Water is an essential component that many industries depend. In fact, we all do! From agriculture to power generation, water is valued for its biological, chemical and physical properties. One key industry that utilizes water in large quantities is the oil and gas sector. Therefore when discussing industrial wastewater treatment, looking to the oil and gas industry can provide some valuable insights.
Refinery wastewater from petrochemical operations are high in difficult-to-degrade compounds that can negatively affect the performance of the facility’s industrial wastewater treatment plant, leading to possible discharge permit violations and other regulatory issues. Oil and gas managers are trying to address this challenge with innovative and out-of-the-box thinking to reinvent the treatment of these organic and inorganic compounds, while simultaneously reducing and reusing water.
If viable solutions can be found, this can potentially turn industrial wastewater treatment plants from mere disposal facilities, to resource recovery centres, which will be beneficial for the operating companies, the surrounding communities, and the environment.
One potential solution may be found in China. China set out to reduce water and energy consumption as part of its Five-Year-Plan in 2006. This included the enhancement of the utilization rate of recycled water and the establishment of screening and evaluation methods for water consumption within industrial projects. This led to the construction of a comprehensive wastewater and recycling treatment plant in 2009 to support the petrochemical refinery built by PetroChina in Chengdu located in China’s Sichuan province.
PetroChina commissioned SUEZ to design the wastewater facility to show compliance with the five-year plan. The refinery produces both oil and ethylene. The treatment system needed to treat the effluent or outflow streams, the oil-based stream from oil production and the salt-based stream from the ethylene production. PetroChina’s goal was to reuse 70 percent of the effluent wastewater for their cooling towers. They needed to comply with the chemical oxygen demand (COD) standard of 60 mg/L.
To achieve this goal, they needed to create a unique new system that can address their COD removal and wastewater reuse rate with a comprehensive, integrated design approach. The first step was to pre-treat the wastewater which included a primary and secondary oil removal process, followed by nitrification and denitrification biological treatment, then finished with secondary clarification and lamellar clarification for polishing. The resulting effluents are then integrated into the reuse treatment line. This then undergoes the process of gravity sand filtration, followed by a two-fold water treatment process of ozone oxidation and biological aerated flooded filters (BAFF). This combination is what makes up the SUEZ Oxyblue process.
Because of the increasing concentrations of complex organic and inorganic chemicals in refinery wastewater, a more aggressive biological treatment method is required. The use of ozone-based treatment has long been the best technology used by municipalities for treating water for drinking. This method has proven to be ideal for wastewater reuse and recycling processes. The combination of ozone with advanced oxidation processes (AOPs) can effectively oxidize a wide array of compounds.
The use of ozone oxidation provides flexibility in their implementation and can be adapted to a treatment plant in several ways making it an affordable way of increasing overall plant performance.
PetroChina’s system is divided into three stages. The first stage is ozone generation where pure oxygen is introduced to produce ozone which is used along three points in the treatment line: the reuse stream, the brine treatment line and the biological treatment process. The second stage is ozonation where the effluent is led to an ozonation dissolution tower for incorporation of ozone gas into the wastewater. This makes the organic matter biodegradable because of the oxidative properties of ozone. The last stage is biological filtration where the pollutants are removed with a biological aerated flooded filter. This process removes carbon and nitrogen compounds from the water.
After the process of ozone pre-treatment and biological active filtration, the effluent undergoes two more steps: ultrafiltration (UF) and reverse osmosis (RO). The final result for PetroChina is a reuse rate of 65 percent of water per year, and a COD removal rate of 95 percent, well within the strict standards set by the Chinese government. This reduces the stress on natural resources and drastically lowers water consumption which results in huge savings for the company.
Advanced oxidation processes are an emerging technology that can greatly improve industrial refinery and petrochemical water treatment. Reuse systems and their versatility makes it viable for use in other industries. If more companies adopt this technology for their industrial needs, then this will result in faster resource recovery and increase profits for the companies willing to invest in this innovation.
You can read our previous blog post on more information about how industrial wastewater is treated in Canada.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.