Environmental Protection Technology Series
LONG-TERM EFFECTS OF LAND APPLICATION
OF DOMESTIC WASTEWATER:
Hoilister, California,
Rapid Infiltration Site
Robert S. Kerr Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Ada, Oklahoma 74820
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-084
April 1978
LONG-TERM EFFECTS OF LAND
APPLICATION OF DOMESTIC WASTEWATER
Hollister, California, Rapid Infiltration Site
by
Charles E. Pound
Ronald VI. Crites
James V. Olson
Metcalf & Eddy, Inc.
Palo Alto, California 94303
Contract No. 68-03-2361
Project Officer
William R. Duffer, Ph.D.
Wastewater Management Branch
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
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DISCLAIMER
This report has been reviewed by the Robert S. Kerr Environmental
Research Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency,'nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
11
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FOREWORD
The Environmental Protection Agency was established to coordinate
the administration of major Federal programs designed to protect the
quality of our environment.
An important part of the agency's effort involves the search for
information about environmental problems, management techniques, and new
technologies through which optimum use of the nation's land and water
resources can be assured and the threat pollution poses to the welfare
of the American people can be minimized.
EPA's Office of Research and Development conducts this search
through a nationwide network of research facilities. As one of these
facilities, the Robert S. Kerr Environmental Research Laboratory is
responsible for the management of programs including the development and
demonstration of soil and other natural systems for the treatment and
management of municipal wastewaters.
Although land application of municipal wastewaters has been prac-
ticed for years, there has been a growing and widespread interest in
this practice in recent years. The use of land application received
major impetus with the passage of the 1972 amendments to the Federal
Water Pollution Control Act. The 1977 amendments to the Act gave
further encouragement to the use of land application and provided
certain incentives for the funding of these systems through the con-
struction grants program. With the widespread implementation of land
application systems, there is an urgent need for answers to several
major questions. One of these questions regards the long-term effects
of land application on the soil, crops, groundwater, and other environ-
mental components. This report is one in a series of ten which documents
the effects of long-term wastewater application at selected irrigation
and rapid infiltration study sites. These case studies should provide
new insight into the long-term effects of land application of municipal
wastewaters.
This report contributes to the knowledge which is essential for the
EPA to meet the requirements of environmental laws and enforce pollution
control standards which are reasonable, cost effective, and provide
adequate protection for the American public.
C
o***^
William C. Galegar
Director
Robert S. Kerr Environmental Research Laboratory
iii
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ABSTRACT
The objective of this study was to evaluate the long-term effects of
applying municipal wastewater after primary treatment to the land using the
rapid infiltration technique. This was accomplished by analyzing groundwater
quality and soil chemistry at a site with a long operating history.
Primary municipal effluent has been applied continuously to rapid
infiltration basins at Hollister, California, for more than 30 years. The
current daily flow is 43.8 L/s (1.0 Mgal/d). Annual wastewater application
equals 15.4 m (51 ft) to 20 infiltration basins intermittently flooded for 1
to 2 days every 14 to 21 days, depending on basin size and season of year.
Infiltration rates were determined, subsurface hydrology was logged, and
water table response to wastewater application was monitored. A sampling and
analysis program covering a 1 year period included samples from (1) primary
effluent, (2) onsite and control site soil profiles, and (3) groundwater at
the site and upgradient and downgradient of groundwater movement from the
site.
n nn of the Pr1mary effl uent and groundwater results indicated that
COD, BOD, TOC, nitrogen, and fecal coliform bacteria were effectively reduced
after percolation through 7 m (22 ft) of unsaturated gravelly and sandy loam
soil. Effective phosphorus removal required longer travel distances but the
sorption capacity of the soil has not been exceeded after 30 years of
continuous wastewater application. Trace element retention by the soil was
low; however, only lead exceeded EPA drinking water limits in the wastewater
and shallow groundwater aquifer. Iron and manganese are both being leached
from the soil with the percolating wastewater. Only slight boron removal in
the percolate was observed.
report was submitted in fulfillment of Contract No. 68-03-2361 by
wetcalf & Eddy, Inc., under the sponsorship of the U.S. Environmental
Protection Agency. This report covers the period January 2, 1976, to
September 2, 1977, and work was completed as of December 2, 1977.
iv
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CONTENTS
Foreword [[[ i i 1
Abstract [[[ .
