes, insurance, etc. Then operating costs have to be calculated. These costs are normally yearly and consist of the following items: 1) Personnel (CP), 2) Maintenance (CM), 3) Electricity (CE), 4) Materials and services (CRM). These costs added to the annual facility costs are the total annual costs. As commented for LCA, this methodology has been designed to estimate costs in industrial processes but can be perfectly used in the laboratory. Obviously, items such as facility costs will lose weight versus items as operating costs or chemical analysis but the ideas are perfectly applicable.

Scope of the work.

In this study we applied LCA to two AOPs used, in two different experimental setups, for the metoprolol treatment in aqueous solution: heterogeneous photocatalysis (HP) with either a solarbox (HP-SB) illuminated by artificial light or a CPC pilot plant (HP-CPC) illuminated by natural solar irradiation, and photo-Fenton (PF) with either solarbox (PF-SB) or natural solar (PF-CPC) irradiation. As commented before, previous examples of the application of the methodologies to environmental or economic impact assessment of similar AOPs can be found in the literature. However, in this paper, emphasis is done on the application to laboratory work and in the use of such methodologies (economic and environmental impact) for comparison of different AOPs, trying to establish several guidelines for its application to any laboratory work on AOPs use. In addition different devices for each AOP have been used, showing the influence of the experimental installations used on the economic and environmental aspects. Summarizing, we attempted to establish a guideline for the evaluation of economic and environmental impacts of AOPs at laboratory level, weighting up the importance of research in this field, because the costs at laboratory level and the costs of research cannot be forgotten or disregarded.

Experimental.

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The experimental devices used are described elsewhere22,23 and metoprolol tartrate salt (MET) was treated by photo-Fenton or photocatalysis with TiO2 in both devices. Briefly, they consist of: a) Solarbox, tubular reactor, Xe lamp (1000 W), pump (250 - 500 W), thermostatic bath (240 W at 20ºC), thermometer, feed tank, stirrer (1-5 W), magnetic stirrer, mirror, pipes (see also Table 4). Experiments were done with 1 L of solution. b) CPCs, pump (250-500 W), thermostatic bath (240 W at 20ºC), thermometer, feed tank, stirrer (55-75 W), cold finger, stirring rod, pipes. Experiments were done with 10 L of solution.

The LCA and economic assessments are based on averaged experimental conditions determined in previous works at laboratory 22,23, as described next. The initial concentration of MET (50 mg/L) was chosen due to analytical limitations and for a better monitoring of the reaction. In photocatalysis experiments, TiO2 concentration was 0.4 g/L. In photo-Fenton experiments, Fe2+ concentration varied between 2.5 and 10 g/L, thus an average value of 6 g/L has been assumed. In the same way H2O2 concentration varied between 25 and 150 mg/L and an average value of 90 g/L has been considered. The average experimental conversions used for MET were: 90% at 0.5h for PF-SB, 95% at 0.5h for PF-CPC, 83% at 4.5 h for HP-SB and 65% at 4h for HP-CPC. The average TOC conversions were: 50% at 3.5h for PF-SB, 45% at 2.5h for PF-CPC, 44% at 5.5 h for HP-SB and 30% at 4h for HP-CPC. The chemicals used for experiments and/or analysis are summarized in Table 5. It should be mentioned that equipment used for analysis must be also considered in both environmental impact and economic assessments: HPLC, TOC, spectrophotometer and water deionization device (see also Table 4).

LCA application.

The processes included are: i) production of electricity consumed by the different AOPs, including resource extraction, transport and energy conversion, and ii) chemicals production, i.e., the catalysts and the stoichiometric reagents consumed by each AOP (H2O2, TiO2 and FeSO4), including resource extraction, chemicals production and transportation. Since the final goal of this LCA is to find out the impacts associated with different AOPs, the analysis was comparative, implying that all the subsystems of AOPs involving the same impacts (pretreatment and post-treatment steps, and chemical nature of effluents) can be ignored.

