reactor to polish the outer surface of the membrane. The membrane bio-reactor is
used when the mixed liquor suspended solids level is higher (15,000–20,000 mg/L)
than the conventional activated sludge process. In general, membrane bio-reactor is
not used in refineries, because it is expensive. But when conventional activated
sludge requires tertiary filtration, it can be a better option, since it acts as an effluent
filter (International Petroleum Industry Environmental Conservation Association
2010). Where reverse osmosis is used for wastewater treatment, membrane
bio-reactor may be an attractive alternative to microfiltration or media filtration
after biological treatment (International Petroleum Industry Environmental Conservation Association 2010; Shahryar 2017; Mareddy 2017).
All advanced technologies are still undergoing research and development.
8.4.5 Wastewater Treatment in Petrochemical Complex
The petrochemical complexes produce valuable products, but its effluent may cause
harmful effects to the environment. The wastewater from the petrochemical complex
contains hazardous compounds, some of which are carcinogenic. Hence, the wastewater treatment requires modern technology to minimize the concentration of
pollutants as per the environment laws. In the petrochemical complex, the wastewater treatment technology is more or less same as in a petroleum refinery. Here also
the wastewater is subjected to preliminary treatment (skimmer, comminuting device,
grit chamber), primary treatment (different separators), secondary treatment
(suspended growth, attached growth process, nitrification and denitrification), tertiary treatment (sand filtration, activated carbon adsorption) and advanced treatment
(powdered activated carbon, sequencing batch reactor, membrane technology, membrane bio-reactor). These have already been discussed in the refinerywastewater
treatment section. However, petrochemical effluents are treated mainly by secondary
biological processes (Patwardhan 2008; Ghimire and Wang 2018; Balasubramani
and Sivarajasekar 2018).
Additionally, new or better wastewater treatment technologies have been developed to convert the complex refractory substances into more simple substances for
improving water quality. Some new technologies are the following (Balasubramani
and Sivarajasekar 2018):
A. Anaerobic treatment:
When aerobic treatment is not sufficient for wastewater treatment adequately,
then anaerobic treatment can be involved.
B. Autotrophic denitrification:
In this process, the nitrogenous as well as sulphur pollutants are removed by
denitrification process followed by biological anaerobic processes.
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used when the mixed liquor suspended solids level is higher (15,000–20,000 mg/L)
than the conventional activated sludge process. In general, membrane bio-reactor is
not used in refineries, because it is expensive. But when conventional activated
sludge requires tertiary filtration, it can be a better option, since it acts as an effluent
filter (International Petroleum Industry Environmental Conservation Association
2010). Where reverse osmosis is used for wastewater treatment, membrane
bio-reactor may be an attractive alternative to microfiltration or media filtration
after biological treatment (International Petroleum Industry Environmental Conservation Association 2010; Shahryar 2017; Mareddy 2017).
All advanced technologies are still undergoing research and development.
8.4.5 Wastewater Treatment in Petrochemical Complex
The petrochemical complexes produce valuable products, but its effluent may cause
harmful effects to the environment. The wastewater from the petrochemical complex
contains hazardous compounds, some of which are carcinogenic. Hence, the wastewater treatment requires modern technology to minimize the concentration of
pollutants as per the environment laws. In the petrochemical complex, the wastewater treatment technology is more or less same as in a petroleum refinery. Here also
the wastewater is subjected to preliminary treatment (skimmer, comminuting device,
grit chamber), primary treatment (different separators), secondary treatment
(suspended growth, attached growth process, nitrification and denitrification), tertiary treatment (sand filtration, activated carbon adsorption) and advanced treatment
(powdered activated carbon, sequencing batch reactor, membrane technology, membrane bio-reactor). These have already been discussed in the refinerywastewater
treatment section. However, petrochemical effluents are treated mainly by secondary
biological processes (Patwardhan 2008; Ghimire and Wang 2018; Balasubramani
and Sivarajasekar 2018).
Additionally, new or better wastewater treatment technologies have been developed to convert the complex refractory substances into more simple substances for
improving water quality. Some new technologies are the following (Balasubramani
and Sivarajasekar 2018):
A. Anaerobic treatment:
When aerobic treatment is not sufficient for wastewater treatment adequately,
then anaerobic treatment can be involved.
B. Autotrophic denitrification:
In this process, the nitrogenous as well as sulphur pollutants are removed by
denitrification process followed by biological anaerobic processes.
266
M. Samanta and D. Mitra