Environmental Impact Study: Performance. Pauli Undesser WQA Director of Regulatory and Technical Affairs. Water Quality Association

Transcription

1 Environmental Impact Study: Water Softener Effects on Septic Tank Performance Pauli Undesser WQA Director of Regulatory and Technical Affairs Water Quality Association

2 Overview Background information Introduction to WQRF study Status of the study 2

3 Background Information Water Quality Association

4 History Early 70 s unspecified septic failures noted and softeners being blamed Specified failures Poor maintenance Tree root infiltration Unwanted objects in system Hydraulic overloading Driving or parking over system 4

5 WQRF Supporting Reports Septic Tank/Water Softener Potential Effects of Water Softener Use on Septic Tanks Soil Absorption On-Site Wastewater Systems University of Wisconsin-Madison The Effect of Home Water Softener Waste Regeneration Brines on Individual Aerobic Wastewater Treatment Plants NSF International 5

6 Results from Supporting Studies Water softener waste stimulate biological action in anaerobic or aerobic systems The volume and flow rate of softener wastes do not cause deleterious problems in anaerobic or aerobic systems. Discharge does not interfere with percolation and might improve soil percolation, in fine textured soils. 6

7 Recent Studies Novak et. al, VA Tech found in aerobic activated sludge systems An imbalance in the monovalent to divalent (M/D) cation ratio can lead to poor settling This has not been tested in anaerobic systems. Poor settling and lack of clear zones may be due to excessive sodium (M) in relation to calcium (D) and magnesium (D). 7

8 Estimated M/D Ratios Novak activated sludge research found that M/D ratio >3 lead to poor 4000 Grains/lb ~ Grains/lb ~ Grains/lb ~ 1000 Grains/lb ~ 55(OldTC) 500 Grains/lb ~ 10 (Old TC) 8 8

9 Introduction to WQRF Septic Study Water Quality Association

10 Study Overview Researcher Dr. Novak Funding WQRF Steering Committee WQA, NOWRA, NSF Question How does softener discharge effect the M/D cation ratio and septic system performance? 10

11 Testing Timeline May 2011 Study kick k off July 2011 Began testing Summer 2012 Wrap up testing 2013 WQA Convention Tentative date for final report 11

12 Study Goals Look at ability to separate layers and quality of effluent Look at amount and capture of suspended solids Illustration from 12

13 Study Design Develop column tests to simulate tanks Evaluate stratification and water quality Compare column studies to real world samples 13

14 Column Set up Overlying Grease Layer Input of water with different cation content Overlying Water Water Discharge (below grease layer) Septic Tank Solids Effluent Filter 14

15 Actual Column Set Up 15

16 Study Design Field testing The Aquasource Group Inc. All water is softened, discharge to ST1 only ST3 Apt Group 1 (softened, no regen to ST) Comm Center Apt Group 2 (softened, regen to ST) ST2 ST1 16

17 Naples Creek Senior Housing

18 Effluent Filter Evaluations Comparing effluent filters visually and by weight

19 Settling Evaluations Comparing solids settling in tank One tank receiving softener regen water versus two tanks without t 19

20 NY Site Status Sub-metering has been completed Water management data is collected weekly Sampling and observing tanks bi-monthly Samples are submitted for analysis at local lab and VA Tech D-box had deteriorated (not project related) and project restarted recently 20 20

21 Additional Studies Nancy Deal and Allison Blodig will collect samples for other real world comparisons Batch anaerobic digestion studies Sodium impact on degradation rates Determine quality of the overlying water Evaluate chloride impact on nitrification ifi ti If insufficient information in literature 21

22 Status of Study Water Quality Association

23 Diverted Regen Column Runs First 3 column runs had softened water, but no regenerant added First 2 runs fine tuned the protocol All 3 runs were done with varying levels of hardness ranging from 0 to 26 gpg 23 23

24 Diverted Regen Runs cont d All 3 runs showed higher hardness levels yielded higher M/D ratios Progressively higher M/D ratios showed an effect on COD but no other effects Note that BOD analysis was conducted, but not working 24 24

25 COD vs M/D Ratio No regen 350 COD con ncentration n (mg/l) R² = M/D Ratio 25 25

26 Regenerant Runs Fourth and fifth column runs had softened water and regenerant added Highest M/D ratio experienced is ~10 BOD and TSS were evaluated over 8 wks Stratification and ion concentration at each level were evaluated No differences were found 26 26

27 Latest Run BOD Evaluation 120 CIDWT BOD < 170 mg/l 100 B O D ( m g / L ) Average M/D ratio Control 1 (No 1 Softening) 0.4 Control 2 (No 2 Regen) 5.1 Slight DIR Na Overshot 2.2 Moderate DIR - TC Na Overshot Large Old Na TCOvershot /20 4/25 4/27 5/2 5/9 5/11 5/14 Date 27

28 Latest Run TSS Evaluation 120 CIDWT TSS < 60 mg/l suspended solids concentra ation (mg/l) Average M/D ratio Control 1 (no 1 softening) 0.4 Control 2 (No 2 Regen) 5.1 Slight DIR Na Overshot 2.2 Moderate DIR - TC Na Overshot Large Old Na TCOvershot /2 5/4 5/7 5/9 5/11 5/14 Time (Days) 28

29 Upcoming Studies A confirmation run is planned to begin soon More intensive i investigation of Naples Site as well as other potential sites If time permits digester studies will be conducted, as well 29 29

30 Summary Septic systems have unspecified failures and softeners are being blamed Earlier studies showed softener discharge does not negatively impact bacteria growth, percolation, nor stratification The WQRF study will investigate the effect of M/D ratio on septic tank performance 30

31 Summary (cont d) WQRF study has one set of column data with regen added Need confirmation run and real world data to make comparisons The outcome may shed light on softener discharge impacts on septic tank performance 31

32 Acknowledgements WQRF SORA WQA Steering committee members NOWRA NSF Regulators WQA members 32

33 Thank you! Questions? Water Quality Association