Urban Sewage Environmental Governance Process: From Traditional Biochemical Treatment to Intelligent Monitoring

Full Analysis of Urban Sewage Environmental Governance Process: From Traditional Biochemical Treatment to Intelligent Monitoring

In today's accelerating urbanization process, proper treatment of domestic sewage and industrial wastewater has become the key to protecting ecological barriers and realizing water resource recycling. Urban sewage treatment is not only an engineering task but also a complex system involving physics, chemistry and biological degradation. To ensure that the discharged water quality meets environmental protection regulations, process selection and real-time data monitoring must be deeply integrated.

As a pioneer in water quality sensing technology, NiuBoL is committed to providing critical parameter feedback for various treatment processes through high-precision monitoring instruments to ensure the efficient and stable operation of sewage treatment systems.

Tertiary Process System of Urban Sewage Treatment

In engineering practice, urban sewage treatment is usually divided into three levels according to the depth of pollutant removal, with each level undertaking different purification missions:

1. Primary Treatment (Pretreatment): Mainly adopts physical treatment methods, using grids, grit chambers and primary sedimentation tanks to remove insoluble suspended pollutants, large particulate matter and parasite eggs in sewage. It serves as a barrier for subsequent biological treatment.

2. Secondary Treatment (Main Treatment): Applies biological treatment methods (such as activated sludge method and biofilm method) to oxidize and degrade complex organic matter in sewage into simple inorganic matter. This is the core link of urban sewage treatment plants, aimed at significantly reducing BOD and COD.

3. Tertiary Treatment (Advanced Treatment): For specific nitrogen, phosphorus, refractory organic matter or inorganic salts, chemical precipitation, adsorption or membrane separation technologies are used to make the effluent meet higher standards for landscape water or reclaimed water.

In-depth Analysis of Core Treatment Technologies

1. Activated Sludge Process: Highly Mature Power System

The activated sludge process is currently the most widely used aerobic biological sewage treatment technology in the world. Its core lies in using suspended growth microbial flocs (activated sludge) to adsorb and degrade organic matter.

System Composition: A complete activated sludge system consists of aeration tank, sedimentation tank, sludge return system and excess sludge discharge system.

Process Flow: Sewage is mixed with return sludge in the aeration tank. Artificial oxygenation maintains aerobic metabolism, and microorganisms fully contact organic matter during stirring. It then enters the sedimentation tank for solid-liquid separation. The supernatant is discharged after meeting standards, and part of the sludge is returned to maintain the biomass concentration in the aeration tank.

Technical Advantages: High purification degree and stable effluent quality.

Limitations: Large footprint, high energy consumption during operation (mainly aeration), and strict monitoring required for sludge bulking risks.

2. Biofilm Method: Efficient Attached Growth Technology

Unlike the suspended growth of the activated sludge method, the biofilm method uses microbial films attached to the surface of solid media (fillers) to purify sewage.

Micro-ecosystem: The biofilm consists of aerobic bacteria, anaerobic bacteria, facultative bacteria, fungi and algae. The filter material structure can be divided from outside to inside into moving water layer, attached water layer, aerobic layer and anaerobic layer.

Operation Logic: Organic matter is first adsorbed on the surface of the membrane body and decomposed by the aerobic layer. As the membrane thickens, the inner layer turns anaerobic, and finally ages and peels off, washed away by the moving water layer, achieving self-renewal of the biofilm.

Applicable Scenarios: Suitable for small, medium and large sewage treatment stations that require high space utilization or strong impact load resistance.

3. Oxidation Method: Highly Promising Pretreatment and Advanced Treatment Technology

For sewage containing refractory organic matter, oxidation methods demonstrate excellent chemical degradation capabilities.

Classification: Includes chemical oxidation, catalytic oxidation, wet oxidation and photocatalytic oxidation.

Photocatalytic Oxidation: Uses light of specific wavelengths to generate excited state molecules. The activation energy comes from photons, producing extremely strong oxidizing free radicals that can completely mineralize complex organic molecules.

