Case study on sustainability of textile wastewater treatment plant based on lifecycle assessment approach

Journal Pre-proof Case study on sustainability of textile wastewater treatment plant based on lifecycle assessment approach Pranav H. Nakhate, Keyur K. Moradiya, Hrushikesh G. Patil, Kumudini V. Marathe, Ganapati D. Yadav PII:

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DOI:

https://doi.org/10.1016/j.jclepro.2019.118929

Reference:

JCLP 118929

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Journal of Cleaner Production

Received Date: 1 May 2019 Revised Date:

27 September 2019

Accepted Date: 16 October 2019

Please cite this article as: Nakhate PH, Moradiya KK, Patil HG, Marathe KV, Yadav GD, Case study on sustainability of textile wastewater treatment plant based on lifecycle assessment approach, Journal of Cleaner Production (2019), doi: https://doi.org/10.1016/j.jclepro.2019.118929. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

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Case study on sustainability of textile wastewater treatment

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plant based on lifecycle assessment approach

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Pranav H. Nakhate; Keyur K. Moradiya; Hrushikesh G. Patil; Kumudini V. Marathe; Ganapati D. Yadav * Department of Chemical Engineering, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga, MUMBAI-400019 INDIA,

*Corresponding author Tel:+91-22-3361-1001 Fax: +91-22-3361-1020 Email: [email protected]; [email protected]

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Abstract

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The present study is aimed at the estimation of the environmental footprints of a textile effluent

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treatment plant in India based on Lifecycle analysis (LCA) thinking of gate-to-gate approach

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with closed-loop recycling. The real-time operational data was collected on a daily basis for a

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year with minimum experimental uncertainties and treated as lifecycle inventory. Based on

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existing plant practice, two-fold functional units of 1,500 m3 (effluent stream 1) and 1,200 m3

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(effluent stream 2) were considered for the study, based on which the system boundary was

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designed. The analysis demonstrated that the ozonation process contributes significantly in

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generating environmental burden, with a global warming potential of 1,440 kg and 2,041 kg

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CO2 equivalent for effluent stream 1 and 2, respectively. Conversely, activated carbon filter

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imparts less to the environmental burden, with a global warming potential of 217 kg and 173.5

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kg CO2 equivalent for effluent stream 1 and 2, respectively, compared to other processes. Based

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on the parametric analysis, it was understood that electricity contributed substantially; and thus

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sensitivity/scenario analysis was carried out, showing 50 % and 90 % attenuation of

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environmental burden with increased renewable energy share from 50 % to 100 %. Increase in

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effluent reuse scenario also found to have augmented the environmental performance of the

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system. Based on the data presented in this study, policy-makers can decide strategies to reduce

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the environmental burden.

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Keywords: Lifecycle Assessment (LCA); Waste Water Treatment; Textile Effluent; Midpoint Assessment; Endpoint Assessment; Closed-loop recycling

31 32 2

33 34

Abbreviations:

35

AA: Aquatic Acidification.; AC: Granular Activated Carbon; ACF, Activated Carbon Filter; ADP: Abiotic

36

Depletion Potential; AOP, Advance Oxidation Process; AP, Acidification Potential; BOD, Biological Oxidation

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Demand; CA, Citric Acid; CCP, Climate Change Potential; CETP, Common Effluent Treatment Plant; CMF,

38

Continuous Membrane Filtration; COD, Chemical Oxidation Demand; CSE, Centre for Science and Environment;

39

DC, Decolorant; DP, Diphosphate; EP, Eutrophication Potential; ES, Effluent stream; ETP, Effluent Treatment

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Plant; ECJRCTES, European Commission-Joint Research Centre-Institute for Environment and Sustainability;

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FAETP, Freshwater Aquatic Ecotoxicity Potential; FU, Functional Unit; GWP, Global Warming Potential; HCL,

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Hydrochloric Acid; HP, Hydrogen Peroxide; HTP, Human Toxicity Potential; IRP: Ionizing Radiation Potential;

43

ISO, International Standards Organizations; LCA, Life Cycle Assessment; LCI, Life Cycle Inventory; LCIA, Life

44

Cycle Impact Assessment; LCT, Life Cycle Thinking; LHV, Low Heating Values; MAETP, Marine Aquatic

45

Ecotoxicity Potential; MBR, Membrane Bioreactor; MIDC, Maharashtra Industrial Development Corporation; MP,

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Monophosphate; NC, Nutrient Culture; NF, Nano Filtration; ODP, Ozone Depletion Potential; PAC, Poly-

47

aluminum Chloride; PE, Polyelectrolyte; PM, Particulate Matter; POF, Photochemical Ozone Formation; PS,

48

Photochemical Smog; PVDF, Polyvinylidene Di-fluoride; RD, Resource Depletion; RO, Reverse Osmosis; SH,

49

Sodium Hydroxide; SHC, Sodium Hypochlorite; SF, Sand Filtration; SM, Sodium Metabisulfite SPF, Solar Photo-

50

Fenton; TAP: Terrestrial Acidification Potential; TDS, Total Dissolved Solids; TETP, Terrestrial Ecotoxicity

51

Potential; UF, Ultrafiltration; UV, Ultraviolet dynamic reactor; UVB, UV batch Reactor; WRD, Water Resource

52

Depletion;

53

Treatment Plant; ZLD. Zero

WSP, Wastewater Stabilization Pond; WWT, Waste Water Treatment; WWTP, Waste Water

liquid discharge

54 55 56 57 58 59 3

60 61 62

1.

Introduction

63 64

Wastewater treatment and reuse have assumed great significance worldwide since freshwater

65

resources are fast depleting. Wastewater is generated at various stages in all segments of industry

66

including upstream and downstream processing. The processed water or industrial effluent is

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then treated at Wastewater Treatment Plant (WWTP) using various unit operations. The ultimate

68

purpose of WWTP is either to eliminate the pollutants from effluent or reclaim the effluent

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within dischargeable limits according to the local standards (Hernández-Padilla et al., 2017).

70

Sustainable effluent treatment is essential because it could reduce the water burden of current

71

and future generations (Opher et al., 2018). However, various treatment technologies consume

72

harmful chemicals and need substantial power for pumping, agitation, aeration, and other unit

73

operations, along with generation of sludge and gases (Godin et al., 2012). Besides generating

74

dischargeable effluent, WWTP aggravates environmental burden depending on treatment

75

technology and effluent stream. Therefore, an assessment has to be done to evaluate every

76

possible environmental impact of the water treatment technologies.

77 78

The textile industry is one of the oldest and important industries in Indian economy, since it

79

accounts for ~2 % of India’s overall GDP and 8 % of custom and excise revenue collection

80

(Restiani, 2016). Constant supply of enormous quantities of clean water is needed for textile

81

processing and a study conducted by Centre for Science and Environment (CSE) estimates that

82

~200-250 m3 water are used per ton of cotton cloth (CSE India, 2019). In the textile industry,

4

83

water is mostly used for dyeing and finishing processes, contributing ~80 % of the total effluent

84

containing high amounts of organics as well as dyestuff such as azo dyes, vat dyes, etc. (Prabhu

85

et al., 2016). Close to 30 % of dyes lose their binding capability and remain in the dye bath at the

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end of processing which could form mutagenic amines, and therefore, textile effluent can be

87

hazardous to the environment, if not treated properly (Arslan-Alaton and Alaton, 2007).

88

Numerous technologies have been adapted so far by WWTP to treat textile effluent including

89

aerobic and anaerobic digestion, Ultra-Filtration (UF), Reverse Osmosis (RO), Advanced

90

Oxidation Process (AOP), coagulation, and flocculation, etc. However, the sustainability of such

91

treatment methods has not been considered thoroughly using Life Cycle Analysis (LCA) which

92

might overshadow the benefits of effluent treatment resulting into different environmental

93

impacts (Zepon Tarpani and Azapagic, 2018).