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SimaPro 7.0 software was used for all impact assessments in this study, and the Swiss database Ecoinvent ver. 1.224 was taken as the source of background inventory data. Concerning the LCA study, the SimaPro version used is appropriate for Europe and new versions of the program (for instance, the current SimaPro 8.0) does not provide substantial changes of the results. Thus, it can be assumed that the use of SimaPro version 7.0 is right according to the scope of our study. Similar comment can be made concerning the use of Ecoinvent database v 1.2 instead of the last version Ecoinvent v 3. In addition, the objective of our study is not to obtain absolute values but to give tools for the study of the environmental impact allowing the comparison of different AOPs and different devices at laboratory level. The following datasets were used as the sources for chemicals and energy consumed: (i) low voltage electricity, UCTE production at grid25; (ii) hydrogen peroxide, 50% in H2O, at plant/RER26; (iii) iron sulfate, at plant/RER25; and (iv) transport, 16-t truck /RER27. The impact data inventoried for TiO2 have been elaborated in our group by taking into account data on emissions and consumption of raw and auxiliary materials28, and the environmental impact of those materials according to BUWAL 250 database29. Since the main goal of this study was to illustrate how LCA can be used to quantify the environmental impact associated with treatment of polluted water by different AOPs at lab scale, we decided to perform the analysis at the simplest level, that is, only impact of consumables (electricity and chemicals), leaving out the impact associated with infrastructure (materials and energy involved in reactor construction). In this study, the functional unit (the service unit whose impact is to be compared) was defined on the basis of same volume treated (1 L) and same amount of pollutants destroyed. From the experimental results commented in section 2 (Experimental), this amount has been set at 3050% TOC removal. Then, the functional unit is defined as “the removal of 30-50% TOC from 1 L of 50 mg·L-1 metropolol aqueous solution”. Since this is a comparative analysis, the final treated water sample should be similar to avoid the impact assessment of the final water sample released. Nevertheless, this involves the assumption that TOC remaining in the final treated water samples is chemically the same. This is consistent with AOP treatment, as HO• radical mineralization of any pure compound produces similar degradation products after long enough treatment times (30-50% TOC removal means important conversion of parent compound), and could be a good approach, considering that the toxicity of the remaining chemicals is similar (no differences in the Human Toxicity and Eco-toxicity impact category), and the same amount of nitrogen atoms are still

present in the remaining TOC (no differences in the eutrophication impact category). 8


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Based on the above definition of the functional unit, the energy and chemicals consumption data for each experiment were the following:

•

Grid electricity (kWh): 10.1 for HP-SB, 0.219 for HP-CPC, 25.4 for PF-SB, 0.138 for PFCPC.

•

2·10-5 kg TiO2 for HP-SB and HP-CPC.

•

3·10-5 kg FeSO4·7H2O and 1.8·10-4 kg H2O2 50% for PF-SB and PF-CPC.

With this input and using the data sources described in the experimental section, the environmental loads per system functional unit were inventoried. The main assumptions in the LCA inventory stage are summarized as follows: 1) The energy used to run the SB is electricity delivered by the Spanish grid. 2) Electricity for pumps, thermostatic baths and stirrers is similar in all reaction scenarios (around 550 W), and the final energy consumed by those accessories depends on the power assumed and the reaction time needed for the functional unit requirements. Solarbox lamps were only considered in the solarbox scenarios. 3) HP has a catalyst recovery stage in which the pH of the effluent is raised by adding a base to reach the point of zero charge, allowing the catalyst to settle. This recovers 95% of the catalyst, and the remaining 5% is lost30. There is no Fe(II) recovery stage in PF because the low dissolved iron content in the treated water has no harmful consequences. 4) The starting amounts of H2O2 and Fe(II) are completely consumed after 30-50% TOC removal. 5) H2O2 and FeSO4 are produced in Spain and carried 100 km to the consumer by a 16-ton truck. The raw material (ilmenite) for TiO2 is transported 5000 km by ship to the production plant (Degussa, Frankfurt), and the finished TiO2 is then carried another 1500 km by a 40-ton truck for delivery to the consumer.

