Biochemical tank and MBR membrane tank are two common process units in sewage treatment, and there are some differences between them in terms of treatment principle, structural design, operation mode and effluent quality.
1.Differences in processing principles:
Biochemical tanks are mainly based on the biodegradation of microorganisms to remove organic matter and nutrients (such as nitrogen and phosphorus) from wastewater. Biochemical tanks can be aerobic, anaerobic, or anoxic, depending on the treatment objectives and the characteristics of the effluent. Biochemical tanks usually require a subsequent sedimentation process (secondary sedimentation tank) to separate the clean water from the activated sludge.
MBR membrane ponds are a process that combines biochemical treatment with membrane separation technology, which usually consists of a bioreactor and a membrane separation unit. In bioreactors, microorganisms degrade pollutants in wastewater;The membrane separation unit replaces the traditional secondary sedimentation tank and separates the purified water directly from the mixture.
2.Differences in Structural Design:
The design of the biochemical tank is relatively simple, mainly one or more reaction tanks, which are agitated or aerated to maintain the suspension of the sludge and provide oxygen to the microorganisms.
The design of MBR cells is more complex, requiring space for modules and associated cleaning and backwashing systems in addition to a biological reaction zone. Membrane modules are typically submerged or later-flow arrangements.
3.Differences in the mode of operation:
The operation of the biochemical tank is relatively simple, mainly by controlling the aeration volume and stirring intensity to adjust the activity of microorganisms and the treatment effect of sewage.
The operation of MBR membrane cells is more complex, requiring both the conditions of the biological reaction (e.g., DO concentration, pH, temperature, etc.) and the parameters of membrane operation (e.g., flux, transmembrane pressure differential, cleaning frequency, etc.).
4.Difference in effluent quality:
Effluent treated from biochemical tanks usually needs to undergo sedimentation or other solid-liquid separation processes to meet discharge standards.
Due to the membrane retention effect, the MBR membrane pool has good effluent quality, very low suspended solids and turbidity, and high bacteria and virus removal rate, which can usually directly meet or approach the standard of reclaimed water.
5.Difference in floor space:
The biochemical tank requires a large footprint because it requires sufficient reaction time to complete the biodegradation process, and a secondary sedimentation tank is required for solid-liquid separation.
Due to the efficient membrane separation, the MBR membrane cell can be operated at a higher MLSS concentration, and the reactor volume can be made smaller, so the relatively small footprint.
6.Difference in cost:
Biochemical pools are relatively inexpensive to build and operate, but may require larger land resources.
The construction cost of MBR membrane cell is high, mainly because of the cost of membrane modules and related equipment, and the operating cost is also high, mainly including energy consumption, membrane cleaning and replacement costs.
In short, compared with traditional biochemical tanks, MBR membrane tanks have better effluent quality and smaller footprint, but at the same time, they are accompanied by higher construction and operation costs. In practical engineering applications, the choice of process needs to take into account multiple factors such as wastewater characteristics, treatment requirements, economic benefits and sustainability.