Kitchen waste wastewater is a type of high-concentration organic wastewater, and its water quality varies significantly depending on the type of waste, the scale of the facility, and the season. Based on water quality analysis of similar projects, the influent BOD/COD ratio generally ranges from 0.3 to 0.6, indicating good biodegradability. Adopting biological treatment processes can effectively remove most COD and SS from the wastewater. Given the characteristics of the wastewater containing oil and high SS concentrations, cyclone oil separators and air flotation are used to remove oil and SS as pretreatment before biological treatment.

Due to the high concentrations of COD and ammonia nitrogen in the wastewater, when using biological treatment, the effluent COD value typically reaches 600–800 mg/L after pretreatment and biological processing due to the presence of many refractory organic substances, making it difficult to achieve levels below 500 mg/L. Characterized by high pollutant concentration and high ammonia nitrogen content, the MBR (Membrane Bioreactor) treatment process is adopted, incorporating nitrification and denitrification treatment facilities, which can effectively remove COD and ammonia nitrogen.

The MBR process for kitchen waste wastewater treatment benefits from high sludge concentration, significantly reducing the volume of treatment structures, resulting in lower project investment, stable treatment effects, and high cost-effectiveness.

Core System Components and Process Flow

1. Comprehensive Equalization Tank: After anaerobic fermentation, the wastewater still contains large amounts of suspended solids and oil. To ensure the normal operation of subsequent treatment processes, oil and suspended solids must first be removed from the wastewater. Therefore, before entering the MBR treatment system, the wastewater first enters a cyclone oil separator and then proceeds to an air flotation tank to remove oil and large particulate matter.

2. Air Flotation Tank: Wastewater flows into a small aeration section equipped with a releaser (or gas-liquid mixing pump), where it fully mixes with micro-bubbles generated during the ascent through the aeration section. Due to the density imbalance between the gas-liquid mixture and the liquid, a vertical upward buoyancy is generated, bringing the SS to the water surface. During the ascent, micro-bubbles attach to the SS, and upon reaching the surface, the SS is supported and maintained there by these bubbles. The SS floating on the surface is intermittently removed by a chain scraper.

3. Biochemical System: The MBR system ultrafiltration section utilizes internal (external) ultrafiltration membrane modules and an online cleaning system. After pretreatment, the wastewater enters the biochemical tank, which is the internal (external) MBR biochemical treatment system. The MBR biochemical reactor consists of a pre-denitrification tank and a nitrification tank, both employing a secondary denitrification and nitrification process. In the nitrification tank, high-activity aerobic microorganisms degrade most organic matter and oxidize ammonia nitrogen and organic nitrogen into nitrates and nitrites, which are then recirculated to the denitrification tank to be reduced to nitrogen gas in an anoxic environment, achieving nitrogen removal. To improve oxygen utilization, an internal circulation jet aeration system is used, with an oxygen utilization rate of up to 35%. Sludge recirculation allows the sludge concentration in the biochemical reactor to reach 15g/L. The microbial flora formed through continuous acclimation can also gradually degrade organic matter in the wastewater that is difficult to biodegrade. The pre-denitrification reactor utilizes carbohydrates present in the wastewater. The ammonia nitrogen removal rate of the nitrification-denitrification tank can exceed 90%, with high pollutant removal load and sludge concentration reaching 15g/L.

Sensor Technology and System Integration Selection Table

Frequently Asked Questions (FAQ)

Q1: Is it normal for COD to remain around 800mg/L after pretreatment of kitchen waste?
A1: Yes, kitchen waste contains refractory organic matter. If standard biological treatment is insufficient, strengthening pretreatment (e.g., adding flocculation) and optimizing the MBR denitrification carbon source supplement is required.

Q2: How to monitor fouling of MBR membrane modules in kitchen waste treatment?
A2: Monitor Transmembrane Pressure (TMP). When TMP increases, the PLC should be linked to trigger an automated Clean-In-Place (CIP) program.

Q3: Do YexSensor sensors require frequent manual calibration?
A3: No. YEX series sensors use high-stability electrodes and optical technology, with a normal maintenance cycle of 3–6 months.

Q4: How to realize closed-loop control of the aeration system with ammonia nitrogen monitoring?
A4: Feed real-time ammonia nitrogen data to the PLC to automatically adjust blower frequency or jet aeration operation cycles, reducing energy consumption.

Q5: Are Modbus address tables provided for system integration?
A5: Yes, every YexSensor unit comes with a detailed register address mapping manual for seamless integration into standard PLCs.

Q6: How to handle decreased nitrification efficiency in low-temperature environments?
A6: Nitrifying bacteria are temperature-sensitive. During winter operation, extend SRT and increase DO monitoring precision to ensure microbial activity.

Q7: How to monitor the micro-bubble density in the air flotation tank?
A7: Currently, air flotation effect is judged indirectly by monitoring effluent turbidity and SS concentration. Optical turbidity sensors can be integrated for dynamic feedback.

Q8: What are the protective requirements for equipment in highly corrosive environments?
A8: All YexSensor probe heads are made of corrosion-resistant materials (e.g., POM or Stainless Steel 316L), suitable for high-salt, high-organic-load environments.

Summary

For kitchen waste wastewater treatment projects, the key to technology lies not in the stacking of single devices, but in the closed-loop integration of "pretreatment + biological treatment + intelligent sensing." YexSensor not only provides high-precision online monitoring terminals for engineering companies but also commits to reducing project integration complexity through standardized bus technology and data processing logic. Through precise sensor networking, system integrators can ensure the stable operation of MBR processes, effectively extend membrane module lifespan, and enhance the overall environmental compliance and economic benefits of the project. We continue to support partners in achieving more efficient automated control in complex wastewater treatment fields.