The Hampton Roads Sanitation District has activated equipment designed to increase the oxygen concentrations in Shingle Creek, thereby helping the waterway recover more quickly from the spill of about 18.3 million of untreated sewage.

The process, known as the Supersaturated Dissolved Oxygen System, was developed by Arkansas-based company BlueInGreen. The equipment pulls water from Shingle Creek, saturates it with oxygen and returns the oxygenated water to the stream, according to HRSD spokeswoman Nancy Munnikhuysen.

“If the process is successful, oxygen concentrations in Shingle Creek will be restored to pre-spill levels faster than would occur naturally,” she wrote in an email.

The increased oxygen will benefit organisms living in the stream and aid in the breakdown of the sewage, she wrote.

The spill began Oct. 29 when a 9-inch hole opened in the concrete pipe. Untreated sewage flowed from the break until Nov. 8, when workers completed installation of a bypass system.

The Nansemond River remains closed to shellfish harvesting. Despite tests that showed low oxygen levels, no reports of fish kills or other “wildlife-related incidents” have been received, said Roger Everton, environmental manager with the Virginia Department of Environmental Quality.

“We’ll keep monitoring to see whether we get any additional impacts that will show themselves later,” Everton said.

Munnikhuysen said the failed section of pipe will be evaluated by engineers to try to determine the cause of the break. No obvious cause has been found, she wrote.

“There could have been a defect at the time of installation, damage caused by others after installation, or settlement that could have caused the pipe to finally break under the increased pressures created by (Hurricane) Sandy,” Munnikhuysen wrote. “It will be a while before we know more.”

Munnikhuysen wrote HRSD regularly assesses the conditions of pipes and replaces those with identified problems.

“There was nothing to indicate problems in this pipeline before the break occurred,” she wrote.