CH2MBR

1. AS-MBR Process: · Conventional membrane bioreactors process immerses
membranes directly into highly concentrated mixed liquor suspended solids.
· MLSS contains high levels of dispersed, small particles comprised of inert and colloidal material.
· High membrane fouling environment, which results
in low membrane flux rates, which require large membrane surface area.

2. AS-MBR Limitations: · MBR requires fine screening (1 mm or less). Fine screening also removes
    substantial amountof untreated waste that must be disposed of. Fine screening also require
    a large area and is more expensive than standard wastewater screening.
· MBR requires high MLSS recirculation rates - AS permeate is removed through the membranes,
    the already high concentration of suspended solids at the membrane surface of MBR increases and fouling rates are compounded.
    This requires recirculating MLSS within the bioreactor and thus results in large amount of Energy Consumption.
· MBR has Low Peak Flow Tolerance ? with the high membrane fouling environment constraining
    the flux , the MBR has very low peak flow tolerance , hence it requires large Equalization Tank Volume
· MBR requires high membrane air scour rates.
· Large amounts of energy must be input to generate air to scour the membrane surface of suspended solids.
· MBR requires high bioreactor aeration rates.
· The high MLSS concentration of MBR reduces oxygen transfer efficiency within the Bioreactor,
    resulting in higher energy requirement in order to aerate the bioreactor.
· MBR has low membrane flux rates.
· Membrane component costs contribute a very high capital and operating costs.
· Nutshell The main Disadvantages of MBR is the high initial cost and regular
    cleaning of membrane filters at least once in 48 hours.

3. UF followed by MBBR: · UF followed by MBBR maintains separate biological and membrane unit processes,
allowing for maximum total system performance.
· Each process is individually controlled and optimized.
· MBBR MLSS particles settle well and exhibit low membrane fouling.
· Reduces the MLSS to the UF membrane by 97%
· This directly increases the membrane flux.

Controlling Membrane Fouling Rates with MBBR-UF: · Can tolerate moderate peak flow rates
· Will require smaller equalization tank
· No fine screening requirement
· No sludge recirculation ? energy saving
· No air scouring requirement ? energy saving
· Since MLSS is low in MBBR, Oxygen Transfer Efficiency is high.
· Flux rates can be much higher, saves cost of membranes.
· Since MLSS is very low, membrane fouling minimum.

Controlling Membrane Fouling Rates with MBBR-UF: · Can tolerate moderate peak flow rates
· Will require smaller equalization tank
· No fine screening requirement
· No sludge recirculation ? energy saving
· No air scouring requirement ? energy saving
· Since MLSS is low in MBBR, Oxygen Transfer Efficiency is high.
· Flux rates can be much higher, saves cost of membranes.
· Since MLSS is very low, membrane fouling minimum.

5. Energy Consumption Comparison

AS-MBR and MBBR-MBR Comparison

ch2mbr