The Membrane Bio Reactor (MBR) is a biological system coupled with a membrane to enhance solid-liquid separation and filtration. The membrane is made of cost-effective non-woven fibrous material. It has many outstanding properties, such as controllable pore sizes and easy fabrication of the membrane module to achieve the desired surface area. The MBR can achieve desired permeation rate at low transmembrane pressure.a3s Enviro offers wide range of MBR based ETP/STP plants which is compact & energy saving .

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Principles of MBR Technology

Membrane bioreactors (MBRs) are a relatively new wastewater treatment technology, which promises exceptional treatment efficiency and a reduced footprint compared to conventional treatment process trains.

MBRs are quite simply an activated sludge process in which the conventional secondary clarifier is replaced by a membrane separation process (either micro- filtration or ultra-filtration). The MBR can be operated without primary clarification, but always requires fine screening (3 mm or smaller) to protect the membranes from abrasive waste components.

Due to the presence of an absolute barrier for suspended solids, MBRs are able to maintain very high solids concentrations (8000 to 12000 mg/lit) and solids retention times which allow for smaller aeration basins and high BOD removals.

Since MBR Sewage is micro- or ultra- filtration permeates, Sewage suspended solids are typically near the detection limit and turbidities are typically less than 0.2 NTU.

Hence, the MBR is typically a combination of suspended growth biomass with micro- or ultra-filtration membrane system that rejects particles. All biomass is retained and becomes returned activated sludge. Biological growth leaves the system as waste activated sludge.

Depending on location of membrane,A3S Enviro MBR system is categorized as below –

  1. External MBR in which membranes are essentially put outside bioreactor;
  2. Submerged MBR in which membranes are immersed inside the bioreactor. Our system is based on this principle since it provides excellent flux rates and hence is more economical.

Thus, the advantages of using MBR can be summarized as follows:

  1. Membrane Bioreactors have proven to be quite effective in removing both organic and inorganic contaminants as well as biological entities from waste water.  It also minimizes use of cleaning chemicals in the secondary treatment.
  2. Since suspended particles are not lost, total separation and control of the solid retention time (SRT) and hydraulic retention time (HRT) are possible, enabling optimum control of the microbial population and flexibility in operation.
  3. With MBR, the required HRT is lower (8-10 hrs) than conventional biological treatment process (15-28 hrs). This results in reduced tank volume.
  4. MBRs operate at low F/M ratio and long SRT. This means less sludge generation. This reduces costs of sludge disposal and hassels associated with it. Further, sludge produced in MBR is of better quality that eliminates sludge bulking.
  5. Since MBRs are operated under low F/M ratio, it minimizes oxygen consumption since microbes are in endogenous respiration phase and not in growth phase.
  6. Under conventional biological treatment the nominal MLSS concentration is from 1,500 to 3,000 mg/L, and it never exceeds 4,000 mg/L. Whereas, with MBR high MLSS concentration (10,000-15,000 mg/L) could be easily achieved which allows more BOD throughput than conventional biological treatment system.
  7. Compared to conventional biological treatment, MBR requires smaller footprint per unit BOD loading or per unit feed flow rate. MBR is ideal for expansion of existing facilities without increase in footprint. Normally, the footprint required for MBR is about half or less compared to conventional biological process.
  8. Due to membrane separation, the need for clarifier is avoided; at the same time, due to total retention of microbes, slow-growing species (nitrifying bacteria and bacteria capable of degrading complex organic compounds) are allowed to persist in the system, improving nitrification and biological degradation. The membrane not only retains microbes, but also extra cellular enzymes and soluble oxidants synthesized by these organisms, thereby creating a more conducive bio-reactive environment capable of degrading a wider range of organic compounds.
  9. High molecular weight organic compounds, which are not readily biodegradable in conventional systems, are retained in MBR. Thus, their residence time is prolonged and the possibility of biodegradation is improved.
  10. Further,A3S Enviro MBR eliminates the problems associated with settling, which is most troublesome part of waste water treatment. The potential to operate MBR at very high solid retention times without having the obstacle of settling allows high biomass concentrations in the bioreactor. Consequently, higher strength waste water can be treated and lower biomass yields are realized. This also results in more compact system than conventional processes, significantly reducing plant footprint and making it desirable for water recycling applications.
  11. The system is also able to handle fluctuations in nutrient concentration due to extensive biological assimilation and retention of decaying biomass. If some portion of complex organics is not digestible by MBR, they shall be retained by the membrane within the system, and let out as sludge.
  12. Membrane Bioreactor shall reject total suspended solids (TSS) in addition to reducing BOD and COD to the desired levels, making the Sewage more suitable for direct treatment with reverse osmosis system for desalination. Post treatments, such as sand-filtration, is not necessary. Membranes provide final barrier for pathogens and suspended solids.
  13. Process control is easier and more amenable to automation. No more clarifier upsets or, Total Suspended Solids carry-over.
  14. Due to efficient retention and recycling of the activated sludge, the MBR system minimizes the energy needed to reduce the BOD and COD to the desired levels when compared with simple aeration or, other primary treatment schemes. Since MBR employs fine bubble diffuser, higher oxygen transfer efficiency is achieved which reduces power consumption.
  15. Conventional biological systems can also be designed to employ fine bubble diffuser. Since required HRT is more with conventional biological systems, the operating cost for aeration shall be higher when compared with MBR.

Stable Operation And Superior Effluent Quality
Easy Revamping Of Existing Plants
Easy Process Control
Small Footprint
Less Sludge Production
It Can Perform With Uneven Inlet Load By Adjusting The Operating Conditions