2026 Full Analysis -- Wastewater Treatment Methods and Technology Selection Guide

       The amendment to the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB 18918—2002) came into force on March 1, 2026, marking a new era of dual-limit control for sewage treatment in China. The new regulation stipulates that the daily average total phosphorus discharge of all municipal wastewater treatment plants shall be kept below 0.5mg/L starting from 2028, and the instantaneous COD emission limit shall not exceed 75mg/L, putting forward higher requirements for the stability and precision of sewage treatment technologies.

       The core goal of sewage treatment has been upgraded from simple discharge compliance to resource recycling. Through the coordination of physical, chemical, biological and other technologies, triple benefits including pollutant removal (COD, nitrogen and phosphorus), sludge volume reduction and reclaimed water reuse can be achieved, while meeting the requirements of energy consumption control and low-carbon operation.

       1. Physical Separation

       ◦ Bar screens / sieves: Remove floating debris with a diameter ≥1mm (such as plastics and fibers). As the first line of defense in sewage treatment, they should be equipped with automatic slag removers to cut operation and maintenance costs.

       ◦ Grit chambers: Separate inorganic particles such as sand by gravity. The typical hydraulic retention time is 30 to 60 seconds, which can reduce abrasion of subsequent equipment.

       In view of the drastic water quality fluctuation of industrial wastewater, an equalization tank with online pH monitoring is installed. Acid and alkali are dosed to keep the water neutral (pH 6-9) so as to guarantee stable operation of follow-up processes.

       1. Biological Treatment (Mainstream Technology)

       

       ◦ Advantages of MBR technology: It occupies 30-50% less land than traditional processes. The sludge concentration can reach 8000-12000mg/L, and the COD removal rate stays steadily above 95%. A water reclamation plant in Beijing produces 100 million cubic meters of reclaimed water annually with this technology.

       ◦ Upgraded Modified A²/O Process: By optimizing the volume ratio of anaerobic, anoxic and aerobic zones (typical ratio 1:2:5) and installing high-efficiency aerators, total phosphorus discharge can be kept consistently below 0.5mg/L, making it the primary option for upgrading municipal sewage plants.

       2. Chemical Treatment: Enhanced Pollutant Removal

       ◦ Coagulation and sedimentation: Polyaluminum chloride (PAC) or polyacrylamide (PAM) is added to form flocs that adsorb colloidal pollutants. This method is widely used to remove heavy metals such as lead and chromium from industrial wastewater.

       ◦ Advanced Oxidation Processes (AOPs): Hydroxyl radicals generated by ozone and Fenton reagents break down refractory organics in wastewater (e.g., pharmaceutical wastewater). The dosage of oxidants should be strictly controlled to lower costs.

       1. Membrane Separation Technology

       ◦ Reverse Osmosis (RO): With a pore size of 0.1-1nm, it can remove dissolved salts. The product water can be used for industrial cooling or groundwater recharge. Pretreatment is required to prevent membrane fouling.

       ◦ Nanofiltration (NF): It intercepts substances with molecular weight ranging from 200 to 1000Da. Suitable for sewage purification in drinking water source areas, it retains beneficial minerals.

       2. Disinfection Process

       Ultraviolet (UV) disinfection replaces traditional chlorination without producing disinfection by-products. At a dosage of 30-40mJ/cm², the fecal coliform count can be controlled below 1000 CFU/L, meeting the standard for reclaimed water reuse.

       The combined process of "Modified A²/O + Advanced Filtration + UV Disinfection" is preferred. MBR can be added if water reuse is needed. Case: The Gaobeidian Reclamation Plant in Beijing realizes cogeneration of heat and power from biogas produced by anaerobic sludge digestion, covering 30% of its energy demand.

       Modular carbon-bacteria coupling equipment is recommended, featuring three merits: ① Three layers of biological carbon plates fix functional bacteria directionally, boosting the anti-shock load capacity by 2.3 times; ② The intelligent control system responds to water quality changes within 15 minutes; ③ Construction cost is 40% lower than that of traditional pipe networks.

       • High-concentration organic wastewater (e.g., food processing): Adopt "anaerobic digestion + aerobic biochemical treatment". Organic acid made from kitchen waste can replace traditional carbon sources to reduce chemical costs.

       • Heavy metal-containing wastewater (e.g., electroplating): The combined process of "chemical precipitation + membrane separation" ensures the heavy metal removal rate reaches above 99%.

       1. Intelligent upgrading: AI algorithms predict membrane fouling and extend the MBR cleaning cycle by 20%. A digital twin system optimizes parameters such as aeration rate and reflux ratio dynamically.

       2. Low-carbon development: Solar-powered aeration and biogas cogeneration are widely applied. The Gushu Water Purification Plant in Shenzhen cut unit energy consumption by 15% through process renovation.

       3. Resource recovery: Phosphorus is extracted from sludge to build a circular chain of "sewage-sludge-fertilizer", which aligns with the Dual Carbon goals.

       1. High upfront investment for membrane components, accounting for 30-40% of total cost. Domestic membrane materials need further improvement in anti-fouling performance.

       2. Rural sewage treatment faces a shortage of on-site operators, so unattended intelligent equipment needs to be developed.

       3. The cost of harmless sludge disposal remains high, and resource recovery technologies need large-scale popularization.

       The selection of sewage treatment processes must follow three principles: compliance, economy and sustainability. With the enforcement of the 2026 national standard, high-efficiency technologies such as MBR and carbon-bacteria coupling will gradually replace traditional processes. The deep integration of intelligence and resource recycling will transform sewage treatment facilities into resource factories. Enterprises can select suitable technical solutions by referring to benchmark projects according to sewage characteristics, emission standards and budgets, so as to achieve a win-win situation of environmental and economic benefits.