When faced with high-concentration shocks, ammonia-nitrogen wastewater recycling treatment requires a comprehensive approach encompassing process optimization, microbial regulation, system enhancement, and emergency management to enhance its load-bearing capacity and ensure stable operation.
Process optimization is key to improving shock resistance. For wastewater with high concentrations of ammonia nitrogen, pretreatment units can be installed to reduce the influent load. For example, chemical precipitation can be used to add magnesium salts and phosphates to form struvite precipitates, rapidly removing some ammonia nitrogen. Alternatively, stripping can be used to adjust the pH to an alkaline level, converting ammonia nitrogen into free ammonia, thereby relieving subsequent stress on the biological system. For wastewater containing recalcitrant organic matter or toxic substances, advanced oxidation processes (such as ozone and Fenton oxidation) or micro-electrolysis technologies are needed to destroy inhibitory substances and enhance the biodegradability of the wastewater. The main process needs to enhance biological denitrification capabilities, for example, by adopting a two-stage AO (anaerobic-anoxic-aerobic) process to improve denitrification efficiency through multi-stage nitrification and denitrification. Alternatively, it can be combined with MBR (membrane bioreactor) technology to leverage the membrane's efficient retention to maintain high sludge concentrations and enhance the system's resilience to shocks.
The stability of the microbial community is key to coping with high-concentration shocks. Special strains tolerant to high ammonia nitrogen levels should be screened and acclimated, such as autotrophic nitrifying bacteria (such as Nitrosomonas and Nitrobacter) and facultative anaerobic denitrifying bacteria (such as Pseudomonas and Bacillus). Acclimation should be achieved by gradually increasing the influent ammonia nitrogen concentration to enhance the bacterial community's resistance to toxic loads. Furthermore, the microbial living environment should be optimized, for example, by controlling dissolved oxygen within an appropriate range to inhibit nitrite-oxidizing bacteria, adjusting the pH to a neutral to alkaline range to maintain optimal activity of nitrifying bacteria, and supplementing alkalinity (such as sodium carbonate) to neutralize the acidity generated during nitrification to prevent a pH drop that inhibits microbial metabolism. In addition, bioaccelerators or external supplementation with high-efficiency bacterial strains (such as specialized nitrifying agents) can be added to quickly restore system activity and shorten the recovery period after a shock.
System enhancement requires both structural design and operational management. In terms of structural design, a buffer tank can be added to regulate fluctuations in water quality and quantity to prevent high-concentration wastewater from directly impacting the biological system. A modular design allows for flexible switching of process units, such as switching to bypass treatment mode under shock loads, to ensure stable operation of the main system. In terms of operational management, a real-time monitoring and early warning mechanism should be established. By online monitoring of key parameters such as ammonia nitrogen concentration, pH, and dissolved oxygen, and integrating with a SCADA system, dynamic adjustment of process parameters (such as automatic adjustment of aeration volume and carbon source dosage) should be achieved. Contingency plans should also be developed, such as stockpiling emergency supplies such as activated carbon and ion exchange resins to rapidly activate adsorption or ion exchange units in the event of a shock to prevent effluent levels from exceeding standards.
Long-term stability maintenance requires a focus on sludge management and resource recycling. Treatment of high-ammonia nitrogen wastewater generates large amounts of nitrogen-containing sludge, which requires anaerobic digestion or aerobic composting to reduce and recycle the sludge and avoid secondary pollution. In addition, ammonia-nitrogen recovery technologies (such as membrane absorption to produce ammonium sulfate fertilizer) can be explored to convert ammonia-nitrogen in wastewater into high-value-added products, achieving a transition from "pollution control" to "resource recycling." Through the integrated application of process optimization, microbial regulation, system enhancement, and resource recycling, ammonia-nitrogen wastewater recycling treatment can significantly improve its ability to withstand high-concentration shocks and ensure long-term stable operation.