Table 2 shows the results of the Life Cycle Impact Assessment for the four cases. As seen in the table, the strongest environmental impacts are always associated with energy consumption, either from the use of electric lamps, or even for the requirement of the energy involved in auxiliary operations like pumping, stirring, etc. The impact electricity consumption is greatly reduced from the SB to CPC experiments. Thus, as expected, the use of natural sunlight has a remarkable improvement on the environmental impact, but even in those scenarios, the impact of producing and delivering the chemicals is more than two orders of magnitude lower than that of producing electricity. This might be due to the fact that no particular effort was made to 9



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optimize the use of pumps, stirrers and thermostatic baths when collecting the experimental data presented here (laboratory and CPC experiments), a usual situation at research lab scale. Thus, a further noticeable improvement could be expected from such optimization if researchers (thousands in AOPs all over the world) properly focus in the environmental impact of their work. In the comparison of HP and PF, the total impact clearly depends on the reaction time and the need for larger amounts of energy for longer reaction times. SB experiments show that TOC removal is faster in the PF system, and thus the HP reaction has the strongest impact. Something similar happens with the CPC experiments. In the PF system under natural solar irradiation (PF-CPC), the main impacts are always associated with the electricity consumed by pumps, thermostats and stirrers, and only a minor share of the impacts is assigned to H2O2 consumption (especially in the case of the Fresh water Aquatic Toxicity Potential). The impact of Fe(II) salt consumption always turns out to be almost negligible. Therefore, the solar energy scenario appears to be the most environmentally friendly of all treatments. In addition, the strongest impact is in Global Warming, which is logical assuming that transport and electricity impacts are large in that category.

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Table 2. Life Cycle Impact Assessment for the different AOPs. Impact* Category GWP ODP AEP AP HTP FATP POFP ARD

HP Units kg CO2 eq. kg CFC11 eq. kg PO43- eq. kg SO2 eq. kg C6H4Cl2 eq. kg C6H4Cl2 eq. kg C2H4 eq. kg Sb eq.

PF

SB TiO2

Energy

9.6·10-5 1.5·10-11 1.5·10-8 8·10-7 5.8·10-6 6·10-6 5.6·10-5 4·10-7

5.1 1.2·10-6 7.9·10-4 3.1·10-2 1.20 8.1·10-2 1.6·10-3 3.8·10-2

CPC Relative impact 100 100 100 100 100 100 100 100

TiO2

Energy

9.6·10-5 1.5·10-11 1.5·10-8 8·10-7 5.8·10-6 6·10-6 5.6·10-5 4·10-7

0.11 2.7·10-8 1.8·10-5 6.8·10-4 2.5·10-2 1.7·10-3 3.5·10-5 8.1·10-4

SB Relative impact 2.1 2.4 2.5 2.3 3.3 0.0 0.0 0.0

CPC

H2O2

FeSO4

Energy

1.2·10-4 1.6·10-9 1.1·10-6 4.3·10-5 1.5·10-3 8.3·10-5 2.3·10-6 5.2·10-5

9.6·10-5 3.0·10-11 1.8·10-8 1.2·10-5 1.4·10-5 6.0·10-7 1.01·10-7 6.7·10-7

2.7 6.5·10-7 4.2·10-4 1.7·10-3 0.58 4.3·10-2 8.7·10-4 2.0·10-2

Relative impact 54 59 58 57 53 58 51 58

H2O2

FeSO4

Energy

1.2·10-4 1.6·10-9 1.1·10-6 4.3·10-5 1.5·10-3 8.3·10-5 2.3·10-6 5.2·10-5

9.6·10-5 3.0·10-11 1.8·10-8 1.2·10-5 1.4·10-5 6.0·10-7 1.0·10-7 6.7·10-7

6.9·10-2 1.6·10-8 1.0·10-5 4.2·10-4 1.5·10-2 1.1·10-4 2.2·10-5 5.1·10-4

Relative impact 1.4 1.6 1.6 1.6 1.6 0.26 1.4 1.6

* Impact categories are: Global Warming Potential (GWP), Ozone Depletion Potential (ODP), Aquatic Eutrophication Potential (AEP), Acidification Potential (AP), Human Toxicity Potential (HTP), Fresh water Aquatic Toxicity Potential (FATP), Photochemical Ozone Formation Potential (POFP), and Abiotic Resource Depletion (ARD). Relative impact data have no units and have been calculated according to that explained for figure 2.

