Textile finishing’s water reckoning: from 250 L/kg to closed loops that pay back

Wet finishing — bleaching, dyeing, washing, padding — is a water story with outsized numbers: typical dyeing/finishing uses 100–250 liters per kg of fabric (sarkengg.in) (mdpi.com). A Bangladesh survey clocked roughly 164 L/kg, with about 119 L/kg discharged as wastewater (sarkengg.in), while field studies report ~120–140 L/kg for cotton fabric dyeing (mdpi.com). That translates to roughly 120–140 m³ per metric ton. Even in mature industries, facilities often use tens of cubic meters per ton of fabric. By contrast, state‑of‑art European plants achieve ≤20 L/kg through extensive re‑circulation (sarkengg.in).

Regulators are tightening the screws. Indonesia’s Green Industry standard caps finishing water at roughly 120–150 m³/ton (~120–150 L/kg) and requires minimum reuse rates of 20% of process water (fr.scribd.com) (fr.scribd.com). Earlier regulations set a 120 m³/ton cap and only 1% recycle, but have been superseded by the stricter 2022 standards (id.scribd.com). In practice many Indonesian mills exceed 200 L/kg, which is why conservation is a front‑burner issue. Global benchmarks underscore the spread: Bangladesh mills average ~164 L/kg (sarkengg.in), India ~200–250 L/kg (sarkengg.in), Turkey 60–120 L/kg for cotton (sarkengg.in), while leading facilities in Germany and Italy target <20–30 L/kg with closed loops (sarkengg.in).

Low‑liquor‑ratio wet‑processing equipment

A foundational move is low‑liquor‑ratio (LLR) machines — equipment that reduces the “liquor ratio” (kg water per kg fabric) used in dyeing and finishing. Traditional batch dyeing ran at ~1:10 (10 kg water per kg fabric). Modern jets, winches, pads, beams, and package dyeing machines operate closer to 1:3–1:5, typically cutting water use 50–80% versus old machines (sarkengg.in). Benninger’s new FabricMaster jet‑dyeing unit is cited for “unmatched low water consumption,” and continuous pad‑steam or pad‑dry lines likewise use minimal liquor (sarkengg.in).

EU BAT studies report that moving from a 1:10 to ~1:4 liquor ratio roughly doubles bath exhaustion and halves water and chemical use (studylib.net) (studylib.net). LLR applicators in finishing — foam pads, short‑range dyeing jets, exhaust winches — cut rinse volumes, and modern machines maintain near‑design liquor ratios even at low loads, avoiding a consumption spike for small batches (studylib.net) (studylib.net). Indonesia’s caps (~140–150 L/kg) effectively drive LLR adoption or heavy reuse to comply (fr.scribd.com), and in combination with counter‑current rinsing, top facilities have pushed overall water use below 20 L/kg (sarkengg.in).

Counter‑current rinsing practice

Counter‑current rinsing — fabric passes sequential tanks while fresh water flows opposite to fabric movement — reuses each rinse stage three to four times, sharply reducing make‑up water (sarkengg.in). Combined with LLR systems, industry reports indicate modern machinery alone can halve or better fresh water consumption (sarkengg.in).

Closed‑loop water recycling trains

Recycling closes the loop. Typical strategies pair physical/biological treatment with reuse of spent baths and rinses. After discharge, liquor is filtered — commonly via ultrafiltration (UF, a membrane step that removes fine solids and macromolecules) or membrane bioreactors — and then sent to reverse osmosis for high‑quality recovery (pmc.ncbi.nlm.nih.gov). Membrane bioreactors (MBR, combining biological degradation with micro/ultra‑filtration) routinely remove >90% of organics and total suspended solids (TSS). In one pilot, an MBBR–MBR train achieved ~93% chemical oxygen demand (COD) and 99% TSS removal with 85% color removal; the treated water met textile standards and was reused in subsequent dyeing without color defects (pmc.ncbi.nlm.nih.gov).

