Industrial Reclaimed Water: Standards Merge Five Use Categories into Two, but the Real Gatekeeper Is in the Cooling Tower

For reclaimed water reuse in industry, the first thing to clarify is that the term "reuse water" simultaneously refers to three different things: a set of influent standards classified by use (GB/T 19923), a equipment specification governing circulating water itself (GB/T 50050), and a statistical framework (reclaimed water utilization rate). This article uses the original texts of GB/T 19923—2024 and the 2005 version, the GB 50335—2016 design specification, the DL/T 300 circulating water control indicators, and publicly available data from five projects—Zhongyang Steel, Shizuishan, Wanhua Chemical, Taozhiwan, and Ningdong—to unpack this interface: why the new version merged five columns into two, where the salinity indicators went, and why the upper limit for chloride ions in make-up water is back-calculated from the concentration ratio.

Gaowutong · Industrial Water Treatment Technology Series · For industry technical personnel · All data annotated with original public standards, government public platforms, and literature sources

I. "Reuse water" is not a single water quality; it is five categories of use in one table

The most error-prone aspect of industrial reuse is treating "reclaimed water meets the standard" as a single conclusion. In reality, the current national standard GB/T 19923 is organized by use from beginning to end—because it must simultaneously answer "what is this stream of water used for," not just "is this stream of water clean."

As of 2024 年 9 月 30 日, the industry implements GB/T 19923—2005. It lists five categories of use in one table: once-through cooling water, make-up water for open recirculating cooling water systems, washing water, boiler feed water, and process and product water. The same table, the same indicator, five numbers: for ammonia nitrogen, the limit for make-up water for open recirculating cooling water is 10 mg/L, while the washing water column has no requirement at all; for sulfate, once-through cooling water is relaxed to 600 mg/L, while the other four categories are all 250 mg/L.

2024 年 3 月 15 日, GB/T 19923—2024 was issued, implemented on 2024 年 10 月 1 日, and fully replaces the 2005 version. The new version did something very specific: it merged these five categories of use into two columns. The first column is "make-up water for indirect open recirculating cooling water, boiler feed water, process water, product water," and the second column is "once-through cooling water, washing water."

What is the basis for the merger? Not water quality level, nor industry, but whether this stream of water needs desalination and further softening. For the categories of use in the first column, natural scale and solutes will accumulate in the equipment (recirculating cooling water is evaporated and concentrated, boilers are heated and evaporated, process and product water directly enters products), so the requirements for salinity are stricter; the once-through cooling water and washing water in the second column are "pass-through" single-use water, where salinity basically does not accumulate, so the standard relaxes the salinity indicators by one level. In other words: the 2005 version classifies by "use," while the 2024 version classifies by "whether salinity will accumulate in the equipment."

II. The 2005 version: one table, five numbers

First, let us lay out the old version. The table below is taken item by item from the original text of Table 1 of GB/T 19923—2005 as cited in three government public documents (the draft regional assessment report for the Guazhou Industrial Concentration Zone in Jiuquan, Gansu; the environmental impact assessment for the wastewater treatment plant in the Huomachong Town Industrial Concentration Zone in Huaihua, Hunan; and the bidding technical document for a landfill leachate treatment project in Hainan), and the three documents are consistent.

Except for pH and fecal coliforms, the unit is mg/L; "—" indicates that the old version had no requirement for that use. The note below the table specifies: when the heat exchangers of an open recirculating cooling water system are made of copper, the ammonia nitrogen index of the circulating water in the recirculating cooling system should be less than 1 mg/L — this is the only note in the old version that extends the "standard to the circulating water."

Two places in this table are most easily misread. The first: the large number of "—" entries in the washing water and once-through cooling water column does not mean there are no requirements—it means this column only assesses toxicity, hygiene, and suspended solids, not organic load or salinity; in engineering practice, internal control values must still be set separately according to equipment materials. The second: the "boiler make-up water" column appears lenient (iron 0.3, hardness 450, alkalinity 350), and this is precisely the pitfall to be stepped into later: the hardness of 450 is two orders of magnitude beyond what an industrial boiler can tolerate, indicating that this column is not "water that can enter the boiler" at all, but rather "raw water that can enter the boiler water treatment system."

