With the accelerated urbanization process and the advancement of the rural revitalization strategy in China, the problem of unregulated discharge of decentralized domestic sewage (such as sewage from rural residents, small and medium-sized communities, scenic area homestays, etc.) has become increasingly prominent. This not only pollutes the surrounding soil, rivers, and groundwater but also threatens the safety of residents' drinking water and the health of the ecological environment. Traditional sewage treatment models (such as large-scale centralized sewage treatment plants) have pain points including high pipeline construction costs, limited coverage, and high operation and maintenance difficulties, making them difficult to meet the sewage treatment needs of decentralized scenarios. Against this backdrop, integrated domestic sewage treatment equipment, with its core advantages of "integration, miniaturization, high efficiency, and easy operation and maintenance", has become a key equipment to solve the problems of decentralized sewage treatment, promoting the transformation of water environment governance from "centralized tackling" to "full-area coverage".

I. Core Definition and Technical Principles of Integrated Domestic Sewage Treatment Equipment: What is "Integration"?

Integrated domestic sewage treatment equipment refers to specialized equipment that integrates traditional sewage treatment processes (such as grids, equalization tanks, biological reaction tanks, sedimentation tanks, disinfection tanks, etc.) into one or more closed boxes through modular design, realizing the automatic operation of the entire process of domestic sewage from "inflow - treatment - up-to-standard discharge/reuse". Its core logic is "process integration, minimum land occupation, and simplified operation and maintenance", which eliminates the need to construct multiple separate structures and significantly reduces site and construction costs.

Its typical treatment process follows a scientific path of "physical pretreatment → biological degradation → advanced purification → disinfection to meet standards", with specific principles as follows:

• Physical Pretreatment Stage: Sewage first enters the grid unit to filter out large particles such as hair, paper scraps, and sand, preventing blockage of subsequent equipment. Then it enters the equalization tank, where the water quality and quantity are balanced (to mitigate the volatility of sewage discharge) to provide stable inflow conditions for subsequent biological treatment.

• Biological Degradation Stage: This is the core stage for pollutant removal, with mainstream technologies including the "biological contact oxidation method" and "MBR membrane bioreactor technology":

  • Biological Contact Oxidation Method: Elastic fillers are filled in the tank, and microorganisms attach to the surface of the fillers to form a "biofilm". When sewage flows through, aerobic bacteria, anaerobic bacteria, and other microorganisms in the biofilm decompose organic pollutants such as COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand), and ammonia nitrogen in the sewage into harmless CO₂ and H₂O through metabolism, while achieving nitrogen and phosphorus removal.
  • MBR Membrane Bioreactor Technology: Combining biological degradation and membrane separation technology, it uses ultrafiltration membranes or microfiltration membranes to replace traditional sedimentation tanks, efficiently retaining activated sludge and macromolecular pollutants. The effluent quality is better (meeting or exceeding the Class 1A standard of Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB18918-2002)), and the sludge production is low, reducing the subsequent sludge disposal cost.

• Advanced Purification and Disinfection Stage: The sewage after biological treatment enters the sedimentation tank to further precipitate residual suspended solids. Finally, ultraviolet disinfection or sodium hypochlorite disinfection is used to kill pathogenic microorganisms such as bacteria and viruses in the water, ensuring that the effluent meets the discharge or reuse standards (e.g., for green irrigation, road flushing).

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II. Core Advantages of Integrated Domestic Sewage Treatment Equipment: Why It Becomes the First Choice for Decentralized Sewage Treatment?

Compared with traditional sewage treatment models, integrated domestic sewage treatment equipment shows significant advantages in multiple dimensions such as technology, economy, and operation and maintenance, perfectly adapting to the treatment needs of decentralized scenarios:

In addition, the equipment also has the advantages of "mobility" and "scalability": for temporary sewage sources (such as construction camps), mobile integrated equipment can be used; for scenarios with increasing sewage volume, the treatment capacity can be expanded through parallel connection of multiple sets of equipment, which is far more flexible than the traditional model.