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The best way to compare the impacts of chemicals consumption alone would be to ignore the large impacts associated with energy (pumping, thermostating and stirring) in the solar CPC scenarios. This is a good approximation, since, as mentioned above, the LCA analysis is comparative and the impacts of those auxiliary operations, even if strong, are assumed to be the same for all four AOPs considered. Table 3 shows the impact data for the CPC experiments ignoring electricity consumption and points out that PF system clearly has more environmental impact in the majority of categories than the HP system. With the exception of Global Warming Potential and Photochemical Ozone Formation Potential, where HP involves the highest impact, H2O2 consumption always has the most negative environmental consequences, while, the consumption of Fe(II) is always less important than the consumption of H2O2. This is not surprising since the first is used as a true reagent, i.e., it is consumed in large quantities, while the latter is only a catalyst.

Table 3. Life Cycle Impact Assessment for the two AOPs under natural solar irradiation ignoring electricity consumption (assumed to be the same in both cases). *Impact Category GWP ODP AEP AP HTP FATP POFP ARD

HP CPC

Units TiO2

kg CO2 eq. kg CFC11 eq. kg PO43- eq. kg SO2 eq. kg C6H4Cl2 eq. kg C6H4Cl2 eq. kg C2H4 eq. kg Sb eq.

9.6·10-5 1.5·10-11 1.5·10-8 8·10-7 5.8·10-6 6·10-6 5.6·10-5 4·10-7

PF CPC

Relative impact 44 0.9 1.4 1.4 0.4 26 100 0.7

H2O2

FeSO4

1.2·10-4 1.6·10-9 1.1·10-6 4.3·10-5 1.5·10-3 8.2·10-5 2.3·10-6 5.2·10-5

9.6·10-5 3.0·10-11 1.8·10-8 1.2·10-5 1.4·10-5 6.0·10-7 1.0·10-7 6.7·10-7

Relative impact 100 100 100 100 100 100 4.3 100

* Impact categories are: Global Warming Potential (GWP), Ozone Depletion Potential (ODP), Aquatic Eutrophication Potential (AEP), Acidification Potential (AP), Human Toxicity Potential (HTP), Fresh water Aquatic Toxicity Potential (FATP), Photochemical Ozone Formation Potential (POFP), and Abiotic Resource Depletion (ARD). Relative impact data have no units.

Finally, a large majority of impact categories always pointed in the same direction:

•

All categories show a more significant impact for artificial light than natural sunlight due to the electricity consumption.

•

All categories show that the use of energy in the PF-CPC experiments impacts more than consumption of chemicals.

•

All categories show that the HP-SB experiments impact more than PF-SB.

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•

Seven out of eight categories show that consumption of chemicals impacts more in the PF-CPC than in the HP-CPC experiments.

•

The eight categories clearly show that the consumption of H2O2 in the PF experiments impacts more than the consumption of Fe(II).

It can be said that LCA has proven to be a useful tool for study of the environmental impact of AOPs. The Global Warming category was the most affected by AOPs, where the impact of electricity consumption is the most relevant item, at least at the scale and with the experimental systems studied in this work.

Economic studies.

