Petroleum is a crucial material for economic development and improving human living standards. It serves as a key energy source for industries like transportation, power, and machinery manufacturing, and is also essential for the petrochemical, light industry, textile, and food sectors. Due to its widespread use in industrial, agricultural, urban, and rural settings, petroleum significantly impacts water pollution. Sustainable economic growth heavily depends on the efficient supply and utilization of energy, but the petrochemical industry inevitably harms the environment, which in turn affects its own operations. Therefore, while developing petroleum resources, ecological protection must be prioritized.

Oil in water primarily originates from wastewater from refineries and petrochemical plants, offshore and seabed oil extraction, and spills from oil tankers and other ships. Currently, petroleum pollution in oceans has become a global environmental issue. It is estimated that around 1,000×10³ m³ of oil and its products are discharged into the oceans each year due to human activities. In polluted waters, oil mainly degrades through natural processes and microbial activity, with small amounts volatilizing into the air or attaching to sediment.

Oil, being lighter than water and insoluble in it, floats on the surface, quickly spreading into a thin film that blocks oxygen from entering the water, disrupting photosynthesis in aquatic microorganisms. The degradation of oil consumes large amounts of dissolved oxygen, leading to severe hypoxia and causing water to turn dark and foul-smelling.

Petroleum hydrocarbons contain various toxic substances, with toxicity increasing in the order of alkanes, cycloalkanes, and aromatic hydrocarbons. Many carcinogenic, mutagenic, and teratogenic chemicals found in petroleum products, such as benzo[a]pyrene and benz[a]anthracene, pose serious threats to animals, aquatic life, and humans. These hydrocarbons prevent plants in water from performing normal photosynthesis, leading to massive die-offs and disrupting the aquatic ecosystem.

The impact on fish and birds is particularly severe. Oil films clog fish gills, suffocating them to death. At concentrations above 0.05 mg/L, the water and fish develop an unpleasant odor; at over 0.5 mg/L, fish die; and at concentrations above 1.2 mg/L, plankton and benthic organisms perish. Additionally, oil contamination results in foul odors in aquatic products, rendering them unusable. The oil film on the water surface obstructs oxygen exchange, significantly reducing dissolved oxygen and threatening aquatic life. Carcinogenic hydrocarbons in oil can accumulate in fish and shellfish, entering the human food chain.

Low-boiling saturated hydrocarbons in oil can anesthetize animals and cause cellular damage at high concentrations, leading to death. Polycyclic aromatic hydrocarbons (PAHs), known for their mutagenic and carcinogenic properties, are of particular concern as they can accumulate in the human body. The concentration of the highly carcinogenic benzo(a)pyrene (BaP) in oilfield wastewater ranges from 0.014 to 9.0 μg/L, while in untreated sewage, it ranges from 0.015 to 1.8 μg/L, compared to just 0.001–0.01 μg/L in unpolluted groundwater. Low-molecular hydrocarbons cause more harm to plants than high-molecular ones. Hydrocarbons with boiling points between 15–275°C, such as crude gasoline and kerosene, penetrate plant tissues and disrupt physiological processes. High-molecular hydrocarbons, although harder to penetrate plant tissues, can form a sticky film on plant surfaces, blocking stomata and affecting transpiration, respiration, and photosynthesis. PAHs can accumulate through the aquatic food chain and enter the human body, where they cause cell membrane damage, disrupt enzyme systems, and induce cancer in organs like the liver and kidneys.

When petroleum pollutants enter the soil, they alter its permeability. Most hydrocarbons in oil are high-molecular components that do not dissolve in water but adhere to soil particles, changing soil properties, damaging its structure, and disrupting microbial life. This forms a film around plant roots, hindering respiration and nutrient absorption, leading to root decay.