Reuse of Industrial Wastewater Effluent in the Petrochemical Industry
339
4.3 Concentrated Phenolic Wastewater
As a result of sudden discharges of phenolic wastewater, Galil et al. (1988)
reported a sudden steep rise of the effluent turbidity and discoloration of the
biomass (the ML VSS), accompanied by a specific strong odor. While at initial
stages of such disturbances biodegradation was still taking place (BOD removal),
within a few days it was followed by complete poisoning of the system and
complete inhibition of the bioactivity.
Investigations of refinery operations revealed that these disturbances occurred
after sudden discharges of large volumes of concentrated phenolic wastes (15000
mg rl of phenols) into the refinery's general wastewater system. There is a
continuous low flow rate discharge of the same concentrated phenolic waste, from
a gasoline washery, being responsible for the phenols in the wastewater which are
normally in the range of 10 to 20 mg rl. Every few months a regeneration
operation of the gasoline washery takes place, discharging in a very short period
large volumes of concentrated phenol solutions. This concentrated waste contains
8000 mg rl phenol, 5000 mg rl para and meta cresol, 2000 mg rIO-cresol and a
few hundred mg rl ofxylenols. During such surges the total phenol concentrations
in the general waste rise steeply to above 100 mg r l , disrupting the process. It
seems that the first bioflocculation is impaired, followed by complete disruption of
the whole process.
Adverse effects of sudden increases in phenols concentration on biological
treatment were also reported by Reitano (1981) and Nayar and Sylvester (1979);
the latter reported a steep decline in ML VSS and in substrate utilization.
Wastewater containing phenol even at relatively high concentrations up to 100
mg rl can be treated biologically as long as the feed is steady and continuous. In
such cases, there is an inhibitory effect of the phenols by reducing the process rate.
When operating at the low rate the process itself is efficient, including good
degradation of phenols. The disruption of the process is caused by sudden
discharges - surges of high phenol liquids. To prevent such disturbances, storage
of suddenly discharged concentrated wastes is necessary and their gradual, low
flow rate-controlled discharge to the general wastewater system.
High turbidity and relatively high concentrations of polysaccharides
(biopolymers), indicating deflocculation of suspended biomass, were reported by
Galil et al. (1998) as a result of phenol supplied to the bioprocess in transient
loading conditions. The importance of preliminary acclimation could be observed
in terms of the phenol removal rates at relatively low transient loading of phenol,
up to 500 mg rl. As shock intensity increased to 1000 and 1500 mg rl, the
acclimated reactors did not show relevant differences when compared to either
partially acclimated or nonacclimated reactors.
Transient load conditions created by phenol caused immediate reduction of the
oxygen uptake rates and affected biomass respiration. Preliminary acclimation of
the biomass indicates possible improvements of these influences, especially for a
phenol load of up to 500 mg rl. The period following the application of phenol
transient load was characterized by symptoms which could indicate that sorptiondesorption mechanisms are involved by biomass, in addition to biodegradation.
339
4.3 Concentrated Phenolic Wastewater
As a result of sudden discharges of phenolic wastewater, Galil et al. (1988)
reported a sudden steep rise of the effluent turbidity and discoloration of the
biomass (the ML VSS), accompanied by a specific strong odor. While at initial
stages of such disturbances biodegradation was still taking place (BOD removal),
within a few days it was followed by complete poisoning of the system and
complete inhibition of the bioactivity.
Investigations of refinery operations revealed that these disturbances occurred
after sudden discharges of large volumes of concentrated phenolic wastes (15000
mg rl of phenols) into the refinery's general wastewater system. There is a
continuous low flow rate discharge of the same concentrated phenolic waste, from
a gasoline washery, being responsible for the phenols in the wastewater which are
normally in the range of 10 to 20 mg rl. Every few months a regeneration
operation of the gasoline washery takes place, discharging in a very short period
large volumes of concentrated phenol solutions. This concentrated waste contains
8000 mg rl phenol, 5000 mg rl para and meta cresol, 2000 mg rIO-cresol and a
few hundred mg rl ofxylenols. During such surges the total phenol concentrations
in the general waste rise steeply to above 100 mg r l , disrupting the process. It
seems that the first bioflocculation is impaired, followed by complete disruption of
the whole process.
Adverse effects of sudden increases in phenols concentration on biological
treatment were also reported by Reitano (1981) and Nayar and Sylvester (1979);
the latter reported a steep decline in ML VSS and in substrate utilization.
Wastewater containing phenol even at relatively high concentrations up to 100
mg rl can be treated biologically as long as the feed is steady and continuous. In
such cases, there is an inhibitory effect of the phenols by reducing the process rate.
When operating at the low rate the process itself is efficient, including good
degradation of phenols. The disruption of the process is caused by sudden
discharges - surges of high phenol liquids. To prevent such disturbances, storage
of suddenly discharged concentrated wastes is necessary and their gradual, low
flow rate-controlled discharge to the general wastewater system.
High turbidity and relatively high concentrations of polysaccharides
(biopolymers), indicating deflocculation of suspended biomass, were reported by
Galil et al. (1998) as a result of phenol supplied to the bioprocess in transient
loading conditions. The importance of preliminary acclimation could be observed
in terms of the phenol removal rates at relatively low transient loading of phenol,
up to 500 mg rl. As shock intensity increased to 1000 and 1500 mg rl, the
acclimated reactors did not show relevant differences when compared to either
partially acclimated or nonacclimated reactors.
Transient load conditions created by phenol caused immediate reduction of the
oxygen uptake rates and affected biomass respiration. Preliminary acclimation of
the biomass indicates possible improvements of these influences, especially for a
phenol load of up to 500 mg rl. The period following the application of phenol
transient load was characterized by symptoms which could indicate that sorptiondesorption mechanisms are involved by biomass, in addition to biodegradation.