Textile plants use 100–200 liters of water per kg of fabric and discharge effluent loaded with dyes and salts. A staged recycling roadmap — from “non‑critical” reuse to zero liquid discharge — is delivering 60–98% recovery at roughly $0.3–0.5 per m³.
In an industry where every batch can swallow hundreds of liters, water has become the textile mill’s priciest ingredient. Typical consumption runs 100–200 L per kg of fabric (mdpi.com), while effluent leaves packed with dyes, salts, organics, and heavy metals (mdpi.com), (mdpi.com). Regulators are responding: Indonesia’s Law 32/2009 and successive PermenLH set strict effluent limits (researchgate.net).
The new operating thesis: recycle where quality allows, starting with non‑critical uses (machine rinses, cleaning, cooling) and pushing toward ZLD (zero liquid discharge, i.e., recycling water until only solid salts remain). Advanced ZLD schemes recover 95–98% of process water — suitable for dyeing, washing, or cooling (link.springer.com). Pilots in Bangladesh are already targeting ~80% water reuse with no discharge (smepprogramme.org), and many mills aim to cut fresh‑water intake by >80% at an operating cost around $0.3–0.5 per m³ (mdpi.com).
Process water quality requirements
Pretreatment steps (desizing, scouring, bleaching) run best on relatively clean water — moderate pH and low turbidity — so chemicals behave predictably. Dyeing and printing demand very soft, low‑conductivity water; reactive dyeing uses large salt doses (leaving effluent highly saline) and achieves only ~20–50% dye fixation (mdpi.com), (mdpi.com).
Residual hardness can shift shades; studies warn that rinsing in hard water “can cause shade changes during drying” and recommend softened water (pdfcoffee.com). Mills commonly deploy softening (softener) or deionization to hit <10–50 mg/L as CaCO₃ for color‑critical processes.
Where lower energy is a priority, nanofiltration (NF) — a membrane that selectively removes multivalent ions like hardness at lower pressure than RO — is often used upstream of high‑purity steps, a role matched by nano‑filtration in water reuse lines.
Utility services have their own bands: finishing consumes smaller volumes but may include toxic chemistries; boilers require low TDS (total dissolved solids) for steam, making ion exchange a fit in many plants via ion‑exchange systems. For non‑critical uses such as machine flushing or cooling, recycled water can tolerate higher residual salts or lower clarity.
Membrane‑based reuse treatment train
Most mills adopt a multi‑barrier train. First is equalization and pre‑treatment: flow and pH are buffered; primary screens remove grit and fibers, with physical steps mirrored by wastewater physical separation hardware.
Coagulation–flocculation with alum or ferric salts, followed by sedimentation or flotation, strips colloidal organics, dyes, and suspended solids — cutting COD_BOD (chemical/biochemical oxygen demand) by ~30–50% in practice (link.springer.com). Coagulant feed control is typically paced by dosing pumps for stable removal.
Sedimentation commonly occurs in clarifiers, with compact installations supported by clarifier systems to manage detention times before filtration.
Sand or dual‑media filtration knocks down residual turbidity ahead of oxidation, a role served by sand/silica filters in most trains.
Advanced oxidation targets color: ozonation or UV/H₂O₂ oxidizes persistent dyes and recalcitrant organics (mdpi.com), (mdpi.com). One study reported 92–97× color removal per stage (mdpi.com). The trade‑off is energy: ozone production runs roughly 10–15 kWh per kg O₃, but it can lighten UF/RO fouling. UV systems (99.99% pathogen kill is typical for ultraviolet disinfection) are frequently specified through ultraviolet units.
Where organics loads are elevated, a biological polish improves downstream stability; textile effluent is notoriously hard to biodegrade, yet any drop in biodegradable load reduces fouling risk (link.springer.com). Aerobic membrane bioreactors (MBR, a biological treatment combined with membranes) are a common choice delivered via membrane bioreactors.
Membranes then do the heavy lift. Ultrafiltration (UF, a pressure‑driven membrane with ~10–100 kDa cutoff) removes remaining colloids, microbes, and high‑molecular‑weight organics (link.springer.com), typically clearing >80% of turbidity/SS and a large share of color. Plants specify UF as a standardized pretreatment step using ultrafiltration skids.
Reverse osmosis (RO, a high‑rejection membrane that removes dissolved salts and small organics) — often in tandem with nanofiltration — polishes to reuse quality. RO has achieved >99% removal of COD, color, and TDS in documented campaigns (mdpi.com), (mdpi.com), producing near‑pure permeate that can meet strict reuse criteria — even potable standards in some studies (mdpi.com). Many mills standardize this stage with brackish‑water RO systems; any required re‑mineralization or pH adjustment is done after RO.