III. Core Parameters and Selection Guidelines of Integrated Domestic Sewage Treatment Equipment: How to Choose the Right Equipment?

Scientific selection directly affects the sewage treatment effect and return on investment. It is necessary to consider the four core factors of "sewage volume, water quality characteristics, discharge requirements, and site conditions", and focus on the following parameters and principles:

(I) Core Selection Parameters

• Treatment Capacity: Determined based on the average daily sewage discharge volume (m³/d), with a 10%-20% margin reserved (to cope with peak water consumption). For example: For 50 rural households (with an average daily water consumption of 150-200L per household), equipment with a treatment capacity of 8-10m³/d should be selected; for small and medium-sized communities (300 households), equipment with a treatment capacity of 50-80m³/d should be selected.

• Influent Water Quality: The concentrations of indicators such as COD, BOD, ammonia nitrogen, total phosphorus, and suspended solids (SS) in the sewage should be clarified. For example: In scenarios with a high proportion of catering wastewater (such as scenic areas, hotels), an additional "oil separation tank" pretreatment unit is required; in scenarios with a large amount of hair in domestic sewage (such as communities), fine grids (grid gap ≤5mm) should be selected.

• Effluent Standards: Determined according to local environmental protection requirements, with core reference to Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB18918-2002):

  • If discharged into the municipal pipe network, equipment meeting the "Class 1B standard" (COD ≤60mg/L, ammonia nitrogen ≤8mg/L) can be selected;
  • If discharged into surface water bodies (such as rivers, lakes), equipment meeting the "Class 1A standard" (COD ≤50mg/L, ammonia nitrogen ≤5mg/L) is required;
  • If reuse is needed (such as greening, toilet flushing), MBR membrane equipment meeting the "Quasi-Class IV surface water standard" or higher (COD ≤30mg/L, SS ≤5mg/L) should be selected.

• Equipment Material: The mainstream materials are fiberglass reinforced plastic (FRP), carbon steel (with anti-corrosion treatment), and stainless steel, which should be selected according to the service environment:

  • Outdoor humid environment: FRP is preferred (corrosion-resistant, lightweight, long service life, up to 15-20 years);
  • Cold regions: Carbon steel with an insulation layer is required (to prevent water from freezing in winter and affecting treatment efficiency);
  • Food-grade scenarios (such as domestic sewage from food factories): Stainless steel material can be selected (good hygiene, easy to clean).

(II) Core Selection Principles

• "Tailor-Made" Principle: Avoid "using a large horse to pull a small cart" (the equipment's treatment capacity far exceeds the actual demand, causing energy waste) or "using a small horse to pull a large cart" (insufficient treatment capacity, resulting in substandard effluent).

• "Localized" Principle: For narrow sites, select "underground-type" equipment (which can be buried underground, with greening or parking lots built above); for areas with severe cold winters, select "above-ground-type + insulation layer" equipment; for remote rural areas without power supply, integrated equipment with a "solar power supply system" can be matched.

• "Operation and Maintenance Priority" Principle: Select equipment equipped with an "intelligent monitoring system" (such as remote liquid level monitoring, online water quality monitoring, and fault alarm) to reduce the difficulty of later operation and maintenance; give priority to manufacturers with local after-sales service points to ensure timely response to equipment failures.

IV. Key Points of Installation and Operation & Maintenance of Integrated Domestic Sewage Treatment Equipment: Ensuring Long-Term Stable Operation

(I) Key Installation Points

• Site Preparation: The site should be leveled to ensure that the equipment foundation meets the load-bearing requirements (concrete foundation is designed according to the equipment weight to prevent equipment settlement); for underground-type equipment, an anti-seepage layer should be reserved (to prevent the treated sewage from leaking and polluting groundwater).

