Question

Self-directed learning question : write no more than 0.5 page (i.e. 2 paragraphs) that answer all of the following questions in that space.

1. Where are membrane bioreactors used?

2. What do they separate?

3. What material(s) is/are they made from?

4. What is the advantage over the usual separation step that MBRs replace?

5. Who are the main manufacturers of MBRs?

6. What is the typical lifetime of an MBR unit?

 

Answer 1

Solution

Membrane bioreactors (MBR) are widely used in municipal and industrial wastewater treatment plants. They separate suspended solids from wastewater in the activated sludge process, which uses biological microorganisms to remove dissolved organic matter. The majority of MBRs are manufactured using microfiltration (MF) and ultrafiltration (UF) hollow fibre or flat sheet membranes, which are made with common materials such as polysulfone, polyvinylidene fluoride (PVDF), polyethylene, as well as other proprietary polymers  [1]. Major manufacturer of MBRs include General Electric Water & Process Technologies (formerly Zenon Environmental), Siemens (formerly US Filter), Kubota and Mitsubishi-Rayon [1]. MBRs are able to replace sedimentation and other downstream unit operations, such as granular filtration and disinfection, in a conventional wastewater treatment process. The main advantage of MBR over conventional sedimentation process is reduction of footprint, as the latter separates suspended solids in wastewater by gravity, which requires considerable footprint to achieve similar capacity using MBRs. MBRs can also provide superior effluent quality compare to conventional processes to meet more stringent discharge requirements [2]. Membrane life in MBR depends on design flux through the membrane, but an average life of 10 years is typically expected provided that membranes are normally operated at design flux and are properly cleaned [2].