III. 2024 version: five categories of use merged into two columns, with the dividing line being "whether salinity will accumulate"

The new version of the table 1 has only two columns, and the structure suddenly becomes clear:

Unit: mg/L (except pH and where otherwise noted); ᵃ When used as make-up water for indirect open circulating cooling water systems and the heat exchangers are of copper alloy material, the ammonia nitrogen indicator shall be less than 1 mg/L; ᵇ refers to the total residual chlorine value in the reclaimed water at the connection point with the user's pipeline; "—" indicates no requirement for this item. Each item is taken from the original text of Table 1 of GB/T 19923—2024, and has been checked item by item against the values in Table 1 of the same standard cited in the 2024 年 7 月 Environmental Impact Assessment Public Notice of the Ecological Environment Bureau of the Xinjiang Production and Construction Corps, and found to be consistent.

Putting the two versions side by side, the most intuitive change is that the number of columns goes from 5 to 2, but what really determines engineering actions is something else: among the same set of indicators, those that are "split into separate columns" are all salinity and hardness indicators—Total Dissolved Solids 1000/1500, chloride 250/400, sulfate 250/600, iron 0.3/0.5, manganese 0.1/0.2, silica 30/50, all six are split in two. Meanwhile, organic and hygienic indicators (BOD₅, COD, ammonia nitrogen, Total Nitrogen, Total Phosphorus, color, fecal coliform, residual chlorine) take the same value for both use categories.

This shows that the new version actually leaves room for "quality-based water supply, optimal water for optimal use": if an enterprise only needs once-through cooling water or washing water, it no longer has to treat the water stage by stage up to the level of circulating cooling water make-up water; conversely, as long as the water is to enter a circulating system or boiler, it must follow the stricter column. After the words "reclaimed water", there must be a use qualifier, otherwise the number cannot be matched.

IV. For the same set of indicators, half go down and half go up

Dividing or subtracting item by item between the two versions reveals a very informative phenomenon: organic and hygienic indicators are tightened across the board, while salinity and hardness indicators are collectively relaxed in the "non-accumulating" column.

"Strict column" refers to indirect closed-circuit open circulating cooling water makeup, boiler makeup water, process water, and product water; "loose column" refers to once-through cooling water and washing water. The direction is self-calculated and is not the original wording of the standard.

Why this direction? Because the risk mechanisms corresponding to the two types of indicators are different.Organic load and hygienic indicators relate to microbial growth, biofilm and biological slime, and algae proliferation. Such problems occur in cooling towers, washing, and once-through cooling systems and are unrelated to "concentration," so they are uniformly tightened; salinity and hardness indicators are the responsibility of equipment materials and scaling. Once-through cooling water is used in large quantities, mostly passes once through shell-and-tube heat exchangers, and has a certain tolerance for scaling. Setting the standard as strict as that for circulating water would amount to forcing it to adopt desalination, which is economically unreasonable, so it is relaxed separately.

V. Two Newly Added Restrictive Items: Total Nitrogen and Fluoride

The 2024 version adds two control items, each with a clear focus.

Total Nitrogen 15 mg/L is a newly added basic control item, with the same value for both types of use. The old version only controlled ammonia nitrogen, not total nitrogen; in circulating cooling water systems, nitrogen is both a nutrient source for microorganisms (directly promoting biological slime and algae) and, during nitrification, consumes alkalinity and lowers pH, thereby changing the balance between scaling and corrosion. Including total nitrogen amounts to changing the "biological slime risk" from a single indicator to a total-quantity indicator.

Fluoride 2.0 mg/L and sulfide 1.0 mg/L are newly added selective control items. Selective control items mean that whether they are assessed and to what extent is determined jointly by the pollutant content of the water source and the equipment conditions of industrial users (Clause 4.1.2 of the standard), and should be fixed in the procurement contract or technical agreement. Fluoride poses a corrosion risk to stainless steel, titanium, and glass materials, while sulfide is directly related to metal corrosion, odors, and biological poisoning—these two items are inherently very low in many water sources, but once the water source is switched to fluoride-containing industrial wastewater or sulfur-containing wastewater, separate limits must be set.Putting these two items under "selective" actually means: the standard has written the values for you, but you must decide whether to use them.

