The "Purification Codes" of Wastewater in Various Industries in One Article

In the industrial landscape of cities, the chimneys of refineries, the cooling towers of power plants, the production lines of pharmaceutical factories, and the sewage outlets of printing and dyeing plants generate a large amount of wastewater every day. These wastewaters may all seem like "dirty water", but they cannot be treated with a "one-size-fits-all" approach — just like people need to prescribe the right medicine for illnesses, wastewaters from different factories have vastly different treatment methods due to their different pollutants. Today, we will break down the "characteristics" of wastewater from various industries and see how different their "purification paths" are.

First, Understand the Core: The "Underlying Logic" of Wastewater Treatment

Regardless of the type of factory, the core goal of wastewater treatment is only one: to remove pollutants from wastewater so that it meets national or local discharge standards and avoids polluting soil, rivers, and groundwater. Overall, wastewater treatment usually consists of three stages: "pretreatment — main treatment — advanced treatment", but the specific processes adopted in each stage will be flexibly adjusted according to the "complexity of composition", "pollutant concentration", and "toxicity level" of the wastewater — this is the core reason why wastewater treatment methods differ among different factories.

Simply put, if the "dirty things" in the wastewater are different, the "cleaning tools" and "steps" used will naturally be different. For example, the first problem to solve when treating oily wastewater and dye-containing wastewater is completely different.

Industry-by-Industry Breakdown: "Exclusive Purification Plans" for Wastewater from Different Factories

We have selected 4 representative types of factories to take a closer look at the "characteristics" of their wastewater and corresponding treatment methods, so as to intuitively feel the differences.

1. Refinery Wastewater: "Oil-Containing + Toxic", First Remove Oil, Then Detoxify

Refinery wastewater (from petroleum refining factories) mainly comes from cooling, washing, separation and other links in the crude oil refining and processing process. It can be called a "difficult molecule" in industrial wastewater. The core pollutants are divided into three categories: petroleum substances (floating oil, emulsified oil), heavy metals (such as lead, cadmium), and toxic organic substances (such as benzene, phenols). This type of wastewater is not only highly polluting, but may also cause fatal harm to aquatic organisms. Therefore, it must be treated by "first removing oil, then detoxifying, and finally meeting standards".

Specific treatment process: The first step is pretreatment, where floating oil on the water surface is removed through an "oil separator", and then emulsified oil is removed by the "air flotation method" (bubbles are blown into the water to make the emulsified oil attach to the bubbles and float to the surface). This step can remove more than 80% of oil pollutants; the second step is main treatment, which adopts the "biochemical treatment method" (using microorganisms to decompose toxic organic substances) combined with "advanced oxidation technology" (such as ozone oxidation) to break down refractory phenols, benzene and other substances and reduce the toxicity of wastewater; the third step is advanced treatment, where residual heavy metals and trace pollutants are removed through filtration and disinfection, and finally discharged up to standard or recycled.

2. Power Plant Wastewater: "Salt-Based", Focus on "Desalination + Recycling"

Unlike refinery wastewater, the core problem of power plant wastewater (especially thermal power plants and nuclear power plants) is not "toxicity", but "high salt content", accompanied by a small amount of suspended solids and heat. Power plant wastewater mainly comes from cooling system drainage, boiler blowdown, and flue gas desulfurization wastewater. Among them, cooling wastewater accounts for the highest proportion, with a salt content several times that of ordinary tap water. Direct discharge will lead to soil salinization and water eutrophication.

Specific treatment process: Due to the relatively simple pollutants, the treatment of power plant wastewater focuses on "desalination + recycling". The first step is pretreatment, where suspended solids are removed through precipitation and filtration; the second step is main treatment, where desalination technologies such as "reverse osmosis (RO)" and "electrodialysis" are used to separate salts from wastewater to obtain recyclable fresh water (for cooling, irrigation); the third step is advanced treatment, where the concentrated brine after desalination is concentrated and solidified to avoid secondary pollution of salts. It is worth mentioning that the focus of power plant wastewater treatment is "resource recovery", and many power plants reuse the treated wastewater in the cooling system to realize water resource recycling.

3. Pharmaceutical Wastewater: "Complex Composition", Requiring "Precise Breaking + Multi-Process Combination"

Pharmaceutical wastewater (chemical pharmaceuticals, biopharmaceuticals) is the "most complex type" of industrial wastewater, with no fixed pollutant composition — because the production processes of different drugs are different, the pollutants in the wastewater also vary greatly. Common ones include: drug residues (such as antibiotics, hormones), refractory organic substances, organic solvents (such as ethanol, acetone), acid-base substances, and some wastewater also contains heavy metals and toxic intermediates. The difficulty of this type of wastewater is "high pollutant concentration and poor biodegradability", and a single treatment method cannot meet the standards at all.

Specific treatment process: Pharmaceutical wastewater treatment must be "tailor-made", usually adopting a "multi-process combination" model. The first step is pretreatment, where "neutralization treatment" is carried out according to the acid-base nature of the wastewater, and then suspended solids and some organic substances are removed through "coagulation precipitation"; the second step is main treatment: if the wastewater has good biodegradability (such as biopharmaceutical wastewater), "anaerobic + aerobic biochemical treatment" (microorganisms decompose organic substances) is adopted; if the biodegradability is poor (such as chemical pharmaceutical wastewater), "advanced oxidation technology" (such as Fenton oxidation) is first used to decompose refractory organic substances into biodegradable small molecules, and then biochemical treatment is carried out; the third step is advanced treatment, where residual drug components and trace pollutants are removed through activated carbon adsorption, membrane separation and other technologies to ensure up-to-standard discharge — after all, if drug residues enter the water body, they may destroy the ecological balance and even affect human health.

Summary: Wastewater Treatment in Different Factories — "Different Paths Lead to the Same Goal, but Each Has Its Own Focus"

By now, you should understand: the wastewater treatment methods of different factories such as refineries, power plants, pharmaceuticals, and printing and dyeing are different. The core reason is the difference in the type, concentration, and toxicity of pollutants, and the focus and processes of treatment also change accordingly.

But they also have "commonalities" — no matter what kind of wastewater, the treatment follows the core logic of "pretreatment — main treatment — advanced treatment", and the ultimate goal is "up-to-standard discharge and protection of the ecological environment". With the continuous improvement of environmental protection requirements, more and more factories have begun to adopt the "recycling" model, reusing the treated wastewater in production, which not only saves water resources but also reduces pollution, achieving a win-win situation of "environmental protection + energy saving".

Wastewater treatment seems to be a "terminal treatment", but it is actually an indispensable part of industrial production — only by "prescribing the right medicine" can each type of wastewater achieve "purification and rebirth" and protect our common water environment.