Environmental life cycle assessment of zero liquid discharge treatment technologies for textile industries, Tirupur A case study

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1 Journal of Scientific & Industrial Research RAJAKUMARI KANMANI: ZERO LIQUID DISCHARGE TREATMENT TECHNOLOGIES FOR TEXTILE INDUSTRIES 461 Vol. 67, June 2008, pp Environmental life cycle assessment of zero liquid discharge treatment technologies for textile industries, Tirupur A case study S Priscilla Rajakumari* and S Kanmani Centre for Environmental studies, Anna University, Chennai Received 29 June 2007; revised 11 April 2008; accepted 15 April 2008 Inventorisation of inputs (chemicals and energy) for treating textile wastewater using pretreatment, reverse osmosis (RO) and evaporator for two representative textile wastewater treatment plants have been studied. All life cycle inventory data were recalculated per functional unit, which was defined as treatment of 1 m 3 of textile wastewater. Evaporator consumes 48 % of electricity, which contributes for more global warming potential (GWP) than other treatment units. Total GWP for plant I and II are 4.49 kg eq and 5.56 kg eq respectively. During electricity generation, emission is comparatively high (98.5 % of total emissions). The results indicate that RO system of plant I and II consumes less energy and GWP are 8.9 x 10-3 kg eq and kg eq respectively. Human health impact is 7.4 E-05 for emission, which is less for other emissions. The results can be used for strategic decisions for minimizing environmental impacts of zero liquid treatment technologies. Keywords: Life cycle assessment, Life cycle inventory, Reverse osmosis, Zero liquid discharge Introduction All textile manufacturing units are required to install zero liquid discharge systems either on their own or as a group form combined effluent treatment plants (CETPs) to achieve zero liquid discharge. Using zero liquid discharge treatment system, effluent (85%) will be recovered as tap grade water and volume (15%) will be recovered as salt solution for direct reuse in dye bath and thus ensure complete elimination of discharge into environment. Source reduction and water reuse are considered justifiable only if they represented economical savings through either recovery of materials or avoidance of treatment costs 1. All wastewater treatment technologies are to varying degree driven by electricity. Although processes such as electrolysis may be characterized as electro-technologies, mechanical operation processes such as filtration, centrifugation, flotation and even chemical oxidation processes such as ozonation and supercritical oxidation are electricity intensive 2. In this case study, environmental assessment of zero liquid discharge treatment technologies for treating *Author for correspondence Tel: ; Fax: textile wastewater is done by life cycle assessment (LCA). Materials and Methods LCA, which assesses total impact of a particular product or process to environment 3, starts from acquisition of raw materials to transport of these materials to manufacturing plant for production. The products are salvaged as waste 4. Next stage in LCA is inventory analysis, wherein a detailed description of product systems and inputs and outputs of that system are traced 5. Within impact assessment, there is a need to characterize pollutants impact to environment, then an indexing or valuation is done to combine results together into one value 6. System Boundaries In system boundaries (Figs 1 & 2), operations were grouped into three sections [pretreatment (P), reverse osmosis (RO), and evaporator (E)]. Inventorisation of inputs (chemicals and energy) for treating textile wastewater using P, RO and E for two representative textile wastewater treatment plants have been studied from an environmental point of view. Since there is no discharge from zero discharge treatment plants, no

2 462 J SCI IND RES VOL 67 JUNE 2008 wastewater Wastewater Effluent collection sump Reactivator I Fluidised Bed Bio Reactor Secondary clarifier Sludge thickener Reactivator II Gravity sand filter Dual media filter Activated carbon filter Filter press Bag filter Cartridge filter Reverse osmosis I Reverse osmosis II Degassifier Evaporator permeate salt sludge Fig. 1 System boundary of life cycle assessment of zero liquid discharge treatment system for Plant I Fig. 2 System boundary of life cycle assessment of zero liquid discharge treatment system for Plant II

