Enhancing Hotel Sustainability by Harnessing Greywater for Reduced Freshwater Consumption

Enhancing Hotel Sustainability by Harnessing Greywater for Reduced Freshwater Consumption

Siddhi Choubey, Shruti Rathore, Ekta Chandra, Shreya Meshram, Aditi Singh

Student, Department of Civil Engineering, Bhilai Institute of Technology, Durg, C.G., India

Mrs. Mallika Jain

Assistant Professor, Department of Civil Engineering, Bhilai Institute of Technology, Durg, C.G., India

Abstract – Municipal freshwater scarcity and large-volume wastewater generation by the hospitality sector present a compelling case for on-site greywater recycling. This study evaluates the feasibility of treating hotel greywater using a dual organic coagulant system comprising Moringa oleifera seed extract and Okra (Abelmoschus esculentus) seed mucilage, coupled with coagulationflocculation sedimentationmulti-media filtration. Composite greywater samples were collected over four sessions from a 45-room, 3-star hotel in Durg, Chhattisgarh, and subjected to comprehensive physicochemical characterisation. Raw greywater exhibited elevated turbidity (53.4 NTU), TSS (178 mg/L), BOD (87 mg/L), COD (221 mg/L), TDS (820 mg/L), and pH 8.4. Jar test experiments identified 15 mL/L Moringa

+ 15 mL/L Okra as the optimum combined coagulant dose, achieving 87.3% turbidity removal, markedly superior to Moringa alone (74%) or Okra alone (65%). Post-treatment analysis confirmed 84.3% TSS removal, 73.8% COD reduction, 69.0% BOD reduction, and

~85% colour removal. All key post-treatment parameters; pH (7.2), turbidity (6.8 NTU), TDS (510 mg/L), EC (890 µS/cm), and Total Hardness (198 mg/L), comply with IS 10500:2012 permissible limits. The treated effluent is assessed as suitable for non-potable reuse in toilet flushing, landscape irrigation, floor cleaning, and cooling tower makeup, collectively representing 3545% of hotel water demand. Annual freshwater savings of approximately 3.65 million litres and monetary savings of 1.09 lakh are projected for the study hotel, with a system payback period of 23 years. This work establishes organic coagulant-based greywater treatment as a technically sound, economically viable, and environmentally responsible strategy for the Indian hospitality sector.

Keywords: Greywater treatment; Moringa oleifera; Okra mucilage; Organic coagulation; Hotel water management; Coagulation flocculation; IS 10500:2012; Non-potable reuse; Durg, Chhattisgarh

1. INTRODUCTION

   Global freshwater stress has intensified sharply over the past three decades. India, which supports over 17% of the world's population on just 4% of its freshwater resources, has seen per-capita surface water availability fall from approximately 2,300 m³ in 1991 to a projected 1,191 m³ by 2050. Well below the internationally accepted water-stress threshold of 1,700 m³ per capita per year (UN- WWDR, 2023). Within this context, the hospitality sector constitutes a disproportionately large freshwater consumer: a typical mid- size hotel (50150 rooms) consumes 200400 litres per guest per night, while luxury properties can exceed 600800 litres, figures four to six times higher than average residential per-capita consumption of 135150 litres per day in Indian cities.

   Greywater; the non-toilet wastewater fraction generated from bathroom showers, washbasins, and laundry operations constitutes 5080% of total hotel wastewater by volume. Unlike blackwater, greywater contains substantially lower concentrations of pathogens and faecal-origin contaminants, making it technically amenable to treatment and non-potable reuse at relatively modest cost. In Chhattisgarh, a state classified as water-surplus at the regional level but experiencing significant urban supply-demand deficits in cities such as Durg and Bhilai, the rapid expansion of the hospitality and tourism sector is adding measurable strain on municipal water infrastructure. Systematic greywater recycling within hotel premises offers a practical, decentralised solution to simultaneously reduce freshwater consumption, lower wastewater discharge loads, and improve operational sustainability credentials.

