In municipal sewage treatment equipment, the choice of biofilter filler plays a crucial role in denitrification effectiveness. As the core carrier for microbial attachment, the filler's physical properties, chemical stability, and surface structure directly influence the growth environment and metabolic efficiency of the denitrifying bacteria, ultimately determining the denitrification capacity of the entire biofilter system.
The filler's specific surface area is the primary factor influencing denitrification efficiency. A large specific surface area provides ample attachment sites for nitrifying and denitrifying bacteria, promoting the formation and proliferation of biofilms. For example, the high specific surface area of multi-porous suspended filler (MBBR) significantly increases the microbial concentration per unit volume, enhancing nitrification and denitrification reactions. If the filler's specific surface area is insufficient, microbial attachment decreases, making it difficult for denitrifying bacteria to form an effective biofilm, resulting in reduced ammonia nitrogen conversion and nitrate reduction efficiency.
The filler's pore structure plays a key role in mass transfer during the denitrification process. A regular pore structure promotes uniform water flow, reduces dead spots and short-circuits, and ensures sufficient contact between wastewater and the biofilm. At the same time, appropriate porosity balances gas flow and water retention, providing the necessary anoxic environment for denitrifying bacteria. For example, zeolite fillers, with their regular microporous structure, not only have a strong ability to adsorb ammonia nitrogen but also promote the enrichment of nitrifying bacteria through ion exchange. An inappropriate filler pore structure can lead to uneven water distribution, localized hypoxia or hyperoxia, and thus inhibit the activity of denitrifying bacteria.
The chemical stability of the filler directly impacts the long-term survival environment of the denitrifying bacteria. In municipal wastewater treatment, fillers must withstand acidity, alkali, temperature fluctuations, and the attack of microbial metabolites. For example, ceramic granular fillers, due to their high-temperature resistance and excellent chemical stability, are suitable for wastewater environments with high temperatures or large pH fluctuations, maintaining stable activity of the denitrifying bacteria. However, fillers with poor chemical stability are prone to decomposition or release of harmful substances, which can disrupt the biofilm structure and reduce denitrification efficiency.
The surface properties of the filler significantly influence the attachment and growth of denitrifying bacteria. A porous or rough surface increases the contact area between microorganisms and the filler, promoting rapid biofilm formation. For example, the porous surface design of bioceramic fillers provides an ideal environment for denitrifying bacteria to attach, significantly increasing the thickness and activity of the biofilm. If the filler surface is too smooth, microbial attachment becomes difficult, biofilm formation slows, and denitrification efficiency is significantly reduced.
The density and particle size distribution of the filler significantly impact the operational stability of the biofilter. An appropriate density ensures uniform distribution of the filler within the filter, preventing it from being swept away or accumulated by the water flow, thus maintaining a stable denitrification environment. For example, suspended fillers, through density control, achieve free flow and uniform distribution within the filter, avoiding localized overload or vacancy. If the filler density is too high, it is prone to sedimentation and clogging; if the density is too low, it is easily carried away by the water flow, both of which can lead to fluctuations in denitrification efficiency.
The cost and availability of fillers are important factors influencing the selection of municipal sewage treatment equipment. While meeting denitrification requirements, the initial investment and long-term operating costs of the filler must be considered comprehensively. For example, plastic granular fillers are a common choice for general biofilters due to their lightweight, non-degradable nature, and low cost. Activated carbon fillers, while offering strong adsorption capacity, are relatively expensive and are primarily used in specialized applications with stringent nitrogen removal requirements. Ignoring cost factors can lead to excessively high equipment investment and operating costs, impacting the project's economic viability.
The selection of biofilter fillers for municipal sewage treatment equipment requires comprehensive consideration of multiple factors, including specific surface area, pore structure, chemical stability, surface properties, density, particle size, and cost availability. Through scientific selection, a suitable environment for the growth of denitrifying bacteria can be established, improving the biofilter's nitrogen removal efficiency and operational stability, providing reliable technical support for municipal sewage treatment.
