Wastewater treatment facilities for oil-containing effluent from the Atyrau Oil Refinery.
Atyrau, Atyrau Oil Refinery.
Treatment-plant capacity: 16,800 m³/day.
The Atyrau Oil Refinery is Kazakhstan’s first oil refinery and one of the country’s largest industrial enterprises. As part of construction of the aromatic-hydrocarbons production complex and the deep-oil-processing complex at the refinery, the project provides for reconstruction of the mechanical and biological treatment facilities and creation of a recirculating-water-supply system.
For the reconstruction project, KST-water specialists developed a wastewater-treatment process capable of removing petroleum products at concentrations of up to 3,500 mg/L. The process scheme is based on preliminary separation of mechanical contaminants, removal of the light floating fraction, and subsequent flotation treatment to remove petroleum products.
After preliminary physicochemical treatment, the wastewater passes through biological treatment. The project provides separate nitrification and denitrification zones and an Aerostrip aeration system, which substantially reduces the energy consumption of the installed blowers and intensifies the biological treatment process.
After the reconstructed biological treatment stage, the wastewater enters a new tertiary-treatment block so that its quality can be brought to the standards required for recirculating water supply.
KST-water engineers, working together with Israeli engineers, developed a treatment process that removes suspended and organic matter from the water and minimizes sulfate and chloride concentrations in order to protect the plant equipment that uses the recirculating-water system.
The project uses a five-stage recirculating-water preparation system:
Multimedia filters for tertiary removal of oil-containing contaminants;
Multimedia coarse-treatment filters;
Multimedia fine-treatment filters;
Micron filters with a 5 µm filtration rating;
Reverse osmosis.
Multimedia filters have up to 4.5 times the dirt-holding capacity of sand filters. The filter media has significant internal porosity and can adsorb organic and inorganic compounds and surfactants and reduce residual oxidant concentrations. An improved automatic backwash process using water filtered by the other filters requires no additional pumps. The filters provide highly efficient removal of up to 98% of all suspended solids and insoluble hydrocarbons (petroleum products) remaining in the water after biological treatment.
Reverse osmosis is one of the finest filtration methods available today. A three-stage reverse-osmosis system is provided for preparation of recirculating water in order to achieve the highest possible conversion. Reverse-osmosis membranes act as a barrier to all dissolved salts and inorganic molecules, as well as organic molecules with a molecular weight above 100. Water molecules pass freely through the membrane to form a stream of purified water. Dissolved-salt rejection reaches up to 99%.
The filtration process was calculated using computer modelling. The equipment is supplied factory-assembled with complete process piping, including valves, instrumentation and automation, the control system, reagent facilities and other required systems. Installation time is minimized through shipment from the manufacturer in large preassembled modules.