   Conventional greywater treatment approaches rely predominantly on chemical coagulants, aluminium sulphate (alum), ferric chloride, and polyaluminium chloride (PAC). While effective, these coagulants introduce secondary chemical residues in treated water, generate large volumes of metal-laden sludge requiring specialised disposal, demand careful chemical storage and handling, and impose recurring procurement costs that can be challenging for small to mid-size hotel operators. Natural organic coagulants, particularly Moringa oleifera seed extract and Okra (Abelmoschus esculentus) seed mucilage, present a compelling biodegradable alternative: they are locally available, non-toxic, produce minimal sludge, and require no specialised chemical infrastructure. Despite

   substantial evidence of their efficacy in treating surface water and domestic wastewater, their application to hotel greywater treatment in the Indian context has not been previously reported in peer-reviewed literature.

   This study addresses that gap by investigating the performance of a combined MoringaOkra organic coagulant system, optimised via jar tests and applied within a bench-scale coagulationflocculationsedimentationfiltration treatment train, for hotel greywater collected in Durg, Chhattisgarh. The specific objectives were: (i) to characterise raw hotel greywater across twelve physicochemical parameters; (ii) to prepare and dose-optimise organic coagulants from Moringa seeds and Okra seed mucilage; (iii) to evaluate post- treatment water quality against IS 10500:2012 permissible limits; (iv) to assess the suitability of treated greywater for non-potable hotel applications; and (v) to estimate the economic and water-conservation benefits of system adoption.

2. LITERATURE REVIEW

   The physicochemical characteristics of greywater have been extensively studied. Eriksson et al. (2002) reviewed data from over 40 studies across Europe, Australia, and North America and established that greywater constitutes approximately 60% of household wastewater flows, with BOD concentrations up to 300 mg/L, elevated suspended solids, surfactants, and trace metals, but with substantially lower pathogen concentrations than blackwater. In the Indian context, Patil et al. (2022) characterised household greywater at COD 150450 mg/L and TSS 100250 mg/L, and demonstrated that a multi-stage physical treatment system (screening

   sand filtration activated carbon) achieved up to 86% BOD and 94% TSS removal. Baxi et al. (2015) investigated greywater reuse at NIT Raipur; geographically proximate to the present study area, and demonstrated the economic viability of a settling filtrationdisinfection system for toilet flushing applications. Sudarsan et al. (2021) reported 6070% treatment efficiency for commercial building greywater using simple physical methods and recommended greywater recycling as standard practice for urban commercial establishments.

   The use of Moringa oleifera as a primary coagulant is well-established. Ndabigengesere et al. (1995) first isolated the active cationic coagulant protein (MW ~13 kDa) from Moringa seeds and demonstrated 8099% turbidity removal from surface water comparable to or exceeding alum at optimal doses. Ghebremichael et al. (2005) confirmed that the Moringa protein operates through charge neutralisation of negatively charged colloidal particles, forming dense, rapidly settling flocs and producing biodegradable sludge in volumes 2030% of those generated by alum. For greywater and wstewater applications, Moringa has been reported to achieve turbidity removal of 7095%, BOD reduction of 5075%, and significant colour removal, with optimal performance at pH 6.58.0.

   Okra (Abelmoschus esculentus) seed mucilage, comprising long-chain galactoserhamnose polysaccharides (galacturonan) with molecular weights of 50800 kDa, acts primarily as a flocculant aid through bridging flocculation. Balasubramanian et al. (2009) demonstrated 6580% turbidity removal from surface water, with the notable advantage of producing only 1015% of the sludge volume generated by alum at equivalent treatment performance. Sanghi et al. (2006) found that Okra achieved up to 85% colour removal from textile effluent, superior to guar gum and comparable to alum, and recommended it for high-colour, high-TSS wastewater a category representative of hotel laundry greywater. Mechanistically, Okra's anionic/neutral polysaccharide chains complement the cationic Moringa protein through bridging flocculation, and Ang and Mohammad (2020) confirmed that binary combinations of such coagulants consistently outperform either component alone, yielding larger, denser, more rapidly settling floc structures.

3. METHODOLOGY

   1. Study Site and Sample Collection

      Greywater samples were collected from a 45-room, 3-star rated hotel in Durg, Chhattisgarh, which operates 365 days per year with a daily freshwater consumption of approximately 25,00030,000 litres at full occupancy. The hotel has no existing greywater treatment or recycling infrastructure. An internal drainage survey identified a suitable sampling point on the grey drainage line, excluding toilet-drain blackwater and kitchen drain (routed separately to a grease trap). Composite samples of 5 litres each were collected over four sessions at 10-day intervals during OctoberNovember 2025, during the peak check-out and housekeeping period (08:0011:00 h), using grab sampling at 30-minute intervals aggregated into pre-cleaned HDPE containers. Samples were transported to the Environmental Engineering Laboratory, Department of Civil Engineering, BIT Durg within 2 hours of collection, stored at 4°C, and analysed within 24 hours. All sampling and preservation procedures followed IS 3025 (Part 1).

