广西省Comprehensive Guide to Medium-sized Sewage Treatment Equipment: Selection, Application and Operation & Maintenance — Efficient Solutions for Reaching Sewage Discharge Standards

          Driven by industrial upgrading and stricter environmental supervision, medium-sized sewage treatment equipment has become the core facility for sewage treatment in industrial parks, urban districts and large communities, boasting the key merits of matched treatment capacity, controllable energy consumption and easy operation and maintenance. Capable of handling 500 to 5,000 tons of sewage per day, such equipment avoids the high investment of large-scale facilities and insufficient capacity of small units. Its mature technology and flexible application have made it a focal point in environmental pollution control. This article professionally analyzes the core value, technical processes, selection criteria and operation guidelines of medium-sized sewage treatment equipment, offering practical references for sewage treatment projects.

       Medium-sized sewage treatment equipment refers to modular or integrated environmental facilities with a daily treatment capacity of 500-5000 tons, integrating sewage pretreatment, core treatment, advanced treatment and sludge disposal. It features intensive design, standardized production and flexible deployment. Operating parameters can be adjusted according to fluctuations in water quality and volume to meet the treatment demands of various polluted sites.

       Sewage treatment for industrial parks: Treat industrial wastewater from food processing, machinery manufacturing, textile printing and dyeing industries to remove COD, BOD, suspended solids and characteristic pollutants, so as to achieve compliant discharge or water reuse.

       Sewage treatment for towns and communities: Deal with domestic sewage from small and medium-sized towns, urban-rural fringe areas and large residential districts. It solves the problem of insufficient coverage of centralized sewage treatment plants and reduces pipeline transportation costs.

       Emergency treatment for special scenarios: It can be quickly hoisted and deployed for river regulation, construction site sewage, post-disaster water purification and other temporary projects to ensure standard-compliant sewage treatment within a short period.

       Treatment performance mainly depends on process selection. The mainstream mode adopts biological treatment as the core supplemented by physical and chemical treatment, together with advanced treatment units to meet discharge standards. Common processes are as follows:

       A/O/A²/O Process: The combination of anaerobic, anoxic and aerobic tanks efficiently removes organic matter, ammonia nitrogen and total phosphorus in domestic sewage and low-concentration industrial wastewater with stable operation and low energy consumption.

       MBR Membrane Bioreactor: Integrates biological reaction and membrane separation technology. The effluent can reach Grade A discharge standard, and the land occupation is only 1/3 to 1/2 of traditional processes. It is suitable for sites with limited land such as central urban areas and industrial parks.

       SBR Sequencing Batch Reactor: Operates intermittently with water inflow, reaction, sedimentation and drainage completed in one tank. It has strong resistance to hydraulic and organic shocks, ideal for industrial wastewater with fluctuating water quality and volume.

       Coagulation Sedimentation + Filtration: For wastewater with high suspended solids and chroma such as printing and dyeing wastewater and mineral processing wastewater, chemicals are added to flocculate pollutants, followed by filtration to improve water clarity.

       Advanced Oxidation Process (Fenton, Ozonation): Used for refractory industrial wastewater from chemical and pharmaceutical industries. Strong oxidizing free radicals decompose organic contaminants and reduce the load of subsequent biological treatment.

       Medium-sized sewage treatment equipment is generally equipped with advanced treatment units including disinfection (UV, chlorine dioxide) and desalination (reverse osmosis, nanofiltration), which can be configured flexibly according to effluent requirements. Desalination and disinfection units are required for water reuse projects; only disinfection is needed to meet the Grade A standard of GB 18918-2002 for direct discharge.

       Scientific selection directly determines treatment efficiency and operating costs. Comprehensive evaluation shall be conducted from multiple dimensions including water quality, water volume, land space and environmental requirements. Key indicators are listed below:

       First confirm the actual daily water volume with about 20% reserved capacity for fluctuation, and analyze water quality indicators including COD, BOD, ammonia nitrogen, total phosphorus, pH value and suspended solids. For instance, MBR or A²/O processes are recommended for high-concentration organic wastewater, while desalination units are required for high-salinity wastewater.

