membrane bioreactor

MBR Design Challenges

The membrane bioreactor plants offer a plethora of advantages. Hence, it is widely used instead of the traditional activated sludge process. Design of MBR plants are complex, a careful pre- treatment design will help in optimizing the operations, extending the life of the membrane and assuring the quality of permeate during the life cycle.

The MBR or the membrane Bioreactor technology is the preferred choice over the activated sludge process. MBR is no doubt one of the innovative outcomes for the wastewater treatment, overcoming the limitations of the activated sludge process. The new technology has been widespread in both the municipal and the industrial wastewater treatment, however, a statistical analysis of the working MBR over 4 years shows the operators do not recommend due to membrane fouling, lower permeate flow, degrading quality and membrane damages.

MBR Design Challenges

The MBR is the hybrid variant combining the traditional biological treatment system and the physical liquid-solid dissection via membrane filtration unified in one system. There are several advantages of MBR technology, and hence its popularity. Green Water Treatment Solutions (GWTS) consider these two parts of the process as an independent process and complimenting each other. MBR membranes do not offer any special considerations or advantages on the biological process, further, it complicates the design due to the immersed membrane which is susceptible for fouling due to oil, biological fouling, metal oxide fouling and hardness related fouling.

Why GWTS MBR offer high Reliability and Operability

  1. GWTS consider end of run (EOR) conditions while designing the permeate flow, which assures design flow even when the membranes are fouled.
  2. Fat and Oil are treated with genetically modified microbes ( GMM), Envirocare Liqui Bac and Augment L-25, which will ensure a consistant total oil of less than 15 mg/L in the aeration section.
  3. Large Pre- MBR aeration to hydrolyse and convert all protines and related high molecular weight foulant to bio-mass.
  4. Enough aeration in the Pre- MBR section to form coagulated bio mass, which will act as filter aid on MBR membrane, reducing the Bio- fouling.
  5. Control of pH, Hardness and Metal in the pre- treatment section using EQC-10 pH buffer, MIDFLOC series flocculant and coagulant for settling and removing metals, metal oxides and hardness in the feed.
  6. Innovative Membrane anti scalant suitable for the Biological process to disperse the scaling particle. Bio-Polymer with organic acid radicals to remove any membrane fouling substrate.
  7. Regular service of Annual Maintenance Contract (AMC) or Operation & Maintenance Contract (O&M) for regular cleaning of membrane, dosing of chemicals and periodic and scheduled maintenance of the system.
  8. For higher COD levels in the inlet an dedicated anaerobic reactor with Augment – L, GMM to achieve 60% in the COD load.

GWTS operates about 30 MBR plants with various capacities and with feed COD ranging from 21,000 mg/L to 600 mg/L. The longest life achieved in MBR membranes are 7 years till date and still operating with no reduction of permeate flow or the quality issues. The capacities of the plants vary from 1200 m3/ Day to 100 m3/ Day.

Online monitoring, data analysis, regular inspection, scheduled maintenance, right operations practices yield high return on investments in these plants. With very conservative design margins the GWTS MBR systems are relatively high capital intensive than competitors, but on long run with assured reliability and operability they achieve break even in a period of six months for moderate size plants.