Figures [[[ ......... vil1
Tabl es [[[ *
List of Abbreviations [[[ x111
List of Symbols [[[ xiy
Acknowl edgments [[[ xvi
Section
1 INTRODUCTION [[[ 1
Background [[[ 1
Objective [[[ 2
Specific Goals ................................................ 2
2 CONCLUSIONS [[[ 4
General [[[ 4
Hydrogeology .......................... ........................ 4
Soil Physical Properties .............. ........................ 4
Infiltration Rates ............................................ 5
Soi 1 Chemistry .................... ............................ 5
pH and Cal ci urn Carbonate .................................... 5
Organic Matter .............................................. 5
Nitrogen [[[ 6
Phosphorus .................................................. 6
Boron [[[ 6
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CONTENTS (Continued)
6 METHODOLOGY 22
Site Selection 22
Study PI an 25
Effluent Sampling 27
Groundwater Sampling 27
Soil Sampling and Analytical Procedures 28
7 HYDROGEOLOGIC INVESTIGATION 30
Regional Hydrogeology 30
Observation Wells 33
Site Hydrogeology 37
Water Level Response 41
Shallow Wells 41
Intermediate and Deep Wells 41
Summary and Discussion 45
8 SOIL INVESTIGATION 46
Introduction 46
Physical Properties 47
Particle Size 47
Surface Area 49
Bulk Density 50
Infiltration Studies 51
Soil Chemistry 55
Introduction 55
Statistical Analysis of Soil Data 58
pH and Calcium Carbonate 62
Conductivity of the Saturated Extract 64
Organic Matter 65
Nitrogen 66
Phosphorus 68
Boron 75
CEC and Exchangeable Cations 76
Heavy Metals 82
Agricultural Potential of Soils Treated with Heavy Metals... 87
9 GROUNDWATER QUALITY INVESTIGATION 90
Introduction 90
Statistical Analysis of Groundwater Data 90
COD, BOD, and TOC 92
Residual Organics (Carbon Chloroform Extract) 94
Nitrogen 94
Phosphorus 96
Fecal Coliform and Total Coliform Bacteria 97
Dissolved Solids TOO
Total Dissolved Solids and Electrical Conductivity 100
Exchangeable Cations and Sodium Adsorption Ratio 100
Major Anions 101
Suspended Solids 102
vi
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CONTENTS (Concluded)
Al kal inity 102
Boron 103
Fl uori de 103
Trace Elements 104
REFERENCES 108
APPENDIX A 116
APPENDIX B 117
APPENDIX C 139
vii
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FIGURES
Number Page
1 Location of study site Hollister, California 11
2 Hollister rapid infiltration system facilities 12
3 Observation well locations at the Hollister
rapid infiltration site 15
4 Proposed soil sampling grid locations at the
Hollister rapid infiltration site 26
5 Relation of groundwater subbasins and
subunits to geologic features 31
6 Hydrogeology of Hollister rapid infiltration site 32
7 Observation well sites 34
8 Typical observation well construction and drilling rig 36
9 North-south geologic section 38
10 East-west geologic section 39
11 Water levels in intermediate and deep
observation wells on four selected days 40
12 Conti nuous water 1 eve! recorders 42
13 Water level response to basin flooding
in observation welIs 5A and 3A 43
14 Water level response of intermediate and deep wells 44
15 Physico-chemical properties of soils
as related to textural classification 47
16 Cylinder infiltrometers 53
17 Vertical distribution of soil pH 63
18 Vertical distribution of soil calcium carbonate 63
19 Vertical distribution of saturated paste, soil conductivity 65
20 Vertical distribution of soil organic matter , 66
21 Vertical distribution of soil total-nitrogen 67
22 Vertical distribution of soil organic-nitrogen ... 67
23 Vertical distribution of soil total phosphorus 69
viii
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FIGURES (Concluded)
Number Page
24 Vertical distribution of soil bicarbonate
extractabl e phosphorus 69
25 Logarithmic plot of Freundlich regression equation
to the experimental data for sorbed phosphorus as
a function of time and equilibrium concentration.
