1. Introduction
Secondary wastewater treatment under low-temperature conditions presents significant challenges for conventional biological processes due to reduced microbial activity. Moving bed biofilm reactors (MBBR) offer a promising solution by providing attached biofilm growth on carriers, which enhances microbial retention and process stability. This study focuses on evaluating MBBR performance for nitrogen and organic matter removal in low-temperature municipal wastewater treatment, exploring operational parameters that influence treatment efficiency, and understanding biofilm development dynamics under cold conditions.
2. Materials and Methods
Pilot-scale MBBR systems were operated at temperatures ranging from 5°C to 15°C to simulate cold climate conditions. Plastic carriers provided a high surface area for biofilm growth, and hydraulic retention times (HRT) were varied from 6 to 12 hours. Dissolved oxygen levels were maintained at 2-4 mg/L, and influent characteristics included typical municipal secondary effluent with moderate BOD, COD, and ammonium concentrations.
3. Results
The MBBR systems achieved stable BOD removal of over 90% and total nitrogen removal of 70-85% under low-temperature conditions. Biofilm analysis revealed gradual colonization of nitrifying bacteria on the carrier surfaces, with sufficient retention even during cold periods. Intermittent carrier mixing improved oxygen transfer and reduced dead zones within the reactor.
4. Discussion
The study confirms that MBBR technology is effective for secondary treatment in cold climates, maintaining high BOD and nitrogen removal despite reduced microbial activity. Biofilm carriers provide a stable habitat for nitrifying and heterotrophic bacteria, mitigating the negative impact of low temperatures.
5. Conclusion
MBBR systems demonstrate high performance in secondary wastewater treatment under low-temperature conditions, effectively removing BOD and nitrogen while maintaining process stability. Biofilm carriers and optimized operational strategies enable resilience against temperature-induced microbial activity reductions.