Papermakers are slashing freshwater intake by filtering and recycling white water—the fiber-laden water drained from the paper web—using save-alls, disc filters, and dissolved air flotation. The result: single-digit m³/ton water intensity, lighter effluent loads, and faster paybacks, supported by data from TAPPI, industry case studies, and corporate reports.
The pulp & paper sector is water-intensive, consuming on the order of 90–100 million m³/day (≈33–36 billion m³/year) (www.resourcewise.com). Roughly half of this is consumed in Asia-Pacific, and Indonesia is the world’s 10th–largest pulp producer (www.resourcewise.com). Within a mill, ~80–85% of water is used in pulping and papermaking stages (www.resourcewise.com).
Performance spans a huge range—from highly optimized paper machines under 5 m³/ton to older or tissue/printing grades over 100 m³/ton (www.watertechonline.com). Top machines run on only 1,000–2,000 gal/ton (3.8–7.6 m³/ton) (paper360.tappi.org), while some conventional kraft mills still use 40–55 m³/ton (www.scielo.br). The trendline is bending: in Indonesia, a major producer cut intensity from ~33.0 to 27.9 m³/ton between 2018–22—a 16% drop—with a targeted project saving ≈11 m³/ton on one fiberline (app.co.id; app.co.id).
Regulatory pressure reinforces the business case. Indonesian regulators (Permen LH 5/2014) set strict effluent limits—COD (chemical oxygen demand) max ~300 mg/L and TSS (total suspended solids) 50 mg/L—pushing mills to recycle water to reduce discharge. The Ministry of Environment urges pulp/paper mills to reach “Green PROPER” status via best practices in water and waste, framing it as good for compliance and business (www.kemenlh.go.id). BOD (biochemical oxygen demand) and COD reflect biodegradable and oxidizable organics; TSS tracks particulate load.
Closed-loop white-water design
At the heart of the shift is the closed-loop paper machine, which maximizes reuse of “white water” (the fiber-laden water drained from the forming wire). In a fully closed white-water loop, water exiting the machine is treated and pumped back to the headbox (the wet-end feed to the forming section) so virtually no fresh water is added after startup, aside from cooling/steam loss makeup. In practice, most machines run three loops: (1) primary white-water loop (former → save-all filter → headbox), (2) a “clear white water” loop for wet-end showers and dilution, and (3) break/pulp loops (paper360.tappi.org).
Ideally, any overflow is the lowest-fiber water (clear filtrate), and bleed is minimal in high-closure designs, though there will be at least some excess/overflow (paper360.tappi.org). TAPPI notes several North American mills now achieve zero water discharge (100% closure) upstream of the wastewater plant (paper360.tappi.org).
Recycling white water slashes intake and effluent. Operations consuming ~4–8 m³/ton are effectively reusing >90% of process water (paper360.tappi.org). Theoretical fresh-water reductions can approach 70–90%; one case reported ~75% savings by fully reusing white water and cooling loops (site-specific) (paper360.tappi.org; www.watertechonline.com). Economically, less intake directly cuts purchase and discharge costs while easing effluent treatment loads.
Process control in high closure
Steady-state closure demands tight control: all machine showers, pump leaks, and secondary uses tie into the recycled circuit, and any fresh additions for temperature or fiber-loss makeup are minimized. Because machines inherently overflow some filtrate, preventing contaminant buildup requires robust primary treatments and vigilant chemistry control. Dissolved organics and inorganics concentrate under closure; mills manage conductivity and pH and add periodic cleans (“boilouts”) or biocides (www.researchgate.net; www.researchgate.net). Many mills standardize these microbial controls using biocides tailored for industrial water circuits.
Machine-side reduction levers
The mantra—reduce, reuse, recycle—applies on the machine as well (paper360.tappi.org). Levers include optimizing drainage and dewatering in the wire and press sections (advanced felts, vacuum control, foil transfers, shoe presses, high‑vacuum foils), which increases mechanical water removal and lowers return flows. Uniform press fabrics and better hydrofoil settings also reduce web breaks and water spills.
Tuning showers and dilution—right-sizing flows and using filtered white water in non-critical showers—cuts fresh draw (paper360.tappi.org). Tightening white-water recirculation via save-alls and disc filters returns most drained water to the headbox (paper360.tappi.org). Process integration—water cascades from cleaner to higher‑quality‑demand points, co-using cooling water in non‑critical loops—adds incremental gains.
The payoff is visible in benchmarks: optimized machines achieve 3.8–7.6 m³/t (paper360.tappi.org) versus typical >40 m³/t, and mills such as APP have cut from 33→27.9 m³/t (2018–22) with projects targeting further double‑digit percentage reductions (app.co.id).
