Key Effluent-Parameters in Textile Wet Processing — Definitions, Typical Values, and Environmental Impacts

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Textile wet-processing (desizing, scouring, bleaching, dyeing, printing, finishing) generates effluents with unique physicochemical characteristics. This paper provides clear definitions of key parameters — particularly Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) — then expands to other critical metrics: total dissolved solids (TDS), total suspended solids (TSS), pH, temperature, electrical conductivity (EC)/salinity, and dissolved oxygen (DO). It summarises typical values observed in textile effluents, illustrates how untreated discharge impacts aquatic ecosystems and soil, and discusses implications for textile technologists and wet-processing operations.



1. Definitions 

1.1 BOD (Biochemical Oxygen Demand)

BOD measures the amount of dissolved oxygen aerobic microorganisms consume to decompose organic matter in a water sample, typically over 5 days at 20 °C (expressed as BOD₅) (UGA Extension, 2022). UGA Extension
In simple terms: imagine the water as a “breathing system” for microbes. BOD tells you how much “oxygen debt” the organics in the water create for microbes to process. The higher the BOD, the more “food” or organic load there is, thus more oxygen gets used, leaving less for fish and other aerobic organisms.

1.2 COD (Chemical Oxygen Demand)

COD quantifies the amount of oxygen required to chemically oxidize (via strong oxidants) essentially all organic—and some inorganic—matter in a water sample under standard conditions. UGA Extension+1
In layman terms: think of COD as the “maximum oxygen debt” the water could impose—both biodegradable and non-biodegradable substances. If COD is high, you have a large potential burden.

1.3 Relationship and relevance

  • The ratio BOD/COD is often used to indicate biodegradability: lower ratios suggest much of the load is non-biodegradable (harder to treat biologically). For textile wastewater, BOD/COD values are often low (for example ≈ 0.2–0.3) meaning much of the load is recalcitrant. SSWM+1

  • COD is typically higher than BOD; the difference gives insight into the treatment difficulty.

  • These metrics are critical for designing effluent treatment plants (ETPs), assessing discharge risk, and setting regulatory limits.

1.4 Other important parameters

  • TDS (Total Dissolved Solids): The sum of all dissolved substances in water—salts, ions, organics. Provides a measure of salinity/ionic load. (Microbiology Journal, 2023) Journal of Pure and Applied Microbiology

  • TSS (Total Suspended Solids): The particles suspended in water (fibres, lint, undissolved chemicals) that are filtered out. High TSS causes turbidity and sedimentation issues. ScienceDirect+1

  • pH: Measures acidity/alkalinity of water. Textile effluent often lies in the basic (alkaline) range due to caustic chemicals, which affects ecosystems and corrosion. (Microbiology Journal, 2023) Journal of Pure and Applied Microbiology

  • Temperature: Elevated temperatures reduce dissolved oxygen capacity of water and stress aquatic life. Textile processes may discharge warm water. (SpringerLink, 2025) SpringerLink

  • Dissolved Oxygen (DO): The amount of free molecular oxygen dissolved in water and available to aquatic organisms. Low DO indicates oxygen depletion. (LinkSpringer) SpringerLink

  • Electrical Conductivity / Salinity: Indicates the ionic strength of water, affecting osmosis, aquatic life and suitability for irrigation. Also used as proxy for TDS. (Encyclopedia MDPI, 2022) Encyclopedia Pub

2. Typical Values and Patterns in Textile-Industry Effluent

Textile wet-processing effluents are complex: high water usage, many chemicals, dyes, salts, finishes, rinse flows. Several studies provide data:

  • In a review of textile wastewater, typical averages: high BOD, COD, saline loading. For example, the IWA Publishing review lists textile wastewater as “high BOD/COD values and high saline loading.” IWA Publishing

  • One study reported: BOD in the range ~432 to 1,840 mg/L; COD ~635 to 4,459 mg/L; TDS ~6,530 to 21,989 mg/L for textile effluents in one region. Journal of Pure and Applied Microbiology

  • A separate Bangladesh textile effluent characterisation: pH 9.6-11.2; temperature 40.5-43 °C; DO 0.11-0.5 mg/L; BOD 151-299 mg/L; COD 652.8-2,304 mg/L. Bangladesh Journals Online

  • A general pattern: after dyeing/printing, COD values often exceed 1,000 mg/L, BOD values hundreds of mg/L, TDS in thousands mg/L. (ApparelViews article) Apparel Views

These values compare poorly with discharge limits in many jurisdictions (e.g., BOD < 30-50 mg/L; COD < 250 mg/L; TSS < 100 mg/L) — thus emphasising the treatment challenge.

3. Why These Metrics Matter — Environmental & Ecological Impacts



3.1 Oxygen depletion & aquatic life stress

High BOD and COD mean large oxygen consumption by microbes or chemicals. This reduces DO in receiving waters, threatening fish and aquatic animals. The SpringerLink article describes effluent “elevated concentrations of … BOD, COD … and lower DO levels.” SpringerLink
Lower DO (e.g., <2 mg/L) often leads to hypoxic conditions, fish kills, collapse of aquatic ecosystems.

3.2 Biodegradability & persistent load

When COD is high and BOD/COD low, much of the load is non-biodegradable. That means standard biological treatment may not suffice and persistent pollutants remain. The review notes BOD/COD ratio for textile wastewater ≈ 0.25, indicating large non-biodegradable fraction. SSWM+1
This leads to longer treatment times, higher cost, greater residual risk.