There is also a fallback clause that must not be missed: Clause 4.2.2 of the standard stipulates that reclaimed water using municipal sewage as its source, in addition to meeting the indicators in Table 1, shall also comply with the limits for "Class I pollutants" and "selective control items" in GB 18918. That is to say, indicators such as heavy metals are not without requirements; rather, they are obtained by reference back to the discharge standard for municipal wastewater treatment plants.

VI. The Real Interface Is in the Cooling Tower: Makeup Water Compliance ≠ System Compliance

At this point, the task of GB/T 19923 is finished—it is a standard for raw water for industrial use, governing "the water that is added." But what the added water does in the cooling tower is evaporate pure water and leave the solutes behind. After N cycles of concentration, the chloride, sulfate, hardness, and alkalinity in the influent are all magnified N times (except for the portion precipitated as scale). Therefore, on the water-using equipment side, an entirely different set of numbers is assessed.

The governing standard on the circulating cooling water side is GB/T 50050—2017 "Code for Design of Industrial Circulating Cooling Water Treatment", which governs the circulating water itself. Common circulating water control indicators in engineering practice (taken from the plant-wide water treatment technical specification of an environmental protection power generation enterprise, whose explicitly implemented standards are DL/T 300—2011 "Guidelines for Anti-corrosion and Anti-scaling of Condenser Tubes in Thermal Power Plants" and GB/T 50050—2017) are: circulating water chloride ion ≤1000 mg/L, sum of total alkalinity and calcium hardness (calculated as CaCO₃) ≤1100 mg/L, circulating water turbidity ≤10 NTU; make-up water chloride ion ≤250 mg/L, turbidity ≤5 NTU. The same specification also gives recommended values for two concentration ratio tiers: natural water 3.0~6.0, reclaimed water 2.0~5.0.

Putting the numbers from the two standards together for a back-calculation is the least effortful criterion.The make-up water chloride ion upper limit is 250 mg/L, and the circulating water chloride ion upper limit is 1000 mg/L; dividing the two gives 4—that is, if the make-up water chloride ion runs right at the 250 upper limit, the concentration ratio can only stay within 4 times; while the recommended upper limit of the concentration ratio when reclaimed water is used as make-up water is 5.0, corresponding to 250×5 = 1250 mg/L, which already exceeds the circulating water upper limit of 1000. To truly achieve 5 times concentration, the make-up water chloride ion must be pressed below 200 mg/L.

The hardness and alkalinity pair is even more worth calculating. The make-up water total hardness upper limit is 450, the total alkalinity upper limit is 350, and the sum of the two is 800; the upper limit of "total alkalinity + calcium hardness" on the circulating water side is 1100. If both make-up water items are taken at the standard upper limits, then with concentration of only about 1.4 times, the sum of this item is already at the circulating water upper limit. This result looks absurd (almost no reuse project operates at 1.4 times concentration), and the absurdity itself illustrates one thing: what the standard table gives is the "admission upper limit", not the "design target value".

The boiler side follows the same logic, and the standard itself states this explicitly. The supporting interpretation of GB/T 19923—2024 points out: when reclaimed water is used as boiler make-up water, even if all the indicators in Table 1 are met, it cannot be fed directly into the boiler; softening, demineralization and other treatments must be carried out according to the boiler operating conditions until the boiler water quality requirements are met. The standards actually implemented on the boiler side are GB/T 1576 "Water Quality for Industrial Boilers" and GB/T 12145 "Water and Steam Quality for Thermal Power Generating Units and Steam Power Equipment", whose requirements for hardness (mostly at the μmol/L level), conductivity, silica and oxygen content are two to three orders of magnitude stricter than those of GB/T 19923. In one sentence: the "boiler make-up water" column in GB/T 19923 refers to the "influent to the boiler make-up water treatment unit", not the "boiler make-up water".

VII. The "reuse rate" has three denominators, and even explaining them clearly is difficult

Now that water quality is clear, next is water quantity. The reuse rate, this seemingly simple percentage, has at least three calculation methods in actual documents, and they are not comparable with one another.