   2. Preparation of Organic Coagulants

      Moringa oleifera seed extract: Dried Moringa seeds procured from a local agricultural market were de-hulled, and the white cotyledon kernels were oven-dried at 60°C for 2 hours and ground to <500 µm particle size. A 50 g/L stock solution was prepared

      by dissolving 5.0 g of seed powder in 100 mL distilled water, stirring at 400 RPM for 30 minutes on a magnetic stirrer, and filtering through Whatman No. 1 filter paper to obtain a clear coagulant filtrate. Fresh stock was prepared for each experimental session and used within 12 hours.

      Okra seed mucilage: Fresh Okra pods were dried at 50°C for 24 hours, seeds were extracted and coarsely ground, and the powder was soaked in distilled water (1:10 w/v) for 2 hours with periodic stirring. The viscous mucilaginous filtrate obtained after Whatman No. 1 filtration served as the Okra stock solution (~1% w/v biopolymer) and was used within 24 hours to prevent fermentation.

   3. Jar Test; Coagulant Dose Optimisation

      Standard jar tests (APHA, 2017) were conducted using a six-position jar test apparatus with 1-litre aliquots of raw greywater per jar. The protocol comprised rapid mixing at 100 RPM for 2 minutes (coagulation), slow mixing at 30 RPM for 20 minutes (flocculation), and quiescent settling for 30 minutes. A 200 mL supernatant aliquot was then withdrawn from each jar and analysed for residual turbidity and pH. Moringa alone, Okra alone, and combined Moringa + Okra (1:1 volume ratio) were tested at doses of 5, 10, 15, 20, and 25 mL/L. All jar tests were conducted in triplicate and mean values reported.

   4. Treatment Train

      At the optimum coagulant dose identified, bulk greywater treatment was conducted through the following sequential stages: (i) pre- screening through a 2 mm mesh; (ii) pH adjustment to 7.58.0 if required; (iii) coagulant addition followed by rapid mixing (100 RPM, 2 min) and slow mixing (30 RPM, 20 min); (iv) quiescent sedimentation in a 2-litre graduated cylinder for 60 minutes; and

      (v) passage through a laboratory-scale multi-media filter column (10 cm PVC pipe, 60 cm height) comprising, from bottom to top: coarse gravel (5 cm), coarse sand (10 cm), fine sand (15 cm), granular activated carbon (10 cm), and fine gravel (5 cm). Post- filtration pH was checked and adjusted to 6.57.5 as required.

   5. Analytical Methods

      Twelve parameters were measured for both raw and treated greywater. pH was measured potentiometrically using an IKON pH/mV Meter calibrated with pH 4.0, 7.0, and 9.0 buffers; turbidity was measured nephelometrically with a Digital Turbidity Meter (Model 331) calibrated with formazin standards. Electrical conductivity was measured using an IKON Conductivity/Temperature Meter calibrated with 0.01 N KCl. Total dissolved solids and total suspended solids were determined gravimetrically. Total hardness was determined by EDTA titrimetry (EBT indicator, pH 10.1 buffer); alkalinity by HSO titrimetry; dissolved oxygen by polarographic membrane electrode (IKON DO Meter). BOD was measured by the 5-day incubation method at 20°C ± 1°C; COD by the open reflux dichromate method; colour and odour by visual/olfactory assessment per APHA. All measurements were performed in triplicate and mean values reported. Treatment efficiency was calculated as: E (%) = [(C C) / C] × 100, where C and C are pre- and post-treatment concentrations respectively.

