Printing and Dyeing Wastewater: The First Step in Treatment Is Not the Reaction Tank, but Flow Separation

The quality of printing and dyeing wastewater is not determined by the treatment plant, but by the seven upstream processes and the greige fabric formulation. In the same plant, the B/C of desizing wastewater is only 0.054, the antimony in alkali weight-reduction wastewater is three to five times that in dyeing wastewater, and the salt in dyeing wastewater is the anhydrous sodium sulfate purchased by the plant. "Treating it all mixed together" sounds like less trouble, but in reality it dilutes the most difficult stream into the largest stream, and then hands the whole problem package to the downstream process chain.

Gaowutong · Industrial Water Treatment Technology Series · For industry technical personnel · All data are annotated with public literature and engineering sources

I. Seven Processes, Seven Kinds of Water: Printing and Dyeing Wastewater Quality Is Not Determined by the Treatment Plant

Woven greige fabric must pass through seven processes in the dyeing and finishing section: desizing, scouring, bleaching, mercerizing, dyeing, printing, and finishing. The water discharged from each process has different characteristics, and mixing them into the same equalization tank amounts to a large-scale dilution.

Desizing is the process with a relatively small water volume but the heaviest load. Public sources are fairly consistent on its water volume: desizing wastewater generally accounts for 10%–20% of the total wastewater volume. But its contribution to COD is much higher. One engineering source states that "the COD amount of desizing wastewater accounts for 50%–60% of the total COD discharge of a printing and dyeing plant"; another writes that "the COD load can account for 50% of the total in printing and dyeing wastewater"; and another breaks it down further: the COD amount of pretreatment wastewater accounts for 55%–65% of the total COD of combined wastewater, while the COD amount of desizing wastewater accounts for 80%–90% of the pretreatment wastewater. There are also several versions of the concentration values: desizing wastewater COD 15 000–70 000 mg/L, or 20 000–50 000 mg/L, pH about 12; the COD of mixed desizing, scouring, and bleaching wastewater drops to 10 000–15 000 mg/L. The reason these figures do not match is that the term "desizing wastewater" itself has no unified definition — it may refer to the discharge from the desizing process alone, or to mixed water from desizing plus scouring and bleaching, and the values for these two statements differ by more than a factor of two. If this is not specified when performing a material balance, all subsequent design flow rates and loads will be off.

The remaining processes each have their own temperament. Alkali weight reduction uses alkali to hydrolyze and strip away part of the surface of polyester fabric (average weight reduction rate about 15%), and the discharged alkali weight-reduction wastewater contains a large amount of terephthalic acid (PTA). The standard engineering practice is to add concentrated sulfuric acid to adjust the pH to about 3 for acid precipitation, causing terephthalic acid to precipitate as a sparingly soluble white solid and be recovered. The dyeing process discharges a large volume of water at low concentration, but brings a large amount of anhydrous sodium sulfate into the system. The printing process uses urea as an auxiliary, and urea hydrolyzes into ammonia in subsequent treatment, making it an important source of ammonia nitrogen in printing and dyeing wastewater. The mercerizing process, meanwhile, involves concentrated alkali. To mix these waters together for "homogenization and equalization" results in the desizing water with the highest COD being diluted to the concentration of the combined wastewater, and the alkali weight-reduction water with the highest antimony concentration being diluted to the level of the dyeing water, while the total water volume becomes larger and the absolute load on the biological system is not reduced at all.

The real use of this table is to translate it into a single design language: each stream's "reason for being difficult to treat" is different, and different reasons correspond to different treatment units. Desizing is difficult in terms of biodegradability, alkali reduction is difficult in terms of antimony and PTA, dyeing is difficult in terms of colority, printing is difficult in terms of ammonia nitrogen and color paste, and mercerizing is difficult in terms of alkali. Mixing them together is equivalent to stacking all these "difficulties" onto the same biological system, while also paying the extra energy cost of diluting them and then concentrating them back again.

II. B/C Is Not Inherent to the Wastewater; It Is Configured Upstream

The statement "desizing wastewater is hard to biodegrade" — just how hard it is depends on a factor that a printing and dyeing plant cannot control: what kind of size is on the greige fabric. Before weaving, the warp yarns must be sized, and the available sizing agents include starch-based types, carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), polyacrylates, and modified polyester types. Currently the most widely used are chemical sizing agents containing PVA, and PVA happens to be the hardest one to biodegrade.