The first set of denominators comes from the design code. Article 4.3.1 of GB 50335—2016 "Code for Design of Municipal Wastewater Reclamation and Reuse" stipulates that the design supply quantity consists of "reclaimed water utilization quantity + pipeline network leakage quantity + unforeseen water quantity", and the design scale is determined according to the maximum daily supply quantity; Article 4.3.2 stipulates that when the water source is the effluent of a wastewater treatment plant, the maximum design scale shall be the effluent quantity of the wastewater treatment plant minus various non-recoverable self-use water quantities of the reclaimed water plant, and should not exceed 80% of the scale of the wastewater treatment plant; Articles 4.3.10 and 4.3.11 further stipulate that the pipeline network leakage quantity is calculated at 10%~12% of the reclaimed water utilization quantity, and the unforeseen water quantity is calculated at 8%~12% of the sum of the former two. In other words, the "scale of the reclaimed water plant" is inherently smaller than the "scale of the wastewater plant", and by more than a little.

The second set of denominators comes from process self-use water quantities. The clause explanation 4.3.12 of the same code gives the self-use water rates of each unit: coagulation-sedimentation-filtration plus disinfection process 8%~12%; microfiltration unit at 10%~15% of the produced water quantity, ultrafiltration unit at 18%~22% of the produced water quantity, reverse osmosis unit at 40%~45% of the produced water quantity (corresponding to a water recovery rate of 70%~75%). These figures are in series, and are all deducted downward based on the "produced water quantity", so they are easily underestimated.

The third set of denominators comes from the statistical scope, and it is the most easily confused set. According to the scope of the "Notice of the General Office of the Ministry of Water Resources on Further Strengthening and Standardizing the Statistics of Unconventional Water Sources", reclaimed water utilization rate = reclaimed utilization water quantity ÷ wastewater treatment quantity × 100%; among them, the reclaimed utilization quantity is the sum of various uses such as industrial, urban miscellaneous, landscape environment, ecological water replenishment and agricultural irrigation, excluding non-ecological water replenishment directly discharged into natural water bodies such as rivers, lakes and wetlands, and also excluding the reuse quantity of wastewater treatment within enterprises.

This last half-sentence is the most easily misstepped point in the whole article: the reuse quantity within an enterprise is not counted in the reclaimed water utilization rate. Therefore, an enterprise announcing an "industrial water reuse rate of 99%" and a city announcing a "reclaimed water utilization rate of 25%" are two completely unrelated things — the former refers to in-plant circulation, and the latter refers to sending the tailwater of a municipal wastewater treatment plant to users outside the plant.

Related to this is the policy target basis. The "Guiding Opinions on Promoting the Resource Utilization of Wastewater" (Fa Gai Huan Zi [2021] No. 13) set the following targets: by 2025 年, the reclaimed water utilization rate in water-scarce cities at the prefecture level and above nationwide should reach 25% or more, and the Beijing-Tianjin-Hebei region should reach 35% or more. The "reclaimed water utilization rate" in this sentence is exactly the third basis mentioned above—the denominator is the wastewater treatment volume, and the numerator does not include in-plant reuse. For reference, the baseline disclosed by the National Development and Reform Commission is: in 2019 年, China's urban wastewater discharge was approximately 750 亿 m³, while reclaimed water utilization was less than 100 亿 m³, giving a utilization rate of approximately 13%.From 13% to 25%, the entire increment comes from the portion of water that "crosses the plant boundary," not from in-plant recycling.

VIII. The Real Accounts of Five Projects

Back to the projects. The public data of the following five projects happen to cover different scales, from county-level wastewater treatment plants to national-level zero liquid discharge bases, and each exposes a basis issue of its own.

Data sources: Ministry of Water Resources "Water-Saving China" case library, public reports from the Department of Water Resources of Ningxia Hui Autonomous Region and the Ningxia Channel of People's Daily Online, and public reports from China Chemical Industry News. Self-calculated figures (unit investment 5000 元/(m³·d), Haixin approximately 5.5 元/m³, investment per mu, etc.) have been annotated in the main text or in the table.

Looking at these five projects together, there are three points worth comparing.

First point: the destination of Reclaimed Water is being "classified by salinity."Zhongyang Steel sends the high-quality Reclaimed Water produced by the dual-membrane process into the clean circulating water system (demineralized water, soft water), while continuing to reuse the originally surplus ordinary reclaimed water (5000 m³/d) in the turbid circulating water system and equipment cooling—this is exactly the engineering version of the classification logic in the previous section, "will salinity accumulate?"In the same plant, two streams of water of different quality each go where they should go. "Best water for best use" is not a slogan; it saves the operating cost of the dual-membrane process.