For the moving‑bed step, MBBR (suspended biofilm carriers) has been validated in the same pilot. Reverse osmosis (RO) then polishes permeate; mills typically select brackish‑water RO when total dissolved solids are moderate. Advanced oxidation rounds out options: studies on cotton reactive‑dye pad washes show ozonation or UV–ozone removes ~95% of color and enables 100% rinse‑water recycle, cutting fresh make‑up by ~40% (researchgate.net). In UV–ozone systems, ultraviolet reactors provide the UV dose; in practice, mills deploy UV systems as low‑operating‑cost modules in the train. Reuse quality has held up under color checks: fabrics re‑dyed with recycled effluent showed ΔE <1 (a small color difference metric) versus virgin water (researchgate.net).

In practice, mills combine these steps in closed loops; backwash and condensate (from steam lines) are reused internally, and without reuse, finishing rinse water often goes straight to drain. High‑efficiency mills and CETP (Common Effluent Treatment Plant) clusters — for example, India’s Tirupur — are now approaching zero liquid discharge (ZLD, a design that eliminates liquid effluent): recent reviews report ZLD reclaiming 95–98% of incoming water (link.springer.com) (link.springer.com). For larger integrated lines, standardized membrane systems help scale reuse across industrial or municipal conditions.

Policy is aligned: Indonesia’s Permenperin 40/2022 requires ≥20% of process water to be recycled (fr.scribd.com). Even a modest 20–40% recycling sharply cuts fresh intake and effluent volume; materially, reusing 1 m³ of treated water directly offsets that volume of fresh water and wastewater load.

Foam finishing and pad alternatives

Foam finishing applies chemicals in an air–liquid foam instead of immersion. A dye or finish is mixed into a stable foam and padded on; as the foam collapses, it leaves the chemical with minimal water. Reports indicate foam dyeing/finishing can use roughly 10% of the water of conventional methods, with overall savings ranging 50–90% depending on process (sarkengg.in). One cotton study showed ~84.6% reduction in chemical usage (and corresponding water) with an optimized foam pad versus standard pad application (researchgate.net).

Commercial use spans hydrophobic (waterproofing) finishes, softeners, some reactive dyes, wrinkle‑free finishes, and fleeces. It is less common on very heavy machinery fabrics but highly effective for garment knits and wovens. Converting pad baths to foam can dramatically reduce a finishing mill’s rinse load; a pilot review noted productivity gains alongside ~85% chemical cost reductions (researchgate.net).

Cost–benefit and payback dynamics

Water reuse is capital‑intensive — treatment trains, pumps, membranes — but savings stack up. A Spain case study of a combined MBBR–MBR system (capex ~€0.46M) saved on fresh water (~€0.56/m³) and on discharge fees (~€0.86/m³), turning net present value positive in about two years with an internal rate of return around 18% (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Recycling let the plant avoid buying ≈70% of its previous water demand (the remainder lost in blowdown) (pmc.ncbi.nlm.nih.gov).

Even in Asia, where water rates vary, the business case often clears if water costs $0.5–$1.00/m³ or higher. Illustration: a mill using 1000 m³/day that recycles 500 m³/day saves about $500/day (~$180k/year) when fresh water ($0.50/m³) and avoided discharge ($0.50/m³) are both counted. Against that, a modest MF/UF (microfiltration/ultrafiltration) + RO system might run $200–300k capex with ~$50k/year O&M in chemicals and energy, implying a few‑year payback; in the cited MBR case the payback was ~2 years, and partial reuse systems (e.g., rinse loops only) often show 3–5 year paybacks (researchgate.net) (pmc.ncbi.nlm.nih.gov). Compliance benefits add lift: meeting Indonesian reuse thresholds may require an MBR if counter‑current rinsing alone cannot reach 20% (fr.scribd.com), and in the Spain case high effluent quality lowered discharge taxes, improving ROI (pmc.ncbi.nlm.nih.gov). Even where discharge fees are low, smaller fresh purchases and sewage volumes deliver direct savings; evaluations consistently show modern recycling systems recover costs in a few years, with IRRs ~15–20% in case studies (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

Sources and technical references

Peer‑reviewed studies, industry reports, and government standards underpin the data cited: including a 2025 review of textile water reuse (link.springer.com) (link.springer.com); Indonesian Ministry of Industry regulations (fr.scribd.com) (fr.scribd.com); dyehouse recycling case studies (pmc.ncbi.nlm.nih.gov) (researchgate.net); technology profiles and benchmarks (sarkengg.in) (researchgate.net); and EU BAT notes (studylib.net) (studylib.net).