Weaving’s water problem is concentrated in warp sizing and desizing — a low‑volume, high‑impact corner of the mill. New size chemistries, membrane recovery, and closed‑loop rinsing are cutting freshwater use by half or more.
Weaving is unusually water‑intensive within textile manufacturing. Millions of liters of water are used to size warp yarns (a temporary film applied to protect yarns during weaving) and remove that size (“desizing”) after weaving. Typical textile wet‑processing consumes on the order of 50–240 L of water per kilogram of product link.springer.com, and dyeing/finishing alone can require ~100–200 L/kg www.mdpi.com. In practice, preparatory steps like sizing and desizing often dominate loom‑stage water use.
Desizing in particular not only uses significant rinse water — typically 2.5–25 L per kg of fabric www.degruyter.com — but also generates very polluted effluent: about 50% of textile water pollution is attributed to desizing alone www.degruyter.com. These “desize” baths are low‑volume but high‑impact effluents, with high biochemical oxygen demand (BOD, a measure of biodegradable load) and size polymers. One example: cotton desizing wastewater may contain ~1.14 kg/m³ PVA (polyvinyl alcohol) along with starch byproducts link.springer.com agris.fao.org. These facts underscore opportunities: sizing chemistry and washwater reuse.
Water‑efficient warp sizing choices
Conventional warp sizes — starch, PVA, CMC (carboxymethyl cellulose), etc. — strengthen yarns but differ sharply in water impacts. PVA‑based sizes give excellent abrasion resistance, but require strong rinses to remove and produce high‑COD (chemical oxygen demand) effluent. Natural starch sizes biodegrade easily, but often are brittle or unstable.
Recent developments highlight greener formulas that cut both water/energy and effluent loads. An “all‑starch eco‑size” using only corn starch plus additives (no PVA/PAA) showed a raw‑starch size with lower viscosity and stable flow, yielding 5–12% higher loom efficiency than conventional mixed sizes and 17–61% lower size chemical cost bioresources.cnr.ncsu.edu. Its desizing wastewater was readily biodegradable (BOD₅/COD ≈0.65) bioresources.cnr.ncsu.edu. By contrast, typical PVA‑based size wastes have very low BOD/COD and are hard to treat.
Beyond starch, polyacrylic and bio‑polymers (e.g., modified soy or feather proteins) are under development, though not yet mainstream. Some mills are exploring film‑forming or “size‑free” weaving by pretreating yarns in organic solvents or hot oil; foam‑based applicators (using minimal water) have succeeded in finishing and could be adapted for sizing in special cases. Practically, “water‑efficient sizing” means maximizing adhesion per mass of size (lower add‑on) and choosing chemicals that require gentler removal. Industry reports note mills that adopt new low‑liquor processes or size recycling see water savings often above 50%.
For planning, a change from mixed PVA/starch size to a starch‑only size can yield multi‑percent loom productivity gains and markedly lower effluent acidity and COD bioresources.cnr.ncsu.edu. Where membrane reuse is anticipated, pairing such chemistry with ultrafiltration can magnify water savings by easing downstream separation.
Membrane recovery from desizing rinse
Effective reuse of desizing washwater is critical. If size polymers can be separated and recovered, the rinse water becomes reusable. For synthetic PVA sizes, ultrafiltration (UF, a pressure‑driven membrane process) and related membrane processes are showing strong promise.
Recent experiments report nearly 100% PVA recovery from alkaline desizing liquor using advanced UF membranes www.researchgate.net. One novel ceramic UF membrane (MWCO ~16 kDa; MWCO is the “molecular weight cut‑off”) achieved ~100% PVA retention and 67 L·m⁻²·h⁻¹ flux (flux is membrane flow per area) at 80 °C, pH 13 www.researchgate.net. Another study using SnO₂/ZnO‑enhanced PVDF membranes with a cellulose nanofiber coating attained 98% PVA rejection with stable flux agris.fao.org. These high rejections indicate that post‑desizing water can be clarified and reused: the recovered PVA may be recycled back into size formulations, and the permeate (free of most polymer) can serve as makeup water.