Second point: unit investment varies enormously, and the reason lies in "what the product is."Zhongyang Steel's project is "hardness removal + dual membrane," 1 万 m³/d with an investment of 5000 万 yuan, calculated at about 5000 元/(m³·d); Ningdong's zero liquid discharge project has an investment of 16.9 亿 yuan, treatment capacity 3.54~5.5 万 m³/d, calculated at about 3.1 万~4.8 万 yuan/(m³·d)—a difference of nearly an order of magnitude. The difference is not in the membranes but in the back end: Ningdong's products, besides reuse water, also include about 4 万 t/a sodium chloride and 4.3 万 t/a anhydrous sodium sulfate, as well as an evaporation crystallization line.Before comparing the unit investment of two reuse projects, first ask whether their product lists include solid salt.

Third point: the true "second water source" volume comes from centralized park systems, not individual plants.Wanhua 20 万 m³/d, Taoziwan 20 万 m³/d, Ningdong 2409 万 m³ per year—these three are of the same order of magnitude; while single-enterprise reclaimed water reuse projects are mostly around 1 万 m³/d.To raise a city's reclaimed water utilization rate from 13% to 25%, what matters is connecting municipal sewage plants with park pipe networks, not having every plant regenerate its own water.Shizuishan's step of "building a new large-diameter main pipe network to connect the Second Domestic Sewage Treatment Plant with more than 10 enterprises" ranks near the top of the investment list, and this is why.

Nine, Two versions of the standard with the same name are being cited at the same time

The last matter is citation norms.GB/T 19923—2024 "entirely replaces" the 2005 version, implemented from 2024 年 10 月 1 日, while a large number of existing documents prepared or issued before 2024 年 10 月 1 日 still write the 2005 version. Three examples are readily available in searches: the regional assessment report (submission draft) of the Liugou Coal Chemical Industry Park in the Guazhou Industrial Concentration Zone, Jiuquan, Gansu, completely copies the 20 items of Table 1 of GB/T 19923—2005 in its standards chapter; the environmental impact assessment of the sewage treatment plant in Huomachong Town and the Industrial Concentration Zone, Huaihua, Hunan, writes that "tailwater 60% is reused after advanced treatment to meet the urban sewage recycling industrial water quality standard," with Table 1 of the 2005 version attached on the same page; the technical document for third-party operation bidding of landfill leachate treatment at a domestic waste landfill in Hainan requires that "effluent meet the GB/T 19923—2005 make-up water standard for open circulating cooling water systems."

There are also two citation issues that are easily overlooked. First, the standard is GB/T recommendatory; its binding force comes from EIA approvals, water withdrawal permits, and water use contracts, not from the standard itself—so in engineering practice it is entirely possible to stipulate stricter internal control values in contracts than the standard (the hardness and alkalinity in Section Six are handled this way). Second, GB/T 19923 is a water quality standard for "raw water for industrial use"; it is not a circulating cooling water standard, not a boiler water quality standard, and not an acceptance standard for reuse water projects. If they are mixed up as one document, judgments such as "accepting boiler make-up water according to GB/T 19923" will appear—seemingly strict but actually misplaced.

Ten, Five engineering truths

1. To ask "does the reuse water meet the standard," three qualifiers must first be added: which version of the standard, which use column, and whether it is raw water or finished water. Table 1 of GB/T 19923—2024 has only two columns, yet the same parameter differs by up to 2.4 times (sulfate 250 vs. 600); the 2005 version has five columns, and the same parameter differs by up to 6 times (ammonia nitrogen 10 vs. no requirement). A water quality figure without qualifiers carries no information.

2. The standard for make-up water and the standard for water-using equipment are separated by the cycles of concentration and cannot substitute for each other. Dividing the make-up water chloride upper limit 250 by the circulating water chloride upper limit 1000 gives 4, which is the only bridge between these two figures. To achieve 5 cycles of concentration, the make-up water chloride must be pressed below 200 mg/L—this figure is not written in any table and must be calculated.