An economic study was done for the same AOPs and the same experimental conditions used for the LCA. Data are shown in Table 4. Estimated cost and lifetime are given for each piece of equipment, which price was obtained from the manufacturers and from own estimations and data (year 2014). The same can be said concerning the cost of electricity or reagents appearing in Table 5. The “% use” shows how much this equipment is used for this kind of experiment. To calculate the cost/year for each piece of equipment, in this case, it was assumed that the devices were devoted to PF and HP MET treatment for 15% of their lifetime. The same can be said for analysis equipment.

Table 4. Cost of equipment.

12000

10

15

1800.00

Yearly cost (€/year) 180.00

Tubular reactor

200

5

15

30.00

6.00

Lamp (1000 W)

150

5

15

22.50

4.50

Pump (250 - 500 W)

2500

10

15

375.00

37.50

Thermostatic bath (240W at 20ºC)

3200

10

15

480.00

48.00

Teflon pipes (3 m)

30

10

15

4.50

0.45

Thermometer

15

10

15

2.25

0.23

Feed tank (1 L)

175

10

15

26.25

2.63

Stirrer (1 - 5 W)

350

5

15

52.50

10.50

Magnetic stirrer

5

5

15

0.75

0.15

Pump pipes (1 m)

15

2

15

2.25

1.13

Mirror

100

10

15

15.00

Price (€)

Lifetime (years)

% use

Cost of use (€)

22000

10

10

2200

1.50 Yearly cost (€/year) 220

Equipment Solarbox

Analysis HPLC

Price (€)

Lifetime (years)

% use

Cost of use (€)

13



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TOC

20000

10

10

2000

200

Spectrophotometer

8000

10

10

800

80

Water deionization device

7000

10

10

700

70

TOTAL CI (facility cost: equipment for installation and for analysis)

7011 €

Project contingency (CC = 20% CI) Facilities + Contingencies (CIC = CI + CC)

1402 € 8413 €

Project engineering (CG = 20% CIC)

1683 €

Replacements (CR = 0,5% CIC)

421 €

Total installed cost (CTI = CI + CC + CG + CR)

10517 €

Facility lifetime (TD = 8 years) Depreciation Factor (FD = 1/TD = 0.125) Depreciation (D = FD x CTI) Interest (I = 4%) Amortization Factor (FA = I/100 = 0.04) Amortization (A = FA x CTI) Taxes, insurance (Tax Factor, 2%, FT = 0.02) Taxes (T = FT x CTI)

1315 €/year

421 €/year

210 €/year

Coefficient of yearly distribution (CD = FD + FA + FT = 0.185) ANNUAL FACILITY COSTS (CAI = CD x CTI)

1946 €/year

Although the results shown in Table 4 are for SB, the considerations made are applicable to all the experimental devices and all AOPs. At the end of the section, we show the summarized results for all the installations and AOPs tested. Following the methodology previously proposed in the economic assessment section21, when the total cost of facilities (CI) has been estimated, it is possible to evaluate the other items (see Table 4) included in the total installed cost (CTI):

•

The project contingencies (CC), in this case, can be estimated as 20% of the facility cost.

•

For project engineering (CG) and considering that the engineering for a laboratory device is simple, the cost is set at 20% of CI+CC.

•

Finally, the replacement costs (CR) are recommended at 0.5% of CI+CC.

It should be mentioned that the percentages may vary depending on the project type and level of development. The sum of CI+CC+CG+CR yields the total installed cost (CTI). The next step is evaluation of the yearly economic impact of the total installed cost (see Table 4). This requires the lifetime of the installation, the depreciation period, interest, taxes, insurance, etc. To simplify calculation, an average depreciation period of eight years (factor FD = 1/8 = 0.125) has been assumed for all the components of the experimental devices, instead of 14


