Proceedings of the 4th Annual Texas Water Reuse Conference. A Case Study for Decentralized Wastewater Treatment Plants in Sugar Land, Texas

Transcription

1 Proceedings of the 4th Annual Texas Water Reuse Conference A Case Study for Decentralized Wastewater Treatment Plants in Sugar Land, Texas Michael Rolen, P.E. Page 1

2 Reasons for this Study Subsidence issues mandate conversion from groundwater to alternate sources of water Increase in population results in increase in demand Limited viable sources of surface water Recent drought conditions in the area Page 2

3 Decentralized Wastewater Treatment Systems Decentralized wastewater treatment systems are so called due to their location away from the main domestic wastewater treatment facility. They are located close to the source, such as homes and businesses. Page 3

4 Scalping Plant Locations Page 4

5 Goals/Objectives Research the use of decentralized wastewater treatment facilities Examine wastewater treatment technology Determine scalability of technology for flows between 0.05 and 0.1 mgd Page 5

6 Goals/Objectives Determine potential for decentralized treatment facilities in Sugar Land and its ETJ through evaluation of current systems, possible installation sites, and total costs of the treatment technology. Determine potential impact of decentralized wastewater treatment facilities on Sugar Land GRP. Page 6

7 Facilities Currently in Use or Planned in Texas City of Midland, Texas City of Odessa, Texas San Antonio, Texas City of Lubbock, Texas City of Fort Worth, Texas El Paso, Texas Page 7

8 Facilities Currently in Use or Planned Hawks Prairie Reclaimed Water Satellite Facility, Washington City of Tempe, Arizona Orange County Water District, California Irvine Ranch Water District, California Singapore NEWater Project Page 8

9 Wastewater Reuse Technologies Activated Sludge Process (ASP) Biological Nutrient Removal (BNR) Process Membrane Bioreactor (MBR) Rotating Biological Contactors (RBC) Sequencing Batch Reactor (SBR) Page 9

10 Technologies for Further Consideration Activated Sludge Process o Proven performance record o Adaptable to various wastewater characteristics o Uncomplicated design and operation o Lower total cost than MBR o Larger footprint than Membrane Bioreactor o Requires clarifier for sludge settling Page 10

11 Technologies for Further Consideration Membrane Bioreactor o Smaller reactor size o No clarifier needed o Smaller footprint and containment building o Effective at removal of nitrogen and phosphorus Note: Both technologies are characterized by ease of operation, ability to operate under low flows, fully contained treatment units, and fit well within the parameters for this application. Page 11

12 Potential Locations for Decentralized Treatment Facilities Area around Lift Station #116 Area around Lift Stations #141 and #142 Area around Lift Stations #33, #52, #60, and #63 Greatwood Area Page 12

13 Recommended Treatment Technology Study recommends the Activated Sludge Process (ASP) over Membrane Bioreactors (MBR) due to its lower total cost. Although ASP is recommended, an MBR unit has a lot of advantages over the ASP and would be a feasible alternative, if funds permit. Page 13

14 ASP and MBR Cost Analysis (2012) Table 1: Projected Operational and Maintenance Costs mgd 0.10 mgd 0.20 mgd Activated Sludge Process $95,000 $140,000 $210,000 Membrane Bioreactors $73,000 $109,500 $146,000 Table 2: Construction Costs for ASP Package Plants with Disk Filter and MBRs Total Costs Item mgd 0.10 mgd 0.20 mgd MBR with Drum Screen * $ 1,588,410 $ 2,182,302 $ 2,955,204 ASP with Cloth Filter * $ 1,658,962 $ 2,046,044 $ 2,798,096 * Includes Other Associated Equipment and Construction Costs Page 14

15 Potential Impact of Decentralized Treatment Facilities Wastewater Collection Systems Wastewater Treatment Plants o North Wastewater Treatment Plant o South Wastewater Treatment Plant o West Wastewater Treatment Plant Page 15

16 Impact on Wastewater Collection System Difficult to predict Actual savings in construction costs could be extensive If new developments are required to utilize reclaimed water, there could be a significant reduction in costs of future expansions. Page 16

17 Impact on Wastewater Treatment Plants North Wastewater Treatment Plant Reduce flows to the plant Reduce flows diverted to other plants Delay or eliminate need to take plant out of service South Wastewater Treatment Plant Possible site for water reclamation facility serving the area Page 17

18 Impact on Wastewater Treatment Plants West Wastewater Treatment Plant Reduced flows diverted to plant Delay and reduce size of expansion for plant and associated costs Possible site for water reclamation facility serving the area Page 18

19 Comparison of Unit Costs of Reclaimed Water to Alternative Sources Treated Surface Water (City of Sugar Land) Raw Surface Water Treated Groundwater Raw groundwater Reclaimed Water (Scalping Plants) Page 19

20 Results of Comparison of Unit Costs The Cost/1,000 Gallons for each Comparison Source of Water Comparison 1 Comparison 2 Comparison 3 Treated Surface Water $ $ $ Raw Surface Water $ $ $ Treated Groundwater $ $ $ Raw Groundwater $ $ $ Reclaimed Water (0.05 mgd Plant) $ $ $ Reclaimed Water (0.10 mgd Plant) $ $ $ Reclaimed Water (0.20 mgd Plant) $ $ $ Page 20

21 Results of Comparison of Unit Costs Raw Surface Water (positive cost) Reclaimed Water (0.2 mgd Plant) Treated Surface Water Raw Groundwater Treated Groundwater Reclaimed Water (0.1 mgd Plant) Reclaimed Water (0.05 mgd Plant) Page 21

22 Recommendations for the Use of Scalping Plants Actively pursue the use of reclaimed water Develop guidelines and requirements for inclusion of reclaimed water systems in all new residential and commercial developments Page 22

23 Recommendations for the Use of Scalping Plants Diversion of LS #141 to LS #142 along with installation of a 0.2 mgd Scalping Plant Installation of a reclaimed water production facility to meet the needs of the Sweetwater Country Club, and other users in that area (Area around Lift Station #116) Page 23

24 Recommendations for the Use of Scalping Plants Installation of Scalping Plants in the area around LS #52, #60, and #63. Future plans for wastewater treatment plants should include consideration of installation of reclaimed water production facilities Page 24

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