Advantages: Simple process, strong adaptability to toxic substances, often used to adjust sewage biodegradability.

The Decision-making Role of Water Quality Monitoring in the Treatment Process

No matter which process is adopted, real-time monitoring is the prerequisite to ensure the system does not "poison" or exceed standards. NiuBoL intelligent water quality monitors can analyze key components in water in real time and provide digital support for process regulation.

NiuBoL Water Quality Online Monitor Technical Indicators

FAQ

Q1. Why does the activated sludge process need a sludge return system?

Since the sludge in the sedimentation tank will be discharged, without return, the microbial concentration in the aeration tank will drop rapidly, resulting in insufficient biochemical reaction efficiency. Return is to supplement the biomass in the aeration tank and maintain the system's treatment capacity.

Q2. Is the biofilm method easier to maintain than the activated sludge method?

To some extent, yes. The biofilm method does not have sludge bulking problems, and microorganisms are attached to the filler, with stronger impact resistance to influent water quality fluctuations, making management relatively simple.

Q3. How to determine whether sewage needs anaerobic pretreatment?

Mainly based on the biodegradability of the sewage. If BOD₅/COD < 0.3, or the content of refractory organic matter is high, an anaerobic section should be added to use acid-producing bacteria to degrade macromolecules into small molecules and improve the efficiency of the subsequent aerobic section.

Q4. What is the main advantage of photocatalytic reaction in oxidation methods?

Photocatalytic reaction has extremely strong oxidation ability and can be carried out under normal temperature and pressure. It does not need to consume a large amount of chemical agents, avoiding secondary pollution caused by a large amount of chemical sludge.

Q5. How is "excess sludge" in urban sewage treatment handled?

Excess sludge is new microorganisms produced by biochemical reactions. It usually needs to be concentrated, dewatered and digested, and finally landfilled, incinerated or used for land application to prevent secondary pollution.

Q6. How does NiuBoL analyzer help sewage treatment plants save energy?

By real-time monitoring of dissolved oxygen (DO) values in the aeration tank, the central control system can automatically adjust fan frequency. Avoiding excessive aeration not only protects sludge flocs but also significantly reduces the plant's electricity costs.

Q7. Why is tertiary treatment not commonly used in ordinary urban sewage plants?

Tertiary treatment is extremely costly and is mainly used in scenarios where the receiving water body has special environmental protection requirements, or where sewage needs to be reused for industrial cooling or landscape replenishment.

Q8. What is the use of the RS485 interface of online water quality analyzers?

The RS485 interface, combined with the Modbus-RTU protocol, allows sensors to transmit data directly to PLC or smart water cloud platforms, enabling remote monitoring, automatic early warning and process linkage.

Urban sewage environmental governance is a progressive process from physical interception to biological degradation and then to chemical upgrading. Activated sludge method and biofilm method, as the twin pillars of biological treatment, solve most organic pollution problems; while oxidation method provides a new path for difficult-to-treat wastewater.

In this process, high-precision detection instruments represented by NiuBoL play the role of "eyes". Through digital monitoring of core parameters such as pH, COD, and ammonia nitrogen, sewage treatment is no longer an experience-based "black box" operation, but a precise and controlled modern production line. Choosing scientific governance solutions and reliable monitoring equipment is the only way to achieve long-term urban water environment governance.

Water Quality Sensor Data Sheet

NBL-WQ-CL Water Quality Sensor Online Residual Chlorine Sensor.pdf    

NBL-WQ-DO Online Fluorescence Dissolved Oxygen Sensor.pdf    

NBL-WQ-NHN Ammonia Nitrogen Water Quality Sensor.pdf    

NBL-WQ-COD Online Water Quality COD Sensor.pdf    

NBL-WQ-PH Online pH Water Quality Sensor.pdf    

NBL-WQ-EC water quality conductivity sensor.pdf    

NBL-WQ-BOD-4A Online BOD Sensor.pdf    

NBL-WQ-TH-4S online total hardness sensor.pdf