Control site composite, 0-16 cm depth 71
26 Logarithmic plot of Freundlich regression equation
to the experimental data for sorbed phosphorus as
a function of time and equilibrium concentration.
Treatment site composite, 0-16 cm depth 71
27 Dynamically predicted values versus equilibrium
observed values of sorption rates (3S/3t). Model 1 74
28 Dynamically predicted values versus equilibrium
observed values of sorption rates (as/3t). Model 2 74
29 Dynamically predicted values versus equilibrium
observed values of log sorption rates (3S/at). Model 3 74
30 Vertical distribution of soil boron 76
31 Vertical distribution of cation exchange capacity 79
32 Vertical distribution of exchangeable sodium 79
33 Vertical distribution of exchangeable potassium 79
34 Vertical distribution of exchangeable magnesium 79
35 Vertical distribution of exchangeable calcium 79
36 Vertical distribution of DTPA-extractable iron 83
37 Vertical distribution of DTPA-extractable manganese 83
38 Vertical distribution of DTPA-extractable cobalt 85
39 Vertical distribution of DTPA-extractable nickel 85
40 Vertical distribution of DTPA-extractable cadmium 85
41 Vertical distribution of DTPA-extractable zinc 85
42 Vertical distribution of DTPA-extractable copper 86
43 Vertical distribution of DTPA-extractable lead 86
ix
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TABLES
Number Page
1 Operating Factors, Hollister Rapid Infiltration System 10
2 Historical Climatic Data, Hollister, California 17
3 Climatic Data During Study Period, Hollister, California 18
4 City of Hollister Water Supply Quality 19
5 City of Hollister Effluent Wastewater Quality 20
6 Wastewater Consti tuent Loadi ng Rates 21
7 List of Candidate Rapid Infiltration Sites
in California, October 1975... 23
8 Initial Site Screening Criteria 24
9 Summary of Design and Operating Information
on Six Candidate Sites 24
10 Summary of Sampling Program 25
11 Soil Constituents and Analytical Procedures 29
12 Observation Wei 1 Construct! on Data 37
13 Particle Size Distribution in Soil Sample From
the Hollister Rapid Infiltration Site 48
14 Surface Area Per Unit Soil Mass 49
o
15 Estimated Surface Area Distribution (cm )
For A 100 g Sampl e of Soi 1 50
16 Soil Bulk Density Measurements (g/cm ) and
Calculated Soil Porosities 51
17 Basin Flooding Infiltration Rates 52
18 Cylinder Infiltrometer Infiltration Rates 54
19 Results of Soil Chemical Analyses 56
20 Analysis of Variance For Selected Soil Parameters 61
21 Sample Output For Statistical Analysis of
Soi 1 Data 62
22 Calculated Freundlich Coefficients From
Phosphorus Sorption Isotherms 70
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TABLES (Continued)
Number Page
23 Evaluation of Three Dynamic Phosphorus Sorption Models 73
24 Measured and Calculated Exchange Ratios For
