coagulant aids together with the regular inorganic coagulants. Polymers are effective
over a wider pH range than inorganic coagulants. They can be applied at lower
doses, and they do not consume alkalinity. However, they are generally much more
expensive than inorganic coagulants.
Previously, Louhichi et al. [44] utilized coagulation and flocculation process to
treat real vegetable oily wastewater and investigated the relationship between coagulant concentration, flocculent dosage, and pH besides two important process
parameters (COD and turbidity removals). Response surface methodology was
used in order to estimate the optimal conditions for maximum real vegetable oily
wastewater treatment. Al 2 (SO 4 ) 3 was found as the best coagulant aiding maximum
COD and turbidity removals when used directly at a concentration of 2.4 g/L
followed by a CHT flocculant (an industrial flocculant) at a dosage of 60 mg/L
under initial pH of real effluent of 9.23 [44].
3.3.3 Biological Treatment
Despite the high efficiency of COD removal by physicochemical treatment, at the
beginning of the WWTP, biological treatment is needed due to presence of lipids in
the form of colloidal suspension [45]. Biological treatment is mainly used to remove
biodegradable organics and SS through biological methods. Adsorption of pollutants
to the organic sludge produced will also remove non-biodegradable materials, e.g.,
heavy metals. Organic nitrogen and phosphorus can also be partially removed from
the wastewater.
Biological treatment options are aerobic processes using dissolved oxygen,
anaerobic processes without oxygen supply, and anoxic processes using biological
reduction of oxygen donors. These systems can be used alone or in combination,
based on the characteristics of the wastewater and the requirements before discharge.
Mostly, aerobic and anaerobic biological treatment systems are used in the oil
industry effluents.
Aerobic and anaerobic fat and oil removal by microorganisms have been reported
in several studies [46–48]. The conventional biological processes such as aerobic
and anaerobic digestion require a BOD/COD ratio to be 0.6 [49]. However, vegetable
oil industry effluents usually have BOD/COD ratios between 0.15 and 0.2 indicating
the requirement of a proper pretreatment before the biological step [50–53].
Aerobic Treatment
The success of the aerobic treatment depends upon sufficient oxygen levels required
by the organisms to sustain their life. For an efficient operation of aerobic reactors to
degrade oil and grease, it is very important to maintain good oxygen transfer
[52]. Activated sludge systems and biofilm processes such as fixed-bed or trickling
filter processes are examples of the aerobic treatment [54].
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over a wider pH range than inorganic coagulants. They can be applied at lower
doses, and they do not consume alkalinity. However, they are generally much more
expensive than inorganic coagulants.
Previously, Louhichi et al. [44] utilized coagulation and flocculation process to
treat real vegetable oily wastewater and investigated the relationship between coagulant concentration, flocculent dosage, and pH besides two important process
parameters (COD and turbidity removals). Response surface methodology was
used in order to estimate the optimal conditions for maximum real vegetable oily
wastewater treatment. Al 2 (SO 4 ) 3 was found as the best coagulant aiding maximum
COD and turbidity removals when used directly at a concentration of 2.4 g/L
followed by a CHT flocculant (an industrial flocculant) at a dosage of 60 mg/L
under initial pH of real effluent of 9.23 [44].
3.3.3 Biological Treatment
Despite the high efficiency of COD removal by physicochemical treatment, at the
beginning of the WWTP, biological treatment is needed due to presence of lipids in
the form of colloidal suspension [45]. Biological treatment is mainly used to remove
biodegradable organics and SS through biological methods. Adsorption of pollutants
to the organic sludge produced will also remove non-biodegradable materials, e.g.,
heavy metals. Organic nitrogen and phosphorus can also be partially removed from
the wastewater.
Biological treatment options are aerobic processes using dissolved oxygen,
anaerobic processes without oxygen supply, and anoxic processes using biological
reduction of oxygen donors. These systems can be used alone or in combination,
based on the characteristics of the wastewater and the requirements before discharge.
Mostly, aerobic and anaerobic biological treatment systems are used in the oil
industry effluents.
Aerobic and anaerobic fat and oil removal by microorganisms have been reported
in several studies [46–48]. The conventional biological processes such as aerobic
and anaerobic digestion require a BOD/COD ratio to be 0.6 [49]. However, vegetable
oil industry effluents usually have BOD/COD ratios between 0.15 and 0.2 indicating
the requirement of a proper pretreatment before the biological step [50–53].
Aerobic Treatment
The success of the aerobic treatment depends upon sufficient oxygen levels required
by the organisms to sustain their life. For an efficient operation of aerobic reactors to
degrade oil and grease, it is very important to maintain good oxygen transfer
[52]. Activated sludge systems and biofilm processes such as fixed-bed or trickling
filter processes are examples of the aerobic treatment [54].
344
D. Kaya and Y.-T. Hung