Membrane Bioreactors

Question 1

What are the advantages of membrane bioreactors

Answer 1

• Capable of simultaneous biological treatment and disinfection of effluent
• Complete separation of hydraulic retention time (HRT) and suspended solids retention time (SRT) provides optimum control
• Ability to deal with variations in hydraulic and organic loading
• Process intensification through high biomass concentrations
• reduced sludge production
• ability to treat high strength wastes
• smaller footprint die to lack of clarifier

Question 2

Why is complete control of sludge age important

Answer 2

To allow development of slow growing micro-organisms such as nitrifying bacteria

Question 3

Draw a membrane bioreactor mass balance

Answer 3

Slide 8

Question 4

What are the assumptions of membrane bioreactor mass balance

Answer 4

• no separation effect across membrane with respect to substrate or DO
• complete removal of biomass from permeate stream
• no biomass in feed
• well mixed
• no DO in feed

Question 5

Produce a substrate mass balance and re-arange for S including hydraulic residence time

Answer 5

Slide 10-11

Question 6

Produce a biomass balance and combine with the substrate

Answer 6

slide 12-13

Question 7

Define the food/micro-organism ratio

Answer 7

f/m = S/(V/Q)X = QS/VX

Question 8

Provide an oxygen balance on an MBR

Answer 8

Slide 18

Question 9

What are the capital costs of MBR’s

4

Answer 9

• tank volume
• membrane installation
• aeration (compressors)
• Off gas treatment (filters scrubbers)

Question 10

What are the operating costs of MBRs

Answer 10

• Pumping
• Aeration (compressing)
• off gas treatment
• sludge disposal
• membrane replacement