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the individual lifetime of each piece of equipment. Interest amortization assumed was 4% (FA factor = 0.04). Finally, taxes and insurance are rounded to 2% (FT factor = 0.02) of total installed cost. Thus, the annual facility cost (CAI) would be 0.185 (yearly distribution coefficient = CD = FD +FA+FT = 0.185) multiplied by the total installed cost (CTI). To find out how much is spent each year on these devices (total annual cost = TAC), the operating costs (TCO) must be added to the annual facility cost (CAI). As shown in Table 5 and commented in economic assessment section, the operating costs include: personnel (CP), maintenance (CM), electricity (CE), materials and services (CRM). In the next paragraphs, the estimation of each one of these costs will be commented and all of them will be summarized in Table 5. For personnel costs, it was assumed that the equivalent of 0.1 person works for one year in this kind of facility and experiment. Assuming a salary of 18000 €/year, the costs are: Personnel Costs = CP = 0.1 x 18000 €/year = 1800.00 €/year The maintenance costs (CM) can easily be calculated by estimating them as 2% of the facility cost plus contingencies (CIC = CI+CC). Thus, according to the CIC shown in Table 4: Maintenance costs = CM = 0.02 x CIC = 0.02 x 8413.20 € = 168.26 €/year The next step in estimating operating costs is to calculate the cost of electricity, which includes consumption by all the electrical equipment and instruments used. The results are shown in Table 5. To end the estimation of operating costs, the cost of materials and services (CRM) must be known, including chemicals, water, etc. (Table 5). The amounts used are according to data indicated in the experimental section.

Table 5. Operating costs. Electricity costs Time use equipment (h/exp)

Power (kW)

Lamp (1000 W)

3.5

1.00

Consumption (kWh) 3.50

Pump(250 - 500 W) Thermostatic Bath (240 W a 20ºC)

3.5 3.5

0.40 0.24

1.40 0.84

Stirrer (1 - 5 W) HPLC (12 samples x 15 min/sample) TOC (12 samples x 15 min/sample) Spectrophotometer (DQO+Fe+H2O2+SUVA) Water deionization device (preparation 1 L water)

3.5 3

0.003 2.50

0.01 7.50

3

2.20

6.60

0.2

0.25

0.05

0.1

0.10

0.01

Equipment

Total consumption by experiment (kWh/exp)

19.91

Nº experiments/year Total consumption by year (kWh/year)

50 995.53

15



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Cost kWh (€)

0.12

Total Cost Electricity (CE) by year

119.46 €/year

Cost of materials and services (CRM): Cost of reagents. Reaction volume = 1L Conc – amount / REAGENTS Total amount / exp. Unit price exp Metoprolol tartrate salt 50 mg/L 50 mg 23,0 €/g FeSO4.7H2O (6 mg/L Fe) 6 mg/L 6 mg 27.3 €/kg

Cost (€) 1,15

H2O2 (90 mg/L)

90 mg/L

90 mg

0.01

H2SO4

0.5 mL

0.5 mL

10.2 €/L

0.01

1.00 L

0.45 €/L

0.45

Millipore Water

18.7 €/L*

0.00

Cost of each experiment Nº experiments by year

1.61 € 50

Total cost experiments (reagents) by year

80.62 €/year

Cost of materials and services (CRM): Cost of reagents used in analysis Total Parameter Amount/Sample Samples/exp Price amount/exp MET analysis

Cost (€)

Acetonitrile HPLC Acidified water HPLC

2.55 mL 10.2 mL

15 15

38.25 153.00

12.0 €/L 0.5 €/L

0.46 0.07

TOC analysis Synthetic air TOC (150 mL/min x 15/min/sample) COD analysis

2250 mL

15

33750

7.98 €/m3

0.27

Dichromate COD H2SO4 COD

1.5 mL 3.5 mL

4 4

6 14

55.3 €/L 55.9 €/L

0.33 0.78

H2O2 analysis Reagents for H2O2 determination

1.5 mL

2

3

2.66 €/L

0.01

Fe analysis Phenanthroline for Fe determination

1.0 mL

2

2

8.72 €/L

0.02

Negligible

4

0.80

BOD Reagents

0.00

0.0625 capsules

4

0.25

3.20 €/capsule

Osmotic adjuster Dilution water

0.25 mL 7.5 mL

6 6

1.5 45

1.94€/mL 0.19 €/mL

2.91 8.73

Bacteria restorative (1 mL/container)

