Tezislər / Theses

THE 3
rd
 INTERNATIONAL SCIENTIFIC CONFERENCES OF STUDENTS AND YOUNG RESEARCHERS 
dedicated to the 99
th
anniversary of the National Leader of Azerbaijan Heydar Aliyev
319
plating, coal and steel, whereas organic one is produced in sectors like 
textiles, dying, tannery, petrochemical, pulp and paper mill, etc. 
[3]
Generally, there are three types of methods used for treatment: physical, 
chemical, and biological. In fact, combination of methods is applied to attain 
the required quality of the water in the most cost-effective manner as 
industrial effluents have complicated structure. Biological wastewater 
treatment technique is a significant biotechnological application that has 
grown into one of the biggest systems worldwide. The positive actions of 
microbial communities in wastewater treatment systems lead to the effective 
elimination of organic materials and harmful chemicals.
The occurrence of heavy metals in industrial wastewater results in 
substantial harm to environment that it is exposed to and since they can 
degrade or deactivate microorganisms that is used to purify waste effluent, 
heavy metals must be removed before any delay happens during treatment. 
Unlikely to organic substances, the degradation or breakdown of heavy 
metals is not applicable to decrease their toxic content, however they can be 
converted into less harmful and non-reactive components. Hence, 
application of microorganisms is currently considered the most promising 
way of bioremediation of heavy metal polluted effluents as they are not only 
eco-friendly, but also economically efficient 
[4
]. The efficiency of biosorption 
is highly influenced by factors, such as pH, biosorbent dose, contact time, 
initial metal concentration and temperature, while pH seems to have more 
effect on chemistry of solution and activity of biomass 
[5, 6]
. At pH levels 
higher than optimum value, metal starts to precipitate as it forms metal 
hydroxide. As temperature increases, biosorptive capacity of bacteria also 
rises due to higher kinetic energy and activity on the surface of biomass, 
however there is certain range for pH and temperature values for each 
bacterial species and if any of them gets out of range both physical and 
chemical damage may occur to the nature of biosorbent decreasing its 
metabolic performance. Regarding contact time, it is always desired to get 
rapid biosorption of heavy metal while getting maximum metal uptake from 
the solution. Initial metal concentration and biosorbent dose are both have 
considerable impacts on biosorption procedure, the higher the amount of 
initial metal ions and biosorbent, the lower the removal efficiency. Considering 
all these factors, it can be concluded that each microorganism has its own 
optimum conditions for maximizing metal uptake (
Table 1
), for instance at 
pH=5 Klebsiella sp. has higher Mn
2+
uptake than that of pH=2, while it gives 
more efficient results for Cd
2+
at the same operating conditions.

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