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Demonstration of acid and water recovery systems: Applicability and operational challenges in Indian metal finishing SMEs
Journal of Environmental Management 217 (2018) 207e213
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Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Research article
Demonstration of acid and water recovery systems: Applicability and operational challenges in Indian metal finishing SMEs M. Balakrishnan a, *, R. Batra b, V.S. Batra a, G. Chandramouli a, D. Choudhury b, 1, €lbig c, P. Ivashechkin c, J. Jain b, 2, K. Mandava a, N. Mense a, 3, V. Nehra b, 4, T. Ha € gener c, 5, M. Sartor c, V. Singh b, M.R. Srinivasan d, P.K. Tewari a F. Ro a
The Energy and Resources Institute (TERI), Darbari Seth Block, IHC Complex, Lodhi Road, New Delhi, 110 003 India STENUM Asia Sustainable Development Society, SFF 101, Palam Triangle, Palam Vihar, Gurgaon, 122 017, India Betriebsforschungsinstitut VDEh-Institut für angewandte Forschung GmbH (BFI), Sohnstraße 65, 40237 Düsseldorf, Germany d Asia Society for Social Improvement and Sustainable Transformation (ASSIST), No. 9, Desika Road, Mylapore, Chennai, Tamil Nadu, 600 004, India b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 17 April 2017 Received in revised form 17 March 2018 Accepted 21 March 2018 Available online 5 April 2018
Diffusion dialysis, acid retardation and nanofiltration plants were acquired from Europe and demonstrated in several Indian metal finishing companies over a three year period. These companies are primarily small and medium enterprises (SMEs). Free acid recovery rate from spent pickling baths using diffusion dialysis and retardation was in the range of 78e86% and 30e70% respectively. With nanofiltration, 80% recovery rate of rinse water was obtained. The demonstrations created awareness among the metal finishing companies to reuse resources (acid/water) from the effluent streams. However, lack of efficient oil separators, reliable chemical analysis and trained personnel as well as high investment cost limit the application of these technologies. Local manufacturing, plant customization and centralized treatment are likely to encourage the uptake of such technologies in the Indian metal finishing sector. © 2018 Elsevier Ltd. All rights reserved.
Keywords: Resource recovery Diffusion dialysis Acid retardation Nanofiltration Metal finishing SMEs Technology demonstration
1. Introduction Metal finishing is a surface treatment process that improves wear and tear resistance, imparts corrosion resistance and improves the aesthetics of metal parts. Various metal finishing techniques like electroplating, painting etc. are used to ensure quality and desired service life of metal components in consumer goods, engineering and construction industries. The electroplating industry in India is composed primarily of small and medium enterprises (SMEs) which are part of the supply chain for automobiles (cars, trucks), 2-wheelers (bicycles, scooters), engineering equipment and consumer goods. There are an estimated 12,000
organized units and around 300,000 small scale units in clusters across India (IITM, n.d). Due to the highly acidic waste streams and the hazardous sludge generated, electroplating is classified by Central Pollution Control Board (CPCB) as one of the major polluting industries (CPCB, n.d). Another key SME sector that employs acid pickling is steel rolling. There are around 1800 small and medium sized steel rolling enterprises across India contributing to nearly 70% of long steel output (bars, sections, industrial products etc.) (Srinivas et al., 2013). As a first step in the metal finishing process, the component is cleaned to remove oil, scales and other surface impurities. Cleaning involves a series of operations including chemicals degreasing and
* Corresponding author. E-mail address: [email protected] (M. Balakrishnan). 1 Current address: National Productivity Council, E e 5, GIDC, Electronic Estate, Sector 26, Gandhinagar, Gujarat e 382 028, India. 2 Current address: Shree Cement Limited, Bangur Nagar, Andheri Deori, Beawar, Ajmer, Rajasthan e 305 901, India. 3 Current address: Frost and Sullivan India Pvt. Ltd., 2nd Floor, Focus Building, Near Kapil Complex, Baner Road, Pune e 411 045, India. 4 Current address: National Productivity Council, Utpadakta Bhavan, 5e6 Institutional Area, Lodhi Road, New Delhi e 110 003, India. 5 Current address: Cologne University of Applied Sciences, Institute of Chemical Process Engineering and Plant Design; Betzdorfer Str. 2, 50679 Cologne, Germany. https://doi.org/10.1016/j.jenvman.2018.03.092 0301-4797/© 2018 Elsevier Ltd. All rights reserved.
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acid pickling. Each cleaning step is followed by single or double water rinse to avoid carryover of chemicals to the next bath. The spent pickling acid and wastewater from all process and rinse baths are collected and treated with lime to precipitate the metals before either evaporating the treated water or discharging it. The dewatered sludge is disposed in hazardous waste landfills. There are several approaches for the recovery of acids from metal finishing waste streams. These include extraction (Agrawal €gener et al., and Sahu, 2009), spray roasting (Kladnig, 2003; Ro 2009), ion-exchange (Sheedy and Pajunen, 2012), freeze crystallization (Sartor et al., 2009) and various membrane separation based processes like electrodialysis (Chen et al., 2009), diffusion dialysis (Jeong et al., 2005) and membrane distillation (Tomaszewska et al., 2001). Integrated process schemes such as electrolysis and electrodialysis (Peng et al., 2011), microfiltration, adsorption and ion exchange (Wong et al., 2002) have also been employed. The best available technologies are electrodialysis and diffusion dialysis but spray roasting and ion-exchange are employed extensively for spent acids regeneration on large scale (Regel-Rosocka, 2010). For recovery of rinse water in electroplating operations, reverse osmosis in combination with ultrafiltration (Qin et al., 2004) or nanofiltration (Castelblanque and Salimbeni, 2004) have been used. Though technologies are available, the practice o f acid and rinse water recovery is not established in Indian SMEs. The SMEs perceive the technologies to be expensive, besides being complex to operate and maintain as technical support from the technology supplier is often limited. They are also not convinced about the technical feasibility of these technologies for their waste streams. At the same time, technology suppliers do not perceive SMEs as a potential market citing lack of technical and financial capacity. This work demonstrates state-of-the-art technologies for acid and rinse water recovery in Indian metal finishing SMEs. Three technologies viz. diffusion dialysis and retardation (ion-exchange) for acid recovery and nanofiltration for rinse water recovery were demonstrated in different industry clusters. Diffusion dialysis is a membrane separation process based on concentration differences across a non-porous anion exchange membrane that allows acids to permeate but retains dissolved metals. Retardation involves sorption of free acid on the ion-exchange resin followed by desorption of the purified acid with deionized water in a counter-current flow. The recovered acid can be recycled while the metal ions and part of the acid that passes through form the waste stream that is usually neutralized and discharged. Nanofiltration is a pressure driven membrane process that concentrates divalent metal ions, allowing the passage of water that can be reused. All the three technologies are well established in Europe. Nanofiltration is widely applied in the European metal finishing industry for acid bath regeneration as well as for the reuse of rinsing water. Diffusion dialysis is used for the regeneration of used acids. With the use of a simple pressure-free design and modular structure, it is suitable for application in SMEs as well as large companies. Acid retardation is widely applied in European steel plants for the regeneration of used acid from pickling plants. Due to its modular design and automatic operation mode, it is also applicable in SMEs.
