An In-Depth Analysis of Treatment Technology Routes for High-Strength Industrial Wastewater

13 Oct, 2026 9:51am

Abstract: High-strength industrial wastewater has a complex composition, contains a large number of refractory substances, and exhibits significant variations in water quality. A single treatment method cannot easily achieve stable compliance with discharge standards. This article systematically analyzes the mainstream treatment technology routes for high-strength industrial wastewater from four perspectives: technology positioning, process combinations, typical treatment routes, and key factors affecting compliance. Particular attention is given to the application principles and limitations of the combined anaerobic–aerobic treatment process.

1. Key Challenges of High-Strength Industrial Wastewater

High-strength industrial wastewater generally refers to wastewater with a COD concentration ranging from several thousand to tens of thousands of mg/L or even higher. It may contain refractory organic compounds, toxic and hazardous substances, high salt concentrations, and significant fluctuations in water quality. The main treatment challenges fall into four categories:

1. High organic loading

Direct aerobic treatment requires a large amount of oxygen, resulting in high energy consumption and substantial sludge production. It is also prone to sludge bulking.

2. Poor biodegradability

A low B/C ratio indicates poor biodegradability. Microorganisms have difficulty utilizing these compounds directly, making pretreatment necessary to improve biodegradability.

3. Toxicity inhibition

Heavy metals, phenolic compounds, cyanides, halogenated hydrocarbons, and other substances can inhibit microorganisms or even cause toxicity-related damage.

4. Significant fluctuations in water quality

Changes in production batches, raw materials, and manufacturing processes can cause substantial fluctuations in pH, COD, salinity, and toxic substance concentrations, placing high demands on the system's resistance to shock loads.

Therefore, high-strength industrial wastewater treatment is not a matter of "selecting one method." Instead, it requires a complete treatment technology chain covering pretreatment, primary biological treatment, and advanced treatment.

2. The Roles and Limitations of Four Types of Treatment Technologies

High-strength wastewater treatment technologies can be divided into four categories: biological treatment, physical treatment, chemical treatment, and physicochemical treatment. These technologies are not alternatives that replace one another; rather, they perform different functions according to the characteristics of the pollutants.

Technology Type	Main Functions	Typical Treatment Units	Role in High-Strength Wastewater Treatment
Biological treatment	Organic pollutant degradation, nitrogen and phosphorus removal	Anaerobic treatment, aerobic treatment	Main treatment stage for substantial COD reduction
Physical treatment	Removal of suspended solids and oils, water quality adjustment	Sedimentation, flotation, filtration, equalization tanks	Pretreatment or post-treatment
Chemical treatment	Destruction of refractory structures, detoxification, pH adjustment	Advanced oxidation, neutralization, chemical reduction	Pretreatment or advanced treatment
Physicochemical treatment	Adsorption, coagulation, membrane separation	Coagulation–sedimentation, activated carbon, UF/RO	Pretreatment, advanced treatment, or water reuse

Key judgment: Biological treatment is the primary treatment method. However, high-strength industrial wastewater can rarely achieve stable compliance through biological treatment alone. Physical, physicochemical, and chemical methods must be used as supplementary processes.

3. Combined Anaerobic–Aerobic Treatment: Why Has It Become a Mainstream Process Route?

3.1 The Role of Anaerobic Treatment: Not Just "Pretreatment," but a Major COD Reduction Process

The value of anaerobic treatment in high-strength organic wastewater treatment is often underestimated. It does not simply break down large molecules; it also undertakes the task of substantially reducing COD.

The main advantages of anaerobic treatment include:

• High-load tolerance: It can handle COD concentrations reaching tens of thousands of mg/L, far exceeding the typical concentrations suitable for direct aerobic treatment.

• Degradation of refractory substances: It can break down certain aromatic compounds and long-chain fatty acids through ring-opening and chain-breaking reactions.

• Improvement of biodegradability: It converts refractory macromolecules into smaller organic acids, alcohols, and other compounds, significantly increasing the B/C ratio.

• Low energy consumption and low sludge production: It does not require aeration, and its excess sludge production is much lower than that of aerobic treatment.

• Energy recovery: It produces biogas, enabling energy recovery.

Common anaerobic reactors:

Reactor Type	Characteristics	Applicable Conditions
UASB	Upflow Anaerobic Sludge Blanket reactor	Medium- to high-strength wastewater with relatively low suspended solids
IC	Internal Circulation anaerobic reactor	Extremely high-strength organic wastewater
EGSB	Expanded Granular Sludge Bed reactor	Wastewater containing toxic substances and requiring strong shock-load resistance
ABR	Anaerobic Baffled Reactor	Small- to medium-scale wastewater treatment and wastewater containing suspended solids

Limitations of anaerobic treatment:

• The effluent COD remains relatively high and generally cannot meet discharge standards directly.

• The process is sensitive to temperature, pH, and toxic substances.

• The start-up period is long, and cultivating granular sludge can be challenging.

Its ability to remove nitrogen and phosphorus is limited.

3.2 The Role of Aerobic Treatment: Advanced Purification and Stable Compliance

Aerobic treatment follows anaerobic treatment to further remove low- to medium-concentration organic pollutants and achieve nitrogen and phosphorus removal.

The main advantages of aerobic treatment include:

• Good effluent quality: It can substantially reduce COD and BOD.

• Nitrogen and phosphorus removal: Nutrient removal can be achieved through processes such as A/O, A²/O, and SBR.