Multiple publicly available sources give highly consistent values for the biodegradability of PVA: BOD₅/COD of about 0.1, 0.05, or 0.055. This set of numbers can be calculated directly — one technical document states it very clearly: each gram of PVA contributes approximately 0.10 g BOD and 1.84 g COD. Dividing the two, 0.10 ÷ 1.84 ≈ 0.054, i.e., B/C ≈ 0.054. The 0.05 and 0.055 in the three documents are three rounded ways of writing the same source data. The point of doing the calculation yourself is this: when you later see "some desizing wastewater with B/C 0.1" and "B/C 0.05", you can judge that they are a rough and a refined expression of the same thing, rather than two contradictory data points.

Why does this number matter? The empirical threshold for conventional aerobic biological treatment is a B/C of no less than 0.3. PVA's 0.054 is an order of magnitude below that threshold, meaning that if PVA-containing desizing wastewater goes directly into an aerobic tank, the microorganisms cannot consume it. Note that PVA is not a toxic substance — one source explicitly points out that "the relative oxygen consumption rate of PVA wastewater is greater than the endogenous respiration oxygen consumption rate, i.e., PVA is non-toxic to microorganisms." Its problem is being slow, not being toxic. But slow is equally fatal: if PVA is discharged with the water, it accumulates in the environment over the long term, increasing surface foam in water bodies, raising viscosity, and impeding reaeration.

What truly turns this into an engineering problem is its position in the industry. One source states this dilemma very bluntly: "As a printing and dyeing enterprise downstream in the industrial chain, it is difficult to control the processing techniques of the upstream textile industry, so in actual production, the sizing agent composition in desizing wastewater is complex and variable, but generally contains PVA." On the same desizing wastewater line, one batch of greige fabric may be starch-sized and the next batch PVA-sized, and the B/C can differ by an order of magnitude, while the treatment system can only be designed for the worst case — this is one of the root causes of the chronically high chemical dosing in printing and dyeing plants.

The standard engineering solution is to insert a Hydrolysis Acidification stage before biological treatment. Its role is not to mineralize the organic matter, but to cut the long chains: facultative anaerobic bacteria secrete extracellular enzymes that break the dye chromophore groups (such as azo bonds) and break PVA long chains into short-chain organic acids and alcohols, raising the B/C accordingly. Three sets of publicly available data point in the same direction:

There is a counterintuitive detail in this section worth highlighting separately. The above pilot test found that the UASB reactor shows no significant removal effect on refractory organics such as PVA, and PVA exhibits a "concentration and enrichment" trend in the system—after UASB, ρ(PVA)/ρ(COD) increased from 0.041 to 0.072. The reason is precisely that PVA is not consumed while other organics are consumed, so its proportion in the remaining COD actually rises. And this "enrichment" is not a bad thing: it causes PVA-degrading bacteria to be directionally enriched in the subsequent Anaerobic Hydrolysis stage, further enhancing PVA removal. The engineering implication is that one should not treat "organic removal rate" as a single indicator—at the same moment when total COD drops by forty percent, the most recalcitrant component may not have decreased at all, and may even be rising in proportion in the remaining COD.

III. There Are Two Rulers for Color: One Is "Times," the Other Is "Degrees"

Color is the most intuitive yet most easily misinterpreted indicator of printing and dyeing wastewater. It has two parallel determination methods, and "the two methods should be used independently and are generally not comparable."

One ruler is the dilution multiple method: the water sample is progressively diluted with optically pure water until the color is just barely invisible against a white background; the dilution multiple at this point is recorded as the color, in units of "times." The current method standard is HJ 1182—2021 "Water Quality—Determination of Color—Dilution Multiple Method," which replaces the dilution multiple method portion of GB/T 11903—1989. The main changes are replacing the original 2-fold dilution with natural multiple dilution, and adding requirements for determination conditions, sample preservation, precision, and quality control. Printing and dyeing wastewater has high color, and its color differs greatly from the yellow-brown tone of the platinum-cobalt standard; the dilution multiple method is precisely the primary method for this industry.