94 95

The international footprint of water standards (ISO 14046) was released in 2014 as a result of

96

which the LCA based water footprint assessment has acquired greater interest from industrial as

97

well as academic sectors (Zepon Tarpani and Azapagic, 2018). LCA appears to be one of the

98

essential techniques which can quantify various environmental impacts associated with product,

99

process, system or service from cradle to grave based on ISO 14040 series guidelines

100

(Büyükkamaci and Karaca, 2017). A normalized international LCA methodology considers the

101

entire life cycle starting from extraction of raw materials from mother earth, manufacturing,

102

transport, distribution, use, and end of life including waste collection, segregation, treatment,

103

recycling, disposal, etc. (Carré et al., 2017). LCA methodology is composed of four vital

104

categories naming, ‘functional unit’ (FU), ‘goal and scope definition’, ‘life cycle inventory’

105

(LCI) and ‘interpretation’ (ISO 2006a ; ISO 2006b). The LCA starts with the collection of all

5

106

inventories within the system boundary including all the direct and indirect input-output flows

107

called as LCI whereas FU is assigned based on LCI to which all impacts are alluded to. The life

108

cycle impact assessment (LCIA) method calculates the set of potential impacts of a system under

109

consideration with the help of a characterization factor related to each flow by using cause-effect

110

chain. As the inventories are related to each phase of the life cycle, it can assess the potential

111

environmental impacts generated by the individual process or the whole system (Carré et al.,

112

2017). The LCA study can assist policy and decision-makers from various sectors to select the

113

best sustainable technique vis-à-vis the alternatives or comparable equivalent options.

114 115

As regards WWTP, LCA was first implemented in the 1990s and more than 200 studies have

116

been published until 2013 (Corominas et al., 2013). Emmerson et al. (1995) carried out LCA of

117

construction, operation and demolition phases of small scale sewage treatment process with a

118

capacity of 200 m3/day. The impact category selected was Global Warming Potential (GWP) (kg

119

CO2 equivalent), according to which over a fifteen-year lifetime, biological filter plant might

120

consume 55 % less energy as well as 35 % fewer air emissions compared to activated sludge.

121

Tangsubkul et al. (2005) carried out LCA of three unit operations including, continuous

122

Membrane Filtration, Membrane Bioreactor (MBR) and Wastewater Stabilization Pond (WSP).

123

The FU of the study was considered to be the delivery of 1 mL of recycled water used for

124

irrigation of several sensitive crops. The interpretation suggested that energy utilization causes

125

higher Eutrophication Potential (EP) impact in every unit operation whereas biosolids

126

application causes nearly 98 % toxicity impacts including Human Toxicity Potential (HTP),

127

Freshwater Aquatic Eco-toxicity Potential (FAETP), Marine Aquatic Eco-toxicity Potential

128

(MAETP), and Terrestrial Eco-toxicity Potential (TETP). Recently, Awad et al. (2019) studied

6

129

the environmental and cost of LCA of different alternatives for WWTP improvements and

130

concluded that LCA had more influence associated with the operational phase than the

131

construction phase in four scenarios, wherein, gaseous emissions and energy consumptions

132

found to have higher environmental footprint. Recent work on LCA of wastewater treatment is

133

provided in Table 1; however, most of the studies have focused on assessing the sustainability of

134

a single or limited unit operations and not the entire plant per se.

135 136

Sr.

Table 1: Literature survey of various case studies related to LCA of WWTP Study Title

No 1

Functional Unit

Goal and Scope

(FU)

Impact

Reference

Categories

LCA of urban water

Annual water

Sustainability of four

AP, HTP,

(Opher et al.,

reuse at various

supply, reclamation

different water reuse

POF, ODP,

2018)

centralization scales

and reuse of water

approaches based on

FAETP, IRP,

consumed by

environmental, social

MAETP,

hypothetical city

and economic aspects

PM, Land

with population of

use, RD.

200,000 2

LCA of conventional

Treatment of 1 m3 of Comparison of

GWP, HTP,

(di Maria and

technologies for landfill

landfill leachate

different technologies

POF, ODP,

Sisani, 2017)

for landfill leachate

PM, AP,

treatment.

FAETP,

leachate treatment

WRD 3

LCA of advanced

Treatment of 1,000

Estimate and

CCP, RD,

(Zepon 7

WWTP for removal of

m3 of effluent from

comparison of LCA

pharmaceutical and

conventional

of GAC, NF, SPF and FAETP, AP,

Azapagic,

personal care products

WWTP.

ozonation for

IRP, land

2018)

treatment of PPCPs

use, HTP.

(PPCP) 4

WRD, ODP,

Tarpani and

LCA on polishing unit

Delivery of 1 m3

Assessment of

GWP, AP,

(Büyükkamaci

for use of treated

recycled water to be

environmental

EP, HTP,

and Karaca,

wastewater in

used for irrigation

impacts of polishing

FAETP,

2017)

agriculture reuse

purpose

units for reuse of

ODP,

treated wastewater for agriculture irrigation of sensitive crops. 5

LCA case study on

Treatment of 1 m3

Assessment of

HTP, IRP,

(Carré et al.,

tertiary treatment

of domestic

environmental

GWP, EP,

2017)

process options for

wastewater

impacts of SF+ UV,

FAETP, AP,

SF+UVB, UF, and

MAETP

wastewater reuse

UF+ UAB 6

Environmental Stability

1 m3 secondary

Evaluation of

HTP,

(Foteinis et

of Photo-Fenton process

treatment of

environmental

MAETP,

al., 2018)

pharmaceutical WWT at

pharmaceutical

impacts of Solar–

FAETP,

semi-industrial scale.

wastewater

Fenton process for

GWP, TAP,

diluted

PM, CCP,

pharmaceutical

POF

8

effluent at semiindustrial scale 7

Assessing the

Treatment of 1 m3

Comparison of

GWP, HTP,

(Hernández-

environmental impacts

municipal

performance of two

PM, CCP,

Padilla et al.,

of WWT in Latin

wastewater over 20-

different unit

FAETP,

2017)

America and Caribbean

year lifespan

operations across all

MAETP,

impacts to select an

TAP

efficient method. 8

Environmental

Management of 10 L Evaluation of

EP, GWP,

(Hospido et

assessment of

primary and

environmental

HTP, TTP

al., 2010)

anaerobically digested

secondary mixed

impacts of mixed

sludge reuse in

(70:30 v/v) sludge

sludge from

agriculture

collected from

anaerobic digester

existing STP

and its reuse method in agriculture

9

LCA of urban

Supply of 1 m3

Assessment of

FAETP,

(Munoz et al.,

wastewater reuse with

treated wastewater

environmental

MAETP,

2009)

ozonation as a tertiary

for irrigation in

advantage and

TTP, HTP

treatment

agriculture

drawbacks of reuse of wastewater focusing on toxicity-related impacts

10

LCA of bio-sludge

Management of 1-

Identification of most

GWP, AA,

(Usapein and

9

sludge disposal with

tonne bio-sludge

environmentally

TTP,

Chavalparit,

different management

friendly option for

FAETP,

2017)

scenarios: A case study

bio-sludge disposal

MAETP

of different olefin factory in Thailand 11

Environmental Impact

Treatment of 1 m3

Evaluation and

TAP, GWP,

(Venkatesh

and research for a more

municipal landfill

comparison of

HTTP,

Prabhu et al.,

suitable chemical

leachate.

environmental

FAETP,

2016)

alternative in municipal

impacts of two

MAETP,

landfill leachate

different coagulants

WRD

treatment

and pH agents in municipal landfill leachate treatment plant

12

LCA of municipal

Treatment of 105 m3

Assessment of

ADP, GWP,

(Li et al.,

wastewater treatment

effluent per day over

environmental

AA, TAP,

2013)

plant: A case study of

50-years

benefits and

EP

Suzhou, China

drawbacks of municipal WWTP with other WWTPs using different advanced treatment processes

10

13

LCA of small scale

Treatment of 1 p.e.