• Stable operation: It is highly effective at removing low concentrations of organic pollutants.

Limitations of aerobic treatment:

• Direct treatment of high-strength wastewater requires substantial oxygen input and high energy consumption.

• Its ability to remove refractory substances is limited.

• Sludge production is relatively high.

3.3 The Logic Behind Combined Anaerobic–Aerobic Treatment

The essence of combined anaerobic–aerobic treatment is staged treatment and complementary advantages.

Anaerobic stage: Reduces COD under high organic loading, improves biodegradability, and reduces the load on subsequent aerobic treatment.

Aerobic stage: Further purifies the wastewater under lower organic loading, removes residual organic pollutants, and achieves nitrogen and phosphorus removal.

Overall result: Strong resistance to shock loads, relatively controllable operating costs, and effluent that can consistently meet discharge standards.

This is why combined anaerobic–aerobic treatment has become one of the most widely used and technically mature mainstream treatment routes for high-strength organic wastewater.

4. "Anaerobic + Aerobic" Is Not a Universal Solution

In the following situations, anaerobic–aerobic treatment alone may have difficulty achieving stable compliance. Additional pretreatment or advanced treatment is required.

Problem Type	Typical Industries	Additional Treatment Units Required
Refractory organic compounds	Textile dyeing, pharmaceuticals, pesticides, coking	Advanced oxidation, including Fenton oxidation, catalytic ozonation, electrochemical oxidation, and wet oxidation
Toxic substances	Electroplating, coking, pharmaceuticals, chemical manufacturing	Chemical precipitation, chemical reduction, adsorption, and dilution or equalization
High salinity	Chemical manufacturing, pesticides, dye intermediates	Dilution, evaporation, membrane concentration, and acclimation of salt-tolerant microorganisms
High ammonia nitrogen	Landfill leachate, fertilizer production, livestock farming	Ammonia stripping, MAP precipitation, enhanced nitrification and denitrification
High color and high suspended solids	Textile dyeing, papermaking	Coagulation–flotation, sedimentation, and filtration
Stringent discharge standards	Sensitive receiving waters, water reuse applications	BAF, activated carbon, ozonation, MBR, and reverse osmosis

5. Typical Treatment Technology Routes for High-Strength Industrial Wastewater

Route 1: High-Strength Organic Wastewater with Good Biodegradability

Process flow:

Equalization Tank → Anaerobic Treatment (UASB/IC) → Aerobic Treatment (A/O) → Sedimentation → Discharge in Compliance with Standards

Applicable to: Food processing, brewing, livestock farming, and certain types of chemical wastewater.

Route 2: High-Strength Organic Wastewater Containing Refractory Compounds

Process flow:

Equalization Tank → Physicochemical Pretreatment (Coagulation/Flotation) → Advanced Oxidation → Anaerobic Treatment → Aerobic Treatment → Advanced Treatment → Discharge in Compliance with Standards

Applicable to: Textile dyeing, pharmaceutical manufacturing, pesticide production, and coking wastewater.

Route 3: High-Salinity, High-Strength Organic Wastewater

Process flow:

Equalization Tank → Dilution/Evaporation → Anaerobic Treatment → Aerobic Treatment → Membrane Treatment → Discharge in Compliance with Standards or Water Reuse

Applicable to: Chemical manufacturing, pesticides, and dye-intermediate wastewater.

Route 4: High-Ammonia-Nitrogen, High-Strength Organic Wastewater

Process flow:

Equalization Tank → Ammonia Stripping/MAP Precipitation → Anaerobic Treatment → Aerobic Treatment (A²/O) → Advanced Treatment → Discharge in Compliance with Standards

Applicable to: Landfill leachate, fertilizer production, and livestock wastewater.

6. Key Factors Determining Whether Effluent Can Meet Discharge Standards

Key Factor	Specific Considerations
Wastewater characteristics	COD, BOD, B/C ratio, toxicity, salinity, pH, and nutrient ratio
Process matching	Anaerobic reactor selection, aerobic process selection, recycle ratio, and retention time
Adequacy of pretreatment	Whether refractory compounds have been broken down and toxicity has been eliminated
Operational control	pH, temperature, dissolved oxygen, sludge concentration, and nutrient dosing
Completeness of advanced treatment	Additional removal of residual COD, color, ammonia nitrogen, and total phosphorus
Shock-load resistance design	Equalization tank volume, emergency storage tank, recycle dilution, and online monitoring

Conclusion：

Biological treatment is the primary approach for high-strength industrial wastewater treatment, and combined anaerobic–aerobic treatment is a mainstream process route.

Anaerobic treatment is responsible for reducing COD under high organic loading, improving biodegradability, and degrading certain refractory substances. Aerobic treatment is responsible for advanced purification, nitrogen and phosphorus removal, and stable compliance with discharge standards.

However, it is important to recognize that "anaerobic + aerobic" is not a universal solution. For high-strength industrial wastewater containing refractory compounds, toxic substances, high salt concentrations, or high ammonia nitrogen, physicochemical and chemical pretreatment must be added upstream, and advanced treatment must be incorporated downstream where necessary to achieve stable compliance with discharge standards.

A truly reliable treatment solution does not simply apply a standard process configuration. Instead, it establishes a systematic treatment technology chain of "pretreatment → anaerobic treatment → aerobic treatment → advanced treatment" based on the actual characteristics of the wastewater, with dynamic operational adjustments as conditions change.

This is the fundamental principle behind achieving compliance with discharge standards in high-strength industrial wastewater treatment.