• Pipeline Connection: The water inlet, water outlet, and sewage discharge pipelines should be accurately connected to the equipment interfaces to ensure tightness (to prevent sewage leakage); the pipeline slope should meet the design requirements (generally, the slope of the water inlet pipeline is ≥0.005, and the slope of the water outlet pipeline is ≥0.003) to prevent pipeline blockage.

• Electrical Commissioning: After installation, the PLC control system, water pumps, fans, disinfection equipment, etc., should be commissioned to ensure the normal linkage of all equipment (e.g., when the inflow reaches the set liquid level, the fan starts automatically to supply oxygen; when the effluent reaches the set liquid level, the disinfection equipment operates automatically).

(II) Daily Operation & Maintenance Points

• Regular Inspection: Check the equipment operation status daily (such as fan noise, water pump flow, and disinfectant residue in disinfection equipment); clean grid debris weekly (to prevent grid blockage and poor water inflow); check the status of biological fillers monthly (if the fillers fall off or scale, they should be replaced or cleaned in time).

• Agent Supplement: Disinfection equipment needs to be supplemented with disinfectants (such as sodium hypochlorite solution) regularly, and the agent dosage should be adjusted according to the effluent residual chlorine value (0.2-0.5mg/L is recommended); MBR membrane equipment needs to be chemically cleaned regularly (generally cleaned with citric acid or sodium hypochlorite solution every 3-6 months to prevent membrane pollution).

• Sludge Disposal: The sludge produced in the equipment sedimentation tank should be discharged regularly (generally once every 1-3 months), and the sludge should be handed over to qualified units for disposal to avoid secondary pollution.

• Emergency Handling: If the equipment alarms (such as high liquid level, fan failure), it should be shut down immediately for inspection, and restarted only after the fault is eliminated; during heavy rain, inspection should be strengthened to prevent rainwater from backflowing into the equipment.

V. Policy Support and Market Prospects of Integrated Domestic Sewage Treatment Equipment: A Promising Future

In recent years, the state has attached great importance to decentralized sewage treatment and issued a number of policies to promote the application of integrated domestic sewage treatment equipment:

• The 14th Five-Year Plan for the Development of Municipal Sewage Treatment and Resource Utilization clearly states that "we will promote the full coverage of county-level domestic sewage treatment, focus on supporting the construction of township-level sewage treatment facilities, and promote miniaturized, ecological, and resource-based sewage treatment technologies and equipment";
• In the rural revitalization strategy, the "Rural Human Settlement Environment Improvement and Upgrading Action" takes rural domestic sewage treatment as a core task, encouraging the adoption of low-cost and easy-to-operate technical models such as integrated equipment.

Driven by policy dividends, the market demand for integrated domestic sewage treatment equipment continues to grow. From the perspective of application scenarios, it will expand in three directions in the future:

• Rural Market: With the improvement of rural sewage treatment coverage (the target is to reach more than 40% of rural domestic sewage treatment rate by 2025), rural areas have become the core demand market;
• Industrial Supporting Market: Domestic sewage in industrial parks (such as sewage from employee dormitories) needs to be treated separately, and the demand for integrated equipment is growing rapidly due to its strong adaptability;
• Resource Utilization Market: With the advancement of "sponge city" construction, integrated equipment with reclaimed water reuse function (such as MBR + reverse osmosis equipment) will become a hot spot, realizing "sewage resource utilization" and alleviating the pressure of water resource shortage.

VI. Conclusion

As an "efficient weapon" for decentralized sewage treatment, integrated domestic sewage treatment equipment not only solves the pain points of traditional models but also conforms to China's development direction of "globalization, resource utilization, and intelligence" in water environment governance. Whether it is rural sewage treatment, community environment improvement, or scenic area ecological protection, selecting suitable integrated equipment can achieve up-to-standard sewage discharge and resource utilization at lower cost and higher efficiency.

In the future, with technological iteration (such as the integration of intelligent control and low-carbon energy-saving technologies) and market maturity, integrated domestic sewage treatment equipment will play a greater role in water environment governance, providing solid equipment support for building a beautiful China with "lucid waters and lush mountains".