The other ruler is the platinum-cobalt standard colorimetric method: a standard color series is prepared with potassium chloroplatinate and cobalt chloride, and compared visually with the water sample; the color is expressed in "degrees" or platinum-cobalt units (PCU). It is suitable for clean water, natural water, and low-color wastewater, with a determination range of approximately 5–70 degrees; samples exceeding 70 degrees require dilution before determination, then multiplying by the dilution multiple.

The two rulers govern completely different scenarios: discharge standards use "times," while water-use quality uses "degrees." In GB 4287—2012, Table 2 (new enterprises) sets color limits of 50 for direct discharge and 80 for indirect discharge, in units of dilution multiple; Table 1 (existing enterprises) sets 70 and 80. On the water-use side, limits are in "degrees": domestic drinking water must not exceed 15 degrees, textile industry water use must be less than 10–12 degrees, and dyeing water use must be less than 5 degrees. In other words, for the same water sample from the same dyeing plant, reporting "80 times" at the discharge outlet is compliant, while reuse in the dyeing process requires "less than 5 degrees"—there is no conversion formula that can be directly applied between these two numbers.

A verifiable compliance example: in the 2025 年 12 月 pollutant discharge permit supervisory monitoring results published by the Qingdao Municipal Ecology and Environment Bureau, a textile dyeing and finishing enterprise had a measured color of 8 times against a judgment limit of 80 times; in the same batch of data, COD was measured at 92 mg/L against a limit of 200 mg/L, and SS was measured at 23 mg/L against a limit of 100 mg/L. When three sets of numbers appear on the same table, whether the "limit 80" is in times or degrees directly determines whether that data point is judged compliant.

Reduction figures in engineering ledgers are likewise reported in "times." In a centralized printing and dyeing wastewater treatment project at an industrial park (commercial data), the influent color was 1200 times, reduced to below 20 times after "coagulation sedimentation—hydrolysis acidification—biological contact oxidation—ozonation—biological activated carbon"; another commercial engineering document gives staged reductions: influent color 800 times, 200 times after hydrolysis acidification, 80 times after A2/O biological treatment, and less than 10 times after coagulation plus Fenton plus activated carbon. Note that the starting points of these two cases differ by 400 times; if one only looks at percentages such as "decolorization rate above 98%," the difference cannot be seen.

IV. The three words "indirect discharge" correspond to the three numbers of COD: 80, 200, 500

Once the process is selected, the next step is to determine what to use for compliance against the standard. GB 4287—2012 is divided into three tables: Table 1 applies to existing enterprises (effective from 2015 年 1 月 1 日), Table 2 applies to new enterprises (effective from 2013 年 1 月 1 日), and Table 3 specifies special emission limits, with the geographic scope and timing of implementation prescribed by the environmental protection department under the State Council or the provincial people's government. The key limits of Table 2 are as follows.

There is another item that is often overlooked: Baseline Water Discharge per Unit Product. Table 2 specifies 140 m³/t of standard product for cotton, linen, chemical fiber, and blended woven fabrics; 85 for yarn and knitted fabrics; 300 for pure silk woven fabrics (including degummed and bleached); 500 for combed wool fabrics; and 575 for carded wool fabrics. The corresponding values in Table 1 are 175, 110, 350, 560, and 640, respectively. The meaning of these figures is that the discharge volume itself is also regulated—different products can be converted according to FZ/T 01002, and if more is discharged, the concentration must be converted based on the baseline water volume. Diluting the effluent to just meet the standard does not truly make it compliant under the conversion basis.

What truly tends to trip people up is the phrase "indirect discharge." The standard amendment issued by 2015 年 (Ministry of Environmental Protection Announcement No. 19 of 2015 年) subdivides indirect discharge into three categories and sets the indirect discharge limits for COD and BOD₅ separately by category:

In the same table of the same standard, the "Indirect Discharge" column simultaneously contains three COD figures — 80 (converted to the direct discharge basis according to Category 3), 200, and 500 — with a maximum difference of more than 6 times. More critically, the amendment also adds emission control requirements for Total Antimony, with both direct discharge and indirect discharge limits set at 0.10 mg/L, and the monitoring location being the "enterprise wastewater total discharge outlet".