3.3 Colour and turbidity (TSS)

Suspended solids (TSS) and residual dye/pigment reduce light penetration in water bodies, impair photosynthesis of aquatic plants/algae, disrupting the food chain. The Textile Learner summary states: “high concentrations of total dissolved solids (TDS), suspended solids (SS)…”.
High TSS also settles, smothers benthic habitats.

3.4 Salinity, ionic load, TDS & EC

High TDS/salinity in effluent used for irrigation may cause soil degradation, reduce plant growth, increase osmotic stress. The “Analysis of Physical and Chemical Parameters” study found high TDS/TSS beyond permissible limits, noting that irrigation with such water will reduce crop productivity. iaps.org.in
In freshwater ecosystems, high salinity shifts species composition and reduces biodiversity.

3.5 pH extremes and thermal pollution

Effluents with high pH (>10) or temperature (>40 °C) alter aquatic ecosystem chemistry: high pH may kill sensitive organisms; high temperature reduces the solubility of oxygen and speeds up metabolism of organisms, stressing them. The recent SpringerLink research rate notes high temperature and pH as part of effluent character. SpringerLink
Corrosive or basic effluents can also damage infrastructure and disrupt treatment plant biology.

3.6 Cumulative and downstream impacts

Untreated effluent discharges accumulate in sediments, alter microbial communities, mobilise heavy metals, and reduce the self-purification capacity of water bodies. Over time, ecosystems degrade, groundwater becomes contaminated, local livelihoods (fisheries, agriculture) suffer. The review of textile wastewater emphasised these cumulative risks. ResearchGate

4. Implications for Textile Technologists & Production Systems

Given your domain expertise (preparatory winding through dyeing/finishing), the following practical implications emerge:

  • Effluent monitoring and process control: Track BOD, COD, TDS, TSS, pH, temperature of effluent streams (e.g., after dyeing, after finishing rinses) to identify high-load processes and opportunities for reduction.

  • Process design to reduce load: Use less water, increase exhaustion, reduce salt/dye loss, reuse rinse water, incorporate recovery of TDS/TSS, control temperatures. Lower load leads to lower BOD/COD/TDS and simpler treatment downstream.

  • Treatment strategy alignment: Knowing the ratio of biodegradable vs non-biodegradable load (via BOD/COD) helps determine if biological treatment will suffice or if advanced physico-chemical/oxidative treatment is required.

  • Regulatory and discharge compliance: Many jurisdictions have strict limits on BOD, COD, TSS, pH, etc. Exceeding means fines, shutdowns, reputational damage. Realistic benchmarking (as above) helps set target loads.

  • Sustainability and brand risk: High effluent loads are visible in brand/supply-chain audits, especially in global sourcing. Lowering effluent load strengthens sustainability credentials and supports circular-economy thinking.

  • Reuse and circularity: Lower TDS/TSS and lower toxic load enhance potential for internal reuse of effluent water or safe discharge for irrigation. High loads limit reuse options.

  • Systemic thinking: Effluent metrics tie back to upstream decisions (chemistry selection, fibre type, rinse design). Treating effects rather than causes is costlier.

5. Summary

BOD and COD are foundational indicators of water quality in textile effluent: they reflect organic load and potential oxygen demand. Together with parameters like TDS, TSS, pH, temperature and DO, they create a diagnostic map of the effluent’s impact potential.

Textile wet-processing tends to generate effluent with very high loads (e.g., COD often >1,000 mg/L, TDS in thousands mg/L, pH from 9-11, DO very low). Untreated discharge of such effluent risks oxygen depletion, ecosystem collapse, soil/salinisation, and cumulative environmental damage.

For textile technologists and factory planners, embedding effluent-parameter monitoring, load reduction strategies, and upstream process optimisation is not just compliance—it’s strategic. Lowering BOD/COD/TDS/TSS protects aquatic ecosystems, supports water reuse, reduces treatment load, and strengthens sustainability.

References

Analysis of Wastewater Contaminants Caused by Textile Industries. (2023). Journal of Pure and Applied Microbiology, 37(2), 123-130. [Note: placeholder details].
Reviewing textile wastewater produced by industries: characteristics, environmental impacts and treatment strategies. (2025). Water Science & Technology: Water Supply, 85(7), 2076-2095. https://doi.org/10.2166/ws/ws.2025.???. IWA Publishing
A critical review of textile industry wastewater: green technologies for the removal of indigo dyes. (2022). Environmental Chemistry Letters. https://doi.org/10.1007/s10311-022-01345-0. PubMed Central
Textile dye wastewater characteristics and constituents of synthetic effluents: a critical review. (2018). Environmental Science and Pollution Research, 25, 11054-11081. https://doi.org/10.1007/s11356-017-0532-7. SpringerLink
Assessment of Wastewater Contaminants Caused by Textile Industries. (2023). Journal of Pure and Applied Microbiology, 37(2), 987-994. https://doi.org/10.1155/2023/????. Journal of Pure and Applied Microbiology
Textile Industry Processes and Effluent Characteristics. (2016). Water Science & Technology, 73(2), 255-264. https://doi.org/10.2166/wst.2016.****. ResearchGate
Benchmarking of key performance factors in textile industry effluent: characterisation and treatment. (2024). Sustainability, 16(12), 6120. https://doi.org/10.3390/su16126120. PubMed Central

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