Expert: "Toilet to Tap" Process Would Greatly Improve San Angelo's Water Quality

This week, the San Angelo City Council heard the results of the reclaimed water study, and what would be the best option for the city as far as an alternative water source.

Ellen McDonald, a professional engineer for Alan Plummer Associates, Inc., was hired to complete a yearlong study focusing on finding an alternative water source. She concluded that the city’s best resource would be direct potable reuse (DPR), also known as 'toilet-to-tap.'

DPR enlists the help of reclaimed water that is piped directly from a wastewater treatment facility to a drinking water treatment and distribution center. In San Angelo, this would combine three different water sources, O.H. Ivie, Hickory Aquifer, with the wastewater.

According to Tymn Combest, Water Quality Supervisor for the city, the reverse osmosis (RO) system required to filter the impurities out of the sewer water would make the public water supply up to 85 percent better than it is now.

(Clarification June 22: The reverse osmosis system would remove up to 85 percent of the minerals from reclaimed water. According to Combest, in reality the final blend at best could make our water 50 percent lower in minerals if the city runs the RO system at full capacity.)

At the wastewater treatment plant there is a high amount of pharmaceuticals and other chemicals present when the water comes into the plant, which was one concern mentioned at the council meeting.

“RO is a membrane that will trap chemicals like sodium, calcium and magnesium, which are very small atoms,” Combest said.  “Those membranes in a RO system are so fine they will remove all of those tiny atoms. Pharmaceuticals like methamphetamines are big molecules, if the membrane will filter out a little bitty sodium atom, a big molecule is easy to take out, and all pharmaceuticals are big molecules.”

Combest said it was comparable to throwing a stick into the RO system, the membranes would not allow it to pass, filtering out all potential contaminates.

“The sewer plant alone probably removes 90 percent of pharmaceuticals and other contaminants by its own process,” Combest said. “When you take that water and run it through the RO system, it knocks that down to almost nothing. Personally, it wouldn’t bother me to use that water as long as I know it’s been treated properly. Water is just water; you just have to get the impurities out. The system that we are looking at putting in out there has so many safeguards the people in the city will notice a difference in taste, smell and feel.”

 If you took a big glass of the Hickory Aquifer and O.H. Ivie surface water (San Angelo’s water now) and you evaporated all of it off until it was dry, you would have a salty looking residue at the bottom of the glass called 'total dissolved solids' or TDS, Combest explained.

The proposed reclaimed wastewater RO system will remove all of those impurities, making dishes and laundry cleaner while leaving plumbing pipes and drains free of buildup. Combest added that it would also greatly improve the taste of our water. So much so, restaurants probably won’t even need to have their own RO unit anymore, because that water will make the water that much better.

(Clarification June 22: As far as restaurants not having to use an RO system and plumbing pipes and drains being free of clogs, this has the possibility of becoming a reality if the city ends up installing the system.)

For citizens that are concerned about health risks associated with wastewater reuse. Combest says that it’s an everyday routine to check the water quality in town. The water quality lab runs tests on San Angelo’s water supply from many different sample stations four or five times daily.

(Clarification June 22: The water quality testing lab has over 100 sampling stations; samples are taken daily from four or five of these sampling stations and tested, not four or five from each of the 100-something stations.)

It was decided by the council Tuesday unanimously to give Bill Riley, the city water utilities director, the authority to enter negotiations between the city and contractor for the final costs of the pilot testing portion of a multi-phase plan to reuse wastewater and bring those plans back to council in July. Riley will also have answers about funding the project at that time.