There is another more subtle change that concerns whether the document in your hands is already outdated. Announcement No. 41 of 2015 年 (2015 年 6 月 17 日) clearly specifies two adjustments: First, temporarily suspend implementation of the aniline and hexavalent chromium discharge control requirements in Table 2 and Table 3 of GB 4287—2012; during the suspension period, these two items shall comply with the relevant requirements in Table 1 (i.e., aniline 1.0 mg/L, rather than "not detectable" in Table 2); Second, temporarily suspend implementation of the provision in the amendment sheet that "wastewater entering urban sewage treatment plants or discharged via urban sewage pipelines shall meet the direct discharge limits"; and it is clarified that the above provisions shall be implemented before the revision of GB 4287—2012 takes effect. This means: if you copy Table 2 and report "aniline not detectable," the conclusion will be stricter than the current implementation requirements; if you copy the amendment sheet and report "discharge into urban sewage treatment plants must meet direct discharge limits," then you have cited a suspended clause. When determining design values and compliance, these two points must be verified against the original announcement text.

V. Antimony: the only characteristic pollutant in printing and dyeing wastewater that is "destined from the source"

The conventional indicators of printing and dyeing wastewater (COD, color, ammonia nitrogen) are all related to process operations and can be adjusted; but there is one pollutant brought in by the greige fabric, and the printing and dyeing plant cannot change its total amount—antimony.

The source is very clear: polyester (PET), the raw material for polyester fiber, requires a catalyst during synthesis. More than 90% of polyester fibers worldwide are produced with antimony trioxide, antimony acetate, or ethylene glycol antimony added as a catalyst for the esterification polymerization reaction. Calculated by elemental atomic weight, antimony accounts for about 40% of these catalysts. Polyester fabrics or polyester blend fabrics mostly require alkaline desizing before printing and dyeing, and some also require special alkali weight reduction treatment. Free antimony enters the wastewater in these two processes.

An industry analysis by the Zhejiang Printing and Dyeing Industry Association calculated this total amount. Here its three input values are copied and the result is recalculated: national polyester output is taken as 4000 万 t/a; for every 1 t of PET produced, the mass ratio of antimony-containing catalyst used is 3 in 10,000 (0.03%), 4000 万 × 0.03% = 1.2 万 t catalyst; converted at antimony accounting for about 40% of the catalyst, elemental antimony is about 1.2 万 × 40% = 4800 t—consistent with the association's figure of "antimony-containing catalyst 4800 t." Assuming further that 50% of polyester fabric undergoes alkaline desizing and alkali weight reduction treatment, with an average weight reduction rate of 15%, the antimony entering printing and dyeing wastewater is about 4800 × 50% × 15% = 360 t/a, also consistent with the association's statement that "at least 360 t of elemental antimony enters printing and dyeing wastewater each year." Running someone else's three input values through the calculation can simultaneously verify his two output values, which shows that this data set is internally consistent—and it also directly shows that antimony cannot be "eliminated" by end-of-pipe treatment at printing and dyeing plants; it can only be transferred.

The concentration distribution determines where it should be intercepted. Public technical materials state: the main sources of antimony in printing and dyeing wastewater are release during alkali weight reduction, scouring/bleaching, desizing, and dyeing of polyester fibers, among which the total antimony content in weight reduction and desizing wastewater is the highest, reaching up to 1000 μg/L; in dyeing wastewater it is about 200–300 μg/L. The limit set by the amendment sheet to GB 4287—2012 is 0.10 mg/L (i.e., 100 μg/L), with the monitoring location at the "enterprise wastewater total discharge outlet."

The targeted engineering approach is segregated treatment. A published patent (CN201610423772.5) provides the following route: first, excess acid is added to alkali-deweighting wastewater and desizing wastewater for acidification (adjust pH to 1.5–4, preferably 2–3); the acidified water is then mixed with dyeing wastewater in the equalization tank, dosed with polyferric sulfate (dosage of 1‰–1.5‰ of the mixed wastewater mass) and pH-adjusted (preferably 4.5–5.0) before entering the air flotation tank to recover scum; the air flotation effluent is dosed with liquid caustic soda and enters the Hydrolysis Acidification tank, followed by the biological tank; after separation in the secondary clarifier, the supernatant is dosed with polyferric sulfate (1.5‰–3‰) and pH-adjusted (preferably 6.2–6.5) before entering the tertiary clarifier. In this entire process, the same coagulant is dosed at three points, and the pH follows a three-stage staircase of 2–3 → 4.5–5.0 → 6.2–6.5 →, which is a typical "stepwise antimony removal" rather than "single precipitation." Another utility model patent (CN209052489U) adopts a combination of Fenton Oxidation tank plus air flotation. Jiangsu Province has also issued a local standard DB32/3432—2018 "Discharge Standard of Antimony Pollutants in Textile Dyeing and Finishing Industrial Wastewater," which is stricter than the national standard.