3. The standard table gives admission upper limits, not design target values. The sum of make-up water total hardness 450 and total alkalinity 350 is 800; if values are taken close to the upper limits, the circulating water threshold of "total alkalinity + calcium hardness ≤1100" will be reached before 1.4 cycles of concentration. Real projects achieving 3–5 cycles of concentration rely on three conditions holding simultaneously: actual water quality below the upper limits, acid dosing to drive alkalinity down to 100–200, and scaling precipitation. Writing upper limits into technical requirements as design values leaves the risk to the commissioning stage.

4. The reuse rate has three denominators, one of which excludes in-plant recycling. The design code basis takes "80% of the wastewater treatment plant scale" as the upper limit (GB 50335—2016, Article 4.3.2); the process basis must deduct the self-use water consumption of Reverse Osmosis 40%–45% and Ultrafiltration 18%–22%; and the statistical basis for reclaimed water utilization rate explicitly "does not include the repeated utilization volume of wastewater treatment within enterprises." An enterprise publishing a "repeated utilization rate of 99%" and a city publishing a "reclaimed water utilization rate of 25%" are not the same thing and cannot be cited interchangeably.

5. The water production rate of the dual-membrane process is written in the code commentary, not an operations issue. According to the commentary 4.3.12 of GB 50335—2016, the self-use water consumption of the Reverse Osmosis unit is calculated as 40%–45% of the water production, and that of Ultrafiltration as 18%–22%; after series connection, every 1 m³ of dual-membrane reclaimed water produced requires approximately 1.65–1.77 m³ of influent at the front end. Only by incorporating this into the project water balance table can the reuse rate target be set; otherwise, a physically unattainable figure will be given at the preliminary design stage.