Assessment of

HTP, GWP,

(Lopsik,

constructed wetland and

(equals to 60 g BOD

environmental

FAETP,

2013)

aeration activated sludge in 24 h ) municipal

impacts from

MAETP,

WWT system

wastewater for 15-

different types of

WRD

year operational

WWTP using impact

period.

2000+ and ReCiPe impact categories

14

15

LCA of water reuse

Treatment of 1 m3

Assessment of

ADP, AP,

(Tong et al.,

system in industrial park

effluent coming

environmental

EP, FAETP,

2013)

from industrial park

impacts and

GWP, HTP,

performance of

MAETP,

WWTP

ODP, TETP

LCA of WWTP

Treatment of 1 m3

Evaluation and

ADP, AP,

(Li et al.,

involving 126

secondary-treated

comparison of

EP, FAETP,

2019)

pharmaceutical and

wastewater

potential

GWP, HTP,

environmental

MAETP,

impacts of advanced

ODP, TETP

personal care products

wastewater treatment processes 137 138 139

As described in Table 1, most of the LCA studies in the field of WWT of textile effluent have

140

focused on assessing environmental impacts generated by either a single or limited set of unit

11

141

operations. As the significance of LCA in treatment of wastewater has been realized, the present

142

study attempts to bridge the gap in research by implementing the LCA technique to understand

143

the environmental impacts of various unit operations at WWTP with reference to

144

industry. The innovativeness of the current study lies in the holistic analysis of physical,

145

chemical and biological treatment methods of the entire WWTP based on life cycle perspective.

146

The prime objective of the present study of textile industry effluent were thus set on the

147

following aspects;

textile

148 149 150

1. To compute the environmental burdens created by entire WWTP based on comprehensive data.

151

2. To carry out the contribution analysis to pinpoint the significant impact categories.

152

3. To perform the parameter analysis to identify the major factors which contribute to the

153

environment.

154

4. To initiate the lifecycle thinking (LCT) by means of scenario analysis in order to generate

155

baseline environmental impacts of entire WWTP for establishing market-oriented

156

policies.

157 158

The comparison of various unit operations based on LCA are not restricted to the current system

159

under consideration, but could be extended to various other effluent treatment plants (ETPs).

160 161

2. Materials and Methods

162

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163

The current study has been carried out based on the real-time data collected from textile WWTP

164

operated by Konark Industry Pvt. Ltd. The system under consideration has been located on the

165

premise of an esteemed textile industry at five star MIDC Park, Kolhapur city, Maharashtra,

166

India.

167 168

2.1 Effluent treatment Plant (ETP) description

169 170

The overall design capacity of the plant is 3,500 m3/ day whereas actual working capacity is

171

2,700 m3/ day. The effluent is generated from various unit operations at Konark including fiber

172

preparation, spinning, sizing, knitting, tufting, souring, bleaching, dyeing, printing, and finishing.

173

The effluent from the textile plant there is then transferred to ETP in two different effluent

174

streams of 1,500 m3 (ES-1) and 1,200 m3 (ES-2) per day. The effluent at Konark Industry is

175

treated at seven major unit operations as follows: Equalization, Aeration, Clarifier (I and II),

176

Activated Carbon Filters (ACF), Ozonation, UF and RO

177

characterization of both the streams is presented in Table 2.

(Figure 1). The effluent

178

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179

Figure 1: Process layout of the textile ETP at Konark Industry, Kolhapur, India under study

180 181

The equalization tank is the first unit operation which receives effluent from the factory. The

182

Textile industrial effluent usually contains high pH due to the presence of a large amount of

183

hydrolyzed alkaline dyes. Microbial growth gets inhibited at higher pH (Padan et al., 2005);

184

therefore, before transferring effluent to an aerobic process, pH adjustment is done by addition of

185

an appropriate amount of hydrochloric acid (HCl). For the aerobic process, a specified microbial

186

culture is added on a monthly basis. The culture is prepared at the plant itself whereas the dosage

187

is depended on effluent characteristics. After the aerobic process, effluent is transferred to two

188

clarifiers. Clarifier I is used to settle the solid particles and to adjust the pH as a microbial

189

activity may affect the effluent pH. In Clarifier II, coagulation and flocculation take place with

14

190

the addition of Poly-Aluminum Chloride (PAC) and Polyelectrolyte (PE) (DKSET-3113). The

191

effluent is then pumped into ACF where activated carbon bed is used to adsorb color and odor.

192

Table 2: Effluent Characterization 193

Parameter

1200 m3 ETP

1500 m3 ETP

ISO standards 194

(IS:2296-1982) Final

195

Initial

Final

Initial

Final

pH

8-9

6.5-7.5

8-9

6.5-7.5

COD(mg/L)

970

36

977

40

<250

BOD(mg/L)

218

20

220

22

< 30

Color (Hazen)

3,536

20

3,476

30

< 100

TDS (mg/L)

3,500

50

3,572

45

< 2100 199

TSS(mg/L)

380

10

386

20

< 100

Effluent (m3)

1,200

1,070

1,500

1,160

-

6.5-8.0 196 197 198

200 201

202 203

The ACF is followed by ozonation process where 15 ozonator tanks with a capacity of 200 L at

204

0.2 kg/cm2 pressure are required to feed 250 g/h ozone dosage to both the streams individually

205

on daily basis. Hydrogen peroxide (H2O2) dosage is also provided at 3.68 L/day basis. Both

206

effluent streams of 1,500 m3 and 1,200 m3 are then treated by a combination of UF and RO

207

membranes. Around 70 Polyvinylidene Di-fluoride (PVDF)- UF membrane units of ZW 1500-

208

600 X are installed at the ETP plant with 0.02 µm diameter 55.7 m2/ module. Nearly 96 brackish

209

water RO membranes of AG-400 LF, 34 having a surface area of 37.1 m2/module (provided by

210

GE-India) are installed next to UF membrane and grouped into RO-I, RO-II and RO-III. Reject

211

from UF membrane is fed to the equalization tank whereas reject from RO membrane is

212

transferred to nearby Common Effluent Treatment Plant (CETP). Bag filters are installed before

15

213

the UF membrane whereas cartridge filters are installed prior to the RO unit in order to protect

214

them from fouling. Both UF and RO membranes are washed after 3-4 days based on flux data.

215

The sludge formed during aeration and clarifiers I and II is collected separately and transported

216

to nearby village Rangangaon for further treatment. All characterizations including Chemical

217

Oxidation Demand (COD), Biological Oxidation Demand (BOD) and Total Dissolved Solids

218

(TDS) are done in the plant for input and output of every unit operation on a daily basis. It is

219

important to note that nearly 50 % permeate from RO is sent back to the industry whereas the

220

reject is transferred to CETP.

221

2.2. Goal and Scope of the study

222

The primary goal of the current study is to estimate the overall environmental impacts of the

223

textile effluent treatment plant. The study was focused on evaluating the environmental impacts

224

of operational parameters only. Construction and demolition phases are not covered in the

225

current study since their impacts are negligible compared to the operational parameters as

226

understood from the literature and mentioned elsewhere (Carballa et al., 2011; Li et al., 2017 and

227

Polruang et al., 2018). The first section of the current study deals with analyzing the seven unit

228

operations based

16

229 230

Figure 2: System Boundary

231

on their respective environmental impacts. Moreover, the scenario analysis of materials, which

232

gives higher impact, is performed in a later section.