VI. Salt: Glauber's salt is bought in, not grown in wastewater

The salinity of Printing and Dyeing Wastewater also has a clear source, and it is an amount that can be calculated from the recipe: Glauber's salt (Na₂SO₄).

When reactive dyes dye cotton, the fiber surface is negatively charged and repels anionic dyes, so electrolytes must be added to compress the electrical double layer and reduce repulsion to promote dye uptake—Glauber's salt is this standard dyeing accelerator. Published dosage references are: at a liquor ratio of 1:10, Glauber's salt 40–80 g/L (light shades 20–40 g/L, medium to dark shades 50–80 g/L), added in 2–3 portions to avoid too-rapid dye uptake. Putting these two numbers together for a conversion: a liquor ratio of 1:10 means 10 L of water per 1 kg of fabric, and at 50 g/L of Glauber's salt, about 500 g of Glauber's salt is dosed per 1 kg of fabric in the dye bath, i.e., 50% of the fabric weight. Almost all of this salt enters the wastewater with the residual dye liquor.

This estimated amount is consistent with actual measurements: the salinity concentration of comprehensive wastewater in a certain Printing and Dyeing Industrial Park reaches 8000–15000 mg/L; Printing and Dyeing Wastewater in Guangdong generally has high salt content (conductivity greater than 8000 μS/cm); the raw water TDS in the continuous operation log of a certain printing and dyeing plant is 3200–3800 mg/L. In other words, the salt in Printing and Dyeing Wastewater is not "water quality fluctuation," but a predictable constant determined by the recipe and output.

The consequences of salt fall into two stages. In the biological stage, the osmotic pressure shock and ion toxicity of salinity on microorganisms suppress treatment efficiency—this mechanism and its countermeasures have already been elaborated in the article "Salt-Tolerant Bacteria Biological Treatment of High-Salinity Industrial Wastewater and the Salinity Red Line," and will not be repeated here. In the reuse stage, salt cannot be removed by filtration and adsorption; it can only be pushed aside by Reverse Osmosis or evaporative concentration—thus producing concentrate, and the concentrate must be disposed of. This is the real cost engine of printing and dyeing reuse.

Let us calculate this account using published operation logs. The continuous operation data of a certain printing and dyeing plant from 2023 年 7 月 to 2024 年 4 月 (commercial operation log, raw water COD 650–820 mg/L, TDS 3200–3800 mg/L, SS 120–180 mg/L, water temperature 25–32 ℃, pH 7.2–8.1) provides a comparison of five reuse combinations:

In this dataset, what deserves the closest attention is not the power consumption, but the relationship between the last two columns and the concentrate disposal cost. Another conversion in the same document makes the logic clear: the evaporative crystallization disposal cost for the concentrate of this process route is approximately 80–120 元/m³. Recalculated for a printing and dyeing plant with a daily treatment capacity of 1000 m³: at a reuse rate of 90%, the concentrate is 100 m³/d, and calculated at 330 天/year, that is 33 000 m³/a; at 100 元/m³, that is approximately 330 万 yuan/year; after the reuse rate is raised to 95%, the concentrate is halved to 50 m³/d, and the annual concentrate disposal cost is approximately 165 万 yuan. In other words, for every 5 percentage point increase in the reuse rate, the annual savings in concentrate disposal cost is approximately 165 万 yuan, which is far higher than the water fee saved itself. Conversely, if the reuse rate is only brought to around 80%, the concentrate volume doubles, and the disposal cost will quickly consume all the water-saving benefits—this judgment shares the same mechanism as "the concentrate lets salts circulate within the system" in the landfill leachate article, except that here the amount of sodium sulfate dosed can be used to calculate clearly from the source where the salt comes from.

The pathway for source reduction of salt is therefore clear: small liquor ratio dyeing, salt substitutes, and improving dye uptake from the dye side to reduce the amount of dyeing accelerant. On the engineering side, the acceptance criteria for reused product water depend on the intended use—the requirements of dyeing reuse water for color, hardness, iron, and manganese are completely different from those for discharge criteria. One cannot use "color 20 times" to accept a water pipe intended for reuse in the dyeing process.