The aim of this work was to (a) evaluate the applicability of diffusion dialysis, acid retardation and nanofiltration for acid/water recovery in Indian metal finishing SMEs (or as a solution for common effluent treatment plants, CETPs) considering climatic conditions, operational stability and economic feasibility and (b) understand the challenges involved in the uptake of such technologies in this sector that will help formulate potential solutions. 2. Methodology The small-scale demonstration plants (Table 1) were fabricated in Europe. The required pre-treatment systems were procured locally. These included oil separators (Pure Tech India, Trichy and Innovation Filter System P. Ltd., Pirangut) and 20 micron polypropylene pleated cartridge filters (Placon Agencies, Chennai) to remove oil and particulate matter from the waste acid/water stream before feeding to the demonstration plant. Fig. 1 shows the installed systems. The demonstrations were conducted between 2013 and 2016 in different locations across India (Fig. 2). The installation and commissioning of the demonstration plant at each location was done by the project team. At each location, one or two persons in the host company were trained on plant operation. Analysis of the acids for free acid and metal content was done by titrating the acid solution with 1N sodium hydroxide (NaOH) in 0.5 ml steps until the pH reaches 12. A graph was drawn between the volume of NaOH added and DpH/DV (change in pH/difference in NaOH volume) for each step (Fig. 3). The peak points in the graph show the free acid and metal content present in the solution in NaOH equivalents. The treated rinse water was analysed for conductivity, total dissolved solids (TDS) and pH using in-house portable conductivity/TDS and pH meter. Where analytical facilities were not available with the host company, testing was done in accredited labs in the region. Two workshops were conducted at each location during the demonstration period for metal finishing industries in that region. The first workshop was to introduce the technology to the companies and the second was to share the performance results of demonstration plant. 3. Results and discussion 3.1. Performance of demonstration plants The results for the demonstrations in terms of acid/water recovery are summarized in Fig. 4. These are average values over the demonstration period in a specific location that ranged from a week (e.g. nanofiltration at Chennai) to several months (e.g. retardation at Pune). The recovered acid from retardation was reused in the pickling process. This resulted in reduction of fresh acid consumption by 35e40% in the electroplating unit in Pune. In the rolling unit in Ahmedabad, the used acid was internally recycled for preliminary descaling. The recovered water in nanofiltration was reused in the rinsing tank in the electroplating process in Chennai. The concentrate from the plant, which is obtained after recovering the water from the feed, was rich in electroplating chemicals and has the
Table 1 Demonstration plants specifications. Technology Diffusion dialysis
Acid retardation
Nanofiltration
Supplier Plant details
Scanacon AB, Sweden MiniFlex with special anion exchange retardation resin SCANACON 02070001; flow range 40e50 L/h Max. 50 C ambient temperature
SIMA-tec GmbH, Germany PSta15-2 universal membrane test stand with two 2.500 spiral wound modules Filmtec NF90-2540 with total surface area of 5.2 m2; permeate flow range 20e100 L/h Max. 50 C ambient temperature; needs cooling above 40 C
Deukum GmbH, Germany Pilot plant with Fumatech anion exchange membranes Fumasep FAD PET 75 with 20 m2 active membrane area; flow range 20e25 L/h Limitations Max. 50 C ambient temperature
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Fig. 1. Demonstration plants with pre-treatment (a) Diffusion dialysis (b) Acid retardation (c) Nanofiltration.
potential to be reused in the electroplating process. The following sections describe in detail the representative operation of the demonstration plants and the corresponding performance. 3.1.1. Diffusion dialysis In Table 2, example of diffusion dialysis operation is presented with used sulphuric acid from a plating line in Gurgaon (North India). The results illustrate that through the reduction of clean acid flow /increase of waste acid flow, high concentrations of free acid can be reached by the overall recovery rate of 69% (Test 2). To maximise recovery rate (95%), clean acid flow can be increased (Test 3). The resulting acid concentration is then however lower. Thus the flows can be adjusted according to the objective and clean acid reuse pathway. Decline in permeate flow over time was pronounced with the initial flow rate of 20 L/h dropping to 3 L/h in later stages. Blocking of the diffusion dialysis membrane stack channels with particulate
matter as well as membrane fouling due to oil in the spent acid feed was suspected. The membrane stack was cleaned using concentrated sulphuric acid, isopropyl alcohol and RO Kleen (commercial cleaner) but this procedure was found to be ineffective. The stack was shipped to the supplier Deukum to clean the channels and replace the membranes before further testing.
3.1.2. Retardation Table 3 shows examples of retardation application based on results from a mixed acid (H2SO4þHNO3þHF) pickling line for steel sheets in Ahmedabad (West India). The recovery of spent acids was initially about 50% and decreased to 30% in later operation. The low recovery rates compared to the theoretical 80e90% could be explained through the oil contamination of the resin surface and resin bed clogging with suspended solids. To address this problem, the resin was replaced with a fresh batch within a year of initiating operation. This resulted in increased acid recovery of 70% accompanied by
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Fig. 2. Summary of test sites.
Table 2 Example of diffusion dialysis operation.
4 3.5
∆pH/∆V
3
Waste acid /clean acid flow ratio
Free acid
Test 1
Test 2
Test 3
20/20 L/h
22.5/ 17.5 L/h
17.5/ 22.5 L/h
Free acid
Free acid
Free acid
g/L
g/h
g/L
g/h
g/L
g/h
8.8 6.6 1.1 75%
175 132 22
8.8 7.8 1.9 69%
197 137 43
8.9 6.5 0.5 95%
155 146 8
2.5 2 Metal content
1.5
Waste acid in Clean acid Waste acid out Free acid recovery
1 0.5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
0 Vol of NaOH (ml)
Fig. 3. Titration graph for the estimation of free acid and metal content in spent and recovered acid.
Table 3 Example of retardation operation. Stream Test 1 Waste acid Regenerated acid By-product Test 2 Waste acid Regenerated acid By-product
R-Ahmedabad (aŌer resin change) R-Ahmedabad R-Pune NF-Chennai
Free acid (g/L)
Metals (g/L)
Acid recovery (%)
Metal retention (%)
32 22 13
42 11 35
70%
73%
24 17 8
49 14 42
73%
70%
NF-Faridabad DD-Gurgaon DD-Mohali DD-Chennai 0%
20%
40%
60%
80%
100%
The regenerated acid can be topped up with concentrated acid and reused. Further, neutralisation of the by-product requires less lime than the neutralisation of the total used acid thereby reducing the amount of sludge generated.
Acid/water recovery rate
Fig. 4. Recovery rate of acid/water by the demonstration plants at different locations (DD-diffusion dialysis; NF- nanofiltration; R-retardation).
high metal retention rates (Table 3). The results indicate that the pre-treatment must be optimized and adopted to the conditions in the metal finishing SME. Moreover, the retardation cycle has to be further optimized for higher recovery.
