1. Reuse “the action of using something again”
Rainwater
Wastewater Effluent
Potable Water
Reuse “the action of using something again”
Reuse typically in water supply planning relates to wastewater management. There is direct reuse (toilet-to-tap), and indirect reuse (discharge to a water body, and it is used again further downstream). I’m going to talk today about reuse in a broader context, including rainwater, because like wastewater reuse rainwater harvesting is an underutilized water management strategy.
Chris Herrington, PE

3. Executive Summary We need a good plan. A really good plan.
We need a better way to manage stormwater (aka, rain).
We need a better way to manage wastewater.

4. What’s the best time to plant a tree?

5. 2017.texasstatewaterplan.org
3x increase in population in the next 50 years
Just the BROC population served in 2070 would be equivalent to current population of Galveston
Population in Hays, Comal and Blanco Counties increasing at about the same rate and will top 1M by 2070.
In the last 10 years, the State of Texas population grew by an amount equivalent to the current size of the population of the state of Colorado.

6. 5M people is about the population of the state of Colorado

8. Blanco/Dripping Springs/Wimberley
By 2070:
Water demand = 2,317,778,163 gal/year
Sewage production = 2,107,409,625 gal/year

9. #1: We need a good plan. A really good plan

10. Who’ll stop the rain?

11. Humans change Hydrology
“The Urban Stream Syndrome”

13. When it rains…
Current stormwater management paradigm in urban areas can cause flooding and erosion impacts downstream, carries pollutants into our Hill Country creeks and aquifers

14. When it stops raining…
29%
11,394,255,872 gal/year

15. 32 inches of rain/year
Every inch of rain that falls on a 2000 sq ft house generates about 1000 gallons.
32” rain per year = 32,000 gallons per house

16. Austin Rain vs. Potable Use Today
Annual rainfall = 161,058,479,155 gal
Austin water demand = 39,290,537,491 gal
(24% of rain)
Austin outdoor use = 11,394,255,872 gal
(7% of rain)
But what about our changing climate?
Total annual average water demand equivalent to 24% of total annual average rainfall
Outdoor annual average water demand equivalent to 7% of total annual average rainfall
Future rainfall predictions incorporating climate change suggest total annual average rainfall will not change, but the distribution of that rainfall will change meaning bigger floods and longer droughts, and temperatures will increase increasing evaporation and meaning our landscape needs more water

17. Fixing Austin flood, erosion and water quality problems
Can I borrow $2,263,142,800?
(let’s talk about maintenance later)
(p.s., it will take 87 years just to fix today’s problems)
Government cannot solve this problem alone on a human time scale
87 years = 2104…that’s the difference between today and 1930.

18. Rainwater Harvesting is Real!

19. #2. We need a better way
to manage stormwater
(aka, rain)

21. Current Options for Wastewater Disposal
Regulated by Texas Commission on Environmental Quality (TCEQ)
Treat and discharge effluent directly to a water body (TPDES)
Treat and irrigate effluent on the land (TLAP)
30 TAC 222; 30 TAC 309
Greater than 5,000 gpd

22. Even highly treated effluent has excessive concentrations of nutrients and will cause water quality degradation in Hill Country creeks

23. Wastewater impacts Hill Country streams
Discharging effluent impacts

24. 30 TAC 210 Beneficial Reuse Authorizations
With either a TLAP or discharge permit, treated effluent (aka, reclaimed water) can be used on-demand to:
Irrigate landscapes
Flush toilets
Fire protection
Dust control
Cooling towers
Etc.
Toilet flushing in Austin accounts for approximately 18.4% of total potable water demand ?
Photo by Ed Clerico

25. Wastewater Disposal by Land Application (TLAP)
Conventional model without beneficial reuse
Wastewater Treatment Plant
Dedicated Disposal Field with Storage Pond

26. TLAP with Beneficial Reuse
Reclaimed water customers may not be known at time of initial permitting, may change over time, or may not be controlled by the wastewater service provider such that they can be incorporated into permits.

27. Changing wastewater management
In the past, most BROC wastewater was effectively managed by TLAP
BROC land is becoming more expensive and is increasingly fragmented (txlandtrends.org/)
Trend to convert TLAP to discharge
66 TLAP facilities in the Edwards Aquifer contributing zone (recharge zone of the Trinity), permitted to treat about 9 MGD

28. BROC wastewater update
Dripping Springs seeking 995,000 gal/day discharge to Onion Creek, plans extensive reuse system
Blanco expanding permit to 1,600,000 gal/day discharge to Blanco River, access to former irrigation area reduced
Wimberley received 75,000 gal/day discharge permit to Cypress Creek, limitations on discharge thru settlement agreement

29. #3. We need a better way
to manage wastewater

30. Wastewater Reuse Outlook
TCEQ modifying rules to provide credit for reuse in TLAP permits
Most cities appear committed to pursuing reuse
$197,103,531 of reuse strategies in 2017 State Water Plan within Hays/Comal/Blanco but:
in Buda, Kyle, San Marcos, New Braunfels
only 4.5% of proposed capital projects
Statewide today, reuse makes up less than 4% of total water supply. By 2070 statewide, reuse expected to provide 14% of total water supply in 2017 State Water Plan

31. Reuse is an important strategy
Conclusions
We need a good plan. A really good plan.
We need a better way to manage stormwater (aka, rain).
We need a better way to manage wastewater.
Reuse is an important strategy
(but still underutilized)