Treatment train: DAF and filters
Closing the loop requires cleaning white water of fibers, fillers, and contaminants. Coarse screening—via bar or rotary screens—removes sticks, rags, and large debris that would damage downstream equipment; mills commonly deploy automatic screens for continuous debris removal.
Fiber recovery follows on a save‑all or pulp pump basket. Most machines use rotating disc vacuum filters to capture fines; these cloth‑covered plates, run under vacuum, remove suspended fiber and minerals typically above 30–50 μm. In one study, the disc filter captured only ~60% of lost fibers—well below the 85–95% theoretical maximum—leaving substantial TSS in the outlet (www.scielo.br).
The core polishing step is dissolved air flotation (DAF), which agglomerates fines and floatables using chemicals (often cationic polymers or alum) and microbubbles, then skims the floated sludge. DAF commonly achieves >94–99% TSS/turbidity removal; one report shows 98.6% TSS reduction in print‑paper white water and ~94% in coating white water (www.scielo.br). The resulting filtrate lands near 20–30 mg/L TSS (www.researchgate.net). Organic contaminants (COD, fatty acids) are partly reduced by DAF—often 30–90% depending on polymer use (www.scielo.br).
DAF is compact, typically running with <3–5 minutes of retention and treating tens of m³/hour per square meter of tank area. Industry data cite about 3 minutes’ retention and throughputs around 4–5 gallons/min/ft² (≈4–6 m³/m²·hr) at high efficiency (www.researchgate.net). Chemical dosing is often automated via a dosing pump, with cationic polymer programs supplied as flocculants. For ultra‑clean applications, secondary polishing with ultrafiltration (UF—membrane filtration targeting colloids/sub‑micron particles) is added after DAF; mills deploy ultrafiltration to protect sensitive wet‑end points.
Clarified water is recycled to the headbox or wet‑end chest, with fresh make‑up minimized. Continuous monitoring of pH, conductivity, and turbidity is essential. Because closure concentrates biodegradable organics, hardness, and microorganisms, mills plan periodic boilouts and biocide dosing; stock chemical programs are adjusted to the changed water chemistry. Each treatment step—screens, DAF, optional membranes—adds capital and OPEX, but water savings and reduced effluent loads typically yield 2–5 year paybacks.
Measured outcomes and costs
Freshwater cuts are measurable. Upgrading from an open to a closed circuit often delivers double‑digit percentage reductions; converting an average 30 m³/t machine into a highly closed system can drop intake to under 10 m³/t—about a 67% saving. APP’s Perawang fiberline logged an 11.3 m³/ton step‑change via white‑water reuse (app.co.id). Metsä Group underscores that “closed cycles play a key role” in shrinking freshwater demand (www.metsagroup.com).
Effluent declines follow naturally. DAF removal rates translate to treated water with TSS near 20–30 mg/L (www.researchgate.net). One report shows overall suspended solids in wastewater dropping ~87% after full‑scale DAF (www.researchgate.net). In practice, PROPER‑compliant Indonesian mills typically hold treated COD <350 mg/L and TSS <50 mg/L; closed‑loop reuse eases the load needed to achieve this (app.co.id).
Water intensity is trending down. APP averaged 27.9 m³/t in 2022 (app.co.id), while leading papers cite 4–8 m³/t on zero‑discharge machines (paper360.tappi.org). Industry sources indicate a ~10–15% drop in water consumption per ton over the past decade. Cost-wise, every cubic meter recycled saves both water purchase and wastewater fees; industry estimates place combined per‑m³ costs around ~$0.20–$1.00 USD, and one large mill reported an 80% drop in water fee obligations after closing loops.
Challenges persist with higher closure: microbial control demand rises (biocide usage often doubles) and scaling risks increase, requiring more frequent cleanings (www.researchgate.net; www.researchgate.net). Yet modern case studies (e.g., TAPPI conferences) show closed-loop investments are typically profitable in 1–5 years, by plant accounting.
Sources and citations
Authoritative literature and industry reports underpin the data: TAPPI Paper360 on paper‑machine water use (paper360.tappi.org); WaterTech on mill water ranges (www.watertechonline.com); Floresta Ambient on DAF efficiency and disc filter capture (www.scielo.br; www.scielo.br); resource‑centric data from Metsä Group (www.metsagroup.com; www.metsagroup.com), APP Group reports (app.co.id; app.co.id), industry analysis (Resourcewise 2024: www.resourcewise.com; IPPTA 2012: www.researchgate.net), Kementerian LH press 2025 (www.kemenlh.go.id), as well as DAF design/performance details (www.researchgate.net; www.researchgate.net). Each supports the quantitative impacts of closed-loop reuse.
