Pigging: Reuse of wastewater for pipeline flushing

Challenge:
A hydrocarbon pipeline required flushing after years without maintenance. To minimise the cost of importing clean water and disposing of dirty water the customer wanted to reuse the water to flush the pipeline clean. This meant the water needed treatment to remove floating hydrocarbons and settling solids before being used to flush the pipeline.

Once the pipeline was flushed the water had to meet set parameters to be discharged to the on-site WWTP. In particular the WWTP couldn’t handle any more than 2ppm of hydrocarbons. 

Solution:  
United Rentals engineered a solution to treat the wastewater efficiently for reuse consisting of:

• A Lamella filter tank to split the phases of water, hydrocarbons and solids.
• A 70 m³ lined tank acted as buffer storage for the transfer of the liquid.
• To recirculate the wastewater back to the customer’s cleaning equipment, a  4” diesel-driven pump was installed.

After the flushing of the pipeline the water was ready to discharge to the WWTP:

• The same 4” diesel- driven pump was utilised to transfer the waste water to the onsite WWTP
• A high flow 8-Bag Filter System equipped with oil absorption bags filtered the level of hydrocarbons to below 2 ppm.

Benefits: 
Thanks to the integrated treatment solution, our customer benefited from a simple, yet semi-automated filtration system. As the grey water was recycled and reused, the customer’s fresh water usage was minimised and very little waste was taken off site for external disposal, resulting in significant time and cost savings.

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