For earthy sizes (starch, CMC), mills combine enzymatic hydrolysis (amylase) with biological treatment or membrane filtration to separate organic solids; the result is lower BOD effluent and reuse of much of the rinse water. Where biology is integrated, a compact step such as a membrane bioreactor can pair efficiently with UF or RO. Some pilot plants use coagulation/settling and low‑pressure membranes to recover up to 80–90% of rinse water for in‑plant cycles; in this configuration, a clarifier upstream of UF supports stable reuse.
Advanced oxidation (ozone, UV/H₂O₂) can mineralize remaining organics, though energy‑intensive. An improved process using UV‑C irradiation for PVA desizing claimed 67% less water use (by minimizing rinse steps) while slashing energy and time by ~68–83% versus conventional hot‑water desizing www.researchgate.net. In practice, a two‑stage wash is common: first capture heavily contaminated rinse with membranes and reuse the filtrate, then polish with ozone or reverse osmosis. Such schemes routinely yield 70–90% water reuse; in RO service, mills typically deploy brackish-water RO as the polishing step.
Economics compare favorably when water is scarce or costly. One case study of a UF–RO reuse system reported ~US$0.44/m³ treatment operating cost www.mdpi.com. Overall, desizing effluent recycling can cut fresh‑water consumption by large fractions (often halving it) while isolating the size chemicals for proper handling or reuse www.rmix.it agris.fao.org. Where enzymes are part of the train, a precise feed system such as a dosing pump helps maintain consistent amylase activity without overdosing.
Closed‑loop washing architectures in mills
Beyond sizing and desizing, mills increasingly adopt closed‑loop wash systems to recycle water across wet processes (scouring, mercerizing, etc.). These systems cascade rinse baths and continuously treat a circulating stream so that no effluent is discharged — a Zero Liquid Discharge (ZLD) configuration. Typical architectures combine ultrafiltration, nano/RO, evaporation, or crystallization of concentrates www.rmix.it www.rmix.it.
One closed‑circuit pattern routes rinse effluent through sequential filters — sand, activated carbon → UF → RO — with the clean permeate pumped back as forward rinse water or fresh makeup. In practice, that means a sand stage, often with a sand/silica filter, followed by adsorptive polishing with activated carbon, then pressure membranes such as ultrafiltration and, if needed, nanofiltration. According to industry summaries, “closed‑loop purification systems… allow treatment and reuse of wastewater, significantly reducing consumption of fresh water” www.rmix.it.
Highlights include membrane trains that recover 90–98% of water, advanced oxidation to break down stubborn chemicals, and vacuum evaporators to recover pure water from brines www.rmix.it www.rmix.it. Trials of such systems in textile plants report 80–90% or more reduction in fresh‑water use. The EU‑funded “Waste2Fresh” project exemplifies this trend, aiming for near‑100% water reuse (multiple cycles without fresh makeup) by integrating catalytic degradation and selective separations sustainablebrands.com sustainablebrands.com.
Even simpler counterflow washers (where the cleanest rinse does the final rinse on new fabric) can cut process water by half relative to single‑bath rinsing. Investment costs are non‑trivial (membranes, energy for RO/evaporation), but payback is driven by freshwater price and effluent discharge fees. A 2019 reuse plant treating denim wastewater reported perchments meeting reuse quality at ~0.44 USD/m³ www.mdpi.com — a cost that can be offset if fresh water costs €0.5–1.0/m³. In water‑scarce regions or where regulation is tightening (for instance Indonesia is moving toward stricter wastewater standards), closed‑loop systems become strongly favorable.
In sum, business cases show that mills adopting water reuse — via UF/RO, AOPs (advanced oxidation processes), or steam evaporation — typically cut fresh‑water purchases by over 70%, energy use for heating water by ~50%, and chemical use by 30–50% www.researchgate.net www.rmix.it. For mills designing these trains end‑to‑end, modular membrane systems help standardize UF/NF/RO blocks across rinse loops and desize recovery alike.
