Reuse of Industrial Wastewater Effluent in the Petrochemical Industry
341
4.5 Biotreatment by Biofilm Systems
Biological treatment of wastewater from a petrochemical complex was studied by
Galil (1994) in order to evaluate the removal mechanisms of hydrocarbons by two
parallel processes: rotating biological contactor (RBC) and activated sludge. The
influent contained 700 mg rl COD, 140 mg rl BOD, 7.5 mg rl phenols, and 32
mg rl hydrocarbons in emulsified form. The hydraulic detention time was 14 to 18
hours for activated sludge and 4 to 5 hours for RBC. It was found that both units
produced an effluent containing a residual hydrocarbon of about 10% from the
initial effluent concentration. The distribution of the removed hydrocarbon was: in
activated sludge 70% by attachment to biosolids and wasted with the removed
sludge; in RBC 15% was stripped to the atmosphere, 25% by biodegradation, and
50% was removed by wasted sludge. The higher fraction of hydrocarbon
biodegraded by the fixed film seems to be the result of higher active biomass
which could concentrate in the RBC reactor. The fact that RBC removes less
hydrocarbon to the atmosphere is considered an environmental advantage.
Although the fixed film attached a major part of the hydrocarbons, the biosludge
production and characteristics for the fixed film were substantially better than for
the suspended growth.
Abadi and Galil (2000) studied sorption characteristics of hydrocarbons oflow
biodegradability to biomass in attached and suspended growth biological
processes. It was found that in both processes sorption to the settled biosolids was
the main oil-removal mechanism; however, differences in the extent and
characteristics of oil sorption were observed. The attached biomass sorbed more
hydrocarbons than the suspended biomass. The settling efficiency in bioprocess
based on suspended growth was damaged during the sorption of oil, while
biomass concentration in the reactor decreased. The attached growth process had
very limited disturbances in biomass separation by settling. The results indicated
that effluent suspended solids concentration in the attached growth process
decreased when oil sorption was high.
5 Future Development Projects
Based on results obtained in several research projects, a new biological treatment
process will be accomplished, by a submerged biological contactor (SBC) system,
which will perform carbonaceous substrate removal and nitrification. The SBC
effluent will be treated for biosolids separation by sedimentation and filtration and
reused as makeup to the recirculated water-cooling system.
The blowdown from the water-cooling system will be treated by reverse
osmosis (RO) and reused in the cooling system for lowering the salt balance.
Another part of the demineralized water will be reused for steam production at the
local power plant. The concentrate from the RO will be discharged to the sea by a
marine outfall (Fig. 3).
341
4.5 Biotreatment by Biofilm Systems
Biological treatment of wastewater from a petrochemical complex was studied by
Galil (1994) in order to evaluate the removal mechanisms of hydrocarbons by two
parallel processes: rotating biological contactor (RBC) and activated sludge. The
influent contained 700 mg rl COD, 140 mg rl BOD, 7.5 mg rl phenols, and 32
mg rl hydrocarbons in emulsified form. The hydraulic detention time was 14 to 18
hours for activated sludge and 4 to 5 hours for RBC. It was found that both units
produced an effluent containing a residual hydrocarbon of about 10% from the
initial effluent concentration. The distribution of the removed hydrocarbon was: in
activated sludge 70% by attachment to biosolids and wasted with the removed
sludge; in RBC 15% was stripped to the atmosphere, 25% by biodegradation, and
50% was removed by wasted sludge. The higher fraction of hydrocarbon
biodegraded by the fixed film seems to be the result of higher active biomass
which could concentrate in the RBC reactor. The fact that RBC removes less
hydrocarbon to the atmosphere is considered an environmental advantage.
Although the fixed film attached a major part of the hydrocarbons, the biosludge
production and characteristics for the fixed film were substantially better than for
the suspended growth.
Abadi and Galil (2000) studied sorption characteristics of hydrocarbons oflow
biodegradability to biomass in attached and suspended growth biological
processes. It was found that in both processes sorption to the settled biosolids was
the main oil-removal mechanism; however, differences in the extent and
characteristics of oil sorption were observed. The attached biomass sorbed more
hydrocarbons than the suspended biomass. The settling efficiency in bioprocess
based on suspended growth was damaged during the sorption of oil, while
biomass concentration in the reactor decreased. The attached growth process had
very limited disturbances in biomass separation by settling. The results indicated
that effluent suspended solids concentration in the attached growth process
decreased when oil sorption was high.
5 Future Development Projects
Based on results obtained in several research projects, a new biological treatment
process will be accomplished, by a submerged biological contactor (SBC) system,
which will perform carbonaceous substrate removal and nitrification. The SBC
effluent will be treated for biosolids separation by sedimentation and filtration and
reused as makeup to the recirculated water-cooling system.
The blowdown from the water-cooling system will be treated by reverse
osmosis (RO) and reused in the cooling system for lowering the salt balance.
Another part of the demineralized water will be reused for steam production at the
local power plant. The concentrate from the RO will be discharged to the sea by a
marine outfall (Fig. 3).