       Modular medium-sized equipment can be installed underground or above ground. Buried installation saves land and conceals facilities, suitable for urban communities and land-scarce industrial parks; above-ground installation facilitates maintenance and is widely adopted in industrial zones. Site size and geological conditions (e.g. groundwater level for buried equipment) shall be verified during selection.

       Focus on electricity bills (aeration system, water pumps), chemical costs (flocculants, disinfectants) and sludge disposal expenses. High-quality equipment equipped with optimized aerators and intelligent control systems can cut energy consumption by around 30%, delivering better long-term cost performance.

       Most mainstream medium-sized equipment adopts PLC intelligent control, which automatically monitors water quality and flow, adjusts operating parameters and sends fault alarms to minimize manual labor. Remote monitoring function is recommended for real-time management.

       Determine effluent criteria (Grade A/B, Class IV surface water, etc.) in accordance with local environmental policies and select corresponding processes. Advanced treatment units are necessary for wastewater discharged into sensitive water bodies to guarantee compliance of total nitrogen and total phosphorus.

       Components in contact with sewage shall be made of corrosion-resistant materials such as 304 stainless steel and FRP, especially for industrial wastewater containing acid, alkali and salt. Material stability directly affects service life; premium equipment can run for 10-15 years.

       Foundation construction: Pour concrete foundations according to equipment weight and dimensions with horizontal deviation controlled within 3mm to avoid vibration during operation. Anti-seepage layers and drainage systems must be built for buried equipment to prevent groundwater ingress.

       Equipment hoisting and piping: Use professional hoisting machinery to prevent collision and deformation. Tight sealing is required for pipelines including water inlet, outlet and sludge discharge pipelines to avoid leakage.

       Commissioning: Carry out a 7-15 day trial run after installation. Gradually increase water inflow load, monitor effluent quality, and adjust aeration intensity and chemical dosage until stable discharge up to standard is achieved.

       Regular inspection: Check the running status of water pumps, aeration systems and blowers every day, and troubleshoot pipeline blockage and leakage. Test influent and effluent water quality weekly and record indicators such as COD and ammonia nitrogen.

       Sludge management: Discharge sludge regularly (once every 1 to 3 months) to avoid deteriorated treatment efficiency caused by sludge accumulation. Sludge must be disposed of by qualified organizations in line with environmental regulations.

       Equipment maintenance: Inspect and replace vulnerable parts such as aerators and agitators every six months. Conduct a full shutdown maintenance annually to clean sediments in reaction tanks and inspect electrical control systems.

       Emergency response: Prepare reserve chemicals and standby pumps to tackle sudden water quality changes and equipment breakdowns and prevent unregulated direct sewage discharge.

       Driven by technological innovation and the carbon peaking and carbon neutrality goals, medium-sized sewage treatment equipment is upgrading toward intelligence, energy conservation and resource recycling:

       Intelligent upgrading: Integrate IoT and big data technology to realize real-time water quality monitoring, automatic parameter optimization and fault early warning, lifting operation efficiency by more than 50%.

       Energy-saving renovation: Adopt high-efficiency energy-saving motors, solar aeration systems and anaerobic sludge digestion biogas generation technology to cut energy consumption per ton of treated water and support low-carbon pollution control.

       Resource recycling: Improve water reuse capacity. Treated water can be used for landscape irrigation and industrial cooling. After harmless treatment, sludge can be made into organic fertilizer or building materials to realize circular economy.

       As a vital link connecting small decentralized treatment and large centralized treatment, medium-sized sewage treatment equipment’s process selection and standardized maintenance directly determine treatment effect and total cost. Enterprises and institutions shall select suitable processes and equipment based on actual water quality, water volume, land space and environmental requirements, and establish a sound maintenance system. With continuous technological progress in environmental protection, medium-sized sewage treatment equipment will play an increasingly important role in water pollution control and provide solid support for ecological protection and sustainable development.