Permeate polishing where needed often uses adsorption media such as activated carbon to quench residual organics or color before reuse.
Integrated deployments typically consolidate these barriers under one controls envelope; in the market this is framed as unified membrane and pretreatment packages similar to membrane systems used across industrial water reuse.
Brine management and ZLD pathway
RO concentrate becomes a high‑salinity brine. To approach ZLD, mills send this brine to evaporation/crystallization (thermal or mechanical vapor recompression) to distill water and isolate solids (link.springer.com). Evaporators typically recover >90% of the brine volume as distillate, and full ZLD schemes often deliver ~95–98% total water recovery (link.springer.com).
If full evaporation is initially prohibitive, RO brine can be recycled into less‑critical rinses or routed to a CETP (common effluent treatment plant) for shared processing (link.springer.com).
Sample schematic and performance data
A representative chain looks like: equalization → coagulation/flocculation → sedimentation → sand filtration → ozone → UF → RO → (permeate → reuse; brine → evaporator/crystallizer). A two‑stage UF/RO pilot with flocculation‑sedimentation and ozone recovered 86.8% of feed water and delivered permeate below reuse thresholds (mdpi.com), (mdpi.com).
Key figures reported: UF removes ~90% of suspended solids and a large share of COD/color, while RO reaches ~99% dissolved organic carbon (DOC) and color reduction (mdpi.com), (mdpi.com). Overall treatment costs are typically in the $0.3–0.5 per m³ range (mdpi.com).
Implementation roadmap and KPIs
1) Water audit and segregation. Map all inflows/outflows, characterize quality, and classify “critical” uses (dyeing, final rinses, boilers) versus “non‑critical” (pre‑rinses, floor cleaning, cooling). Quantify how much can be substituted by recycled water.
2) Define reuse targets and KPIs. Set goals for % reduction in fresh intake, % of wastewater recycled, and concentration targets. Track liters saved per kg of fabric and overall recovery. Singapore/EU guidelines or industry benchmarks (e.g., COD <50 mg/L for reuse, mdpi.com) can set targets; ensure these meet or exceed discharge limits with margin.
3) Pilot testing. A representative pilot couples coagulation and sand filtration — the latter typically built with dual‑media filters — ahead of oxidation, then a UF skid, and finally RO. UF units are commonly packaged, as in ultrafiltration systems, to validate removal on real effluent before scaling.
RO performance and fouling behavior are proven at pilot scale before plant rollout, often using integrated packages akin to membrane systems for reliable data transfer.
4) Phase 1 — reuse implementation. Install full‑scale pretreatment and first‑pass membranes. Divert RO permeate to low‑sensitivity uses such as cooling towers or boiler feed after softening, where classical exchange trains like ion‑exchange ensure steam‑side quality. Early phases routinely deliver ≥50–80% water reuse (smepprogramme.org).
5) Phase 2 — expanded reuse and quality lift. Extend reuse to first‑rinse baths and sizing machines; add permeate polishing where needed with UV disinfection or activated carbon. Push RO to higher recovery, consider 2‑pass RO or diafiltration (a staged dilution/flush membrane technique) as reported in literature (mdpi.com), (smepprogramme.org) to approach ~90%+ recovery.
6) Phase 3 — zero/minimal discharge. Add evaporators/crystallizers for RO brine to reach ~95–98% water recovery (link.springer.com). At this stage, all usable water is recycled; the only waste is solids (dyes/salts). Integration with a CETP can share energy costs (link.springer.com).
Regulatory compliance and expected outcomes
In Indonesia, textile effluent standards (PermenLH 5/2014, etc.) cap COD, BOD, TSS, color, and other parameters; any discharge — including blowdowns — must comply. Reuse quality should ideally exceed these limits (mdpi.com).
A full program can cut freshwater use by 60–80% initially and approach near‑ZLD levels (>95% recovery) (mdpi.com), (link.springer.com). Pollutant loads in any residual effluent fall sharply — RO permeate has been reported with COD below drinking‑water standards (mdpi.com).
On costs, one published case pegs reuse water at $0.44 per m³, with 65% of that tied to ozone/RO energy (mdpi.com), (mdpi.com); similar figures can guide economic planning. Studies conclude that ZLD can “optimize water recycling” while minimizing wastewater (mdpi.com), a trajectory hastened by rising water costs and stricter discharge rules.
Evidence base and references
Findings draw on case studies of UF/RO reuse systems (mdpi.com), (mdpi.com), reviews of ZLD technology (mdpi.com), (link.springer.com), and industry pilots like the SMEP project targeting ~80% reuse with no discharge (smepprogramme.org). Indonesian context aligns with regulatory analyses and national standards (e.g., PermenLH 5/2014) (researchgate.net).