0.056 mL

6

0.333

0.24

0.056 containers

6

0.333

0.72 €/mL 62.9 €/cont

Lyophilized capsules Toxicity

Bacteria

20.97

Cost of each experiment

35.58 €

Nº experiments by year

50 1779.19 €/year

Total cost experiments (analysis) by year * Cost of 1L of H2O2 (30%) purchased

The cost of the commercial product (formula was taken into account) was used to calculate the final cost of each reagent. Reagent costs (Table 5) are for laboratory-quality (high-purity) 16


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grade. Of course, the cost of industrial reagents is substantially lower, and would be reflected in the economic impact if this methodology was applied on an industrial scale. In this way, all the system operating costs can be estimated, as summarized in the first column of Table 6. These costs added to the annual facility costs yield the total annual costs. Tables 4 and 5 show results for MET treatment with PF-SB. Similarly, the annual facility costs can be calculated for the other three used devices (HP-SB, PF-CPC, HP-CPC). It should be mentioned that 10 L are treated in each CPC experiment and 1 L in SB experiments. Final results, including the percentage corresponding to each item, appear in Table 6.

Table 6. Costs, and percentage of different costs, of AOPs in different installations. All costs are in €/year. Type of Costs Personnel Maintenance Electricity Reagents Reagents analysis Total operating costs Annual facility costs Total annual costs Cost (€/experiment) Cost (€/L)

PF-SB Amount % item 1800 30.6 168 2.9 119 2.0 81 1.4 1779 30.2 3948

67.0

1946 33.0 5893 100.0 117.86 117.86

HP-SB Amount % item 1800 28.0 168 2.6 139 2.3 84 1.3 2303 35.8 4494

69.8

1946 30.2 6440 100.0 128.80 128.80

PF-CPC Amount % item 1800 27.7 160 2.5 92 1.4 806 12.4 1779 27.4 4638

71.4

1854 28.6 6491 100.0 129.82 12.98

HP-CPC Amount % item 1800 25.5 160 2.3 96 1.4 840 11.9 2303 32.7 5199

73.7

1854 26.3 7053 100.0 141.06 14.11

Although CPC allows the treatment of 10 L of solution and SB just 1 L, the annual facility cost is lower because CPC is mounted particularly in our own laboratory, while in SB a commercial solarbox have to be purchased and costs increase. From Table 6, it may be seen that facility costs vary from 33% to 26% and operating costs can vary from 67% to 74%. That is, operating costs are at least twice installation costs, and this proportion increases when scaling up, as observed when comparing estimations for SB (1L treated volume) and CPCs (10L treated volume). Other aspect to remark from Table 6 is the total cost of the experiments by year (total annual costs), for the two AOPs and two devices tested. Assuming that a research team make the four types of commented experiments in one year, the total cost, adding the costs for each AOP and every installation, amounts to nearly 26,000 €, which is not a negligible figure at all. Thus, our work makes clear the value of economic studies at laboratory level like the one carried out here. The amount of money spent is really important. 17



