Petrochemical industry is amongst the major consumers of processed, or ‘make-up’ water, especially for cooling systems, stripping, fractionation, and desalting. Additionally, the treatment and refining of fossil fuels generates large quantities of wastewater that varies widely, depending on the type of crude oil, composition of condensate and treatment processes. As an example, the average refinery requires 2.5 gallons of water for every gallon of crude oil processed.
As environmental regulations for wastewater disposal are getting stricter and fresh water resources are becoming increasingly limited, the industry requires more efficient management and reuse of this wastewater. The design and operation of modern refinery wastewater treatment is challenging and is driven by the latest technology.
We are one of the few companies with a considerable background in the application of reverse osmosis technology in the desalination of seawater and brackish water, as is demonstrated by more than 80 facilities worldwide, in which the production of potable desalted water is circa three million m3/day.
We have extensive experience in desalination, comprising the entire life cycle of the project – design, construction, start-up, plant operation and maintenance – each of these stages is strongly supported by our R&D department. We are really proud that many of the technological innovations incorporated by the designs of the current desalination plants in the entire world have been developed and optimised by our company.
In the oil and gas sector, water management involves assets such as desalination plants that provide processed water to the refineries and wastewater treatment plants to deal with the sometimes quite challenging residual water that the refineries may generate.
The treatment process
Depending on the amount of process water needed and the quality of the product water that is required to be achieved, ACCIONA can accommodate the technical solution that fits the purpose.
Reverse osmosis desalination plants provide high-quality demineralised water to the refineries not only through the use of membrane-based technology, such as microfiltration, or ultrafiltration but also through non-membrane based electrodeionisation (a continuous process to obtain ultra-pure water without the need for chemicals). The product water with these technologies is able to be used in the complex industrial processes carried out by the refineries.
As far as residual water produced in refineries is concerned, the associated treatment plants usually start with a mechanical separation followed by secondary and tertiary treatment stages that may also include membranes.
But, let us start from the very beginning: Oil is a liquid hydrocarbon. In the transformation of oil at the respective refineries, water is mixed with hydrocarbons and other sulphurised, oxygenated and nitrogenous substances. The treatment of wastewater produced by refineries consists of a set of procedures, or processes to change their physical, chemical, or biological composition, making them substances that are more innocuous, or that can be reused.
Given the environmental impact that hydrocarbons have on the ecosystems and taking into account that the production of hydrocarbons produce three to five barrels of water for each barrel of oil, it is very important to treat such amount of wastewater. In general, the process of wastewater treatment in the oil industry generally consists of oil removal, disinfection, desalination and treatment by membranes through reverse osmosis, which is the most efficient technology to desalinate water and the one that least affects the environment.
Combination of different process trains and treatment methods
Keeping in mind the complex and diverse nature of refinery wastewater pollutants, a combination of physical, chemical and biological process trains and treatment methods are usually required before it is finally discharged into the aquatic environment. The wastewater from the refining processes is collected in wastewater pools so the viscosity of the waste in these pools can vary considerably depending on the content of water, oil and solids.
The remaining substances are eliminated by a biological treatment, or if they are biodegradable, they can be subjected to physical-chemical elimination. After the previous treatment, they undergo a mechanical treatment to eliminate floating, or sediment substances.
In fact, should wastewater from the petrochemical industry contain hazardous chemicals, the petrochemical companies must go through challenging and multifaceted procedures in order to treat and clean this water and avoid the environmental pollution.
The benefits in the wastewater refinery treatment are numerous, especially from the environmental point of view: (i) The wastewater treatment of the petroleum industry can be beneficial for the same industry through a secondary recovery. (ii) Through the treatment of wastewater, it can be reinjected into the subsoil for storage and subsequent use. (iii) Water can be reused, thus saving natural water sources. (iv) It allows the recycling of water through the reinjection of water that can be used in the internal and external needs of the oil production plant. (v) The wastewater treatment in the oil and gas industry allows that the water produced in this type of industry can be reused in agriculture. (vi) When the water treatment meets the quality standards of the country, it can even be discharged into natural water sources, such as oceans, lakes, rivers, or allow their evaporation.
For an example of desalination plant for industrial use, we have built in Sardinia, Italy, the largest desalination plant used by a refinery. The plant has a daily production capacity of 12,000m3 and the treated water is used in the industrial systems that the Italian energy company needs at its refinery near Cagliari, one of the largest and most complex facilities of its type in Europe.
The demand for efficient and cost-effective wastewater treatment technology in the refining and petrochemical sector is being driven by not only ever-tightening environmental legislation, but also by the sector’s own desire to follow a meaningful sustainability agenda and to take its responsibilities around product stewardship seriously.
However, refining and petrochemical companies are continually confronted with the challenge of striking a balance between making their activities profitable while ensuring the industrial processes involved in the production and application of a chemical product, across its lifecycle, have minimal impact on the environment. Treatment of wastewater from petrochemical plants can be a challenging and costly matter, particularly when needing to comply with the government and international requirements of operational permits specially when there is a discharge of treated wastewater into community plants, or natural water bodies such as rivers, lakes and oceans.
It is a fact that the petrochemical industry has demanding environmental management challenges to protect water, soil and atmosphere from the refinery pollution. Keeping this in mind along with the ACCIONA’s commitment to sustainability, we come up with different kinds of technologies and processes to the wastewater and the process water from the refining industry, providing solutions with lower installation costs that optimise wastewater treatment plant processes that without any doubt represent an ideal technology for the petrochemical industry.
Our technology can deal with the wide range of challenges that must be confronted in wastewater treatment such as populations of very different sizes, domestic urban waters, or high industrial loads, highly seasonal populations, plants located in areas with limited available space, or high visual and/or environmental impact, as well as different discharge levels. The result is the construction of more than 300 wastewater plants worldwide, with a total capacity of more than 13.5 million m3/day, equivalent to a population of more than 55 million.
Most of the oil and gas companies consider the importance of optimising one of our greatest natural resources – water. Therefore, water management is an unavoidable activity that refineries must incorporate into their daily operational protocols. In this case, water companies have researched and developed various technological processes capable of optimising water management from 15% to 30%, which well applied, would generate significant savings in this sector.
The current moment is key for the petrochemical sector, and all of us that take part of water management, from the public, or private sector must reinvent and promote our roles, orienting ourselves towards the sustainability of the most relevant resource. It is not only part of a global trend, but also part of a local perspective, focused on the care of natural resources and water sustainability.
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