While oil companies use 230 to 290 million gallons of water a year to stimulate oil wells, about 134 billion gallons of this wastewater are considered waste. Many of these waters are classified as produced water and disposed of through wastewater pits or underground injections. This practice has been associated with earthquakes. As a result, a significant portion of this wastewater is recycled for agricultural use.
Oil field wastewater is treated and discharged into natural drainage channels or unlined surface impoundments. The wastewater may also be diluted in a receiving body of water. The problem with the direct application of sewage to the ground is the elevated concentration of some contaminants.
Processes used to treat oil field wastewater
During the oil and gas industry’s life cycle, produced water will go through several stages of treatment. The first phase, pre-treatment, removes oil and other coarse particles. The second phase, known as the primary treatment, removes smaller droplets of hydrocarbons. The de-oiling equipment used in this process is divided into two parts: the primary step removes larger hydrocarbon droplets, and the secondary step removes smaller ones.
As a result of crude-oil extraction, produced water has a complex composition that is highly toxic. While most regulations target dispersed hydrocarbons, newer ones focus on dissolved compounds and effluent toxicity. Therefore, the effectiveness of produced water treatment must be improved to reduce toxicity and improve efficiency, especially for offshore facilities.
A comprehensive treatment system is used to process oil field wastewater for reuse. These processes can include grit separation, oil separation, air stripping, downflow filtration through walnut shell filters, chemical conversion, heavy metal precipitation, monitoring, and solids separation. The final stage of this treatment is to inject the wastewater back into a disposal well. Sometimes, solids are produced along with oil and must be removed and disposed of separately.
Reuse of treated wastewater for farm irrigation
Reusing treated oil field wastewater for farm water irrigation can help offset the high cost of treating freshwater for farming. Reusing treated oil field wastewater for farm irrigation could significantly reduce the amount of fertilizer and pesticides that irrigate croplands. The reused water will cycle nutrients through irrigation water and natural processes occurring in the reservoir. This process is not ideal, however, because if the water is not treated correctly, it could have harmful effects on fish, waterfowl, and other species that feed in these bodies of water.
Reusing oil field wastewater for farm irrigation has long been used by Kern County farmers for farming. This has the benefit of conserving freshwater resources and restoring soil fertility. While the EPA has several concerns, farmers are already using wastewater from oil fields as an alternative to using groundwater. It costs less than $1 per barrel for injection and is a less expensive method. Moreover, it is unknown if humans can consume the water produced by oilfields.
As climate change worsens, treated water for farm irrigation becomes an increasingly crucial alternative water source for farmers. This method reduces production costs and increases crop production and income. Farmers are more likely to utilize water from treated oil fields to meet growing demands. It is a viable alternative to conventional sources of water. This method also reduces stress on traditional water resources. While the results are limited to Italy, farmers are likely to welcome it.
Risks to groundwater and soils
Oil-related pollutants have permeated the soil and groundwater bodies in Yibin, China, and the groundwater in the area is an essential source of drinking water for residents.
The risks associated with oil field wastewater are often overlooked. Although it is used for agricultural purposes, such as irrigating crops, it must be evaluated for toxicity before being used for agriculture. If misused, oil field wastewater can cause severe problems to human health and aquatic resources. Because of this, there is a pressing need to protect the soil and groundwater. Therefore, these pollutants must be disposed of properly.
The main methods to assess the risks to groundwater and soils are numerical models, which calculate pollutants’ concentration trends and migration paths. Numerical models are also helpful in designing various working conditions. The changes in environmental risk assessment methods are mainly due to the transition from post-pollution to pre-pollution prediction.
The Monterey oil basin is located near several major fault lines in California, including the San Andreas and Garlock faults. Seismic activity affects the earth’s complex plumbing system, including oil wells. In addition, wastewater injection wells store toxic byproducts of fracking. The wastewater is injected into the water table if these wells are damaged, polluting groundwater.
The Monterey basin in California is a prime example of a region with a high risk of oil and gas water pollution. Oil-water mixtures can degrade groundwater quality and cause significant problems for the state. However, this process is not simple and could be complicated by earthquakes, operator error, and equipment failure. So, there is an urgent need for regulation to protect California’s environment from this pollution.
Impact on agriculture
A new report from PSE Healthy Energy shows that oil field wastewater in agriculture may be more severe than first thought. The water from oil wells has been used in agriculture for decades, including for livestock and crops and even for recharge of aquifers at the Lawrence Berkeley National Laboratory.
A recent study outlines the potential health risks of oilsands production on crops and suggests ways to mitigate them. The study’s authors say that the water quality of oilfields’ wastewater is different from that of other produced waters. For example, there are no well-established methods to test it for toxicity.
The impact of oil field wastewater on agriculture is difficult to quantify. Still, some scientists say that farmers in California’s Central Valley may be ingesting toxic chemicals from nearby oil fields. The federal chemical database flagged more than 100 chemicals for acute toxicity, biodegradability, and environmental persistence. And ten of those chemicals are carcinogenic, which raises concerns about their long-term effects on humans.
Although the effects of oil field wastewater on agriculture are not well understood, the study found significant changes in gene expression in wheat and other crops grown in contaminated water. Although the researchers didn’t find specific chemicals in the produced water, they hypothesized that a combination of contaminants suppressed the immune system and made plants more susceptible to diseases and stress. This result would mean that food produced in the oil fields may not be safe.