References

1. GB/T 19923—2024 "Urban Sewage Reclamation and Reuse — Water Quality for Industrial Uses", issued by the State Administration for Market Regulation and the Standardization Administration of China on 2024-03-15, implemented on 2024-10-01, fully replacing GB/T 19923—2005; competent department: Ministry of Housing and Urban-Rural Development; centralized management by the National Technical Committee for Standardization of Urban Water Supply and Drainage (TC434). The limit values in Table 1 and Table 2 and the provisions of Articles 4.1.2, 4.2.2, and 5.1 are taken item by item from the standard clauses.
2. GB/T 19923—2005 "Urban Sewage Reclamation and Reuse — Water Quality for Industrial Uses", Table 1: limit values for 20 indicators across five categories of use (once-through cooling water, make-up water for open recirculating cooling water systems, washing water, boiler make-up water, process and product water), and the note below the table "when the heat exchanger is made of copper, the ammonia nitrogen in the circulating water shall be less than 1 mg/L".
3. Jiuquan Municipal Ecological Environment Bureau of Gansu Province, public "Regional Assessment Report of Liugou Coal Chemical Industry Park in Guazhou Industrial Concentration Zone (Draft for Approval)": fully cites all 20 limit values in Table 1 of GB/T 19923—2005.
4. Huaihua Municipal People's Government of Hunan Province, public EIA document "Huomachong Town and Industrial Concentration Zone Wastewater Treatment Plant": the tail water 60% of the wastewater treatment plant is reused after advanced treatment, implementing GB/T 19923—2005, with Table 1 of that standard attached.
5. Hainan Provincial Department of Finance, public procurement document "Third-Party Management and Operation Service for Landfill Leachate Treatment" (2022-10): the effluent implements the standard for make-up water for open recirculating cooling water systems in GB/T 19923—2005.
6. Ecological Environment Bureau of the Xinjiang Production and Construction Corps, "Public Notice on the Proposed Review of 5 Environmental Impact Assessment Documents Including the 55 万 t/a Electrolytic Aluminum Project in the Corps Zhundong Park" (2024-07-19): the reuse of production wastewater and domestic sewage implements the limit values in Table 1 of GB/T 19923—2024 for make-up water for indirect open recirculating cooling water, boiler make-up water, process water, and product water (pH 6~9, COD 50, ammonia nitrogen 5, Total Nitrogen 15, Total Phosphorus 0.5, chloride 250, silica 30, total hardness 450, fluoride 2).
7. State Administration for Market Regulation (Standardization Administration of China), recommended national standard interpretation "One-Picture Guide to the Recommended National Standard 'Urban Sewage Reclamation and Reuse — Water Quality for Industrial Uses'": the new version adjusts water quality indicators into basic control items and selective control items, simplifies water quality classification, adds a fluoride limit, and revises determination methods for pH, color, etc.
8. National Standards Information Public Service Platform (std.samr.gov.cn) and National Standards Full-Text Public System (openstd.samr.gov.cn): standard status, publication date, implementation date, replacement relationship, and drafting organization information of GB/T 19923—2024.
9. GB 50335—2016 "Code for Design of Urban Sewage Reclamation and Reuse Engineering", Article 4.3.1 (composition of design supply quantity, design scale determined by maximum daily supply quantity), Article 4.3.2 (when the water source is the effluent of a wastewater treatment plant, the maximum design scale should not exceed 80% of the wastewater treatment plant scale), Article 4.3.10 (pipe network leakage water quantity calculated at 10%~12% of the Reclaimed Water utilization quantity), Article 4.3.11 (unforeseen water consumption calculated at 8%~12% of the sum of the former two).
10. GB 50335—2016 clause explanations, Article 4.3.12: self-use water rate of Reclaimed Water plants — coagulation-sedimentation-filtration plus disinfection process 8%~12%, microfiltration unit at 10%~15% of produced water, Ultrafiltration unit at 18%~22% of produced water, Reverse Osmosis unit at 40%~45% of produced water (corresponding water recovery rates are 93%~95%, 88%~92%, 70%~75% respectively).
11. GB/T 50050—2017 "Code for Design of Industrial Recirculating Cooling Water Treatment": corrosion and scaling control indicators for recirculating cooling water systems, Article 3.1.10 (when the sum of calcium hardness and total alkalinity is greater than 1100 mg/L or the stability index RSI is less than 3.3, acidification or softening must be applied), Article 3.1.11 (the design cycles of concentration for indirect open systems should not be less than 5.0 and shall not be less than 3.0).
12. DL/T 300—2011 "Guidelines for Anti-Corrosion and Anti-Scaling of Condenser Tubes in Thermal Power Plants" and the circulating water control indicators under the citation of GB/T 50050—2017 (technical specification for the procurement of water treatment chemicals for the whole plant of an environmental protection power generation enterprise, publicized by Chongqing Public Resources Trading Center): circulating water chloride ion ≤1000 mg/L, sum of total alkalinity and calcium hardness ≤1100 mg/L; make-up water chloride ion ≤250 mg/L; recommended cycles of concentration 3.0~6.0 for natural water and 2.0~5.0 for Reclaimed Water.
13. GB/T 1576 "Water Quality for Industrial Boilers" and GB/T 12145 "Water and Steam Quality for Thermal Power Generating Units and Steam Power Equipment": control indicators such as hardness, conductivity, silica, and oxygen content on the boiler side differ from the "boiler make-up water" column in Table 1 of GB/T 19923 by two to three orders of magnitude.