233 234

The scope of the LCA study in the field of WWT is very well defined in other comprehensive

235

studies mentioned earlier. For the current study, the “Gate-to-Gate” methodology followed by

236

closed-loop of recycling was considered. Around 50 % effluent is reused within the factory

237

premises and used for various purposes whereas resource utilization for the same quantity is

238

considerable. A system boundary for the current study is presented below in Figure 2.

239 240

2.3.

Functional Unit (FU)

241 242

FU is the central entity around which the study revolves making it the prominent aspect of the

243

assessment (Marathe et al., 2019). This will be useful in scale up or scale down. The textile plant

244

of Konark under consideration generates two different effluent streams of 1,500 m3 and 1,200

245

m3 per day based on the manufacturing of textile garments. Both streams have different physical

246

and chemical characteristics and thence treated individually. Therefore, the treatment of effluent

247

stream-1 (ES-1) with 1,500 m3/day and effluent stream-2 (ES-2) with 1,200 m3/day are

248

considered as two-fold functional units.

249 250

2.4.

LCA Methodology

251

17

252

The various aspects of assessment protocol need to be followed along with some inclusions and

253

assumptions in order to conduct an organized study. The LCA methodology can be used as an

254

environmental assessment technique to evaluate the performance of the system under

255

consideration. The LCA methodology has been defined by ISO 14040: 2006 series (ISO 2006a

256

and ISO 2006b) which deals with principles, frameworks, and guidelines required to conduct

257

study. GaBi 8.7 along with commercial dataset was used as the operating tool to calculate the

258

environmental impacts generated by various unit operations in the Indian context (included in

259

GaBi). The midpoint assessment method CML 2001: Jan 2016 comprises various impact

260

categories which oriented for human health, climate change and environmental burdens

261

concerning at emission level. On the other hand, ReCiPe 1.08 (I), individualistic endpoint

262

assessment method, is the most recent one which delivers a judgment about the relative

263

importance of each impact (Corominas et al., 2013). Therefore, the midpoint assessment method

264

CML 2001: Jan 2016 and endpoint assessment method ReCiPe 1.08 (I) are considered as impact

265

assessment techniques for a holistic understanding of the results. The CML 2001: Jan 2016

266

midpoint assessment method comprises twelve different impact categories out of which Abiotic

267

Depletion Potential (ADP), Acidification Potential (AP), HTP, GWP, FAETP, EP, MAETP and

268

TETP impact categories are considered for a comprehensive overview of the results.

269 270

2.5.

Lifecycle Inventory (LCI)

271 272

The Konark ETP was surveyed thoroughly and specialized input-output data sheets were

273

prepared based on respective unit operations. The input-output data of the effluent was collected

274

for a year on a daily basis from January to December 2017 whereas collected data were analyzed

18

275

and compared with the previous three years’ data for the internal consistency check. The

276

chemical and energy consumption data were also collected for every individual unit operation.

277

Transportation of materials during various stages has significant impact in lifecycle modeling.

278

Therefore, transportation required for chemicals and sludge deposition was also calculated. The

279

transportation distance covered is considered 350 km whereas the vehicle considered for the

280

transportation is truck trailer BS III with diesel containing 350 ppm sulfur content. The monthly

281

averaged data for a complete year along with model can be seen in the supported file. According

282

to the data obtained, the effluent discharged from the WWT facility is considerable and of good

283

quality and hence reused within the campus for other applications like gardening, flushing,

284

washing, etc. Site-specific LCA data modeling was done because extensive datasets were

285

available. Therefore, the generalized datasets are avoided as much as possible. All the data used

286

have a tolerance limit of 5% and the consistency was checked by experts. The averaged LCI

287

values for both the streams have been presented in Tables 3 and 4. However, the detailed LCI

288

values considered for model development are presented in the supplementary information (SI).

19

Unit Operations

289

COD

BOD

TDS

(mg/L)

(mg/L)

(mg/L)

Output sludge (kg)

Electricity Chemicals (kWh)

312.01

HCl

PAC

PE

DC

NP

MP

DP

Ozone

HP

SHC

SH

CA

SM

(L)

(kg)

(kg)

(kg)

(kg)

(kg)

(kg)

(kg/h)

(L)

(kg)

(kg)

(kg)

(kg)

32.4

1.10

1.12

3.1

2.1 31.70

2.49

1.30

ET

972.3

216.25

3,571

AP

1,020.1

226.97

3,613

38.91

1,873.21

2,333.6

Cl

179.91

93.75

3,498

35.69

312.01

ACF

134.25

44

3,490

312.01

OP

95.91

20

3,340

2,052.54

UF

93.08

15.16

3,286

1,432.33

5.23

RO

88.66

11.83

2,899

1,427.66

213.50

413.1

2.1

52.8

1.82

1.35

Table 3: Lifecycle Inventory (LCI) for stream 1 of the system under consideration

290 291

Table 4: Lifecycle Inventory (LCI) for stream 2 of the system under consideration Unit Operations

COD

BOD

TDS

Output sludge

Electricity

(mg/L)

(mg/L)

(mg/L)

(kg)

(kwh)

Chemicals

140.14

HCL

PAC

PE

DC

NP

MP

DP

Ozone

HP

SH

SHC

CA

SM

(L)

(kg)

(kg)

(kg)

(kg)

(kg)

(kg)

(g/h)

(L)

(kg)

(kg)

(kg)

(kg)

26.1

0.89

0.94

2,993.1

3.58 25.53

2.2

1,802.2

ET

970.25

219.33

3,534.

AP

1,009

223.91

3,617

16.68

840.88

Cl

197.58

96.83

3,631

15.31

140.14

ACF

123.25

48.83

3,673

140.14

OP

96.08

19.83

3,428

1,641.80

UF

92.5

14.41

3,250.

1,142.15

4.4

2.15

RO

89.66

8.91

3,171

1,142.15

181

1.08

290.7

1.82

42.4

1.4

20

292

2.6.

Allocation Methods

293 294

For the credit of the closed-loop recycling, two approaches, i.e. Cut-Off mechanism and System

295

expansion were considered as has been explained elsewhere (Shen et al., 2010). In the Cut-off

296

mechanism, the impacts generated by every unit operation is analyzed. The impact generated by

297

reused water is considered as an impact for the raw water, i.e. water required at the textile

298

industry for various purposes including flushing, washing, gardening and others are replaced by

299

reused water. Therefore, the impact is compensated in the lifecycle of an entire process. Due to

300

such a practice, the impact for the system under consideration gets reduced and considered as

301

reused credit (Jensen et al., 1997). In system expansion mechanism, two lifecycles of operating

302

material are merged and considered to be a single system; therefore, scenarios generation can be

303

done depending upon the parameters considered while modeling. This practice could provide

304

future lifecycle of treated effluent coming from WWTP and save disposal of water. Such a

305

method could appeal to the process of recycling and reusing the effluent as most of the industries

306

are eyeing zero liquid discharge (ZLD) nowadays (Jensen et al., 1997).

307 308

2.7.

Limitations, Assumptions and Uncertainties

309 310

LCA study often imparts theoretical and practical limitations because of different assumptions

311

made at various places. After elaborating goal and scope of the system under study, many

312

parameters are left unattended as they may have fewer impacts (Bai et al., 2018). It has been

313

assumed that the life span of the entire WWTP is 20-25 years whereas the lifespan of RO and UF

314

membrane and activated carbon techniques is assumed to be 5-6 years. The impacts generated by

21

315

process equipment used for WWT including ozonator, UF or RO membrane module are not

316

considered for the study. This consideration is in line with other studies (Niero et al., 2014). The

317

impact generated by materials and construction of building the facility, housing and private or

318

public facilities including roadways, etc. are not considered due to inadequacy and inconsistency

319

of data. Maintenance phase, demolition phase, and land occupation are also excluded from the

320

current study. Nevertheless, the environmental impacts generated by the means of LCA analysis

321

are the probable impacts rather than factual impacts which are typically not specified in space

322

and time (Muñoz et al., 2009).