Soils at the Hollister Rapid Infiltration Site 80
25 Exchangeable Mg/Ca Ratio 81
26 Comparison of Soil Microelement Content After
Long-Term Sludge and Wastewater Application 88
27 Comparison of Soil DTPA-Extractable Heavy Metal
Wi th Heavy Metal Contents of Sel ected Crops 88
28 Average Effluent and Groundwater Quality
Resul ts 91
29 Sampl e Output From SPSS Oneway 93
30 Comparison of Trace Element Levels to
Irrigation and Drinking Water Limits 105
A-l Wastewater Quality Results 116
B-l pH. 117
B-2 Calcium Carbonate 118
B-3 Electrical Conductivity Soil Extract 119
B-4 Organic Matter 120
B-5 Total Nitrogen 121
B-6 Organic Nitrogen 122
B-7 Total Phosphorus 123
B-8 Bicarbonate Extractable Phosphorus 124
B-9 Boron 125
B-10 Cation Exchange Capacity 126
B-ll Exchangeable Sodium 127
B-12 Exchangeable Potassium 128
B-l3 Exchangeable Magnesium 129
B-l4 Exchangeable Calcium 130
B-l 5 DTPA-Iron 131
B-l 6 DTPA-Manganese 132
B-l 7 DTPA-Ni ckel 133
B-18 DTPA-Cobalt 134
B-l 9 DTPA-Zi nc 135
B- 20 DTPA-Cadmi urn 136
xi
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TABLES (Concluded)
Number Page
B-21 DTPA-Copper ] 37
B-22 DTPA-Lead 138
C-l Well 3A Groundwater Quality Results 139
C-2 Well 5A Groundwater Quality Results 140
C-3 Well IB Groundwater Quality Results 141
C-4 Well 3B Groundwater Quality Results 142
C-5 Well 1C Groundwater Quality Results 143
C-6 Well 2C Groundwater Quality Results 144
C-7 Well 4C Groundwater Quality Results 145
C-8 Well 6C Groundwater Quality Results 146
C-9 Well 7C Groundwater Quality Results 147
C-10 Well 8C Groundwater Quality Results 148
C-ll Well 9C Groundwater Quality Results 149
xi 1
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LIST OF ABBREVIATIONS
Special
ABS Alkylbenzenesulfonate
ANOVA Analysis of variance
BMDP2V Computer program designation
to generate two-way analysis
of variance
BOD Biochemical oxygen demand
CCE Carbon chloriform extract
CEC Cation exchange capacity
COD Chemical oxygen demand
DTPA Diethylenetriamine pentacetic
acid
EC Electrical conductivity
E. Coli Escherichia coli
EPA Environmental Protection Agency
EPR Exchangeable potassium ratio
ESR Exchangeable sodium ratio
JTU Jackson turbidity units
LAS Linear alkyl benzene sulfanate
M Molarity
N Normality
Nm Not measurable
PAR Potassium adsorption ratio
PVC Polyvinylchloride
SAR Sodium adsorption ratio
SPSS Statistical package for the
social sciences
SS Suspended solids
IDS Total dissolved solids
TEA Triethanolamine
TKN Total Kjeldahl nitrogen
TOC Total organic carbon
USPHS United States Public Health
Service
Quanti ty
kg/ha Kilogram per hectare
Ib/acre Pound per acre
mg/kg Milligram per kilogram
meq/100 g Mi 111 equivalents per
100 grams
meq/L MilHequlvalents per litre
yg/g Micrograms per gram
pmhos/cm Mlcromhos per centimeter
ppm Parts per million
g/cm grams per cubic centimeter
X111.