VII. Real Engineering Ledger (Public Engineering Cases and Government Documents)

VIII. Six Points to Watch Closely During Selection and Acceptance

1. For "indirect discharge," first ask which type of wastewater treatment plant it discharges to. Discharge to a municipal wastewater treatment plant (Category 3, currently deferred), discharge to a dedicated industrial park wastewater treatment plant with centralized pretreatment (Category 4, COD 500), and other indirect discharge (Category 5, COD 200) — the three tiers differ by more than 6 times. The category must be specified in the environmental impact assessment and design scheme; it is not acceptable to simply state "comply with Table 2 indirect discharge."
2. Colority reporting must include units and basis. For discharge outlets, it is dilution ratio (50/80 times); for reuse, it is platinum-cobalt units (dyeing water <5 units). The two methods should be used independently and are generally not comparable. Writing only "colority 20" is as good as writing nothing.
3. PVA-type desizing wastewater cannot enter aerobic treatment directly. The B/C ratio is approximately 0.054, an order of magnitude below the empirical threshold of 0.3; hydrolysis acidification is a necessary pretreatment stage, and its effectiveness should be judged by the B/C ratio rising to 0.3–0.4 as the acceptance criterion, rather than by COD removal rate. Conversely, note that the COD removal rate of hydrolysis acidification is typically not high (around 25%); its value lies in biodegradability improvement rather than removal quantity.
4. "Total COD removal rate" masks the most recalcitrant component. UASB pilot testing shows that PVA barely degrades in this stage, while its proportion actually rises from 0.041 to 0.072. Assessment should set separate indicators by component (PVA, dyes, auxiliaries) to avoid total-quantity indicators masking the loss of control over individual items.
5. Antimony must be segregated by stream, and the upstream account must be calculated. The total antimony in alkali weight reduction and desizing wastewater can reach 1000 μg/L, which is 3–5 times that of dyeing wastewater, while the limit only looks at the total discharge outlet at 0.1 mg/L. Compliance through mixed discharge depends on dilution ratio and will lose control once the production capacity structure changes; at the same time, it must be recognized that antimony is merely transferred from water to sludge and then to the atmosphere — source substitution (non-antimony catalysts, alkali-free weight reduction) is the true reduction pathway.
6. The cost engine of reuse projects is concentrated water, not electricity consumption. Salts cannot be removed by filtration and adsorption; they can only be concentrated into the concentrated water stream by membranes or evaporation. Recalculating at concentrated water disposal cost of 100 元/m³, a reuse rate of 90% versus 95% means an annual difference of 165 万 yuan for a plant of 1000 m³/d; when preparing a reuse scheme, the destination of the concentrated water must be determined before the investment decision.

