Dallas Wastewater Keeps Trinity Flowing, Houston Drinking

Dave Fehling/StateImpact Texas

FM 3278 crosses the Trinity River just downstream from the Lake Livingston Dam

Once called the “River of Death” because it was so polluted with sewage and waste from slaughterhouses, the Trinity River has defied the great drought and helped maintain one of Houston’s critical supplies of water. And much of the credit goes to what a century ago made the river so polluted: the wastewater from Dallas-Fort Worth.

The Trinity flows past Dallas and goes south 200 miles to Lake Livingston. Even after the long summer of record drought and heat,

Map courtesy TRA

Click on the image above to trace the Trinity River Basin's route.

thousands of gallons of water still cascade every second down the lake’s spillway. From there, the flow again takes the form of a river and 80 miles later, the Trinity ends at Trinity Bay on the Gulf of Mexico.

At the Lake Livingston spillway, all that water creates a steady, low roar.

Dave Fehilng/StateImpact Texas

The waters of the Trinity River escaping Lake Livingston Dam

“It’s the roar of many showers and toilets using water in the Dallas-Fort Worth area,” said a smiling Jim Lester, a lead environmental scientist with the Houston Advanced Research Center in The Woodlands.

It has long been a joke to those who know where Houston gets it’s water: take a drink from a tap in Houston and say ‘thank you’ to your friends in Dallas for flushing their toilets and doing all the other things that create a city’s wastewater.

In fact, without the Dallas-Fort Worth wastewater, the drought may have nearly dried up the Trinity. Decades ago, that happened. But now, the Metroplex sends so much wastewater down the Trinity, even in the driest year in Texas, the river continues to flow. Which means the wastewater is far more concentrated.

The Trinity River Authority (TRA) said in a normal year, just one-eighth of the flow as it reaches Lake Livingston is Dallas-Fort Worth wastewater. But this summer, that wastewater accounted for one-half the flow.

Dave Fehling/StateImpact Texas

Scientists Stephanie Glenn (left) and Lisa Gonzalez at the Houston Advanced Research Center

“Water quality is affected by drought,” said Stephanie Glenn, a water quality scientist at the Houston Advanced Research Center.

Contaminants are at concentrated levels in droughts because of the lack of rainwater to dilute them. But it’s a concern Glenn said more for the fish than humans.

“That’s important for aquatic life. It’s not necessarily for drinking water,” said Glenn. She said the good news for both is that the waste water treatment plants in Dallas are highly effective.

The river authority uses a series of treatments to clean the waste water before it’s released to flow down the Trinity. They include screens, aeration, filters made of sand and cloth, and chlorine (which is then removed through dechlorination).

Trinity River Authority

Trinity River Authority waste water treatment facility in Dallas

“[The] pathogens, the bacteria, the viruses, these are removed very, very efficiently through the normal wastewater treatment process. So what’s coming out of those [treatment plant] discharges…really is quite clear,” said Glenn Clingenpeel, the TRA’s senior environmental manager.

The Houston Public Works and Engineering Department said it has made no changes in what it does to make the Trinity River water drinkable.

“The treated water has met all Federal and State standards during the drought, and no significant changes were observed in constituent levels,” department spokesperson Alvin Wright said in an email to StateImpact Texas.

Dave Fehling/StateImpact Texas

Houston purifies the water it pumps from the Trinity and San Jacinto rivers

Houston gets roughly a third of its water from the Trinity, pumping water from the river near Dayton and sending it through canals to a purification plant in east Houston. But as demand grows, Houston has plans to build a second canal known as the Luce Bayou Project. It will tap the Trinity at a point 10 miles north of Dayton, diverting more river water westward over to Lake Houston.(The other two-thirds of Houston’s water comes from Lake Houston which is part of the San Jacinto River watershed and from underground aquifers.).

No one knows when the drought will end, but with lower temperatures and some decent rain storms, there has been some re-filling of the depleted Lake Livingston. This summer it had dropped some four feet. It has now regained one foot of that level, thanks also to all that wastewater from Dallas-Fort Worth.