3.1.3. Nanofiltration Table 4 presents the example operation conditions for the nanofiltration demonstrations in this work for two different feed streams. The first case refers to the filtration of industrial wastewater from a CETP in Faridabad (North India). The effluent had a pH of 7.5 after neutralisation with lime and contained oils and heavy metals as well as salts. It was pre-treated by particle filter and oil separator
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Table 4 Example of nanofiltration operation. Parameter
Unit
Case 1 (Faridabad)
Case 2 (Chennai)
Permeate flow Permeability Transmembrane pressure Temperature Conductivity in permeate Conductivity in concentrate Salt separation rate Permeate recovery rate
L/h L/(m2*h) bar C mS/cm mS/cm % %
130 25 10 35 0.6 11.5 95 80
60 11.5 10 35 0.4 7.6 95 80
before nanofiltration. The conductivity was over 10 mS/cm. The obtained permeate with 0.5e0.6 mS/cm could be reused as feed water for production processes. With time, permeability gradually decreased due to precipitation of salts on the membrane surface. To maintain constant flow, it is recommended that nanofiltration should be applied to the less polluted process water streams before their mixing in the treatment plant. The second study was performed with rinsing water from a zinc coating line in Chennai (South India). The aim was to reuse the permeate as rinsing water and to return the concentrate into the zinc coating bath. The permeate was of sufficient quality to be reused whereas the concentrate would have to be further concentrated e.g. in an evaporator. Though high permeate recovery rate of 80% was obtained with both feed streams, there was an issue of decline in permeate flow over time. With the rinse water, in addition to precipitating salts like calcium sulphate and zinc hydroxide, degreasing oil was also suspected to be the cause of membrane fouling. To restore the flow, chemical cleaning with isopropyl alcohol and RO Kleen was done and the flow could be partially restored from 51 L/h to 78 L/h at 10 bar. 3.2. Challenges in the operation of demonstration plants The following challenges were encountered in the demonstration of these technologies. Oil contamination of acids and rinsing waters: The electroplating SMEs received parts for processing from a number of different customers. These parts are coated with oil of different grades and compositions, to prevent rusting during handling prior to electroplating. Degreasing is an important step in the electroplating process and a well operated degreasing bath will also lead to reduced acid and rinsing water consumption. As oil content varies with varying batches of the parts, continuous oil separation in degreasing baths becomes essential to avoid oil contamination of the subsequent processes. Currently this is not practiced in most SMEs. Thus efficient pre-treatment was required to ensure oil-free feed to diffusion dialysis/retardation/ nanofiltration plants. Non-availability of suitable oil separators: Though local commercial systems are available for oil removal from alkaline degreasing baths, suitable systems for removing oil from acid streams to the desired level (<70 ppm) could not be identified. The system supplied by Pure Tech India was constructed of a lower grade stainless steel and was therefore not compatible with acid streams. An acid resistant polypropylene based system was procured from Innovation Filter System, but the performance was not effective. Besides, material compatibility of the accessories (e.g. pump seals) with acids was also not guaranteed. Temperature and feed limitation of demonstration plants: The demonstration plants were specified to operate at ambient
Fig. 5. Damaged diffusion dialysis membrane module.
temperatures below 50 C. In all locations, ambient temperatures in the summer months (AprileAugust) would rise over 40 C. Thus, in each of the companies hosting the demonstration, the plant was installed in a suitably shaded and ventilated area. In spite of these precautions, temperatures in the demonstration plants appear to have exceeded the limits, perhaps due to pressure build up and normal heating up of components during long operation. This was observed in the diffusion dialysis membrane stack where the spacers and membranes melted, blocking the flow channels (Fig. 5). The polyester netting in some spacers also had holes in them. In the acid retardation plant, due to the high strength of mixed acid feed, level sensors in the acid tank got short circuited after every shutdown. Ambient temperature seems to contribute strongly to the issue, as the nanofiltration plant operated during winter months in Faridabad did not encounter operational problems despite hours of operation, while for the same feed during summer months, the plant had to be shut down after 30 to 40 min of operation. The nanofiltration plant had a provision for connecting to an external heat exchanger for cooling, but this could not be utilized during the trials as cold/chilled water was not readily available at the demonstration sites. Lack of corrosion resistance of demonstration plants: The demonstration plants were installed in the company close to the process line so feed acid/rinse water would be readily available. This exposed the plants to acid fumes and dust. As a result of continuous exposure to acid fumes, the metal skid of the plants as well as metal components of membrane stacks experienced corrosion (Fig. 6). Lack of analytical support: Most metal finishing SMEs had very limited analytical facilities in-house. In particular, reliable chemical analysis of the acid streams for measuring active acid and metal content was not available. Apart from evaluating the demonstration plant performance, this measurement is also necessary to monitor the composition of the pickling acid baths to decide when to discard the spent acid. Infrastructure limitations in SMEs: Because of limited space, most SMEs lack separate clean rooms where sophisticated equipment may be kept. As such, the demonstration plants had to be kept in the SME, exposed to dust and acid fumes. Apart from corrosion, dust can choke air operated diaphragm pump/ alter functionality resulting in change in the cycle time. Another issue is that electrical connections in most SMEs are complex and somewhat haphazard. This can lead to malfunction of the demonstration plant as experienced with the above mentioned electronic circuitry failure in the retardation plant. Soft/
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Fig. 6. Corrosion of diffusion dialysis plant components (a) membrane stack (b) skid on which plant was mounted.
demineralized water availability is limited and cannot be spared from the production process. As a result, against the suppliers' recommendations, municipal/ground water supply had to be used for nanofiltration membrane rinsing/cleaning, acid elution from retardation resin etc. Lack of technical support for demonstration plant operation: At each location where the plants were demonstrated, one or two persons in the host company were trained on plant operation by the project team. Due to production pressures and because the number of skilled personnel available in such SMEs is limited, the persons trained on demonstration plant operation could often not be spared for long durations to operate the respective regeneration plant. The pre-treatment step could also be time consuming and labour intensive. For example, in one company, due to high suspended solids content in the mixed acid feed, a filter press was used to remove the solids. This involved 3e4 workers for 4 h each time the retardation plant was operated, requiring considerable planning. Further, problems associated with demonstration plant operation required inputs from the plant suppliers in Europe to resolve the problem. In extreme cases (e.g. electronic malfunction and resin change in the retardation unit), an expert from the demonstration plant supplier had to be called on-site. Overall, troubleshooting was time consuming, expensive and needed the intervention of the project team. This reinforced the perception of the metal finishing SMEs that the acid and rinse water recovery technologies are too complex and expensive to suit their needs.
