198

13 Biosorption of Heavy Metals and Metal-Complexed Dyes Under the Influence

Outlet

Vertical pipes

Valve

Air compressor

Waste sludge

Figure 13.4

Schematic representation of packed bed reactor [32]. Source: Azazi et al. [33].

The obtained results revealed that the heavy metal ions such as Cu²⁺, Cd²⁺, and

Zn²⁺ can be remediated by the P. aeruginosa in the multi-metal system with 100%

efficiency. Azizi et al. [33] concentrated on the determination of efficacy on the selec-

tive removal of heavy metals such as cadmium, copper, nickel, and zinc using a

packed bed bioreactor (PBBR). In this process, PBBR is used to remediate the heavy

metals as well as the organic contaminants by the attached-growth process. The per-

formance of the bioreactor was evaluated and assessed by varying different metal

concentrations.

Figure 13.4 shows the laboratory unit of the biological reactor (PBBR) to deter-

mine the strength of composite heavy metals in the system. The major significance

of the PBBR system developed with a different layer with a fixed bed, and the vertical

pipeline helps to confirm the effluent flow and simultaneously increases the oxygen

transfer in each layer in the PBBR. In addition to that, the void ratio is around 98.18%.

Once the sewage sludge entered through the bottom of the reactor, enough upflow

velocity has to be maintained to prevent clogging. Polypropylene is used as a carrier

media with a density of 0.95 g/cm³ and an active surface area of 350 m²/m³ and is

designed with outer grooves to restrict biofilm formation. Similarly, the packed bed

bioreactor shows a high retention time of about two hours for copper and zinc metal

ions than cadmium and nickel ions. The maximum tolerable limit for the composite

material used for the heavy metal is around 20 ppm for about two hours.

13.7

Biosorption of Reactive Dyes

Reactive dyes are the combination of various types of reactive groups such as vinyl

sulfone and chlorotriazine with azo-based chromophores. The dyes are impregnated

with the textile fibers by covalent bond interaction. These dyes have inevitable char-

acteristics in making optimistic colors, water fastedness, and consumption of low

energy. But these dyes are very tough to remediate in the presence of light, higher

temperature, oxidizing agents, and also nondegradable by the biological compounds.

In most practical applications, activated carbon shows an effective adsorption for the

removal of color in the effluents discharged from the textile industries. But, it is very