Wastewater Treatment in Petrochemical Industry: Five Essential Biological Methods You Should Know!

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The petrochemical industry, depending on its processes or products, can be divided into three stages: upstream, midstream, and downstream. It is a high-tech, high-value-added, high-investment, high-energy-consuming industry. The sources and characteristics of pollutants in the wastewater generated vary greatly, posing a certain impact on the environment. With increasingly stringent environmental requirements domestically, the content and control of specific substances in petrochemical wastewater will become important issues.

 

1,Various Types of Petrochemical Wastewater with Complex Composition and High Toxicity，the main characteristics are as follows:

 

1.Large water volume, complex and variable water quality: Petrochemical production tends to be large-scale, involving the addition of various solvents, additives, and agents, followed by various reactions. Therefore, wastewater volume is large, with a fairly complex composition.

 

2.Severe organic pollution: Organic compounds in petrochemical wastewater are mainly hydrocarbons and their derivatives. Even after treatment by methods such as incineration, wastewater from certain petrochemical processes still has high COD.

 

3.Presence of heavy metals in wastewater: Petrochemical production involves many reactions catalyzed by catalysts. A large petrochemical plant may use dozens of catalysts, resulting in wastewater often containing heavy metals.​

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2，Methods for Petrochemical Wastewater Treatment:

 

Common wastewater treatment methods can be broadly categorized into physical, chemical, and biological methods. Among them, the biological method relies on the metabolic action of microorganisms in activated sludge to degrade pollutants in wastewater, which is less environmentally impactful, eco-friendly, and more economically viable. This article focuses on introducing biological treatment methods. Biological treatment methods transform organic pollutants in wastewater from dissolved, colloidal, and finely suspended states into stable, harmless substances and can be divided into aerobic and anaerobic biological treatment methods. Below are five biological treatment methods,Let's continue to delve deeper and explore together!

 

1.Activated Sludge Method: The activated sludge method is the primary method for biological wastewater treatment using activated sludge. This technology mixes wastewater with activated sludge (microorganisms) and aerates it to decompose organic pollutants in the wastewater. Biologically solid matter is then separated from the treated wastewater and can be partially returned to the aeration tank as needed. The activated sludge method consists of an aeration tank, a settling tank, a sludge return system, and residual sludge removal system. Bacteria in the activated sludge form a mixed community, often existing in the form of bacterial flocs, with fewer free-living bacteria. The degradation (removal) of organic matter during aeration can be divided into two stages: adsorption stage and stabilization stage.(Extended Reading:Struggling with Industrial Wastewater COD Treatment? Meet KB-660W-100: Your Eco-Friendly Solution for Non-Toxic Bioremediation.)​

 

2.Anaerobic-Aerobic Biological Treatment Method: The anaerobic-aerobic biological treatment method combines anaerobic and aerobic processes to treat wastewater. In addition to removing organic pollutants from wastewater, it can also simultaneously remove ammonia and nitrogen, making it widely used. The characteristics of the anaerobic-aerobic biological treatment method include high efficiency, simple process, high volumetric load in the low oxygen denitrification process, and strong resistance to load impact.

 

3.Biofilm (MBR)-A/O Method: The biofilm (MBR)-A/O method combines MBR with the A/O process. The process includes removing coarse suspended solids and settling in a grid and then pumping the raw water into the pre-denitrification A section (anaerobic tank) through a pump. It then overflows into the aerobic reaction O section (aerobic tank), and membrane filtration is performed under the suction of the effluent pump. The aerobic tank is continuously aerated.

 

4.Biofilm Method (MBR): The biofilm treatment method is a sewage aerobic biological treatment technology parallel to the activated sludge method. The essence of this treatment method is to allow bacteria, fungi, microorganisms such as protozoa, and metazoans such as protozoa to attach to fillers or some carriers to grow and reproduce, forming a film-like biological sludge—biofilm—on them. Organic pollutants in sewage are used as nutrients and are absorbed by microorganisms on the biofilm, purifying the sewage, and the microorganisms themselves also proliferate.

 

5.Hydrolysis Acidification-Aerobic Biological Treatment Method: Hydrolysis refers to the biochemical reactions that occur outside microbial cells before organic matter enters the cells. Microorganisms complete biocatalytic reactions by releasing extracellular free enzymes or fixed enzymes connected to the extracellular wall. Acidification is a typical fermentation process, and the main metabolites of microorganisms are various organic acids. Hydrolysis and acidification are two stages of anaerobic digestion. The purpose of hydrolysis acidification-aerobic biological treatment method's hydrolysis is mainly to convert insoluble organic matter in original wastewater into soluble organic matter, especially industrial wastewater, mainly converting difficult-to-biodegrade organic matter into easily biodegradable organic matter to improve the biodegradability of wastewater for subsequent aerobic treatment.