323 324

3. Results

325

The first part of the study deals with assessing environmental impacts generated by various unit

326

operation whilst the treatment of ES-1 and ES-2. The overall environmental impact for both the

327

streams was obtained using CML 2001: Jan 2016 midpoint assessment method and presented

328

later.

329 330

3.1.

Overall Lifecycle Impact Assessment (LCIA) using CML 2001: Jan 2016 Method

331

From Tables 5 and 6, it can be observed that ES-1 has fewer impacts in every selected impact

332

category compared to ES-2. Besides ES-1 has a higher effluent volume to treat. This represents

333

that ES-2 has a high amount of pollutants and therefore requires a moderately greater stock of

334

electricity and chemicals. The environmental impacts of each individual unit operation have been

335

analyzed in all categories for both the streams, in order to identify the factors which impart high

336

environmental burden.

337

22

338

Table 5: CML 2001: Jan 2016 Midpoint assessment Impacts of Effluent Stream 1 (1,500 m3)

339

No

Impact Categories

Combined Impact of WWT unit (0 % Reuse)

Impacts with 50 % Reuse ( Current Scenario)

1

Abiotic Depletion (ADP fossil) [MJ]

6.68 × 104

3.85 × 104

2

Acidification Potential (AP) [kg SO2-Equiv.]

68.8

64.9

3

Eutrophication Potential (EP) [kg PhosphateEquiv.] Freshwater Aquatic Ecotoxicity Pot. (FAETP inf.) [kg DCB-Equiv.] Global Warming Potential (GWP 100 years) [kg CO2-Equiv.] Global Warming Potential (GWP 100 years), excl biogenic carbon [kg CO2-Equiv.] Global Warming Potential (GWP 100 years), excl biogenic carbon [kg CO2-Equiv.] Marine Aquatic Ecotoxicity Pot. (MAETP inf.) [kg DCB-Equiv.] Terrestric Ecotoxicity Potential (TETP inf.) [kg DCB-Equiv.]

67.4

23.4

15.3

17

6.20 × 103

4.81 × 103

6.19 × 103

4.16 × 103

1.89 × 103

1.83 × 103

8.31 × 106

8.31 × 106

15.4

14.8

4 5 6 7 8 9 340

Table 6: CML 2001: Jan 2016 Midpoint assessment Impacts of Effluent Stream 2 (1,200 m3)

341

No.

Impact Categories

Combined Impact of WWT unit ( 0 % Reuse)

1

Abiotic Depletion (ADP fossil) [MJ]

7.56 × 104

Impacts with 50 % Reuse (Current Scenario) 6.78 × 104

2

Acidification Potential (AP) [kg SO2-Equiv.]

83.5

82.09

3

Eutrophication Potential (EP) [kg PhosphateEquiv.] Freshwater Aquatic Ecotoxicity Pot. (FAETP inf.) [kg DCB-Equiv.]

51.9

83.26

17.3

17.31

4

23

5

Global Warming Potential (GWP 100 years) [kg CO2-Equiv.]

7.17 × 103

6.69 × 103

6

Global Warming Potential (GWP 100 years), excl biogenic carbon [kg CO2-Equiv.]

7.16 × 103

6.55 × 103

7

Global Warming Potential (GWP 100 years), excl biogenic carbon [kg CO2-Equiv.]

2.18 × 103

2.14 × 103

8

Marine Aquatic Ecotoxicity Pot. (MAETP inf.) [kg DCB-Equiv.]

9.34 × 106

9.32 × 106

9

Terrestric Ecotoxicity Potential (TETP inf.) [kg DCB-Equiv.]

18.7

18.43

342

24

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

Equalisation

Aeration

Clarifier I & II

ACF

Ozonation

UF

RO

343 344

Figure 3: CML 2001: Jan 2016 Impact of Effluent Stream 1 (ES-1)

345 346

25

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

Equalisation

Aeration

Clarifier I & II

ACF

Ozonation Process

UF

RO

347

Figure 4: CML 2001: Jan 2016 Impact of Effluent Stream 2 (ES-2)

348 349 350

3.2.

Abiotic Depletion Potential (ADP)

351

ADP is the correlation between extractions of resources to its available stock in the geosphere.

352

ADP fossil fuels are associated with low heating values (LHV) since LHV is reviewed as a

353

completely substituted fossil fuel (Burchart-Korol and Kruczek, 2016). Therefore, according to

354

the international reference lifecycle data system (ILCD) handbook, ADP method is 26

355

recommended for analyzing resource depletion at midpoint level and it is expressed in terms of

356

MJ/ kg or m3 of fossil fuel (ECJRCIES, 2010). From Figure 3, it can be observed that aeration

357

and ozonation process from ES-1 imparts higher ADP impacts compared to other processes,

358

whereas ozonation, UF, and RO from ES-2 gives higher ADP impacts compared to other unit

359

operations. Ozonation process in both ES-1 and ES-2 was found to be as high as 23.5 % and 27.4

360

% of the overall impacts, respectively whereas ACF was found to be an effective process

361

contributing only 3.5% and 2.3 % ADP impacts respectively.

362 363

3.3.

Acidification Potential (AP)

364 365

AP has usually incorporated with atmospheric pollution originated from anthropogenic sulfur

366

(S), nitrogen (N), NOx and SOx. The constant deposition of anthropogenic materials elevates the

367

acidification rate which may lower the neutralizing capacity of the soil. Such anthropogenic

368

emissions are produced while mining and refining stages of fossil fuels (Yang et al., 2009). It can

369

be seen from Figure 3 that AP is higher in aeration and ozonation process for ES-1, imparting

370

21.5 % and 23.5 % of the total impact, respectively, whereas for ES-2 system, ozonation give

371

30.4%, UF and RO give 21.1 % of the total impacts respectively. Ozonation was again found to

372

be contributing higher impact while equalization and ACF contributed least AP impact.

373 374

3.4.

Eutrophication Potential (EP)

375 376

EP is majorly caused by constant deposition of phosphorus and nitrogen in water or soil. The

377

wastewater treatment process is said to be efficient if it has lower EP (Renou et al., 2008). The

27

378

input EP for the system is 41.2 kg phosphate equivalent for ES-1 and 32.5 kg phosphate

379

equivalent for ES-2 whereas EP of the RO permeate is 0.89 kg phosphate equivalent and 1.06 kg

380

phosphate equivalent for ES-1 and ES-2, respectively. Nearly 97 % reduction of EP was

381

observed for the streams indicating the effectiveness of the system. From Figures 3 and 4, it was

382

observed that, in the equalization tank, around 60 % of EP was increased as a single process for

383

both streams. As the current effluent contains very high pH, equalization tank uses nearly 2,300

384

L HCl for ES-1 whereas it uses 1,300 L HCl for ES-2 in order to maintain the pH so that it does

385

not obstruct the microbial growth in the aeration process. However, this increased EP drops

386

down considerably in the subsequent aeration process where reduction of 78 % and 76 % in ES-1

387

and ES-2 in EP was observed, respectively.

388 389

3.5.