3.3. Overall assessment of the technologies and next steps The response of metal finishing SMEs and stakeholders (e.g.
representatives of regulatory authorities like the state pollution control boards, cleaner production councils) towards these technologies was assessed during the two awareness building workshops held at each site (Fig. 7) and through discussions with the companies hosting the demonstrations. Overall, the SMEs and the regulators are interested in using acid/rinse water recovery technologies. The motivation arises from increasing external pressures like limited availability of hazardous landfills, high cost of transporting sludge to landfills, fresh water scarcity etc. They are also partially convinced about the technical feasibility of the technologies. However, the high equipment cost (Euro 53,000e61,000 for each of the demonstration plants) is a major deterrent to their adoption. The demonstrations also established that the technologies need to be customized for the SME requirements, keeping in view the on-site challenges, particularly the pre-treatment and temperature compatibility requirements. High investment costs can be reduced if the plants are manufactured in India. The demonstrated technologies are basically known to the local plant producers who are familiar with ionexchange and membrane processes; therefore it should be possible for them to construct plants for the Indian SME market. Besides, locally manufactured components like nanofiltration membranes are available. As an individual SME could find it difficult to operate and maintain an acid/water recovery plant, an alternative is to build a large plant treating acids and rinsing waters from several companies in an industrial cluster. This centralized approach will reduce specific investment and operational costs as well as address capacity utilization issues. Furthermore, such centralized facilities can employ competent specialists providing reliable plant operation as well as good chemical analysis. This is an established approach with over 150 common effluent treatment facilities (CETPs) operational in industrial areas across India
Fig. 7. Awareness raising on the demonstration plants (a) Acid retardation (b) Diffusion dialysis.
M. Balakrishnan et al. / Journal of Environmental Management 217 (2018) 207e213
(Verma, 2012). More facilities are expected to come up in response to a recent directive to municipal bodies by the Supreme Court to set up CETPs in industrial areas within three years. Acid/water recovery could therefore be an additional service provided by the CETP. Alternately, another solution to address problems related to spent acids/rinse waters is to develop a service provider who operates a mobile plant that can be transported to various companies in an industrial cluster to provide acid/water recovery service. This would be especially suited for locations where state pollution control regulations prohibit the transport of spent acid from the SME premises. There is a gap in reliable and timely analytical service to measure active acids and metal ions in metal finishing SMEs in India. This limitation was partially addressed during the demonstrations by developing a simple titration procedure (as explained in Methodology). As a trained in-house chemist would be expensive, the possibility to hire an analytical chemist serving several SMEs at the industrial cluster level could be considered. 4. Conclusions Diffusion dialysis, acid retardation and nanofiltration technologies were demonstrated for acid/rinse water recovery in Indian metal finishing SMEs across different locations. Recovery rates were in the range of 78e86%, 80% and 30e70% for diffusion dialysis, nanofiltration and retardation respectively. The demonstrations created awareness among the metal finishing industries about the potential to recover resources such as acid/water from effluent streams. Lack of efficient oil separators, reliable chemical analysis and trained personnel, as well as high investment cost limit the application of these systems. These can be addressed by local manufacturing combined with customizing the plants to suit local requirements, and providing cluster level service for acid/water recovery. Acknowledgement This work is part of the 4-year (2012e2016) project “Sustainable production through market penetration of closed loop technologies in the metal finishing industry (ACIDLOOP)” (DCI-ASIE/2011/263160) co-funded by the European Union SWITCH Asia Programme. The authors gratefully acknowledge Ambattur Electroplaters Association (Chennai), Electroplating Industrial Welfare Association (Gurgaon), Faridabad Small Scale Pollution Control Co-op. Society (Regd.) (Faridabad), Mohali Industries Association (Mohali), Pune
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Metal Finishers Association (Pune) and Stainless Steel Re-Rollers Association (Ahmedabad) for facilitating the demonstrations and their member companies for hosting the demonstrations. The authors also thank V S Parthiban and P R Rajkamal (ASSIST) and Kumar Pawar (STENUM Asia) for assistance in conducting some of the tests. References Agrawal, A., Sahu, K.K., 2009. An overview of the recovery of acid from spent acidic solutions from steel and electroplating industries. J. Hazard. Mater. 171 (1), 61e75. Castelblanque, J., Salimbeni, F., 2004. NF and RO membranes for the recovery and reuse of water and concentrated metallic salts from waste water produced in the electroplating process. Desalination 167, 65e73. Chen, S.S., Li, C.W., Hsu, H.D., Lee, P.C., Chang, Y.M., Yang, C.H., 2009. Concentration and purification of chromate from electroplating wastewater by two-stage electrodialysis processes. J. Hazard. Mater. 161 (2), 1075e1080. CPCB (Central Pollution Control Board) http://envfor.nic.in/legis/ucp/ucpsch8.html Accessed on 30 March 2017. IITM. http://www.ceteddd.iitm.ac.in/uxf/msmes/83763Electroplating%20report_5. 8.14.pdf. Accessed on 27 September 2016. Jeong, J., Kim, M.S., Kim, B.S., Kim, S.K., Kim, W.B., Lee, J.C., 2005. Recovery of H 2 SO 4 from waste acid solution by a diffusion dialysis method. J. Hazard. Mater. 124 (1), 230e235. Kladnig, W.F., 2003. A review of steel pickling and acid regeneration an environmental contribution. Int. J. Mater. Prod. Technol. 19 (6), 550e561. Peng, C., Liu, Y., Bi, J., Xu, H., Ahmed, A.S., 2011. Recovery of copper and water from copper-electroplating wastewater by the combination process of electrolysis and electrodialysis. J. Hazard. Mater. 189 (3), 814e820. Qin, J.J., Wai, M.N., Oo, M.H., Lee, H., 2004. A pilot study for reclamation of a combined rinse from a nickel-plating operation using a dual-membrane UF/RO process. Desalination 161 (2), 155e167. Regel-Rosocka, M., 2010. A review on methods of regeneration of spent pickling solutions from steel processing. J. Hazard. Mater. 177 (1), 57e69. € gener, F., Buchloh, D., Reichardt, T., Schmidt, J., Knaup, F., 2009. Total regeneration Ro of mixed pickling acids from stainless steel production. Stahl Eisen 10, 69e73. € gener, F., Reichardt, T., 2009. Removal of iron fluorides Sartor, M., Buchloh, D., Ro from spent mixed acid pickling solutions by cooling precipitation at extreme temperatures. Chem. Eng. J. 153, 50e55. Sheedy, M., Pajunen, P., 2012. Acid separation for impurity control and acid recycle using short bed ion exchange. In: TT Chen Honorary Symposium on Hydrometallurgy, Electrometallurgy and Materials Characterization. John Wiley & Sons, Inc, pp. 383e395. Srinivas, S.N., Das, A.C.R., Iyer, S., 2013. The web of steel. In: Energy-efficient Steel Re-rolling. United Nations Development Programme, New Delhi, pp. 2e16, 146 pp. Tomaszewska, M., Gryta, M., Morawski, A.W., 2001. Recovery of hydrochloric acid from metal pickling solutions by membrane distillation. Sep. Purif. Technol. 22, 591e600. Verma, N.K., 2012. Overview of CETPS in India: Status, Issues and Challenges. http:// www.igep.in/live/hrdpmp/hrdpmaster/igep/content/e48745/e49028/e51431/ e51453/NKvermaprstrb.pdf. (Accessed 18 March 2017). Wong, F.S., Qin, J.J., Wai, M.N., Lim, A.L., Adiga, M., 2002. A pilot study on a membrane process for the treatment and recycling of spent final rinse water from electroless plating. Sep. Purif. Technol. 29 (1), 41e51.
