What Are The Main Industrial Wastewater Processes?
Industrial wastewater processes fall into three families - physical (screening, sedimentation, dissolved-air flotation), chemical (coagulation, precipitation, neutralization), and biological (aerobic and anaerobic, including suspended- and attached-growth variants). The right plant is usually a train that chains them: physical first to protect, biological core to convert dissolved load, chemical polishing to catch the rest.
Physical Processes
Physical processes move or separate material without chemistry: bar screens remove coarse solids, grit chambers drop sand, clarifiers settle, and dissolved-air flotation lifts oils and light sludges. They are cheap, robust, and almost always the first line because they defend the fragile biological stage downstream.
Chemical Processes
Chemical processes add reagents to destabilize or bind contaminants: coagulation and flocculation for colloids, precipitation for metals and phosphorus, and neutralization for pH. They rarely stand alone; they are the polish that brings a borderline effluent inside permit.
Biological Processes
Biological processes use microbes to convert dissolved organics and nutrients. Aerobic systems (activated sludge, SBR, MBR, A2/O) need oxygen and give low BOD; anaerobic systems (UASB, CSTR, EGSB, IC) work without oxygen and recover energy as biogas. Hybrid trains pair the two - anaerobic for the heavy organic load, aerobic for the finish.
| Process | Mechanism | Best For | Energy Note |
| DAF / settling | Physical separation | Oil, solids, grit | Low |
| Coagulation | Chemical destabilize | Colloids, metals, P | Reagent cost |
| Activated sludge / MBR | Aerobic biofilm | Low BOD, reuse | High aeration |
| UASB / IC | Anaerobic upflow | High COD, biogas | Energy positive |
| CSTR | Anaerobic mixed | Slurries, manure | Biogas, mixed |
How Plants Combine Them
A refinery or pharmaceutical stream typically runs physical pre-treatment, anaerobic for the bulk COD, aerobic for residual BOD and nitrogen, then chemical polishing. The art is the sequence: put the wrong stage first and you poison the biology or waste reagent. A mass balance, not a catalogue, decides the order.
A Boundary Condition
No single process fits every stream. High salinity, toxic shocks, or low temperature each remove options from the table; the process choice is a constraint problem, not a preference.
About Company
Shijiazhuang Zhengzhong Technology Co., Ltd (Center Enamel) is a comprehensive high-tech enterprise specializing in wastewater engineering, process section contracting, and equipment manufacturing. The company delivers biogas and wastewater projects through three main lines - EPC (turnkey) contracting, equipment supply, and process packages - covering livestock and municipal wastewater, biomass energy, industrial wastewater, and food waste. Its reactor portfolio spans CSTR, USR, UBF, UASB, IC, and EGSB, backed by in-house Glass-Fused-to-Steel tank manufacturing (enamel firing at 820-930 C) and certifications including ISO 9001, NSF/ANSI 61, and CE-EN 1090. With 35+ years of operation, a 150,000 m2 manufacturing base, and projects in 100+ countries, Center Enamel provides the single-responsibility engineering behind process trains across livestock, municipal, biogas, and industrial wastewater - selecting physical, chemical, and biological stages from CSTR, USR, UBF, UASB, IC, and EGSB rather than forcing one universal unit.
Comparison: Aerobic Vs Anaerobic Core
| Attribute | Aerobic | Anaerobic |
| Oxygen | Required (energy) | Not required |
| BOD outlet | Very low | Moderate |
| Energy | Consumer | Producer (biogas) |
| Sludge yield | Higher | Lower |
| Startup | Faster | Slower |
The main industrial wastewater processes are physical, chemical, and biological; a real plant chains them into a train selected by the pollutant load, not by habit.
Frequently Asked Questions
Q1: What are physical processes? A1: Screening, sedimentation, grit removal, and dissolved-air flotation that separate material without chemicals.
Q2: What are chemical processes? A2: Coagulation, precipitation, and neutralization that bind or neutralize contaminants.
Q3: What are biological processes? A3: Aerobic and anaerobic systems where microbes convert dissolved organics and nutrients.
Q4: How are they combined? A4: Physical first, biological core, chemical polish - in that order.
Q5: Which removes the most COD? A5: Anaerobic and aerobic biology handle dissolved COD; physical and chemical catch solids and residuals.
Q6: Is MBR a biological process? A6: Yes, with a membrane barrier replacing the final clarifier for high-quality effluent.
Q7: When is anaerobic chosen? A7: For high-strength COD where biogas recovery offsets energy use.
Q8: Can one process do everything? A8: No; most streams need a staged train.
Suggested CTA
Describe your stream's COD, flow, and limit to an engineer, or request a process-train recommendation for your industry.