Global Warming Potential (GWP)

390 391

GWP is one of the crucial environmental impacts which allows comparison of global warming

392

impacts of various emissions of gases. It is a common reference standard for greenhouse gases

393

including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), chlorofluorocarbons

394

(CFC’s), etc. GWP has been used as a relative measure which is represented as the amount of

395

energy trapped by the emission of gases compared to CO2 over a period of time (Liu et al.,

396

2017). GWP 100 is an effect of the emission occurring over the period of 100 years. Therefore,

397

climate change has been indirectly considered as a problem for next 100 years (European

398

Commission- Joint Research Centre-Institute for Environment and Sustainability, 2010). From

399

Figures 3 and 4, higher GWP impact can be spotted for the unit operations which consume

400

higher energy. Aeration and ozonation process from ES-1 was found to contributing around 23

28

401

% and 25 % of GWP, respectively. On the contrary, ozonation with 28.5 %, UF, and RO with 20

402

% each were found to be the prime contributors of GWP. It was also observed that ACF

403

contributed less GWP in both the streams. Ozonation, UF, and RO operations are energy-

404

intensive and consume a huge amount of electricity for pumping (and ozone generation in case

405

of ozonator). As the Indian grade electricity mix comes from the combustion of coal and natural

406

gas, these unit operations give higher GWP impact.

407 408

3.6.

Toxicity Potential

409 410

Toxicity potentials are referred to as adverse effects on a living organism caused by pollutant or

411

contaminant. Heavy metals, organic solvents, pesticides, etc. are some of the examples which

412

cause toxicity impact (ECJRCIES, 2010). The toxicity potential is expressed in ecotoxicity

413

potential and human toxicity potential. The ecotoxicity potential is further categorized into

414

FAETP, MAETP, and TEP based on the release of a contaminant into the ecosystem whereas

415

HTP considers the impact generated by contaminants on human health. All the toxicity potentials

416

are relatively measured in terms of release of kg of 1, 2-dichlorobenzene (DCB) into the

417

ecosystem. From Figure 3, it can be depicted that aeration and ozonation process delivers high

418

impacts in all the toxicity potential categories including FAETP, MAETP, TETP, and HTP

419

compared to any other process in ES-1. In HTP, MAETP, and TETP impact category, aeration

420

and ozonation process generate nearly 25 % and 27 % of the total impact, respectively, whereas,

421

in FAETP impact category, they generate 21 % and 23 % of the total impact, respectively. In ES-

422

2, the ozonation process still dominates the impact in all the toxicity impact categories imparting

29

423

28 % in FAETP and nearly 30 % in all other categories. UF and RO processes also impart high

424

impact of nearly 20 % in all the categories.

425 426

3.7.

ReCiPe (End Point (I)) 2016. 1.1

427 428

The ReCiPe endpoint (I) assessment method is the latest and unified method in lifecycle

429

assessment. It is a robust method that comprises both midpoint and endpoint impact categories

430

(Foteinis et al., 2018). The endpoint method usually deals with human health, natural resources,

431

and environment. Endpoint method offers long term environmental impacts, associated with

432

uncertainty, compared to that of midpoint analysis. There are three versions of endpoint

433

assessment available in LCA, which are individualistic (I), Hierarchist (H) and Egalitarian (E)

434

approach. The individualistic approach has been selected because the current system under

435

consideration will improve over a short period of time. The impacts generated by ReCiPe (I)

436

method for both the streams is presented in Figures 5 and 6. For ES-1, it can be observed that

437

ozonation, UF and RO processes impart high impact in almost every impact category whereas

438

ACF process was found to be sharing the least percentage in every impact category and can

439

considered as a more environmentally friendly process. In ES-2, along with UF, RO, and

440

ozonator, the clarifier was found to be contributing a higher share, especially in the marine

441

ecotoxicity category. ReCiPe analysis delivers a value judgment about the relative importance of

442

each impact as a dimensionless number which may help the policy-makers to develop a strategy.

30

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Climate change [DALY]

Fine Particulate Matter Formation [DALY]

Equalisation

Fossil depletion [$]

Aeration

Freshwater ecotoxicity [species.yr]

Human toxicity, cancer [DALY]

Clarifier I & II

ACF

Ionizing Radiation [DALY]

Marine ecotoxicity [species.yr]

Metal depletion [$]

Ozonation Process

UF

Terrestrial Acidification [species.yr]

RO

443 444

Figure 5: ReCiPe (End-Point (I)) 1.1 Method for Effluent Stream-1 (ES-1)

445 446 447 448 449 450 451

31

Hundreds

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Climate change [DALY]

Fine Particulate Matter Formation [DALY]

Equalisation

Fossil depletion [$]

Aeration

Freshwater ecotoxicity [species.yr]

Human toxicity, cancer [DALY]

Clarifier I & II

Ionizing Radiation [DALY]

ACF

Marine ecotoxicity [species.yr]

Metal Terrestrial depletion [$] Acidification [species.yr]

Ozonation

UF

RO

452

Figure 6: ReCiPe (End-Point (I)) 1.1 Method for Effluent Stream-2 (ES-2)

453 454 455

4.

Discussion

456 457

The present LCA study of the textile industry effluent system under consideration may also be

458

beneficial to those who are working in the fields of policy development, by establishing a

459

baseline of environmental impacts for various effluent treatment operations and subsequently for

460

promotion of most sustainable operation. A thorough understanding of different materials,

461

associated in the process life cycle of WWTP is required to fathom out the hotspots in the entire

462

WWT process and suggestive precautions can be made. With this approach, material and

463

economic efficiency as well as optimal wastewater management, can be promoted.

464 32

465

4.1.

Parameter Analysis

466 467

The midpoint and end-point analysis of the present system under consideration has been carried

468

out on a lifecycle basis. The results show that aeration, ozonation, UF, and RO processes

469

contribute higher impacts in almost every impact category. In these processes, chemical,

470

electricity and transportation were identified as major inventories which attribute to the

471

environmental burden. Therefore, in order to understand the influence of actual parameter

472

responsible for the higher environmental burden, parameter analysis was carried out for both the

100%

95%

90%

85%

80%

75%

Electricity 473

Chemical

Transport

streams.

474 33

475

Figure 7: Parameter Analysis of Effluent Stream 1 (ES-1)

100%

95%

90%

85%

80%

75%

Electricity

Chemical

Tranport

476 477

Figure 8: Parameter Analysis of Effluent Stream 2 (ES-2)

478 479

For parameter analysis, all the electricity, chemical, and transportation required for the ES-1 are

480

normalized and presented in Figure 7. It can be clearly observed that electricity dominated in

481

most of the impact categories for ES-1. Electricity imparts 95 % impact in AP, 92 % in EP, 98.6

482

% in HTP, 99.4 % in MAETP and 96 % in TETP impact categories. On the other hand, chemical

483

process contributes only 15 % impact in ADP whereas it is 16 % in FAETP. Transportation does

34

484

contribute to the environmental burden in ADP, FAETP, and GWP impact categories but the

485

quantity is so small that it was overshadowed by electricity and chemical process.

486

The parameter analysis for ES-2 was also calculated and presented in Figure 8, where it was

487

observed that electricity contributes higher impact here as well. Electricity was found to be

488

contributing 93 % in AP, 94.5 % in HTP, 95.4 % in MAETP and 90.5 % in TETP impact

489

categories. Chemicals also contribute significantly to ADP with 16 %, 14.5 % in FAETP and

490

nearly 87 % in GWP potential compared to all the parameters. The environmental burden caused

491

by chemicals is slightly higher in this stream compared to the previous stream which is because

492

the chemical consumption in ES-2 is higher than that of ES-1. HCl is used in more quantity at

493

the equalization stage for pH adjustment whereas it is used at UF and RO stage for membrane

494

cleaning purposes. Clarifier stage also consumes a large quantity of PAC and PE as coagulation

495

and flocculation agent which elevates the environmental burden. At the ozonation process,

496

hydrogen peroxide is the major contributor of environmental burden whereas, in the aeration

497

process, microbial nutrient powder along with monophosphate and diphosphate contribute to the

498

environmental burden.