4. RESULTS AND DISCUSSION

   1. Raw Greywater Characterisation

      The raw hotel greywater was consistently characterised across four sampling sessions (Table 1). The slightly alkaline pH (8.4 ± 0.3) is attributable to sodium-compound-rich laundry detergents. Turbidity (53.4 ± 4.2 NTU) substantially exceeds the IS 10500:2012 maximum permissible limit of 10 NTU for non-potable use. The BOD/COD ratio of 0.39 indicates that approximately 40% of the organic load is biodegradable, consistent with bathroom greywater dominated by soaps and personal care products. Low dissolved oxygen (2.8 ± 0.4 mg/L) confirms partial oxygen depletion attributable to biological activity during sample storage, validating the urgency of timely treatment. All observed raw-water values fall within the typical greywater quality ranges reported in global literature (Eriksson et al., 2002), confirming the representativeness of the study site.

      Table 1: Physicochemical Characterisation of Raw and Treated Hotel Greywater

      36.1

      Parameter	Unit	Raw GW (Mean ± SD)	Treated GW (Mean ± SD)	IS 10500:2012 Limit	Removal (%)
      pH		8.4 ± 0.3	7.2 ± 0.2	6.58.5
      Turbidity	NTU	53.4 ± 4.2	6.8 ± 0.7	10 (max)	87.3
      EC	µS/cm	1240 ± 87	890 ± 55	2500	28.2
      TDS	mg/L	820 ± 62	510 ± 40	2000	37.8
      TSS	mg/L	178 ± 15	28 ± 5		84.3
      Total Hardness	mg/L	310 ± 24	198 ± 17	600
      Alkalinity	mg/L	196 ± 18	112 ± 12	600	42.9
      DO	mg/L	2.8 ± 0.4	5.4 ± 0.5		+92.9
      BOD	mg/L	87 ± 9	27 ± 4		69.0
      COD	mg/L	221 ± 21	58 ± 7		73.8
      Colour	Hazen	~20	~3	15 (max)	~85.0
      Odour		Mild soapy	Odourless	Unobjectionable

   2. Jar Test – Optimum Coagulant Dose

      Jar test results established a clear doseresponse relationship for all three coagulant configurations (Table 2). Moringa alone achieved a maximum turbidity removal of 74.0% at 20 mL/L, with no further improvement at 25 mL/L – a pattern consistent with overdosing-induced floc restabilisation. Okra alone reached a ceiling of approximately 65.5% at 25 mL/L, confirming that, as an anionic/neutral biopolymer, it is less effective as a standalone primary coagulant for the negatively charged colloids in hotel greywater. The combined Moringa + Okra system at 15+15 mL/L achieved 87.3% turbidity removal, the maximum performance point, which represents a 13.3 percentage-point improvement over Moringa alone and a 21.8 percentage-point improvement over Okra alone. This synergistic enhancement is mechanistically attributable to the cationic Moringa protein first neutralising the surface charge of colloidal particles, while Okra's long-chain polysaccharides subsequently bridge between the destabilised particles to form large, dense, rapidly settling floc aggregates; z a complementary mechanism consistent with the theoretical basis of binary organic coagulant systems described by Ang and Mohammad (2020).

      Table 2: Jar Test Results Turbidity Removal at Varying Coagulant Doses

      Coagulant System	5 mL/L	10 mL/L	15 mL/L	20 mL/L	25 mL/L
      Moringa only (% removal)	28.5%	59.9%	72.5%	74.0%	73.6%
      Okra only (% removal)	21.2%	44.2%	63.8%	65.0%	65.5%
      Moringa + Okra (% removal)	48.9%	74.5%	87.3% OPT.	86.7%	86.1%

   3. Post-Treatment Performance

      Following treatment at the optimum dose (15+15 mL/L Moringa + Okra) through the full treatment train, the treated water was visually clear, colourless to faintly pale yellow, and odourless. Table 1 summarises the complete pre- and post-treatment comparison.

      Turbidity and TSS: The 87.3% turbidity reduction (53.4 6.8 NTU) and 84.3% TSS reduction (178 28 mg/L) bring both parameters to compliance with IS 10500:2012. Residual turbidity of 6.8 NTU is within the 10 NTU maximum permissible limit and suitable for toilet flushing, irrigation, and floor cleaning applications.

      Organic Load: BOD reduction of 69.0% (87 27 mg/L) and COD reduction of 73.8% (221 58 mg/L) result from a combination of mechanisms: coagulation of colloid-associated organics, sedimentation of organic-laden floc, and activated carbon adsorption of dissolved chromophoric and odour-causing compounds. The residual BOD (27 mg/L) and COD (58 mg/L) represent non-adsorbable soluble surfactant metabolites and low-molecular-weight organics acceptable for all non-potable, non-body-contact reuse applications. For potential body-contact applications, a biological polishing stage would be advisable.

