The exploration of the coupling process path between phosphorus recovery and carbon source preparation in sewage treatment experimental equipment is a key direction for achieving resource recycling and energy conservation and emission reduction. Based on existing technology and practical cases, the following paths can be explored:
1、 Selection and optimization of phosphorus recovery process
Phosphorus recovery requires selecting appropriate methods based on the composition of wastewater. The chemical precipitation method generates calcium phosphate or guano stone (MAP) precipitate by adding calcium and magnesium salts, which is suitable for high concentration phosphorus containing wastewater, but requires control of pH value and interference from coexisting ions. For example, Tianjin Jinnan Sludge Treatment Plant adopts a process of adding MgCl ₂ to the sludge dewatering filtrate, promoting MAP crystallization through aeration blowing, with a phosphorus recovery rate of over 85%, while improving sludge dewatering performance and reducing flocculant dosage. Biological methods such as Enhanced Biological Phosphorus Removal (EBPR) enrich phosphorus through polyphosphate accumulating bacteria, and then recover phosphorus through sludge digestion solution or incineration ash residue, but the problem of heavy metal pollution needs to be addressed.
2、 Collaborative pathway of carbon source preparation and phosphorus recovery
Carbon source preparation needs to balance economy and biodegradability. Taking the hydrolysis of kitchen waste to produce acid as an example, by controlling temperature, pH, and residence time, it can be converted into a high concentration organic acidification solution, replacing commercial carbon sources such as sodium acetate. Experiments have shown that under the conditions of 35 ℃ and pH=6, after 4 days of hydrolysis, the carbon equivalent of the food waste acidification solution can meet the denitrification requirements and has no toxic effects. By coupling phosphorus recovery with carbon source preparation, carbon sources can be enriched in the high load carbon capture (HLSBR) stage, while phosphorus can be separated through precipitation or crystallization. The supernatant enters the subsequent processing unit, achieving efficient separation of carbon and phosphorus resources.
3、 Process integration and experimental verification
Construct an integrated experimental device for "carbon capture phosphorus recovery autotrophic denitrification". The raw water first enters the HLSBR reactor and adsorbs carbon sources through anaerobic/micro aeration mode. After sedimentation, the remaining sludge is discharged, and the supernatant flows into the phosphorus recovery unit (such as PRSBR). The MAP crystallization method is used to recover phosphorus, and finally enters the anaerobic ammonia oxidation (AMXSBR) reactor to complete autotrophic denitrification. The experiment requires monitoring the effluent quality of each unit, optimizing parameters such as pH and magnesium phosphorus ratio to ensure phosphorus recovery and carbon source utilization. For example, by adjusting the pH to 9.5, MAP crystallization can be promoted while avoiding competition from carbonate ions and improving the purity of phosphorus recovery.
4、 Economic and Sustainability Assessment
The coupling process requires a comprehensive evaluation of costs and benefits. Phosphorus recovery products such as MAP can be used as slow-release fertilizers with significant market value; Carbon source preparation can reduce the cost of purchasing carbon sources from sewage treatment plants. Taking the Jinnan project in Tianjin as an example, phosphorus recycling saves about 3.71 million yuan in chemical agent costs annually, with a MAP income of about 1.64 million yuan, which has significant economic benefits. In addition, the coupling process can reduce sludge production and carbon emissions, which meets the requirements of sustainable development.
Through process optimization and experimental verification, the sewage treatment experimental device can achieve efficient coupling of phosphorus recovery and carbon source preparation, providing technical support for resource recycling.