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As observed in Table 6, the reagents for analysis represent more or less half of the operating costs. Table 5 shows that toxicity tests represent the largest part of the cost of analyses. In fact, if toxicity tests were not done, the percentage of each item would change significantly and personnel costs became the most important item in the operating costs. In addition, operating costs continue to be higher than facility costs, but the difference is not that big anymore. This illustrates how the experimentation protocol could dramatically affect the costs and clearly show the importance of analysis costs at laboratory scale. Comparing the costs of analyses, the operating cost of HP is higher than for PF, mainly due to the requirement of using an expensive filter for each sample taken to separate the TiO2 particles before analysis. As expected, the cost of reagents increases from SB to CPCs because the volume to be treated is 10 L in CPCs and 1 L in SB, also underlining how decisions about where the experimentation protocol should be run affect costs. With these amounts broken down by experiment and assuming that 50 experiments of each type are performed per year, the costs per liter of solution treated and the cost of each experiment carried out are as shown in Table 6. Perhaps the most interesting thing is the effect of scaling up. Notice that the CPC facilities are larger than for SB, while the increase in facility costs is lower than in operating costs, and therefore, the per liter treatment cost is nearly ten times lower in CPCs than in SB. For instance, the cost of analysis is practically the same in SB and CPCs, and this contributes to lowering the overall costs as treated volume increases. If scaled to an industrial size, other items, such as the cost of reagents, would be much cheaper, decreasing the final price even more. However, the cost by experiment (see Table 6) increases from lab scale to pilot plant scale meaning that scaling-up cannot be addressed in any way. Difference in cost could be even bigger if pilot plant installation was, as the lab set-up, a commercial model. This implies that we have to think about what are we looking for with the scaling and if it is truly useful for the subsequent industrial scale because it really has a considerable cost. Perhaps the pilot plant size is a key parameter and we have to try to work with as small as possible pilot plants. Note that, in our case, only a little scaling-up was tested because the aim of our study was the economic assessment at laboratory level and not industrial level. A final reflection can be made concerning the total cost of photocatalysis experiments around the world. An estimation was obtained coming from the number of research works published and indicated in Table 1. The cost for each experiment of photocatalysis is 123.33 €/exp, which is the average of the costs of experiments at lab scale: 117.86 €/exp for PF-SB and 128.80 €/exp for HP-SB (see Table 6). Assuming that each published paper implies between 10 and 50 18


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experiments, the cost of each paper would vary between 1233.30 € and 6166.50 €, considering only the experimental work (the hours devoted to discussion and writing are not included). Considering the total number of papers published in year 2014 according to SC source (10772 papers, Table 1), the total cost of these papers would be between 13,285,108 € (10 exp. by paper) and 66,425,538 € (50 exp. by paper). According to WS source (3043 papers in 2014, Table 1), these values would vary between 3,752,932 € and 18,764,660 €. These results can be considered as surprising. The cost of one paper can vary between 1233 and 6166 €. In addition, in the most conservative of the cases, the cost worldwide is approx. 3,752,932 € and, in the opposite side, the total cost is higher than 66,000,000 €. In any case the figures are not absolutely negligible. Summarizing, economic studies show that percentages of facility and operating costs can change depending on the scale and the items included in the operating costs. Thus analytical techniques, like toxicity tests, can significantly increase operating costs. In addition, it was proved that the cost of the experiments is not a negligible amount, implying that a good planning and design have to be made. Therefore, we need to very accurately foresee what kind of experiments and what type of analysis and tests have to be done in order to reduce costs as much as possible, especially taking into account the public financing of many researches. This reasoning can be also applied to scaling-up, which represents an increase in the costs, and has to be accurately planned. Thus, the implementation of AOPs requires economic and environmental evaluation to enable decision-making to follow a consistent protocol. The proposed methodologies have demonstrated to be valid tools for the analysis of cost and environmental consequences at laboratory scale. Obviously, some costs can change from one country to other according to the prices of equipment, materials, products, electricity, etc. Consequently, their percentage in the total cost can also change. However, the explained methodology can be useful for any installation anywhere and results obtained in each case can point out the relevance of each item on the total costs.

Acknowledgements

The authors thank the Spanish Ministry of Science and Innovation (Projects CTQ2011-26258 and NOVEDAR 2010 CSD2007-00055) and AGAUR – Generalitat de Catalunya (Project 2009SGR 1466) for funding. The authors also thank Dr. Violette Romero for her collaboration. 19



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TOC GRAPHIC

Title: Advanced Oxidation Processes at laboratory scale: Environmental and Economic Impacts Authors: Jaime Giménez, Bernardí Bayarri, Óscar González, Sixto Malatob, José Peralc, Santiago Esplugasa.

Synopsis: LCA and economic assessment techniques are useful tools in showing the environmental and economic impacts of AOPs at lab level.

23


Advanced Oxidation Processes at Laboratory Scale: Environmental

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