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Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Research article
Demonstration of acid and water recovery systems: Applicability and operational challenges in Indian metal finishing SMEs M. Balakrishnan a, *, R. Batra b, V.S. Batra a, G. Chandramouli a, D. Choudhury b, 1, €lbig c, P. Ivashechkin c, J. Jain b, 2, K. Mandava a, N. Mense a, 3, V. Nehra b, 4, T. Ha € gener c, 5, M. Sartor c, V. Singh b, M.R. Srinivasan d, P.K. Tewari a F. Ro a
The Energy and Resources Institute (TERI), Darbari Seth Block, IHC Complex, Lodhi Road, New Delhi, 110 003 India STENUM Asia Sustainable Development Society, SFF 101, Palam Triangle, Palam Vihar, Gurgaon, 122 017, India Betriebsforschungsinstitut VDEh-Institut für angewandte Forschung GmbH (BFI), Sohnstraße 65, 40237 Düsseldorf, Germany d Asia Society for Social Improvement and Sustainable Transformation (ASSIST), No. 9, Desika Road, Mylapore, Chennai, Tamil Nadu, 600 004, India b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 17 April 2017 Received in revised form 17 March 2018 Accepted 21 March 2018 Available online 5 April 2018
Diffusion dialysis, acid retardation and nanofiltration plants were acquired from Europe and demonstrated in several Indian metal finishing companies over a three year period. These companies are primarily small and medium enterprises (SMEs). Free acid recovery rate from spent pickling baths using diffusion dialysis and retardation was in the range of 78e86% and 30e70% respectively. With nanofiltration, 80% recovery rate of rinse water was obtained. The demonstrations created awareness among the metal finishing companies to reuse resources (acid/water) from the effluent streams. However, lack of efficient oil separators, reliable chemical analysis and trained personnel as well as high investment cost limit the application of these technologies. Local manufacturing, plant customization and centralized treatment are likely to encourage the uptake of such technologies in the Indian metal finishing sector. © 2018 Elsevier Ltd. All rights reserved.
Keywords: Resource recovery Diffusion dialysis Acid retardation Nanofiltration Metal finishing SMEs Technology demonstration
1. Introduction Metal finishing is a surface treatment process that improves wear and tear resistance, imparts corrosion resistance and improves the aesthetics of metal parts. Various metal finishing techniques like electroplating, painting etc. are used to ensure quality and desired service life of metal components in consumer goods, engineering and construction industries. The electroplating industry in India is composed primarily of small and medium enterprises (SMEs) which are part of the supply chain for automobiles (cars, trucks), 2-wheelers (bicycles, scooters), engineering equipment and consumer goods. There are an estimated 12,000
organized units and around 300,000 small scale units in clusters across India (IITM, n.d). Due to the highly acidic waste streams and the hazardous sludge generated, electroplating is classified by Central Pollution Control Board (CPCB) as one of the major polluting industries (CPCB, n.d). Another key SME sector that employs acid pickling is steel rolling. There are around 1800 small and medium sized steel rolling enterprises across India contributing to nearly 70% of long steel output (bars, sections, industrial products etc.) (Srinivas et al., 2013). As a first step in the metal finishing process, the component is cleaned to remove oil, scales and other surface impurities. Cleaning involves a series of operations including chemicals degreasing and
* Corresponding author. E-mail address: [email protected] (M. Balakrishnan). 1 Current address: National Productivity Council, E e 5, GIDC, Electronic Estate, Sector 26, Gandhinagar, Gujarat e 382 028, India. 2 Current address: Shree Cement Limited, Bangur Nagar, Andheri Deori, Beawar, Ajmer, Rajasthan e 305 901, India. 3 Current address: Frost and Sullivan India Pvt. Ltd., 2nd Floor, Focus Building, Near Kapil Complex, Baner Road, Pune e 411 045, India. 4 Current address: National Productivity Council, Utpadakta Bhavan, 5e6 Institutional Area, Lodhi Road, New Delhi e 110 003, India. 5 Current address: Cologne University of Applied Sciences, Institute of Chemical Process Engineering and Plant Design; Betzdorfer Str. 2, 50679 Cologne, Germany. https://doi.org/10.1016/j.jenvman.2018.03.092 0301-4797/© 2018 Elsevier Ltd. All rights reserved.
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acid pickling. Each cleaning step is followed by single or double water rinse to avoid carryover of chemicals to the next bath. The spent pickling acid and wastewater from all process and rinse baths are collected and treated with lime to precipitate the metals before either evaporating the treated water or discharging it. The dewatered sludge is disposed in hazardous waste landfills. There are several approaches for the recovery of acids from metal finishing waste streams. These include extraction (Agrawal €gener et al., and Sahu, 2009), spray roasting (Kladnig, 2003; Ro 2009), ion-exchange (Sheedy and Pajunen, 2012), freeze crystallization (Sartor et al., 2009) and various membrane separation based processes like electrodialysis (Chen et al., 2009), diffusion dialysis (Jeong et al., 2005) and membrane distillation (Tomaszewska et al., 2001). Integrated process schemes such as electrolysis and electrodialysis (Peng et al., 2011), microfiltration, adsorption and ion exchange (Wong et al., 2002) have also been employed. The best available technologies are electrodialysis and diffusion dialysis but spray roasting and ion-exchange are employed extensively for spent acids regeneration on large scale (Regel-Rosocka, 2010). For recovery of rinse water in electroplating operations, reverse osmosis in combination with ultrafiltration (Qin et al., 2004) or nanofiltration (Castelblanque and Salimbeni, 2004) have been used. Though technologies are available, the practice o f acid and rinse water recovery is not established in Indian SMEs. The SMEs perceive the technologies to be expensive, besides being complex to operate and maintain as technical support from the technology supplier is often limited. They are also not convinced about the technical feasibility of these technologies for their waste streams. At the same time, technology suppliers do not perceive SMEs as a potential market citing lack of technical and financial capacity. This work demonstrates state-of-the-art technologies for acid and rinse water recovery in Indian metal finishing SMEs. Three technologies viz. diffusion dialysis and retardation (ion-exchange) for acid recovery and nanofiltration for rinse water recovery were demonstrated in different industry clusters. Diffusion dialysis is a membrane separation process based on concentration differences across a non-porous anion exchange membrane that allows acids to permeate but retains dissolved metals. Retardation involves sorption of free acid on the ion-exchange resin followed by desorption of the purified acid with deionized water in a counter-current flow. The recovered acid can be recycled while the metal ions and part of the acid that passes through form the waste stream that is usually neutralized and discharged. Nanofiltration is a pressure driven membrane process that concentrates divalent metal ions, allowing the passage of water that can be reused. All the three technologies are well established in Europe. Nanofiltration is widely applied in the European metal finishing industry for acid bath regeneration as well as for the reuse of rinsing water. Diffusion dialysis is used for the regeneration of used acids. With the use of a simple pressure-free design and modular structure, it is suitable for application in SMEs as well as large companies. Acid retardation is widely applied in European steel plants for the regeneration of used acid from pickling plants. Due to its modular design and automatic operation mode, it is also applicable in SMEs.
