Modification in Asphalt Texture by Heavy Metal Tolerant Bacteria Isolated from Industrial Effluent

Asphalt is a sticky, black and highly viscous liquid or semi-solid form of petroleum. It is also known as bitumen which may be found in natural deposits or may be a refined product; classed as a pitch. Earlier reports show that most natural bitumen contains sulphur and several heavy metals, such as nickel, vanadium, lead, chromium, mercury, arsenic, selenium, and other toxic elements. The primary use of asphalt/bitumen is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Many studies demonstrated microbial utilization of asphalt and related hydrocarbons, particularly the petroleum hydrocarbons. Investigation was carried out to isolate and characterize microorganisms and determine their heavy metal tolerance activity from such kind of ponds in which the pitch waste effluent was released. Later, it was checked whether they have any role in the modification of asphalt texture. Experiments were executed by first determining the physical and chemical characteristics (flame test) of the pitch effluent, then isolating the microorganisms from it and found Gram positive Coccus. Flame test revealed the presence of arsenic (As) and lead (Pb). Then, it was checked whether the isolated microorganisms are tolerant to these heavy metals. Later, the use of these heavy metals by the isolated microorganisms was detected by Atomic Absorption Spectrophotometric study. The pattern of growth indicated it to be Staphylococcus sp., and when incubated with asphalt, it not only utilizes the hydrocarbon, but also prevents it from hardening. Thus, a pathogenic bacteria can be utilized in recycling of complex hydrocarbon and it continue to sustain itself for a prolong period even in the absence of suitable substrate.