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LIST OF SYMBOLS
%p
3s/3t
2.5 Y 5/2
B,m,a,b,d
A
Ap, Al
Cl, C2
Miscellaneous
Degrees Celsius
Soil particle density
True mean of a subscripted
soil variable
Level of significance attached
to statistical test; the proba-
bility of rejecting a true
hypothesis; also a multiple
regression constant
Percent
Percent pore volume
Partial differential of sorbed
phosphorus with respect to time
Soil Conservation Service (SCS)
soil color symbol
Multiple regression constants
Soil surface area (Eq. 1); also
shallow well designation
Soil morphogenic master horizon
designations
Chemical activity of solution
ions
(Ax), (Bx) Exchanger concentrations
B Intermediate well
C Deep well
C:N Carbon to nitrogen ratio
D1'D2'D3'D4 Depth Increments 1 through 4
Soil bulk density
Oxidation-reduction potential
Variance ratio
Selectivity coefficient
ub
Eh
k,n
N
P
r
S
t
Mathematical
± Plus or minus
> Greater than
< Less than
1:1 1 to 1 ratio
Constants related to energy of
sorption (Eq. 4); also multiple
regression constants
Hypothesis
Mass of soil
Probability level relative to
predetermined "a" value; also
phosphorus
Soil particle radius
Correlation coefficient squared
Sorbed phosphorus
Statistic for testing difference
between means
Control site statistical treat-
ments
Application site statistical
treatment
Observation
xiv
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LIST OF SYMBOLS (Continued)
Elements
Ag
As
B
Ba
Ca
Cl
Cd
Co
Cr
Cu
F
Fe
H
Silver
Arsenic
Boron
Barium
Calcium
Chlorine
Cadmium
Cobalt
Chromium
Copper
Fluorine
Iron
Hydrogen
Hg
K
Mg
Mn
N
Na
Ni
P
Pb
Se
Zn
Mercury
Potassium
Magnesium
Manganese
Nitrogen
Sodium
Nickel
Phosphorus
Lead
Selenium
Zinc
CaC03
CaF2
CaN03
Ca5(P04)3F
H20
HCL
H3B03
HCL04
K2Cr207
MgHC03
Mn02
NaC03
NaHC03
NH3-N
NH4OAc
N02-N
N03-N
PO,
so,
-3
I
-2
Compounds
Calcium carbonate
Calcium fluoride
Calcium nitrate
Fluorapatite
Water
Hydrochloric acid
Boric acid
Perchloric acid
Potassium dichromate
Magnesium bicarbonate
Manganese dioxide
Sodium carbonate
Sodium bicarbonate
Ammonia-Nitrogen
Ammonium ion
Ammonium acetate
Nitrogen gas
Nitrous oxide
Nitrite nitrogen
Nitrate nitrogen
Oxygen gas
Phosphate
Sulfate
XV
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ACKNOWLEDGMENTS
The authors wish to thank the many individuals and agencies whose
assistance was essential to the success of this project. The support of Mr.
Roger Grimsley, City Engineer, and Mr. Ray Petregon, Treatment Plant
Operator, City of Hoi lister, is gratefully acknowledged.
Interpretation and statistical analysis of soil chemistry results were
performed by Mr. Paul E. Levine, Soil Scientist, Metcalf & Eddy, Inc., and
Professor Richard Burau, Department of Land, Air and Water Resources, Soil
Section, University of California, Davis. Supervision of observation well
construction and interpretation of hydrogeologic data were performed by the
Metcalf & Eddy, Inc., Geotechnical Department in Boston, Massachusetts.
Laboratory analysis of effluent, groundwater, and soil samples was performed
by the Metcalf & Eddy, Inc., Water Chemistry Laboratory in Palo Alto,
California, under the direction of Dr. Charles D. Siebenthal, Director of
Laboratory Services, and Mr. Paul E. Levine (soil testing). Richard D.
Shedden, Environmental Engineer, aided in the infiltration studies and
sampling program.
The authors wish to express appreciation to the Robert S. Kerr
Environmental Research Laboratory for its support of this project, and
especially to Dr. William R. Duffer, Project Officer, for his guidance
throughout the course of the study.
Special thanks are also due to Mrs. June B. Miller for her very capable
job of editing this report.
xvi
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SECTION 1
INTRODUCTION
BACKGROUND
Land treatment processes for renovating wastewater have been
demonstrated successfully on many occasions in the past, and in the last 40
years the number of land treatment facilities has increased steadily in the
United States [1, 2]. Land treatment has demonstrated equal or superior
pollutant removal when compared to conventional treatment and, in many cases,
beneficial water reuse is an integral part of the process. In the future, as
construction costs increase and water resources become more scarce, land
treatment will become even more competitive as a wastewater management
alternative.