The aim of this work was to (a) evaluate the applicability of diffusion dialysis, acid retardation and nanofiltration for acid/water recovery in Indian metal finishing SMEs (or as a solution for common effluent treatment plants, CETPs) considering climatic conditions, operational stability and economic feasibility and (b) understand the challenges involved in the uptake of such technologies in this sector that will help formulate potential solutions. 2. Methodology The small-scale demonstration plants (Table 1) were fabricated in Europe. The required pre-treatment systems were procured locally. These included oil separators (Pure Tech India, Trichy and Innovation Filter System P. Ltd., Pirangut) and 20 micron polypropylene pleated cartridge filters (Placon Agencies, Chennai) to remove oil and particulate matter from the waste acid/water stream before feeding to the demonstration plant. Fig. 1 shows the installed systems. The demonstrations were conducted between 2013 and 2016 in different locations across India (Fig. 2). The installation and commissioning of the demonstration plant at each location was done by the project team. At each location, one or two persons in the host company were trained on plant operation. Analysis of the acids for free acid and metal content was done by titrating the acid solution with 1N sodium hydroxide (NaOH) in 0.5 ml steps until the pH reaches 12. A graph was drawn between the volume of NaOH added and DpH/DV (change in pH/difference in NaOH volume) for each step (Fig. 3). The peak points in the graph show the free acid and metal content present in the solution in NaOH equivalents. The treated rinse water was analysed for conductivity, total dissolved solids (TDS) and pH using in-house portable conductivity/TDS and pH meter. Where analytical facilities were not available with the host company, testing was done in accredited labs in the region. Two workshops were conducted at each location during the demonstration period for metal finishing industries in that region. The first workshop was to introduce the technology to the companies and the second was to share the performance results of demonstration plant. 3. Results and discussion 3.1. Performance of demonstration plants The results for the demonstrations in terms of acid/water recovery are summarized in Fig. 4. These are average values over the demonstration period in a specific location that ranged from a week (e.g. nanofiltration at Chennai) to several months (e.g. retardation at Pune). The recovered acid from retardation was reused in the pickling process. This resulted in reduction of fresh acid consumption by 35e40% in the electroplating unit in Pune. In the rolling unit in Ahmedabad, the used acid was internally recycled for preliminary descaling. The recovered water in nanofiltration was reused in the rinsing tank in the electroplating process in Chennai. The concentrate from the plant, which is obtained after recovering the water from the feed, was rich in electroplating chemicals and has the
Table 1 Demonstration plants specifications. Technology Diffusion dialysis
Acid retardation
Nanofiltration
Supplier Plant details
Scanacon AB, Sweden MiniFlex with special anion exchange retardation resin SCANACON 02070001; flow range 40e50 L/h Max. 50 C ambient temperature
SIMA-tec GmbH, Germany PSta15-2 universal membrane test stand with two 2.500 spiral wound modules Filmtec NF90-2540 with total surface area of 5.2 m2; permeate flow range 20e100 L/h Max. 50 C ambient temperature; needs cooling above 40 C
Deukum GmbH, Germany Pilot plant with Fumatech anion exchange membranes Fumasep FAD PET 75 with 20 m2 active membrane area; flow range 20e25 L/h Limitations Max. 50 C ambient temperature
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Fig. 1. Demonstration plants with pre-treatment (a) Diffusion dialysis (b) Acid retardation (c) Nanofiltration.
potential to be reused in the electroplating process. The following sections describe in detail the representative operation of the demonstration plants and the corresponding performance. 3.1.1. Diffusion dialysis In Table 2, example of diffusion dialysis operation is presented with used sulphuric acid from a plating line in Gurgaon (North India). The results illustrate that through the reduction of clean acid flow /increase of waste acid flow, high concentrations of free acid can be reached by the overall recovery rate of 69% (Test 2). To maximise recovery rate (95%), clean acid flow can be increased (Test 3). The resulting acid concentration is then however lower. Thus the flows can be adjusted according to the objective and clean acid reuse pathway. Decline in permeate flow over time was pronounced with the initial flow rate of 20 L/h dropping to 3 L/h in later stages. Blocking of the diffusion dialysis membrane stack channels with particulate
matter as well as membrane fouling due to oil in the spent acid feed was suspected. The membrane stack was cleaned using concentrated sulphuric acid, isopropyl alcohol and RO Kleen (commercial cleaner) but this procedure was found to be ineffective. The stack was shipped to the supplier Deukum to clean the channels and replace the membranes before further testing.
3.1.2. Retardation Table 3 shows examples of retardation application based on results from a mixed acid (H2SO4þHNO3þHF) pickling line for steel sheets in Ahmedabad (West India). The recovery of spent acids was initially about 50% and decreased to 30% in later operation. The low recovery rates compared to the theoretical 80e90% could be explained through the oil contamination of the resin surface and resin bed clogging with suspended solids. To address this problem, the resin was replaced with a fresh batch within a year of initiating operation. This resulted in increased acid recovery of 70% accompanied by
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Fig. 2. Summary of test sites.
Table 2 Example of diffusion dialysis operation.
4 3.5
∆pH/∆V
3
Waste acid /clean acid flow ratio
Free acid
Test 1
Test 2
Test 3
20/20 L/h
22.5/ 17.5 L/h
17.5/ 22.5 L/h
Free acid
Free acid
Free acid
g/L
g/h
g/L
g/h
g/L
g/h
8.8 6.6 1.1 75%
175 132 22
8.8 7.8 1.9 69%
197 137 43
8.9 6.5 0.5 95%
155 146 8
2.5 2 Metal content
1.5
Waste acid in Clean acid Waste acid out Free acid recovery
1 0.5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
0 Vol of NaOH (ml)
Fig. 3. Titration graph for the estimation of free acid and metal content in spent and recovered acid.
Table 3 Example of retardation operation. Stream Test 1 Waste acid Regenerated acid By-product Test 2 Waste acid Regenerated acid By-product
R-Ahmedabad (aŌer resin change) R-Ahmedabad R-Pune NF-Chennai
Free acid (g/L)
Metals (g/L)
Acid recovery (%)
Metal retention (%)
32 22 13
42 11 35
70%
73%
24 17 8
49 14 42
73%
70%
NF-Faridabad DD-Gurgaon DD-Mohali DD-Chennai 0%
20%
40%
60%
80%
100%
The regenerated acid can be topped up with concentrated acid and reused. Further, neutralisation of the by-product requires less lime than the neutralisation of the total used acid thereby reducing the amount of sludge generated.
Acid/water recovery rate
Fig. 4. Recovery rate of acid/water by the demonstration plants at different locations (DD-diffusion dialysis; NF- nanofiltration; R-retardation).
high metal retention rates (Table 3). The results indicate that the pre-treatment must be optimized and adopted to the conditions in the metal finishing SME. Moreover, the retardation cycle has to be further optimized for higher recovery.
