{UAH} Membrane bioreactor (MBR) technology in waste water treatment operations

Membrane bioreactor (MBR) technology,which combines biological-activated

sludge process and membrane filtration has became more popular, abundant,

and accepted in recent years for the treatment of many types of wastewaters,

whereas the conventional activated sludge (CAS) process cannot cope

with either composition of wastewater or fluctuations of wastewater flow rate.

MBR technology is also used in cases where demand on the quality of effluent

exceeds the capability of CAS. Although MBR capital and operational costs

exceed the costs of conventional process, it seems that the upgrade of conventional process occurs even in cases when conventional treatment works well.

It can be related with increase of water price and need for water reuse as well

as with more stringent regulations on the effluent quality. Along with better

understanding of emerging contaminants in wastewater, their biodegradability,

and with their inclusion in new regulations, MBR may become a necessary

upgrade of existing technology in order to fulfill the legal requirements in

wastewater treatment plants (WWTPs).

Anerobic treatment may be used for denitrification, depending on the effluent

nitrate and total nitrogen requirements. Anaerobic zones may be used to

achieve enhanced biological phosphorus removal in any of its possible configurations.

 

Membrane Classification

The membrane process is a very important separation process in water and

wastewater technology, which becomes increasingly competitive and is supeMembrane

Bioreactor (MBR) as an Advanced Wastewater Treatment Technology 41

prior to the traditional water technology with proven performance and process

economics. The most widely applied membrane separation processes are microfiltration

(MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis

(RO), electrodialysis (ED) and electro deionization (EDI),whereas the first four

processes produce permeate and concentrate.

Firstly, application of membrane-based technologies in wastewater

treatment was focused on tertiary treatment of secondary effluent, so as

to obtain a high-quality final effluent that can be reused for different purposes.

However, over the past 10 years, MBRs have emerged as an effective secondary

Treatment technology, whereas membranes applied are usually in the range of

those of MF and UF.

Membranes are usually made from different plastic and ceramic materials,

but metallic membranes also exist. The most widely used materials are celluloses,

polyamides, polysulphone, charged polysulphone and other polymeric

materials such as polyacrylonitrile (PAN), polyvinylidene difluoride (PVDF),

polyethylsulphone (PES), polyethylene (PE), and polypropylene (PP). All of

these polymeric materials have a desirable chemical and physical resistance.

All commercially available membranes are therefore modified by

chemical oxidation, organic chemical reaction, plasma treatment, or by grafting

to achieve more hydrophilic surface. This modification process usually

differs one membrane from another together with the method of fabrication

of the membrane module.

 

Types of Membrane Bioreactor Configurations

Membrane separation is carried out either by pressure-driven filtration in

side-stream MBRs  or with vacuum-driven membranes immersed directly

into the bioreactor, which operates in dead-end mode  in submerged

MBRs. The more common MBR configuration for wastewater treatment

is the latter one, with immersed membranes, although a side-stream

configuration is also possible, with wastewater pumped through the membrane

module and then returned to the bioreactor.

The energy consumption required for filtration in submerged MBR is

significantly lower . Both configurations need a shear over the membrane

surface to prevent membrane fouling with the constituents of mixed

liquor. Side-stream MBRs provide this shear through pumping, as with most

other membrane processes, whereas immersed processes employ aeration

in the bioreactor to provide it.

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revolution inevitable"**…  *J.F Kennedy

 

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