Petrochemical wastewater treatment technology

Author：

Huanke

The treatment technologies for petrochemical wastewater are mainly divided into two categories: anaerobic treatment and aerobic treatment. Anaerobic treatment is mainly used to improve the biodegradability of wastewater, with the advantages of low sludge yield, low operating costs, high production efficiency, and simple operation, but with long start-up time and unstable operation.
1.1 Upflow anaerobic sludge bed (UASB)
The UASB reactor has high sludge concentration, high organic load, short hydraulic retention time, low operating cost, and simple operation. However, its start-up process is time-consuming and requires strict cultivation conditions for granular sludge, which is commonly used in the treatment of high concentration organic wastewater.
1.2 Anaerobic Attached Membrane Expanded Bed (AAFEB)
AAFEB is a new and efficient anaerobic digestion process, in which the bed operates at a certain expansion rate (10% to 20%), improving the mass transfer conditions inside the reactor. The small particle size of the carrier can provide a huge surface area for the attachment and growth of microorganisms, maintaining a high concentration of microorganisms in the reactor.
1.3 Anaerobic Fixed Membrane Reactor
The anaerobic fixed membrane reactor is equipped with fixed packing, which can intercept and attach a large number of anaerobic microorganisms. Under its action, organic matter in the influent is converted into methane and carbon dioxide, which can be removed. It has the advantages of long microbial residence time, strong resistance to impact loads, and convenient operation and management.
Aerobic treatment includes the following types:
2.1 Sequential Batch Reactor (SBR)
The SBR process has a simple process flow, good pollutant removal efficiency, small footprint, flexible operation, and is easy to control. However, it is not suitable for treating large amounts of wastewater and requires high control and management requirements. A two-stage SBR process system consisting of two identical SBRs connected in series is used to treat petrochemical wastewater. The first stage mainly degrades acetic acid, while the second stage mainly degrades aromatic compounds.
2.2 Efficient Aerobic Bioreactor (HCR)
HCR integrates technologies such as high-speed jet aeration, enhanced phase transfer, and turbulent shear, and has the characteristics of deep well aeration and sludge fluidized bed. Scholars have conducted pilot studies on the treatment of petrochemical wastewater using HCR. The results show that HCR has a fast start-up speed, high oxygen utilization rate, strong shock load resistance, stable and reliable removal effect, and a BOD removal rate of 75% to 85%. However, due to the short HRT, low ammonia nitrogen removal rate, and the special nature of petrochemical wastewater, the sludge in the reactor is prone to non filamentous bacterial expansion, resulting in poor sludge settling performance. Compared with the ordinary activated sludge process, the HCR process has higher energy consumption, but at a shorter HRT, the BOD removal rate is higher, making it suitable as a pretreatment process.
2.3 Biological contact oxidation
Biological contact oxidation is a new type of biofilm reactor, whose core component is a special filler that can maintain a suspended state in the reactor. The reactor is easy to operate, has good ventilation and water permeability, and has the effects of collision and cutting bubbles. It can strengthen the mass transfer of microorganisms, pollutants, and dissolved oxygen, improve the efficiency of oxygen utilization, and has no special requirements for aeration and water distribution. The experimental results of using it to treat petrochemical wastewater show that the suspended carrier bioreactor has strong oxygenation capacity and resistance to load impact. When the filler addition rate is 50%, under the same conditions as a regular aeration tank, the oxygen filling capacity of the reactor can be increased to more than twice that without fillers, resulting in good pollutant removal efficiency and stable effluent quality; When the filler addition rate is 50% and HRT is 8 hours, the removal rates of COD, ammonia nitrogen, turbidity, and SS are 75.0%, 85.2%, 85.7%, and 86.2%, respectively.

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