      TDS, EC, and Hardness: Moderate reductions in TDS (37.8%, 820 510 mg/L), EC (28.2%, 1240 890 µS/cm), and Total Hardness (36.1%, 310 198 mg/L) reflect partial co-precipitation of hardness ions as carbonate complexes and activated carbon adsorption of dissolved organics, while the bulk of dissolved ionic species remain in solution as expected from a physical- chemical treatment process. All post-treatment values comfortably comply with IS 10500:2012 limits (TDS < 2000 mg/L, EC < 2500 µS/cm, TH < 600 mg/L).

      DO, Colour, and Odour: Dissolved oxygen improved markedly from 2.8 to 5.4 mg/L (+92.9%), a consequence of atmospheric oxygen dissolution during mixing operations and filtration confirming that treated water is aerobically stable for storage and distribution within the hotel. Colour was reduced by ~85% (20 ~3 Hazen units, well within the 15-Hazen IS limit), and soapy odour was completely eliminated, both attributable to activated carbon adsorption of volatile organic compounds and residual surfactants.

   4. Non-Potable Reuse Suitability

      Based on post-treatment quality data and applicable reuse guidelines (IS 10500:2012; WHO, 2006), the treated greywater is assessed as suitable for the following hotel applications: toilet flushing (turbidity < 10 NTU, odourless); landscape and garden irrigation (pH 7.2, turbidity 6.8 NTU, TDS 510 mg/L all within permissible ranges); floor and surface cleaning; cooling tower makeup water (TDS 510 mg/L < 1000 mg/L threshold; TH 198 mg/L < 300 mg/L threshold); and car washing. Collectively, these applications account for 3545% of total hotel water demand, representing the most impactful reuse opportunity. Swimming pool makeup and potable applications are not recommended without additional disinfection (UV or chlorination) and, in the case of potable use, membrane filtration.

   5. Economic and Water Conservation Analysis

      At the study hotel (45 rooms, ~70% average annual occupancy, daily freshwater consumption 27,000 litres), implementation of the proposed treatment system is projected to recycle approximately 10,000 litres per day for toilet flushing and irrigation, reducing annual freshwater consumption by approximately 3.65 million litres. At the prevailing municipal water tariff in Durg (approximately

      20/kL), annual water procurement savings amount to approximately 73,000, with a further 36,500 saved on sewage discharge charges yielding total annual monetary savings of approximately 1.09 lakh. The estimated capital cost of a complete hotel-scale system (collection sump, coagulant dosing unit, clarifier, filter column, and distribution piping) is 2.02.5 lakh, indicating a payback period of approximately 23 years. These projections do not account for potential green hotel premium pricing, carbon credit opportunities, or regulatory compliance cost avoidance factors that would further improve the economic case.

5. CONCLUSION

This study demonstrates that hotel greywater from a mid-size hospitality establishment in Durg, Chhattisgarh, can be effectively treated using a combined Moringa oleifera seed extract and Okra seed mucilage coagulant system to meet IS 10500:2012 physicochemical quality standards for non-potable water reuse. The combined coagulant at 15+15 mL/L achieved 87.3% turbidity removal, significantly superior to either coagulant applied individually with overall removals of 84.3% TSS, 73.8% COD, 69.0% BOD, and ~85% colour across the full coagulationflocculationsedimentationfiltration treatment train. The treated effluent is confirmed suitable for toilet flushing, landscape irrigation, floor cleaning, cooling tower makeup, and car washing within the hotel premises, representing 3545% of daily freshwater demand. Organc coagulants offer compelling operational advantages over conventional chemical alternatives they are locally available throughout India, biodegradable, non-toxic, produce minimal sludge, and require no specialised chemical handling infrastructure, making them particularly well-suited to adoption by small and mid-size hotel operators. The economic analysis projects a capital investment payback period of 23 years through water and sewage savings. This approach aligns with India's National Water Policy, the Sustainable Development Goal 6 (Clean Water and Sanitation), and

green building certification frameworks such as LEED India and Green Key, positioning greywater recycling as an accessible and high-impact sustainability intervention for the Indian hospitality sector.

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