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Helma Hakala, VA TECH WABAG GmbH, introduces an innovative biological process for produced water treatment in Romania.
or oil production, the treatment of produced water has a large influence on the level of environmental protection and economic success. The treatment employed should utilise sophisticated technology that is able to cope with well characteristics that can vary significantly from borehole to borehole. WABAG has built a new produced water treatment plant in Romania. Due to specific oil extraction processes, the produced water contains large quantities of non-biodegradable organic compounds. Therefore, an innovative process was developed for the specific requirements of the oilfield. The design includes physical/chemical and biological process steps, as well as advanced filtration and adsorption technologies, which represents a first in this specific field. This advanced, multi-stage treatment process was tested successfully on the spot over several months, and the plant was commissioned in 2017.
Produced water A major factor in the economic success of oilfields is the treatment of the large quantities of water emanating from production. Every barrel of oil that is pumped is accompanied by six to eight barrels of produced water. It is the largest waste stream generated in the oil and gas industry, and consists of a mixture of different compounds, both organic and inorganic.
The priority of the project in Romania was the reduction of pollutants in the produced water to produce a more environmentally friendly discharge. The main issue was the elimination of non-degradable chemical oxygen demand (COD). For this reason, adsorption using activated carbon technology was implemented which proved to be successful. A three-stage treatment system has been installed comprising a physical-chemical stage, an innovative combination of biological treatment, and adsorption using activated carbon. By incorporating this, the plant effectively decreased the COD in the produced water by 92% to 95%.
New process design Based on the specific average and maximum values of the incoming water (Figure 1) and the discharge limits imposed on the river, the following concept has been developed for produced water treatment. The main units in the treatment plant design consist of: Two inlet tanks for buffering and equalisation of flow and loads and for oil removal. Two dissolved air flotation units for the removal of suspended solids and oil after adding coagulants and flocculants. Cooling towers for cooling water. Two activated sludge tanks designed as aerobic tanks. Two clarifiers for settling the mixed liquor. HYDROCARBON 47
ENGINEERING
July 2021