14. "Guiding Opinions on Promoting the Resource Utilization of Sewage" (Fa Gai Huan Zi [2021] No. 13, National Development and Reform Commission and nine other departments): by 2025 年, the Reclaimed Water utilization rate of water-scarce cities at prefecture level and above nationwide shall reach above 25%, and that of the Beijing-Tianjin-Hebei region shall reach above 35%; water-scarce areas shall take municipal Reclaimed Water as an important source of industrial production water in parks and strictly control new water intake; focus on organizing internal wastewater reuse within enterprises in high water-consuming industries such as thermal power, petrochemicals, steel, nonferrous metals, papermaking, and printing and dyeing.
15. Relevant responsible person of the National Development and Reform Commission answering reporters' questions on the "Guiding Opinions on Promoting the Resource Utilization of Sewage" (2021-01-14): in 2019 年, China's urban sewage discharge was about 750 亿 m³, while the Reclaimed Water utilization volume was less than 100 亿 m³.
16. Dongli District of Tianjin, "Reclaimed Water Utilization Plan (2023—2035 年)", citing "Notice of the General Office of the Ministry of Water Resources on Further Strengthening and Standardizing the Statistics of Unconventional Water Sources": Reclaimed Water utilization rate = reclaimed water utilization volume ÷ sewage treatment volume × 100%; the reclaimed utilization volume is the sum of various uses such as industrial, urban miscellaneous, landscape environment, ecological water replenishment, and agricultural irrigation, excluding non-ecological water replenishment directly discharged into natural water bodies such as rivers, lakes, and wetlands, and excluding the reuse volume of wastewater treated within enterprises.
17. Ministry of Water Resources "Water-Saving China" case library "Zhongyang County, Shanxi: Reclaimed Water 100% Reuse from Wastewater Plant, Saving More Than 250 万 Tons of New Water Annually" (2025): the advanced treatment and reuse project of Reclaimed Water from Yujie Wastewater Treatment Plant has a design scale of 1 万 m³/d, a total investment of 5000 万 yuan, and a construction period of 8 months, adopting hardness removal high-density clarifier + filter pretreatment + double-membrane process; maximum water supply 9800 m³/d, daily average 7000 m³/d, Reclaimed Water directly supplied to the clean circulating water system, and surplus Reclaimed Water 5000 m³/d reused in the turbid circulating system and equipment cooling.
18. Department of Water Resources of Ningxia Hui Autonomous Region, "Successful Completion of the Pilot City Construction of Reclaimed Water Utilization Allocation in Typical Areas of Shizhishan City" (2026-08): 2025 年 industrial Reclaimed Water utilization volume 1585 万 m³; newly built main pipelines connecting the Second Wastewater Treatment Plant with more than 10 enterprises including Jianlong Special Steel and Guoneng Shizuishan No. 1 Power Generation; Guoneng Shizuishan No. 1 Power Generation invested more than 5400 yuan to upgrade its Reclaimed Water treatment system, switching the whole plant's industrial water to Reclaimed Water; Haixin Reclaimed Water Company treats 361 万 m³ annually with an annual output value of about 2000 万 yuan.
19. Ministry of Water Resources "Water-Saving China" case library "Yantai Wanhua Chemical: Building a Full-Chain Systematic Water-Saving Model for a Large Industrial Park": municipal Reclaimed Water supply to the park scale 20 万 m³/d; 2025 年 municipal Reclaimed Water utilization volume 5590 万 m³, desalinated seawater 824 万 m³; the park built its own 18 万 m³/d wastewater treatment plant and 6 万 m³ rainwater recovery system, with an investment of more than 20 billion yuan, and a designed Reclaimed Water reuse rate of 85%; the Reclaimed Water utilization volume of the Yantai industrial park accounts for 82.9% of total water consumption, and the industrial water reuse rate is 99%.
20. China Chemical Industry News "Water Treatment Project Led by Wanhua Chemical Wins Zhan Tianyou Award" (Yantai Taoziwan Sewage, Reclaimed Water and Sludge Circular Economy Demonstration Project): total sewage treatment scale 47 万 m³/d, effluent stably reaching quasi-Class IV; Reclaimed Water production capacity 20 万 m³/d, reuse rate 46.8%, annual Reclaimed Water production 7300 万 m³; adopting Ultrafiltration-Reverse Osmosis and CDRO concentrated Reverse Osmosis processes, the chemical cost per ton of water is only 0.08 元, more than 60% lower than traditional processes.
21. People's Daily Online Ningxia Channel "Ningdong: Not a Single Drop of Wastewater into the Yellow River" (2026-07): total investment of the industrial wastewater zero discharge project 16.9 亿 yuan; annual reused water 2409 万 m³, by-product sodium chloride about 4 万 t and anhydrous sodium sulfate about 4.3 万 t; the "large zero discharge" average daily treatment capacity increased from 3.54 万 to 5.5 万 m³, with a load rate exceeding 90%, effluent COD ≤15, ammonia nitrogen ≤0.5 mg/L; Reclaimed Water reuse saves the base 2000 万 m³ of new water annually, saving more than 1 亿 yuan in water fees and pollution control fees.
22. "Scheme Design of Advanced Treatment System for Reclaimed Water in a Certain H-Class Gas Turbine Power Plant" ("Southern Energy Construction", Issue 2 of 2021 年): when Reclaimed Water is directly used as make-up water for open recirculating cooling water systems and boiler make-up water, it must simultaneously meet the relevant provisions of GB/T 19923 and GB/T 50050; typical advanced treatment schemes for Reclaimed Water in power plants are filtration plus disinfection, coagulation-clarification plus filtration, and lime coagulation-clarification plus filtration; the lime coagulation-clarification process is suitable for water sources with carbonate hardness (calculated as CaCO₃) higher than 100 mg/L.