3 RAJAKUMARI & KANMANI: ZERO LIQUID DISCHARGE TREATMENT TECHNOLOGIES FOR TEXTILE INDUSTRIES 463 Table Life cycle inventory profile of coal electricity generating systems Inventory category Ammonia (NH 3 ) 0.10 Carbon dioxide ( ) 1020 Carbon monoxide (CO) 0.27 Hydrogen chloride (HCl) 1.8 x10-6 Hydrogen fluoride (HF) 1.7 x10-7 Methane (CH 4 ) 0.91 Nitrogen oxides (NO x ) 3.4 Nitrous oxide (N 2 O) 4.4 x10-3 Particulate matter (PM) 9.2 Sulfur oxides (SO x ) 6.7 Life cycle inventory data g/kwh Table 2 Emissions from transportation of trucks 8 Parameter, g/km Emissions at different speed and fuel use Speed, km/h Fuel consumption CO NO x SO Soot PM downstream activities were considered. Functional unit for the study was 1m 3 of wastewater to be treated. Analysis of Data Data from inventorisation was normalized to functional unit to get total energy, chemicals and emissions generated to treat textile wastewater (1 m 3 ). Normalized data was then classified under impact categories [global warming potential (GWP), acidification potential (AP) and human health impact (HHI)]. Estimates of emissions during transportation of materials were made using emission factors and transported distance. On emissions from transportation and electricity production, country specific (India) average emission data were used. In this case study, inventory of emissions during production of electricity has been collected from coal based electricity generating systems in India, where about 60% of electricity is being generated from coal (Table 1) 7. Inventory of emissions during transportation of chemicals has been calculated based on emission factors for trucks in India (Table 2) 8. Emission factors for transportation are based on speed (50 km/h). Global Warming Potential (GWP) GWP factors are multiplied by life cycle inventory (LCI) to get green house effect of different processes considered in this study. GWP for green house gases (, CH 4, N 2 O, CO and NO x ) are expressed as equivalents 9 as Potential green house effect (kg eq.) = ΣGWP i x m i where, GWP i = GWP equivalency factor in kg eq./ kg of greenhouse gas (i), 100 year time horizon and m i Table 3 Inventory of electricity consumption S No. Treatment units Electricity based equipments Power for Power for plant I plant II kwh kwh 1 Effluent treatment Feed pump, lime dosing pump, ferrous sulphate plant dosing pump, HCl dosing pump, ferric chloride dosing pump, backwash pump, hydraulic pump 2 Reverse osmosis Feed pump, high pressure pump system 3 Evaporator Feed pump, circulation pump, condensate pump, cooling tower, cooling tower fan, crystaliser feed pump

4 Table 4 Global Warming Potential due to electricity generation for Plant I and Plant II Parameters Effluent treatment plant Reverse osmosis Evaporator Plant I Plant II Plant I Plant II Plant I Plant II Electricity consumption, KWh, kg CO, kg (x10-4 ) CH 4, kg (x10-3 ) N 2 O, kg (x10-6 ) GWP, kg eq Table 5 Acidification Potential due to electricity generation for Plant I and Plant II Parameters Effluent treatment plant Reverse osmosis Evaporator Plant I Plant II Plant I Plant II Plant I Plant II Electricity consumption, KWh NH 3, kg 0.128x x x x x x J SCI IND RES VOL 67 JUNE 2008 HCl, kg 2.31x x x x x x10-9 HF, kg 2.18x x x x x x10-10 NOx, kg 4.36x x x x x x10-3 SOx, kg 8.59x x x x AP in kg SO 2 eq x

5 RAJAKUMARI & KANMANI: ZERO LIQUID DISCHARGE TREATMENT TECHNOLOGIES FOR TEXTILE INDUSTRIES 465 Table 6 Human health impact (HHI) S No. Substance Characterization Plant I Plant II DALY*/kg factor E E E-05 2 NO x 4.48E E E-09 3 CH E E E-07 *DALY, Disability adjusted life year = mass of greenhouse gas (i), released to air per functional unit. Acidification Potential (AP) AP factors are multiplied by LCI to get acidification effect of different processes considered in this study. AP for Ammonia (NH 3 ), hydrogen chloride (HCl), hydrogen fluoride (HF), nitrogen oxides (NO x ) and sulfur oxides (SO x ) are expressed as SO 2 equivalents 9 as Potential acidification effect (kg SO 2 eq.) = ΣAP i x m i where, AP i = GWP in kg SO 2 eq./kg gas and m i = amount of emitted gas (i) in kg. Results and Discussion Life Cycle Inventory (LCI) of Electricity Generation Table3 shows inventory of electricity consumption for P, RO and E in two treatment plants. GWP due to consumption of electricity for zero liquid discharge treatment for plant I and II are kg eq. and kg eq. respectively (Table 4). AP due to consumption of electricity for plants I and II are 0.04 kg SO 2 eq. and 0.05 kg SO 2 eq. respectively (Table 5). Evaporator consumes 48% of electricity, which contributes for more GWP than other treatment units. GWP due to consumption of electricity by evaporator of plant I is found to be kg eq. and AP is found to be SO 2 eq. During electricity generation, emissions of and SO x are more when compared to other air emissions. Therefore, because of more energy consumption, evaporator also contributes for more AP than other treatment units. Raluy et al 10 also found that multiple effect evaporator consumes more electricity in LCA of desalination technologies. Emissions during production of electricity (Fig. 3) show that emission is comparatively high (98.5% of total emissions). RO system of plants I and II consumes less energy (8.9 x 10-3 kg eq.) and GWP (0.011 kg eq.). Health impact of global atmospheric changes is in general directly related to the severity of diseases affected, measured in terms of disability and death. These effects can be quantified as number of years of healthy life lost. Concept of a disability adjusted life year (DALY) is therefore used as a measure of change in disease burden in human populations, which can be associated with atmospheric changes 11. Emissions of, NO x and CH 4 from electricity generation and transportation of chemicals can be specified in terms of HHI (Table 6). HHI for (7.4 E-05) using the scale is less for other emissions. DALY scale 12 lists many different disabilities on a scale between 0 and 1 (0, perfectly healthy; 1, death). Transportation of Chemicals Chemicals required for treatment processes are supplied to zero discharge plant through trucks. Emission factors for transportation are based on speed (50 km). (415.1g/km) and NOx (275.7 g/km) are leading pollutants, which affect environment especially air quality. Emissions of (67.5 %) and NO x (31%) together are maximum (98.5%) of total emissions (Fig. 4). Coal ash and dewatered sludge from raw water coagulation process are reported 13 major solid wastes produced during life cycle of electricity generation. Truck is shown to be a heavy polluter in terms of its emission factors. With the use of natural gas as an alternative fuel, emission levels can be reduced for and NO x. Truck can be an environmentally adapted vehicle if its engine is converted to an alternative fuel engine like compressed natural gas 14. For treating textile wastewater, lime, ferrous sulphate, ferric chloride, hydrochloric acid and polyelectrolyte are used in primary treatment. Role of primary treatment is