3.1.3. Nanofiltration Table 4 presents the example operation conditions for the nanofiltration demonstrations in this work for two different feed streams. The first case refers to the filtration of industrial wastewater from a CETP in Faridabad (North India). The effluent had a pH of 7.5 after neutralisation with lime and contained oils and heavy metals as well as salts. It was pre-treated by particle filter and oil separator
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Table 4 Example of nanofiltration operation. Parameter
Unit
Case 1 (Faridabad)
Case 2 (Chennai)
Permeate flow Permeability Transmembrane pressure Temperature Conductivity in permeate Conductivity in concentrate Salt separation rate Permeate recovery rate
L/h L/(m2*h) bar C mS/cm mS/cm % %
130 25 10 35 0.6 11.5 95 80
60 11.5 10 35 0.4 7.6 95 80
before nanofiltration. The conductivity was over 10 mS/cm. The obtained permeate with 0.5e0.6 mS/cm could be reused as feed water for production processes. With time, permeability gradually decreased due to precipitation of salts on the membrane surface. To maintain constant flow, it is recommended that nanofiltration should be applied to the less polluted process water streams before their mixing in the treatment plant. The second study was performed with rinsing water from a zinc coating line in Chennai (South India). The aim was to reuse the permeate as rinsing water and to return the concentrate into the zinc coating bath. The permeate was of sufficient quality to be reused whereas the concentrate would have to be further concentrated e.g. in an evaporator. Though high permeate recovery rate of 80% was obtained with both feed streams, there was an issue of decline in permeate flow over time. With the rinse water, in addition to precipitating salts like calcium sulphate and zinc hydroxide, degreasing oil was also suspected to be the cause of membrane fouling. To restore the flow, chemical cleaning with isopropyl alcohol and RO Kleen was done and the flow could be partially restored from 51 L/h to 78 L/h at 10 bar. 3.2. Challenges in the operation of demonstration plants The following challenges were encountered in the demonstration of these technologies. Oil contamination of acids and rinsing waters: The electroplating SMEs received parts for processing from a number of different customers. These parts are coated with oil of different grades and compositions, to prevent rusting during handling prior to electroplating. Degreasing is an important step in the electroplating process and a well operated degreasing bath will also lead to reduced acid and rinsing water consumption. As oil content varies with varying batches of the parts, continuous oil separation in degreasing baths becomes essential to avoid oil contamination of the subsequent processes. Currently this is not practiced in most SMEs. Thus efficient pre-treatment was required to ensure oil-free feed to diffusion dialysis/retardation/ nanofiltration plants. Non-availability of suitable oil separators: Though local commercial systems are available for oil removal from alkaline degreasing baths, suitable systems for removing oil from acid streams to the desired level (<70 ppm) could not be identified. The system supplied by Pure Tech India was constructed of a lower grade stainless steel and was therefore not compatible with acid streams. An acid resistant polypropylene based system was procured from Innovation Filter System, but the performance was not effective. Besides, material compatibility of the accessories (e.g. pump seals) with acids was also not guaranteed. Temperature and feed limitation of demonstration plants: The demonstration plants were specified to operate at ambient
Fig. 5. Damaged diffusion dialysis membrane module.
temperatures below 50 C. In all locations, ambient temperatures in the summer months (AprileAugust) would rise over 40 C. Thus, in each of the companies hosting the demonstration, the plant was installed in a suitably shaded and ventilated area. In spite of these precautions, temperatures in the demonstration plants appear to have exceeded the limits, perhaps due to pressure build up and normal heating up of components during long operation. This was observed in the diffusion dialysis membrane stack where the spacers and membranes melted, blocking the flow channels (Fig. 5). The polyester netting in some spacers also had holes in them. In the acid retardation plant, due to the high strength of mixed acid feed, level sensors in the acid tank got short circuited after every shutdown. Ambient temperature seems to contribute strongly to the issue, as the nanofiltration plant operated during winter months in Faridabad did not encounter operational problems despite hours of operation, while for the same feed during summer months, the plant had to be shut down after 30 to 40 min of operation. The nanofiltration plant had a provision for connecting to an external heat exchanger for cooling, but this could not be utilized during the trials as cold/chilled water was not readily available at the demonstration sites. Lack of corrosion resistance of demonstration plants: The demonstration plants were installed in the company close to the process line so feed acid/rinse water would be readily available. This exposed the plants to acid fumes and dust. As a result of continuous exposure to acid fumes, the metal skid of the plants as well as metal components of membrane stacks experienced corrosion (Fig. 6). Lack of analytical support: Most metal finishing SMEs had very limited analytical facilities in-house. In particular, reliable chemical analysis of the acid streams for measuring active acid and metal content was not available. Apart from evaluating the demonstration plant performance, this measurement is also necessary to monitor the composition of the pickling acid baths to decide when to discard the spent acid. Infrastructure limitations in SMEs: Because of limited space, most SMEs lack separate clean rooms where sophisticated equipment may be kept. As such, the demonstration plants had to be kept in the SME, exposed to dust and acid fumes. Apart from corrosion, dust can choke air operated diaphragm pump/ alter functionality resulting in change in the cycle time. Another issue is that electrical connections in most SMEs are complex and somewhat haphazard. This can lead to malfunction of the demonstration plant as experienced with the above mentioned electronic circuitry failure in the retardation plant. Soft/
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Fig. 6. Corrosion of diffusion dialysis plant components (a) membrane stack (b) skid on which plant was mounted.
demineralized water availability is limited and cannot be spared from the production process. As a result, against the suppliers' recommendations, municipal/ground water supply had to be used for nanofiltration membrane rinsing/cleaning, acid elution from retardation resin etc. Lack of technical support for demonstration plant operation: At each location where the plants were demonstrated, one or two persons in the host company were trained on plant operation by the project team. Due to production pressures and because the number of skilled personnel available in such SMEs is limited, the persons trained on demonstration plant operation could often not be spared for long durations to operate the respective regeneration plant. The pre-treatment step could also be time consuming and labour intensive. For example, in one company, due to high suspended solids content in the mixed acid feed, a filter press was used to remove the solids. This involved 3e4 workers for 4 h each time the retardation plant was operated, requiring considerable planning. Further, problems associated with demonstration plant operation required inputs from the plant suppliers in Europe to resolve the problem. In extreme cases (e.g. electronic malfunction and resin change in the retardation unit), an expert from the demonstration plant supplier had to be called on-site. Overall, troubleshooting was time consuming, expensive and needed the intervention of the project team. This reinforced the perception of the metal finishing SMEs that the acid and rinse water recovery technologies are too complex and expensive to suit their needs.
