Bioreactors for metal bearing wastewater treatment

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Bioreactors for the treatment of metal-bearing wastewaters have typically the same configuration as that of traditional catalytic chemical reactors used in the petrochemical industry or bioreactors used in biotechnology applications, or the activated sludge reactors employed in municipal wastewater treatment plants (WWTP). Microorganisms, immobilized mainly in the form of biofilm on the surface of a carrier material, act as live bio-catalysts with the advantage of the self-regenerating feature. The sequestering of metal ions from a liquid phase usually differs from the utilization and removal of the organic content (BOD/COD) from wastewaters. The main mechanisms involved in the sequestering of metal ions have been described in the learning object entitled “Metal Immobilisation Process” and are responsible for the interaction of microbial biomass with metals, in order to reduce the mobility of the last. These mechanisms are hosted in the environment of a reactor as described in the following sections.

The purpose of this material is:

  1. To give a brief overview of reactor types suitable for freely suspended or immobilized cells/biofilm systems mainly used for wastewater treatment purposes
  2. To discuss some operational characteristics and design criteria
  3. To give a few examples of applications.

The major goals of immobilization/biofilm formation are to increase reactor efficiency and improve cell stability with higher reaction rates and less sludge production. Immobilization also allows for continuous operation and alternative reactor configurations.

Single Phase Reactors - Reactor Types and Operating Characteristics

Single phase reactors: All reactors, either chemical reactors or bioreactors, have in common the selected characteristics of four basic reactor types:

(a) The well-stirred batch reactor - Well-stirred batch reactors

(b) The semi-batch reactor or fed batch reactor - Semi batch reactors or fed batch reactors

(c) The continuous-flow stirred-tank reactor (CSTR) - Continuous-flow stirred-tank reactor (CSTR)

(d) The tubular reactor or plug flow reactor - Tubular reactor or plug flow reactor

Any reactor may be represented by or modeled after one or a combination of these types.


Mixed suspended particles reactors

Fluidized Bed Reactors

Air Lift or Bubble Column Reactors

Fixed stationary particles or surface reactors

Packed bed reactors

Trickle Bed Reactors

Moving surface reactors

Rotating Biological Contactors (RBC)

Moving Bed Sand Filter

Types of Anaerobic Reactors

Selection of Bioreactors

Applications – Case studies


Suggested Readings - References

1. [1]

2. [2]

3. [3]

4. [4]

5. [5]

  1. L.G. Gibilaro, (2001), Fluidization – Dynamics: The formulation and applications of a predictive theory for the fluidized state, Butterworth Heinemann eds. An excellent book concerning fluidization theory.
  2. S. M. Walas, (1988), Chemical Process Equipment - Selection and Design. An excellent guide to the selection of chemical process equipments.
  3. F. Woodard, (2000), Industrial Waste Treatment Handbook, Butterworth Heinemann eds. Descibes the approach used to develop systems to treat and dispose industrial wastes.
  4. Kirk-Othmer - Encyclopedia of Chemical Technology, (2001). An excellent source of information for chemical engineering technology.
  5. G.V. Baron, Willaert R.G., De Backer L. Chapter 4. Immobilised cell reactors: In Immobilised Living Cell Systems: Modelling and Experimental Methods. Edited by R.G. Wilaert, G.V. Baron and L. De backer, 1996 John Wiley and Sons Ltd.

External links

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