499 500

From parameter analysis, it was identified that electricity attributes higher share towards

501

increasing environmental burden, compared to other parameters which are in good agreement

502

with other studies (Carré et al., 2017). Electricity consumption is huge in aerobic, ozonation, UF

503

and RO processes in both the streams. At the aerobic process, electricity is mainly consumed for

504

sparging constant air to the aeration tank. At the ozonation process, 15 different ozonator units

505

are required simultaneously with electricity consumption of 2,052 kWh/ day for ES-1 and 1,640

506

kWh/ day for ES-2. UF and RO processes require high pressure to pump the effluent through the

35

507

membrane and therefore, consume around 1,500 kWh electricity per day for ES-1 and 1,200

508

kWh electricity per day for ES-2. For the rest of the unit operations, electricity is mainly used for

509

pumping the effluent and thus, the overall consumption of electricity per day at the plant for both

510

the streams is very high. Increase in electricity consumption not only affects the environmental

511

aspects but the economic aspects as well.

512 513

4.2.

Sensitivity/ Scenario Analysis and Uncertainties

514 515

The parameter analysis examined the incremental contributor in WWTP over its entire life cycle

516

which can be comparatively simplistic for a process. Nevertheless, the issue arises when this

517

strategy is applied to form any sort of policy. The hot spots identified over the parameter analysis

518

can be vanquished by posing a series of “what if” questions in order to assist the decision-makers

519

to accomplish the sustainable outcome (Serenella et al., 2016). Sensitivity and scenario analysis

520

are employed for estimating the prominent portfolio for the system under consideration. The

521

sensitivity analysis imparts the outcome for the uncertainty involved in the system whilst,

522

scenario analysis gives results for uncertainty in various situations (Baek et al., 2018). The prime

523

motive of uncertainty analysis is to assess the uncertainty of environmental footprints (LCIA)

524

while considering the uncertain inventories (LCI).

525

simultaneously with uncertainty analysis wherein, its sole purpose is to understand the

526

robustness of the results and the model, data or assumption (Wei et al., 2015). The uncertainty in

527

a parameter can be easily promoted into LCA results using Monte-Carlo simulation, as

528

mentioned elsewhere (Baek et al., 2018), whereas, model and parameter uncertainties can be

529

obtained by evaluating environmental footprints for various scenarios (Geisler et al., 2005).

The sensitivity analysis can be used

36

530

Experimental uncertainties are minimum as the concentration of key components are measured

531

on a daily basis for an entire year and the fluctuation in deliverables are ˂ 5 %. Scenario analysis

532

for the present system under consideration is associated with two major aspects of lifecycle were

533

carried out with rigid logic in order to establish substantial results. This may help in

534

understanding the perspective about different stages and get insight into them.

535 536

A close analysis was performed to identify the major contributing parameter. From Figures 7 and

537

8, it is observed that electricity contributes more in all impact categories, as detailed above.

538

Currently, grid-connected solar capacity of 20 GW has been installed in India until 2018 and it

539

is aimed by the Government of India to improve this capacity to 100 GW by 2022 (Dawn et al.,

540

2016). India heads the Global Solar Alliance having committed to Paris Climate Change Accord

541

and has revised this target to 175 GW by 2022, according to the recent announcement on

542

September 25, 2019 in New York. India on the course to achieving 175 GW renewable energy

543

target and 40% of India’s electricity generation is set to be from non-fossil fuels, by 2022

544

(Economic Times, 2019). India is amongst the few countries of the world where forests are

545

growing in spite of exponentially rising population and livestock pressures. India's pledge to

546

increase its non-fossil fuel target to 450 GW is massive and that it is a significant step in making

547

the country a fossil-fuel-free economy. Therefore, a scenario is made where grid mix electricity

548

is replaced by renewable energy (particularly solar) in order to estimate the environmental

549

burden. Solar energy is the most well-known form of renewable energy, which may help us to

550

tackle the common problem of climate change. A stable structure of the solar panel, which gather

551

the abundant source of sustainable energy, does not release any CO2 while working. However,

37

552

some emissions are generated while the manufacturing of solar panel which can be further

553

reduced through the use of recycled material and is also considered in scenario analysis.

554 555

It can be observed in Figure 9 that by replacing 50 % grid mix electricity with solar, the

556

environmental impacts for ES-1 from all the categories can significantly go down. AP and all the

557

toxicity potentials can be reduced nearly by 50 % whereas GWP can be reduced by nearly 70 %.

558

The EP potential doesn’t show promising reduction which is due to the fact that it was

559

predominantly dependent on the quality of the effluent and not the parameters involved to treat

560

it. For ES-2, the same behavior can be observed from Figure 10 where all the impacts can be

561

reduced to nearly 50 %. As the solar share increased to 100 %, it was observed that the

562

environmental burden is reduced to 90 % in AP, MAETP and HTP impact categories whereas

563

roughly 80 % in TETP and GWP impact category. For ES-2, the same trend was observed and

564

the environmental burden may get reduced to about 90 % in almost all the categories. The

565

exponential reduction in all the impact categories with an increase in solar share was observed as

566

it was understood that no combustion process was involved while producing this renewable

567

energy. As the Indian electricity grid mix prone to get upgraded in renewable energy, this

568

scenario appears more realistic in near future. A carbon payback period for the solar panel was

569

established on life cycle basis in prior studies (Marimuthu and Kirubakaran, 2014, 2013), which

570

estimated that the energy consumed during production, operation, and end of life processes can

571

be recovered in not more than 2 years. Furthermore, this period can be reduced by technical and

572

innovative enhancement whereas such aspects may help in achieving sustainability with

573

environmental and economic benefits

574

38

575 576 577 578 579 580 581 582 583

TETP [kg DCB-Eqv.] MAETP [kg DCB-Eqv.] HTP [kg DCB-Eqv.] GWP 100 years, excl biogenic carbon [kg CO2-Eqv.] GWP 100 years [kg CO2-Eqv.] FAETP [kg DCB-Eqv.] EP [kg Phosphate-Eqv.] AP [kg SO2-Eqv.] ADP fossil [MJ] -100% -90%

100% Solar

-80%

-70%

50% Solar

-60%

-50%

-40%

-30%

-20%

-10%

0% Solar

584 585

Figure 9: Effect of solar energy in various impact categories of Effluent Stream 1 (ES-1)

39

0%

TETP [kg DCB-Eqv.] MAETP [kg DCB-Eqv.] HTP [kg DCB-Eqv.] GWP 100 years, excl biogenic carbon [kg CO2-Eqv.] GWP 100 years [kg CO2-Eqv.] FAETP [kg DCB-Eqv.] EP [kg Phosphate-Eqv.] AP [kg SO2-Eqv.] ADP fossil [MJ] -100% -90%

-80%

100% Solar

-70%

-60%

-50%

-40%

-30%

-20%

-10%

50% Solar

586 587

Figure 10: Effect of solar energy in various impact categories of Effluent Stream 2 (ES-2)

588 589

At the present stage, around 50 % effluent coming out of RO permeate gets reused within the

590

plant itself, where it is used for various purposes based on its quality. From Tables 5 and 6, it

591

was already clear that with 50 % recycling, the environmental burden gets moderately reduced.

592

Likewise, a scenario was established where the environmental impacts were calculated based on

593

reuse share. For this analysis, a scenario was considered where recycling amount gets reduced to

594

0 % or increases to 75 % and 100 %. The results are presented in Figures 11 and 12. It can be

595

understood that, as the recycling quantity get reduces, the environmental burden increases to

596

many folds in case of GWP, FAETP, and ADP for both effluent streams. The parameters

597

including electricity, chemical, and transportation are allied to these environmental impacts,

40

0%

598

therefore, as the recycling reduces, the current system under the consideration could not take

599

credit from other processes. The other impact categories, like MAETP, HTP, EP, and AP are

600

mainly dependent on effluent quality. Therefore, as the recycling share decreases, the

601

environmental burden generated by these category increases moderately. On the other side, as

602

the recycling share increases, the environmental burden decreases with the same magnitude for

603

both the streams. In this case, as recycling increases, the current system under the consideration

604

can take credit for reused water so that the freshwater requirement gets reduced and the water

605

can be circulated within the system itself. For ES-2, it was observed that as the recycling share

606

increases, the EP reduces many folds, which may be concluded as the ES-2 system has scope to

607

improve the effluent quality at current 50 % recycling stage.