6 466 J SCI IND RES VOL 67 JUNE Emission, kg CO2 CO CO CH4 N20 2 CO CH 4 N 2 O Air emissions Emissions in kg in Plant I Emissions in kg in Plant II Fig. 3 Emissions during production of electricity Emissions, kg CO2 CO NOX SO2 2 CO x 2 PM Air emissions Emissions at Plant I Emissions at Plant II Fig. 4 Emissions during transportation of chemicals Table 7 GWP and AP due to transportation for Plant I and Plant II Parameters Total emission GWP AP kg kg eq kg SO 2 eq Plant I Plant II Plant I Plant II Plant I Plant II CO NO x SO

7 RAJAKUMARI & KANMANI: ZERO LIQUID DISCHARGE TREATMENT TECHNOLOGIES FOR TEXTILE INDUSTRIES 467 to remove colour and solids in effluent so as to make it fit for feeding to RO system. Antiscalant and antifoulant were used in RO system to eliminate scaling and minimize fouling of membranes by colloidal impurities and bacteria. Major input used in the treatment is lime. Treatment plant I that has two clarifier units consumes more chemicals than treatment plant II. Total dosage of lime is more for treatment plant I (800 mg/l) than that in plant II (360 mg/l). GWP and AP are more for plant I. GWP due to emission during transportation of chemicals for plants I and II are kg eq. and kg eq. respectively (Table 7). AP during transport of chemicals for treatment plants I and II are 0.04 kg SO 2 eq. and kg SO 2 eq. respectively (Table 7). Conclusions From pollutant emissions in transportation stage, and NO x are leading pollutants, which affect environment specifically air quality. is major emission during life cycle of treatment of textile wastewater using zero liquid discharge treatment technologies. Acidification potential due to emissions from NO x and SO x has a high impact in transport of vehicles. Using natural gas as an alternative fuel, emission levels can be reduced for and NO x. During electricity generation, emission of is more and for treating 1 m 3 of textile wastewater for treatment Plants I and II, emissions are 4.39 kg and 5.44 kg respectively. Global warming potential for plants I and II are 4.5 kg eq. and 5.6 kg eq. respectively. emission from power plants can be saved using biomass gasification. The results can be used for strategic decisions for minimizing environmental impacts of zero liquid treatment technologies. References 1 Zhou H and Smith D W, Advance technologies in water and wastewater treatment, J Environ Engg & Sci, 1 (2002) Angela Arpke, Neil Hutzler P E & Asce M, Operational Life- Cycle Assessment and Life Cycle cost analysis for water use in multi occupant buildings, J Architect Engg, 11 (2005) Ortiz M, Raluy G, Serra L & Uche J, Life cycle assessment of water treatment technologies: wastewater and water reuse in a small town, Desalination, 204 (2007) Inga Silvestraviciute & Inga Karaliunaite, Comparison of Endof-life tyre treatment technologies: Life cycle Inventory analysis, Environ Res, Engg Manage, 1 (2006) Goran Finnveden & Lars-Gunnar Lindfors, Data quality of life cycle inventory data-rules of thumb, Int J LCA, 3 (1998) Gerilla G P, Teknomo K & Hokao K, An environmental assessment of wood and steel reinforced concrete housing construction, Building & Environment, 42 (2007) David V S and Gregory A K, Life Cycle Environmental and Economic Assessment of Willow Biomass Electricity: A Comparison with Other Renewable and Non-Renewable Sources, Centre for sustainable systems, University of Michigan, 2005; 8 CPCB, Transport Fuel Quality for 2005 (Central Pollution Control Board, New Delhi). 9 Landu L & Alan C Brent, Environmental life cycle assessment of water supply in South Africa : The Rosslyn industrial area as a case study, Water SA, 32 (2006) Raluy R G, Serra L, Uche J & Valero A, Life-cycle assessment of desalination technologies integrated with energy production systems, Desalination, 167 (2004) Martens W J M, Global atmospheric and human health: an integrated modeling approach, Climate research, 6 (1996) Koroneos C, Roumbas G, Gabari Z, Papagiannidou E & Moussiopoulos N, Life cycle assessment of beer production in Greece, J Cleaner Production, 13 (2005) Malgorzata Goralczyk, Life cycle assessment in the renewable energy sector, Appl energy, 75 (2003) Gloria P Gerilla, Kardi Teknomo & Kazunori Hokao, Environmental assessment of International transportation of products, J Eastern Asia Soc for Transportation Studies, 6 (2005)