Environmental Impact Study: Water Softener Effects on Septic Tank

Environmental Impact Study:
Water Softener Effects on Septic Tank
Performance
Pauli Undesser
WQA Director of Regulatory and Technical Affairs
Water Quality Association
Overview
• Background information
• Introduction to WQRF study
• Status of the study
2
Background Information
Water Quality Association
History
• Earlyy 70’s – unspecified
p
septic
p failures noted
and softeners being blamed
• Specified
S
ifi d ffailures
il
– Poor maintenance
– Tree root infiltration
– Unwanted objects in system
– Hydraulic overloading
– Driving or parking over system
4
WQRF Supporting Reports
• Septic Tank/Water Softener “Potential
Potential Effects
of Water Softener Use on Septic Tanks Soil
Absorption
p
On-Site Wastewater Systems”
y
– University of Wisconsin-Madison
• “The Effect of Home Water Softener Waste
Regeneration Brines on Individual Aerobic
Wastewater Treatment Plants”
– NSF International
5
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.
systems
g does not interfere with p
percolation
• Discharge
and might improve soil percolation, in fine
textured soils.
6
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
Estimated M/D Ratios
• Novak activated sludge
g research found
that M/D ratio >3 lead to poor settling
– @ 4000 Grains/lb
G i /lb ~ 1.8
1 8 (DIR)
– @ 3000 Grains/lb ~ 2.2 (DIR)
– @ 2000 Grains/lb ~ 3.1
– @ 1000 Grains/lb ~ 5.5
5 5 (Old TC)
– @ 500 Grains/lb ~ 10 (Old TC)
8
8
Introduction to
WQRF Septic Study
Water Quality Association
Study Overview
• Researcher – Dr.
Dr Novak
• Funding
g – WQRF
• Steering Committee – WQA, NOWRA, NSF
• Question – How does softener discharge
effect the M/D cation ratio and septic
system performance?
10
Testing Timeline
• May
M 2011 – Study
St d kick
ki k off
ff
• July 2011 – Began testing
• Summer 2012 – Wrap up testing
• 2013 WQA Convention – Tentative date
for final report
11
Study Goals
Look at ability
to separate
layers
y
and
quality of
effluent
Look at
amount and
capture of
suspended
solids
Illustration from www.genie.com
12
Study Design
• Develop column tests to simulate tanks
• Evaluate stratification and water quality
• Compare column studies to real world samples
13
Column Set up
Overlying
Grease Grease
Layer
Input
of water
with different different
cation content
Septic
Tank Solids
14
Water Discharge
(below grease layer)
Overlying
Water
Effluent Filter
Actual Column Set Up
15
Study Design
• Field testing
– The Aquasource Group Inc.
– All water is softened, discharge to ST1 only
Apt Group 1
(softened, no regen to ST)
ST3
ST2
16
ST1
Comm Center
Apt Group 2
(softened, regen to ST)
Naples Creek Senior Housing
Effluent Filter Evaluations
Comparing
C
i effluent
ffl
t
filters visually and by
weight
Settling Evaluations
Comparing solids
settling in tank
One tank receiving
softener regen water
versus
t
two
tanks
t k without
ith t
19
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
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
E l t chloride
hl id iimpactt on nitrification
it ifi ti
– If insufficient information in literature
21
Status of Study
Water Quality Association
Diverted Regen Column Runs
• First 3 column runs had softened water
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
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
COD vs M/D Ratio – No regen
COD con
ncentration
n (mg/L)
350
300
250
R² = 0.9367
200
150
100
50
0
0.0
1.0
2.0
3.0
4.0
M/D Ratio
25
25
5.0
6.0
7.0
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
Latest Run BOD Evaluation
120
CIDWT BOD < 170 mg/L
g
100
B
O
D
80
(
60
m
g
/
L
Average M/D ratio
Control
1 (No
Control
1 Softening)
0.4
Control
2 (No
Control
2 Regen)
5.1
SlightDIR
Na Overshot2.2
Moderate
Na Overshot
DIR - TC
56
5.6
)
40
Large
OldNa
TCOvershot
10.0
20
0
4/20
27
4/25
4/27
5/2
Date
5/9
5/11
5/14
Latest Run TSS Evaluation
120
CIDWT TSS < 60 mg/L
suspended s
solids concentra
ation (mg/L)
100
80
Average M/D ratio
Control
1 (no
Control
1 softening)
0.4
Control
2 (No
Control
2 Regen)
5.1
60
SlightDIR
Na Overshot2.2
Moderate
Na Overshot
DIR - TC
56
5.6
40
Large
OldNa
TCOvershot
10.0
20
0
5/2
5/4
5/7
5/9
Time (Days)
28
5/11
5/14
Upcoming Studies
• A confirmation run is planned to begin soon
• M
More intensive
i t
i iinvestigation
ti ti off N
Naples
l Sit
Site
as well as other potential sites
• If time permits digester studies will be
conducted as well
conducted,
29
29
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
f
• The WQRF study will investigate the effect of
M/D ratio on septic tank performance
30
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
Acknowledgements
• WQRF
• SORA
• WQA Steering committee members
– NOWRA
– NSF
– Regulators
– WQA members
32
Tha k you!
Thank
o!
Questions?
Water Quality Association