TETP [kg DCB-Eqv.] MAETP [kg DCB-Eqv.] HTP [kg DCB-Eqv.] GWP 100 years, excl biogenic carbon [kg CO2-Eqv.] GWP 100 years [kg CO2-Eqv.] FAETP [kg DCB-Eqv.] EP [kg Phosphate-Eqv.] AP [kg SO2-Eqv.] ADP fossil [MJ] -160%

-120%

-80%

-40%

0%

40%

0%

75%

80%

100%

608 609

Figure 11: Effect of reuse percentage of treated water on various impact categories of Effluent

610

Stream 1 (ES-1) 41

MAETP [kg DCB-Eqv.] HTP [kg DCB-Eqv.] GWP 100 years, excl biogenic carbon [kg CO2-Eqv.] GWP 100 years [kg CO2-Eqv.] FAETP [kg DCB-Eqv.] EP [kg Phosphate-Eqv.] AP [kg SO2-Eqv.] ADP fossil [MJ] -55%

-45%

-35%

-25%

-15%

-5%

5%

15%

25%

611 612

Figure 12: Effect of reuse percentage of treated water on various impact categories of Effluent

613

Stream 2 (ES-2)

614 615

It has been a tradition to focus on minimizing the pollution from a single source and improvise

616

the environmental aspects. For example, in the past few decades, prime attention has been given

617

on minimizing the environmental burden generated by various emissions from factories or

618

effluent discharge into the river or lake. However, lifecycle thinking (LCT) endeavors the

619

probable enhancement in product/process or system by lowering the environmental impacts as

620

well as reducing the utilization of resources during the lifecycle stages (Frostell, 2013). The

621

essential objective of LCT is to avoid burden shifting, as the strategy adapted at a particular

622

process should help in minimizing the burden elsewhere. This LCT approach commences with

623

raw material acquisition, manufacturing, distribution stages and terminates with re-use or 42

624

recycling, recovery, and disposal. For example, a scenario analysis was carried out for two cases

625

wherein case 1, a grid mix electricity was replaced by renewable energy and in case 2, the share

626

of reuse water was increased. In both cases, overall environmental impacts were reduced many

627

folds while the quantity of materials required to achieve this is not increased. On the other hand,

628

a lower carbon payback period of solar energy and higher reuse of treated water may benefit the

629

industry with environmental and economic sustainability. This approach can be a huge uplift for

630

policy-makers and government organizations to identify a hotspot in a particular process and

631

establish alternative solutions through scenario analysis. This LCT may benefit process or

632

product designer of WWTP to expect and evade the futuristic risks by incorporating it in their

633

design consideration. The present LCT approach may help in encouraging industries to adopt the

634

WWTP and reuse the treated water for their own purposes. It may serve as a tool for policy-

635

makers, government bodies, and regulators in order to establish firm policies and legislative

636

regulations. Nevertheless, it requires substantial acceptance and value additions from policy-

637

makers, environmental managers, design engineers, regulators, etc.

638 639

4.3.

Future Challenges

640 641

The outcome of the current study has many limitations for the existing practice because some of

642

the results may not be valid for different environmental perspectives. The existing practice at the

643

ETP in Konark is to treat two different effluent streams with a maximum 50 % recycling

644

capacity. The traditional practice can be modified beyond it and a strategy can be arrived such as

645

utilizing fewer chemicals, generating low sludge and consuming less electricity along with

646

enhancing the recycling capacity. As mentioned earlier, the residues from aeration tank majorly

43

647

contain biological debris. However, the residues from clarifier I and II tanks considerably

648

contains polymeric materials. Moreover, around 55 kg of biological sludge, collectively

649

generated from both the streams of the aeration process can be further used for producing bio-

650

based fertilizers. Similarly, 51 kg of polymeric sludge, collectively generated from both the

651

streams of clarifier I & II process can be used as a secondary raw material for the production of

652

paver blocks. In both cases, the residues can be effectively reused as a raw material and the

653

overall environmental footprints could be reduced.

654 655

Every available impact category in LCA is relative and does not describe the actual

656

environmental consequence at the present stage. Therefore, further research is required to

657

establish relevant and precise environmental impact. The calculated lifecycle impacts are more

658

location-specific and cannot be justified everywhere. Globally approved characterization factor

659

need to be developed for every impact category. The data improvement need to be prioritized as

660

the inventory selected for model development has a huge impact. Even though LCA is not at a

661

primitive stage, the efforts need to be made for its wide acceptance. The strategy and policy-

662

makers need to accept the current form of LCA methodology for establishing their strategies so

663

that awareness can be spread. The inclusion of social or economic allocation in inventory may

664

complete the sustainability approach of the study.

665 666

5.

Conclusions

667 668

In the present study, the environmental hotspots in the operational phase of regionalized WWTP

669

of a textile industry were assessed using the gate-to-gate with closed-loop recycling approach.

44

670

The study emphasized on seven unit operations of two different effluent streams, based on CML-

671

2001 baseline method. The ozonation step was found to have high environmental footprints, in

672

all the impact categories, due to substantial energy requirement, as the parametric analysis

673

revealed that electricity was a prominent contributor towards the impacts followed by chemical

674

consumption and transportation. ACF process had shown the least environmental burden for both

675

the streams whereas, around 85-90% of EP was reduced in the aeration process alone, albeit, its

676

energy consumption and subsequent other environmental impacts were high. The

677

sensitivity/scenario analysis with a change in electricity source and increased reuse share was

678

carried out to assist policy-makers in reducing the overall impacts of the system under

679

consideration. Replacing grid mix electricity with renewable solar energy had a pronounced

680

impact, as 50 % solar share reduces around 50 % overall burden whereas adapting 100 % solar

681

energy could reduce 90 % of the overall environmental burden. Moreover, minimizing effluent

682

discharge limit and increasing reuse share was also found to have a positive impact, as the

683

system under study could take credit for reused water. Additional work is still needed to consider

684

socio-economic aspects or uncertainties pertaining to model development. Nevertheless, the

685

present LCA study deals with a practical approach of sustainability in regionalized WWTP

686

which could help LCA practitioners and local policy-makers to increase profitability and also

687

reduce environmental burden.

688 689

Acknowledgment

690 691

We gratefully acknowledge University Grant Commission (UGC) Gov. of India for availing

692

financial support under the scheme F.25-1/2014-15 (BSR)/ No. F.5-64/2007 (BSR) and Konark

693

Industries Ltd., Kolhapur for availing the data required for the study. GDY acknowledges 45

694

support as R.T. Mody Distinguished Professor, Tata Chemicals Darbari Seth Distinguished

695

Professor of Leadership and Innovation, and J.C. Bose National Fellow (DST-GOI).

696 697

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54

Sustainability Analysis of Textile Wastewater Treatment Plant based on Lifecycle Assessment Approach

Highlights

•

Environmental footprints of Textile effluent were estimated on Lifecycle Basis

•

Two-fold functional units of 1500 m3 and 1200 m3 were considered

•

The prime hot-spot in both the streams was the electricity consumption

•

Ozonation was found to have large environmental footprints compared to other processes

•

Sensitivity/Scenario analysis bestows that increasing effluent reuse share strengthens the environmental performance.