3.3. Overall assessment of the technologies and next steps The response of metal finishing SMEs and stakeholders (e.g.
representatives of regulatory authorities like the state pollution control boards, cleaner production councils) towards these technologies was assessed during the two awareness building workshops held at each site (Fig. 7) and through discussions with the companies hosting the demonstrations. Overall, the SMEs and the regulators are interested in using acid/rinse water recovery technologies. The motivation arises from increasing external pressures like limited availability of hazardous landfills, high cost of transporting sludge to landfills, fresh water scarcity etc. They are also partially convinced about the technical feasibility of the technologies. However, the high equipment cost (Euro 53,000e61,000 for each of the demonstration plants) is a major deterrent to their adoption. The demonstrations also established that the technologies need to be customized for the SME requirements, keeping in view the on-site challenges, particularly the pre-treatment and temperature compatibility requirements. High investment costs can be reduced if the plants are manufactured in India. The demonstrated technologies are basically known to the local plant producers who are familiar with ionexchange and membrane processes; therefore it should be possible for them to construct plants for the Indian SME market. Besides, locally manufactured components like nanofiltration membranes are available. As an individual SME could find it difficult to operate and maintain an acid/water recovery plant, an alternative is to build a large plant treating acids and rinsing waters from several companies in an industrial cluster. This centralized approach will reduce specific investment and operational costs as well as address capacity utilization issues. Furthermore, such centralized facilities can employ competent specialists providing reliable plant operation as well as good chemical analysis. This is an established approach with over 150 common effluent treatment facilities (CETPs) operational in industrial areas across India
Fig. 7. Awareness raising on the demonstration plants (a) Acid retardation (b) Diffusion dialysis.
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(Verma, 2012). More facilities are expected to come up in response to a recent directive to municipal bodies by the Supreme Court to set up CETPs in industrial areas within three years. Acid/water recovery could therefore be an additional service provided by the CETP. Alternately, another solution to address problems related to spent acids/rinse waters is to develop a service provider who operates a mobile plant that can be transported to various companies in an industrial cluster to provide acid/water recovery service. This would be especially suited for locations where state pollution control regulations prohibit the transport of spent acid from the SME premises. There is a gap in reliable and timely analytical service to measure active acids and metal ions in metal finishing SMEs in India. This limitation was partially addressed during the demonstrations by developing a simple titration procedure (as explained in Methodology). As a trained in-house chemist would be expensive, the possibility to hire an analytical chemist serving several SMEs at the industrial cluster level could be considered. 4. Conclusions Diffusion dialysis, acid retardation and nanofiltration technologies were demonstrated for acid/rinse water recovery in Indian metal finishing SMEs across different locations. Recovery rates were in the range of 78e86%, 80% and 30e70% for diffusion dialysis, nanofiltration and retardation respectively. The demonstrations created awareness among the metal finishing industries about the potential to recover resources such as acid/water from effluent streams. Lack of efficient oil separators, reliable chemical analysis and trained personnel, as well as high investment cost limit the application of these systems. These can be addressed by local manufacturing combined with customizing the plants to suit local requirements, and providing cluster level service for acid/water recovery. Acknowledgement This work is part of the 4-year (2012e2016) project “Sustainable production through market penetration of closed loop technologies in the metal finishing industry (ACIDLOOP)” (DCI-ASIE/2011/263160) co-funded by the European Union SWITCH Asia Programme. The authors gratefully acknowledge Ambattur Electroplaters Association (Chennai), Electroplating Industrial Welfare Association (Gurgaon), Faridabad Small Scale Pollution Control Co-op. Society (Regd.) (Faridabad), Mohali Industries Association (Mohali), Pune
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Metal Finishers Association (Pune) and Stainless Steel Re-Rollers Association (Ahmedabad) for facilitating the demonstrations and their member companies for hosting the demonstrations. The authors also thank V S Parthiban and P R Rajkamal (ASSIST) and Kumar Pawar (STENUM Asia) for assistance in conducting some of the tests. References Agrawal, A., Sahu, K.K., 2009. An overview of the recovery of acid from spent acidic solutions from steel and electroplating industries. J. Hazard. Mater. 171 (1), 61e75. Castelblanque, J., Salimbeni, F., 2004. NF and RO membranes for the recovery and reuse of water and concentrated metallic salts from waste water produced in the electroplating process. Desalination 167, 65e73. Chen, S.S., Li, C.W., Hsu, H.D., Lee, P.C., Chang, Y.M., Yang, C.H., 2009. Concentration and purification of chromate from electroplating wastewater by two-stage electrodialysis processes. J. Hazard. Mater. 161 (2), 1075e1080. CPCB (Central Pollution Control Board) http://envfor.nic.in/legis/ucp/ucpsch8.html Accessed on 30 March 2017. IITM. http://www.ceteddd.iitm.ac.in/uxf/msmes/83763Electroplating%20report_5. 8.14.pdf. Accessed on 27 September 2016. Jeong, J., Kim, M.S., Kim, B.S., Kim, S.K., Kim, W.B., Lee, J.C., 2005. Recovery of H 2 SO 4 from waste acid solution by a diffusion dialysis method. J. Hazard. Mater. 124 (1), 230e235. Kladnig, W.F., 2003. A review of steel pickling and acid regeneration an environmental contribution. Int. J. Mater. Prod. Technol. 19 (6), 550e561. Peng, C., Liu, Y., Bi, J., Xu, H., Ahmed, A.S., 2011. Recovery of copper and water from copper-electroplating wastewater by the combination process of electrolysis and electrodialysis. J. Hazard. Mater. 189 (3), 814e820. Qin, J.J., Wai, M.N., Oo, M.H., Lee, H., 2004. A pilot study for reclamation of a combined rinse from a nickel-plating operation using a dual-membrane UF/RO process. Desalination 161 (2), 155e167. Regel-Rosocka, M., 2010. A review on methods of regeneration of spent pickling solutions from steel processing. J. Hazard. Mater. 177 (1), 57e69. € gener, F., Buchloh, D., Reichardt, T., Schmidt, J., Knaup, F., 2009. Total regeneration Ro of mixed pickling acids from stainless steel production. Stahl Eisen 10, 69e73. € gener, F., Reichardt, T., 2009. Removal of iron fluorides Sartor, M., Buchloh, D., Ro from spent mixed acid pickling solutions by cooling precipitation at extreme temperatures. Chem. Eng. J. 153, 50e55. Sheedy, M., Pajunen, P., 2012. Acid separation for impurity control and acid recycle using short bed ion exchange. In: TT Chen Honorary Symposium on Hydrometallurgy, Electrometallurgy and Materials Characterization. John Wiley & Sons, Inc, pp. 383e395. Srinivas, S.N., Das, A.C.R., Iyer, S., 2013. The web of steel. In: Energy-efficient Steel Re-rolling. United Nations Development Programme, New Delhi, pp. 2e16, 146 pp. Tomaszewska, M., Gryta, M., Morawski, A.W., 2001. Recovery of hydrochloric acid from metal pickling solutions by membrane distillation. Sep. Purif. Technol. 22, 591e600. Verma, N.K., 2012. Overview of CETPS in India: Status, Issues and Challenges. http:// www.igep.in/live/hrdpmp/hrdpmaster/igep/content/e48745/e49028/e51431/ e51453/NKvermaprstrb.pdf. (Accessed 18 March 2017). Wong, F.S., Qin, J.J., Wai, M.N., Lim, A.L., Adiga, M., 2002. A pilot study on a membrane process for the treatment and recycling of spent final rinse water from electroless plating. Sep. Purif. Technol. 29 (1), 41e51.