Land treatment of municipal wastewater encompasses a wide variety of
processes or methods. The three principal processes, are:
1. SIow rate
2. Rapid infiltration
3. Overland flow
The major concepts involved in these processes are defined herein.
The term slow rate land treatment is used to focus attention on
wastewater treatment rather than on irrigation of crops. However, in slow
rate systems, vegetation is a critical component for managing water and
nutrients. The applied wastewater is treated as it flows through the soil
matrix, and a portion of the flow percolates to the groundwater. Surface
runoff of the applied water is generally not allowed.
In rapid infiltration land treatment (referred to in previous U.S.
Environmental Protection Agency (EPA) reports as infiltration-percolation),
most of the applied wastewater percolates through the soil, and the treated
effluent eventually reaches the groundwater. The wastewater is applied to
rapidly permeable soils, such as sands and loamy sands, by spreading in
basins or by sprinkling, and is treated as it travels through the soil
matrix. Vegetation is not usually used, but there are some exceptions. In
many cases, recovery of renovated water is an integral part of the system.
This can be accomplished using underdrains or wells.
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In overland flow land treatment, wastewater is applied over the upper
reaches of sloped terraces and allowed to flow across the vegetated surface
to runoff collection ditches. The wastewater is renovated by physical,
chemical, and biological means as it flows in a thin film down the relatively
impermeable slope.
With the relatively large number of successful land treatment systems
currently in operation, a wealth of monitoring data should be available.
Most of the existing land treatment systems, however, are inadequately
monitored. As a result, there is concern about limitations on the operating
life of land treatment systems. Specific questions regarding (1) the level
of preappl ication treatment necessary; (2) the movement of persistent
organics, nitrates, and trace elements into groundwaters; (3) accumulations
of salt or toxic materials in soils; or (4) translocation of potentially
toxic trace elements from the soil into crops remain to be answered. Answers
to these and other related questions will assure that sound design criteria
can be established and that land treatment systems can be implemented without
risk to public health.
The EPA and others have recently funded research on the environmental
effects of different land application techniques in pilot and experimental
studies; however, operating land treatment systems with substantial longevity
have not been studied or monitored extensively. Complete case studies of the
effects of groundwater quality and movement in a number of these systems
should provide some answers to the concerns that were mentioned. This report
presents the findings of a research study at a 3U-year old land treatment
system at Hollister, California, where primary municipal effluent is applied
to rapid infiltration basins.
OBJECTIVE
The objective of this study was to evaluate the long-term effects on
groundwater quality and soil chemistry at a site with a long operating
history of applying primary municipal effluent to the land using the rapid
infiltration technique. The long-term effects were determined by comparing
groundwater quality and soil chemistry data at this site with data from a
nearby control site having similar physical characteristics and management
except that wastewater has never been applied.
SPECIFIC GOALS
To accomplish the overall objective, the following specific goals were
selected:
1. Determine the nature of the site hydrogeology for the purpose of
relating subsurface conditions to the efficiency of the soil matrix
in removing constituents from the applied primary effluent and,
subsequently, the danger of contaminating native groundwater
aquifers.
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2. Determine the current treatment efficiency of the soil matrix by
comparing the quality of the applied primary effluent with the
groundwater at the site.
3. Determine the long-term ability of the soil matrix to treat
wastewater by calculating the mass of selected constituents
retained in the soil profile applied over the 30 year operating
life.
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SECTION 2
CONCLUSIONS
GENERAL
Effective long-term treatment capability has been demonstrated at a
rapid infiltration site where unchlorinated primary effluent from the City of
Hoi lister, California, has been managed successfully for 30 years. Thus, a
fully managed groundwater recharge system for renovating primary municipal
effluent by surface spreading at high rates should provide excellent
treatment for a long period of time.
