How can municipal sewage treatment equipment achieve sludge reduction or even "zero sludge" operation?
Publish Time: 2025-12-12
Against the backdrop of accelerated urbanization, the scale of municipal sewage treatment continues to expand, and the resulting large amount of excess sludge has become a key bottleneck restricting the sustainable development of the industry. In traditional processes, approximately 5-10 tons of sludge with a moisture content of 80% are generated for every 10,000 tons of sewage treated, resulting in high disposal costs and significant environmental risks. Municipal sewage treatment equipment is actively exploring technical pathways for sludge reduction and even "zero sludge" operation. Through process innovation and system integration, it aims to build a closed-loop sludge management model that ensures effluent quality while reducing sludge at the source, degrading it during the process, and recycling it at the end of the line.1. Source Control: Optimizing Biological Metabolic Pathways to Reduce Sludge YieldSludge mainly originates from the excess activated sludge formed by the proliferation of microorganisms during the degradation of organic matter. To achieve sludge reduction, it is necessary to start with the biological reaction mechanism. Modern municipal equipment widely adopts low sludge yield processes, such as extended aeration, high-load membrane bioreactors, or anaerobic-aerobic coupled systems. Among them, novel nitrogen removal technologies such as anaerobic ammonia oxidation and simultaneous nitrification-denitrification significantly reduce sludge production because they do not require a large number of heterotrophic bacteria. Furthermore, by precisely controlling dissolved oxygen, carbon-to-nitrogen ratio, and sludge age, microorganisms can be encouraged to enter the endogenous respiration stage, achieving "living off their reserves"—that is, using their own cellular material to maintain metabolism, thereby reducing net proliferation.2. Process Enhancement: In-situ Digestion and Cell Lysis Technology Breaks Down Cell WallsEven with optimized metabolic pathways, some residual sludge will still be produced. At this point, in-situ reduction technology becomes crucial. Some integrated equipment incorporates ozone cell lysis, ultrasonic disruption, or enzymatic pretreatment units. Before the returned sludge enters the aerobic tank, it breaks down the cell walls of microorganisms, releasing intracellular organic matter. This dissolved organic matter can be reused by other microorganisms in the system as a carbon source or energy source, achieving "sludge self-consumption." For example, when the ozone dosage is controlled at 30–60 mg/g MLSS, it can efficiently lyse cells while avoiding inhibition of subsequent biological activity, resulting in a sludge reduction rate of 30%–60%.3. Resource Conversion: A Value Leap from "Waste" to "Energy/Materials"True "zero residual sludge" doesn't mean physical disappearance, but rather the transformation of it into harmless, resource-efficient products. Advanced municipal equipment often couples anaerobic digestion with biogas reuse systems, fermenting concentrated sludge in sealed tanks to produce biogas for power generation or heating, while the residue is dried and made into nutrient soil or building material raw materials. More cutting-edge directions include microbial fuel cell technology, utilizing electroactive bacteria to generate electricity while degrading organic matter and inhibiting sludge growth; or employing aerobic granular sludge processes to form particles with excellent settling properties and high biomass density, significantly reducing sludge discharge frequency and volume.4. Intelligent Control: Data-Driven Dynamic Balance ManagementAchieving stable sludge reduction relies on intelligent support. Modern equipment is equipped with online MLSS, ORP, and ammonia nitrogen sensors, combined with AI algorithms to adjust aeration intensity, reflux ratio, and lysis frequency in real time, ensuring the system always operates under optimal conditions of "low sludge production - high degradation." When the influent load changes abruptly, the system can automatically switch operating modes to prevent sludge bulking or loss, maintaining long-term sludge reduction effects.
Municipal sewage treatment equipment can now achieve sludge reduction of over 80%, moving towards near-zero emissions. This not only significantly reduces disposal costs and carbon footprint but also drives the transformation of sewage treatment plants from "energy-consuming facilities" to "energy-resource factories," providing a green and sustainable new paradigm for urban water environment management.