References

1. Ministry of Ecology and Environment, "Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industry" (GB 4287—2012), Table 1, Table 2, Table 3, Table 4, original text
2. "Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industry" (GB 4287—2012) Amendment, Ministry of Environmental Protection Announcement No. 19 of 2015 年 (indirect discharge classified into three categories, addition of total antimony 0.10 mg/L)
3. Ministry of Environmental Protection Announcement No. 41 of 2015 年, "Announcement on Adjusting the Implementation Requirements for Certain Indicators of the 'Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industry' (GB 4287—2012)"
4. Taicang Municipal Environmental Protection Bureau, "Notice on Implementing the Amendment to the National 'Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industry' (GB 4287—2012)", 2015-04-21
5. Jiangsu Provincial Ecological Environment Assessment Center, "Explanation on the 'Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industry'"
6. "Water Quality — Determination of Colority — Dilution Multiple Method" (HJ 1182—2021)
7. "Water Quality — Determination of Colority" (GB/T 11903—1989) and explanation of the applicable scope of the platinum-cobalt standard colorimetric method
8. "Standards for Drinking Water Quality" (GB 5749—2022), colority limit and colority requirements for industrial water use
9. Qingdao Municipal Ecology and Environment Bureau, "2025 年 12 月 Qingdao Pollutant Discharge Permit Unit Supervisory Monitoring Results"
10. Huidong County People's Government, "Pollution Source Monitoring of National Key Monitoring Enterprises" public notice (Huidong Henghua Garment Manufacturing, GB 4287—2012, Table 2)
11. Yancheng Meiyi Home Textiles, Environmental Impact Report for the Technical Renovation Project of an Annual Production Line of 10000 tons of blankets (comparison table for stricter connection standards)
12. Hubei Qili Real Estate, Environmental Impact Report for the Annual Production of 8 万 tons of synthetic leather base fabric construction project (GB 4287, Table 2, indirect + stricter of park connection standards)
13. Jiangsu Provincial Academy of Environmental Science / Jiangsu Provincial Key Laboratory of Environmental Engineering / College of Environment, Hohai University, "UASB-Anaerobic Hydrolysis Process for Pretreatment of Desizing Printing and Dyeing Wastewater"
14. Jiang Bin et al., "Engineering Case of Advanced Treatment of Printing and Dyeing Wastewater", Industrial Water Treatment (Hydrolysis Acidification + A/O(MBR) + Ozonation + BAF)
15. Engineering case of a printing and dyeing wastewater treatment plant using coagulation-hydrolysis acidification-AAO-MBR-ozonation (operating cost 2.33 元/m³)
16. "PVA Recovery Technology and Methods in Desizing Wastewater", Wastewater Treatment Engineering Network
17. "Method for Preparing Paper Tube Adhesive Using High-Concentration Printing and Dyeing Desizing Wastewater" (desizing wastewater accounts for 10%～20% of water volume, COD 15 000～70 000 mg/L)
18. Liyuan Environmental Protection, "Treatment Methods for PVA-Containing Desizing Wastewater" (each gram of PVA contributes 0.10 g BOD, 1.84 g COD; case of a wastewater treatment plant in a Guangdong printing and dyeing industrial park)
19. Hengchang Environmental Protection, "Overview of Integrated Zero Liquid Discharge Processes for Printing and Dyeing Wastewater Treatment" (proportion of desizing COD, alkali reduction acidification pH 3)
20. Zhejiang Printing and Dyeing Industry Association, "Some Thoughts on Solving Environmental Protection Problems in the Printing and Dyeing Industry from the Source" (polyester output, proportion of antimony catalyst and annual antimony entering wastewater)
21. Patent CN201610423772.5, "A Method for Removing Antimony from Printing and Dyeing Wastewater" (acidification and three-stage coagulation pH steps)
22. Patent CN209052489U, "A Treatment System for Efficiently Removing Antimony from Printing and Dyeing Wastewater"
23. "Removal of Antimony from Printing and Dyeing Wastewater", Wastewater Treatment Engineering Network (total antimony in alkali reduction and desizing wastewater 1000 μg/L, dyeing wastewater 200～300 μg/L)
24. Jiangsu Province, "Discharge Standard of Antimony Pollutants in Wastewater from Textile Dyeing and Finishing Industry" (DB32/3432—2018)
25. Data on the accelerating dyeing dosage of sodium sulfate in reactive dye dyeing of cotton (liquor ratio 1:10, 40～80 g/L, added in 2～3 portions)
26. Zhongsheng Environment, "Integrated Wastewater Treatment Equipment Scheme for Printing and Dyeing Wastewater" (MBR colority removal 60%～70%, PVDF membrane lifespan 3～5 年, RO membrane 2～3 年, case of a Changzhou knitting printing and dyeing plant)
27. Continuous operation log of a Shandong printing and dyeing plant from 2023-07 to 2024-04 (comparison of five reuse combinations, commercial data)
28. Zhejiang Dongfang Huaqiang Textile Printing and Dyeing MBR + RO 15 000 m³/d project (government technology promotion catalog)
29. Weilin Environmental Protection · High COD wastewater treatment case in the printing and dyeing industry (centralized treatment and segregated pretreatment in industrial parks)
30. Keqiao printing and dyeing wastewater treatment and emerging pollutant treatment data (substitution of fluorine-containing auxiliaries)

Manuscript Service · Industrial Water Treatment Technology Series | All data in this article are annotated with public sources; commercial technical materials have been individually marked as "commercial data / not peer-reviewed" and are for directional reference only. Design values shall be based on bench tests, pilot tests, and actual measured data from the plant. All assumptions in the [self-calculated] sections have been stated; cited standard limits have been verified against the original standards and announcements.