There was once a chemical company whose utilities workshop manager showed us two bills. The first was a water bill from the municipal water supplier: RMB 470,000 for one month. The second was a wastewater discharge fee notice from the industrial park: RMB 310,000 for the same month. He placed the two sheets side by side on the desk and said something very straightforward: "I pay for the water once when I buy it, and then I pay again to get rid of it after using it. In the end, I'm paying twice for essentially the same batch of water."
That statement basically captures the absurdity of industrial water use over the past two decades. Water comes in, is used once, becomes wastewater, and then another payment is made to send it away. The entire chain is linear, and both ends of that line come with a bill. Reclaimed Water Treatment is intended to bend that line into a circle.
A Concept That Has Been Misunderstood for Many Years
Let's clarify one thing first. When many people hear the term "reclaimed water," they think of "treated wastewater," with a sense that it is merely a compromise. This understanding is neither accurate nor does it reflect the technical complexity involved.
The core of reclaimed water is not "where it comes from," but "what it can be used for." Once a stream of water has been treated to meet the water quality requirements for a specific application (water reuse requirements), it becomes a qualified water source for that application. Its original source is simply background information. A wastewater treatment plant in Tianjin, for example, processes 450,000 tonnes of water per day, with 100% of its reclaimed water supplied for industrial cooling, municipal miscellaneous uses, and river replenishment. A reclaimed water plant in Yinchuan supplies more than 40 million tonnes annually, mainly for ecological replenishment of urban rivers and canals and for industrial cooling. In these places, reclaimed water is not merely an alternative supply; it is part of the city's water security framework.
Three Factors Are Turning "Optional" into "Necessary"
The first is the tightening of both water prices and water withdrawal quotas. The reclaimed water supply price at an industrial water plant in one region is only about one-third of the price local companies previously paid for municipal water. A price difference of nearly threefold requires little additional persuasion. More importantly, there are water withdrawal permits. In water-scarce regions, obtaining approval for additional water withdrawal quotas can be even more challenging than the equipment investment itself.
The second is increasing pressure on the wastewater discharge side. The national Implementation Plan for Industrial Wastewater Recycling clearly proposed that, by 2025, the water reuse rate for industrial water use among enterprises above the designated size should reach approximately 94%, with specific phased improvement targets set for key industries such as papermaking and textiles. These figures are not merely recommendations; they are assessment targets broken down for local authorities. Local water conservation regulations also explicitly state that industrial enterprises located in areas covered by reclaimed water distribution networks and capable of using reclaimed water should give priority to reclaimed water.
The third has been the slowest to arrive, but may ultimately be the most stringent-ESG and supply chain audits. An increasing number of multinational brands are adding "water withdrawal per unit of product" and "water reuse rate" to their supplier assessment questionnaires. GRI 303 requires disclosure of total water withdrawal and total water discharge, while the CDP Water Security Questionnaire treats "reuse rate" as a key indicator. When your customers start asking these questions, it is no longer simply an issue for the environmental authorities; it becomes an issue that can affect orders.
There Are Actually Three Ways to Approach Water Reuse
Many companies immediately think, "I need to build a system," but the form of reuse should be determined before the technology is selected.
On-site water recycling is the easiest place to start. Cooling tower blowdown, backwash water, and condensate can be collected, treated to meet cooling water makeup requirements, and then returned to the system. The water volume may not be large, but the water quality is relatively stable, and the payback period is usually less than two years.
Park-level separated water supply has been one of the fastest-growing models in recent years. Some industrial parks integrate their industrial water plants, wastewater treatment plants, and reclaimed water plants into a "three-water integration" system, laying dedicated water supply pipelines for key enterprises within the park and continuously expanding the distribution network. Some parks have gone a step further by developing wastewater treatment and reclaimed water reuse capacities of hundreds of thousands of tonnes per day and establishing reclaimed water rights trading mechanisms. Companies with lower wastewater discharge volumes can sell their quotas to major water users, reducing the cost of purchasing desalinated water for enterprises in the park by a significant amount in just one year.
Connecting to municipal reclaimed water may appear to be the simplest option, but the negotiation costs are often underestimated. What you need to confirm is not simply "Is there water available?" but rather "Is the water pressure stable? What is the chloride concentration? What is the minimum annual water supply?"
A System Essentially Comes Down to Four Variables
Putting aside all the terminology, designing a reclaimed water treatment system for industrial reuse essentially means answering four questions.
What is coming into the system? This is the starting point for every discussion. Is the COD 80 or 8,000 mg/L? Does the water contain oil? What is the background chloride concentration? How much does the water quality fluctuate within a single day? We have seen too many projects where the influent data came from a single water sample, only for membrane fouling to occur much faster than expected three months after commissioning. The problem was not that the equipment was inadequate; the design input was wrong. A common industry rule of thumb is to design for the 95th-percentile worst-case operating condition rather than the average value.
Where will the treated water go? This is the question most likely to be skipped, yet it should never be skipped. Water used for landscape irrigation and water used as boiler feedwater require two completely different process routes, and the capital investment can differ by three times. Clearly defining water reuse requirements is the first gate for controlling project investment.
Which technologies should be used in between? When it comes to water reuse treatment technologies, UF, RO, and MBR are the three technologies most frequently discussed in the market, but they are not mutually exclusive choices. MBR addresses solid-liquid separation in the biological treatment stage and replaces the secondary clarifier; Industrial ultrafiltration systems are more commonly used for fine filtration and as pretreatment protection for RO, reducing SDI to below 3 and turbidity to below 0.2 NTU so that downstream RO membranes can achieve a longer service life. What really determines whether RO is necessary is the total dissolved solids, or TDS. If the reuse point has no requirements for chloride or conductivity, ultrafiltration alone is often sufficient.
What should be done with the concentrate? This is the cost item that newcomers are most likely to overlook. At a 75% recovery rate, the salt concentration on the RO concentrate side is four times that of the feedwater; at a 90% recovery rate, it is ten times higher. This stream must have a destination-discharge, evaporation and crystallization, or centralized disposal by the industrial park. Different options can completely change the investment structure of the entire plant.
Calculate the Water Economics First, Then Talk About Equipment
In the projects we have worked on, what truly convinces companies to move forward is almost never the technical solution itself. It is a clearly calculated water cost analysis: how much water is withdrawn each year, how much is discharged, the unit price, how much can be saved by achieving 60% reuse, the equipment investment, and the payback period. Once this table is completed, it naturally becomes clear whether the project should proceed.
Moving from "treating water for disposal" to "reusing treated water" may appear to be a technical choice, but at a deeper level, it represents a change in the way water costs are calculated. Once you begin treating water as an asset that can be continuously reused rather than a disposable consumable, many decisions become clear on their own. Reclaimed Water Treatment simply makes this approach technically feasible from an engineering perspective.
Taihe Environmental Protection has more than two decades of experience in industrial water treatment. One of the things we say most often is: "Let's build the water balance sheet first, and then talk about the process." Because for a project where the water economics have not been properly calculated, regardless of the process technology selected, the final result will most likely be an account that no one can clearly explain.