7.8 Wastewater Treatment of Oil Industries
161
7.8 Wastewater Treatment of Oil Industries
Wastewater that is produced from oil-based industries can be managed using simple
conventional treatment processes since water and oil do not mix. The process of
treatment only becomes complex in the presence of soap that naturally forms when
caustic soda is added. Generally, the most crucial step in oil removal is the use of
a mechanical separation unit. The dissolved air flotation (DAF) system treatment
also needs to reduce the chemical oxygen demand (COD) level prior to the final
biological process taking place at the aeration tank.
Dissolved air flotation (DAF) is a process of water treatment that clarifies
wastewaters by removing suspended matter, including solids or oil. Removal is
attained through the dissolution of air within the water and then released at
atmospheric pressure within a flotation tank basin (Asatekin and Mayes 2009).
Released air develops tiny bubbles that adhere to suspended matter, thus making
suspended matter float to the water surface, whereas removal could be facilitated by
a skimming device.
Chemical oxygen demand (COD) is the measure of water capacity required
for consuming oxygen during organic matter decomposition and the oxidation of
inorganic chemicals, including nitrite and ammonia. Large buffer tanks play a beneficial role in containing wastewater and providing more control of the system setup
since fluctuations regarding incoming water quality will not result in substantial
differences that impact other processes. This could deter automatic systems, like
pH adjustment devices, that occasionally are unable to respond to changes. Ideally,
the first step towards oil recovery entails the discharge of water to equalization
tanks. These special-made tanks consist of two unique compartments and have a
plate that enables water to go through. Despite this being crude separation, it also
provides a pertinent way of recovering back oil waste. Furthermore, the next step
is usually the process of acidulation as the pH is reduced to between 3.0 and 4.0
(Asatekin and Mayes 2009). This can be attained through the addition of sulfuric
acid to decompose large oil particles that elude from the equalization tank into
smaller particles. Lighter molecules often float to the top that can be scraped off
using a scraper. Wastewater will then undergo the chemical and physical treatment
processes by entering the aeration tank where additional purification takes place.
In wastewater treatment plants, the first process entails draining water to the main
sewer system. The first mechanical stage is often referred to as preliminary treatment
or pre-treatment. Grit and large object separation occur at this stage as water flows
through gravel chamber and then disposed of.
The primary treatment in these plants allows the wastewater to flow to the presettling basins. It is the point where pre-treatment ends while secondary wastewater
treatment begins. After primary treatment, wastewater pollution level is reduced to
60% (Spellman 2013). Secondary treatment/biological stage is founded on natural
processes. Wastewater treatment plants utilize bacteria which consumes organic
residue then turns it into sludge. In the course of the biological stage, excess
sludge is often pumped and moved to settling tanks. At this point, the sludge gets
transported to digestion tanks for more treatment.
161
7.8 Wastewater Treatment of Oil Industries
Wastewater that is produced from oil-based industries can be managed using simple
conventional treatment processes since water and oil do not mix. The process of
treatment only becomes complex in the presence of soap that naturally forms when
caustic soda is added. Generally, the most crucial step in oil removal is the use of
a mechanical separation unit. The dissolved air flotation (DAF) system treatment
also needs to reduce the chemical oxygen demand (COD) level prior to the final
biological process taking place at the aeration tank.
Dissolved air flotation (DAF) is a process of water treatment that clarifies
wastewaters by removing suspended matter, including solids or oil. Removal is
attained through the dissolution of air within the water and then released at
atmospheric pressure within a flotation tank basin (Asatekin and Mayes 2009).
Released air develops tiny bubbles that adhere to suspended matter, thus making
suspended matter float to the water surface, whereas removal could be facilitated by
a skimming device.
Chemical oxygen demand (COD) is the measure of water capacity required
for consuming oxygen during organic matter decomposition and the oxidation of
inorganic chemicals, including nitrite and ammonia. Large buffer tanks play a beneficial role in containing wastewater and providing more control of the system setup
since fluctuations regarding incoming water quality will not result in substantial
differences that impact other processes. This could deter automatic systems, like
pH adjustment devices, that occasionally are unable to respond to changes. Ideally,
the first step towards oil recovery entails the discharge of water to equalization
tanks. These special-made tanks consist of two unique compartments and have a
plate that enables water to go through. Despite this being crude separation, it also
provides a pertinent way of recovering back oil waste. Furthermore, the next step
is usually the process of acidulation as the pH is reduced to between 3.0 and 4.0
(Asatekin and Mayes 2009). This can be attained through the addition of sulfuric
acid to decompose large oil particles that elude from the equalization tank into
smaller particles. Lighter molecules often float to the top that can be scraped off
using a scraper. Wastewater will then undergo the chemical and physical treatment
processes by entering the aeration tank where additional purification takes place.
In wastewater treatment plants, the first process entails draining water to the main
sewer system. The first mechanical stage is often referred to as preliminary treatment
or pre-treatment. Grit and large object separation occur at this stage as water flows
through gravel chamber and then disposed of.
The primary treatment in these plants allows the wastewater to flow to the presettling basins. It is the point where pre-treatment ends while secondary wastewater
treatment begins. After primary treatment, wastewater pollution level is reduced to
60% (Spellman 2013). Secondary treatment/biological stage is founded on natural
processes. Wastewater treatment plants utilize bacteria which consumes organic
residue then turns it into sludge. In the course of the biological stage, excess
sludge is often pumped and moved to settling tanks. At this point, the sludge gets
transported to digestion tanks for more treatment.