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Modern Society’s Wastewater Types: A Comprehensive Guide to Pollution Sources and Treatment Importance
2026-05-20
1. Domestic Sewage: The Common "Daily Pollutant" in Our Lives
Domestic sewage is the most widespread type of wastewater, coming from our daily routines and public spaces. It is produced in large volumes, covers wide areas, and has a relatively complex makeup—though it is less toxic than industrial wastewater. There are two main categories:
Residential domestic sewage: This comes from everyday activities like cooking, doing laundry, bathing, and flushing toilets. Key pollutants include grease, detergents, nitrogen, phosphorus, organic matter, and fecal waste. While individual pollutant concentrations are low, the sheer volume of wastewater adds up, making it a major contributor to eutrophication in rivers, lakes, and other water bodies.
Public domestic sewage: Generated in places like shopping malls, hotels, schools, hospitals, office buildings, and commercial districts, this wastewater is similar in composition to residential sewage but tends to be discharged in larger, more variable quantities. For instance, hotel wastewater has higher oil content, while school wastewater contains more suspended solids and organic matter.
Direct discharge of untreated domestic sewage not only pollutes surface and groundwater but also fosters bacteria and viruses, raising the risk of waterborne diseases.
2. Industrial Wastewater: The Complex "Pollution Threat" of Industrial Production
Industrial wastewater is the most complex and harmful type of wastewater, created during manufacturing processes. Its composition varies widely across industries, and many varieties contain toxic substances like heavy metals and non-degradable organic compounds—making treatment difficult and posing long-term environmental risks. The main types are:
Food processing wastewater: From slaughterhouses, breweries, beverage plants, grain and oil facilities, and cooked food production, this wastewater is high in organic matter, oil, and suspended solids. Untreated, it causes severe odor pollution and water eutrophication.
Textile printing and dyeing wastewater: Released during dyeing and rinsing, this wastewater is highly colored, has high chemical oxygen demand (COD), and contains various dyes, auxiliaries, and acidic or alkaline substances. Decolorization is a major challenge, making it one of the hardest industrial wastewaters to treat.
Papermaking and pulping wastewater: Including black liquor and white water from papermaking, this wastewater has high COD, high lignin content, and large amounts of fiber suspended solids—all of which severely pollute water bodies and soil.
Chemical wastewater: From petrochemical plants, fine chemical facilities, fertilizer and pesticide manufacturers, this wastewater contains heavy metals, toxic organic compounds, and acid-base salts. These substances are highly toxic, carcinogenic, and can accumulate in the food chain, endangering human health.
Electroplating and metallurgical wastewater: Produced during electroplating part cleaning and smelting, this wastewater contains heavy metals like chromium, nickel, copper, and zinc. These toxic, non-degradable substances can contaminate groundwater for decades and cause chronic poisoning in humans and wildlife.
Mechanical processing wastewater: Including cutting fluid, quenching water, and cleaning wastewater, this type contains engine oil, emulsified oil, and iron filings. It harms water environments and can clog drainage networks.
As industrial production advances, industrial wastewater becomes more diverse and complex—placing higher demands on treatment technology. Many industrial parks now use classified collection and separate treatment to improve efficiency.
3. Agricultural Wastewater: The "Hidden Pollutant" in Our Ecosystems
Agricultural wastewater is a key part of modern wastewater pollution, coming from farming and livestock activities. It is often overlooked because its sources are scattered, covering large areas and making collection and treatment difficult. The main types include:
Breeding wastewater: From large-scale pig, chicken, duck, and aquatic farms, this wastewater has high ammonia nitrogen levels, large amounts of fecal waste, and numerous pathogens. It severely pollutes surface and groundwater and produces unpleasant odors.
Farmland runoff: The water left after agricultural irrigation carries residual fertilizers, pesticides, and sediment. These pollutants flow into rivers and lakes with rainwater, causing eutrophication and disrupting aquatic ecosystem balance.
Agricultural product cleaning and processing wastewater: Generated when sorting, cleaning, and cold-chain processing fruits and vegetables, this wastewater contains small amounts of pesticides, fertilizers, and organic matter. While less polluting, it is produced in large volumes.
4. Special Sewage: The High-Risk "Priority Pollutant"
Special sewage refers to wastewater with unique properties and high environmental risks—requiring targeted treatment to prevent serious harm to the environment and human health. The main types are:
Hospital medical sewage: Discharged from hospital outpatient clinics, wards, operating rooms, and other areas, this wastewater contains large numbers of bacteria, viruses, disinfectants, and pharmaceutical agents. It is a key source of infectious disease transmission and must be thoroughly disinfected before discharge.
Catering kitchen wastewater: From restaurants, canteens, and other food service locations, this wastewater is high in oil, which can easily clog drainage networks. Overflow can cause environmental pollution and disrupt residents’ living environments.
Garbage leachate: The wastewater that seeps from domestic garbage landfills, this type has extremely high pollutant concentrations and a complex makeup—including high COD, ammonia nitrogen, humus, and toxic substances. It is one of the most difficult wastewaters to treat.
Laboratory wastewater: From schools, research institutions, and quality inspection labs, this wastewater contains acids, bases, various chemical reagents, and trace toxic substances. It must be collected separately and treated based on its properties to avoid cross-pollution.
Construction and car washing wastewater: Construction wastewater is mostly muddy water and foundation pit drainage with high sediment content. Car washing and auto repair wastewater contains oil, sediment, and cleaning agents—and can be recycled with simple treatment.
5. Urban Comprehensive Miscellaneous Sewage: The "Mixed Pollutant" of City Life
As cities grow, mixed wastewater from urban operations has become an important part of wastewater treatment. It mainly includes urban road rainwater runoff and mixed pipe network wastewater:
Urban road rainwater runoff: When rain washes roads, it collects dust, exhaust sediment, oil, and other impurities. While pollutant concentrations are low, the large volume of runoff during rainstorms can cause short-term surface water pollution.
Mixed pipe network wastewater: In older urban areas, imperfect rainwater and sewage separation systems mean rainwater and domestic sewage are discharged together—adding to the difficulty and cost of treatment.
Conclusion: Wastewater Treatment is Key to Sustainable Development
Modern society produces a wide range of wastewater, each with distinct pollution risks. From the domestic sewage we generate daily to complex industrial wastewater, from scattered agricultural wastewater to high-risk special sewage—all require scientific treatment and standardized discharge. According to the "14th Five-Year Plan for Urban Wastewater Treatment and Resource Utilization Development," improving wastewater collection and treatment efficiency, and promoting wastewater recycling, are crucial to advancing ecological civilization.
Wastewater treatment is not just about protecting water ecosystems and drinking water safety—it is also a vital part of promoting green, sustainable social development. As treatment technology advances, more efficient, energy-saving, and eco-friendly solutions are being used across industries, helping turn wastewater from a "pollutant" into a "resource."
We will continue to follow developments in the wastewater treatment industry, sharing the latest technologies and industry news, as we work together to protect our planet’s precious water resources.