HYDROGEOLOGY
1. The subsurface hydrology at the rapid infiltration site consists of a
complex network of water-bearing and impermeable material deposited as
stream sediments. Beneath the site there are probably three water-
bearing zonesshallow, less than 12.7 m (42 ft); intermediate, between
15 m to 25 m (45 to 75 ft); and deep, greater than 55 m (165 ft)--each
separated by semi continuous to continuous clay and silt layers.
2. The infiltrating effluent apparently forms a mound caused by perching of
the effluent on top of the clay layer that underlies the shallow
permeable zone. When infiltration ceases, the mound subsides mainly by
lateral outflow from the site.
3. The intermediate wells showed no response to effluent application to the
infiltration basins. However, some vertical leakage may be occurring,
especially where the clay and silt between the shallow and intermediate
zones is the thinnest. This conclusion is based on a comparison of
concentrations of some mobile ions in the shallow and intermediate
groundwater.
4. The deep observation wells did not show any response to effluent
application. The lower permeable zone is overlain by an average of 26 m
(85 ft) of clay and silt that is probably continuous beneath the
treatment site and is an effective barrier to vertical groundwater
movement.
SOIL PHYSICAL PROPERTIES
1. The most appropriate soil mapping terms for the alluvial deposits at the
site appear to be gravelly sand or gravelly sandy loam.
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2. There were insufficient bulk density measurements to determine if
conclusive differences existed between control ana treatment sites or
among depth increments. Measurements taken ranged from 1.27 to 1.72
g/ciTH. Lower than average bulk densities of the near surface
measurements at the treatment sites were probably the result of disking
operations.
INFILTRATION RATES
1. The maximum long-term infiltration rate obtainable, based on wastewater
intake rates monitored over the study period, was 64.6 m/yr (212 ft/yr).
2. Initial wastewater intake was slowed by clogging of soil pores at the
surface from wastewater solids applied during the flooding cycle.
However, the initial water intake rate was restored by surface disking
between each wastewater application. No significant decrease in soil
profile infiltration capacity was indicated after 30 years of wastewater
application. This conclusion is based on the results of cylinder
infiltrometer tests at an actual treatment site location and a similar
offsite location where wastewater has never been applied.
3. The water intake capacity of the treatment site soils did not, on the
average, limit the amount of wastewater that could be applied as measured
by the time it took for complete infiltration of the applied effluent.
However, reflcoding a basin without prior surface disking caused a
greater degree of soil pore clogging and a subsequent lower infiltration
rate.
4. Final infiltration rates measured by cylinder infiltrometers were
generally consistent, but overestimated by a factor of 16, the rates
obtained by flooding an entire basin. No significant difference between
buffered and unbuffered cylinder infiltrometer infiltration rates was
observed. The clogging effect of wastewater solids was not observed
during cylinder infiltrometer tests comparing primary effluent (SS = 275
mg/L) and clear tap water.
SOIL CHEMISTRY
pH and Calcium Carbonate
The addition of wastewater to the treatment site significantly decreased
the soil pH at all depth increments through 3UO cm (10 ft). Simultaneous
calcium carbonate depletion from the site reduced the buffering capacity of
the soil permitting a pH reduction. Surface soil pH was less than applied
wastewater pH, suggesting nitrification as an additional mechanism for pH
reduction.
Organic Matter
Only a slight buildup of organic matter was observed as a result of
wastewater application, thus suggesting that the soil microbial population
existed in sufficient numbers to bio-oxidize most of the incoming organic
matter.
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Nitrogen
Significant concentration increases resulting from wastewater treatment
were observed for the nitrogen species measured (total and organic nitrogen)
to a depth of 100 cm (39 in.). The greatest accumulation of nitrogen was
found at the surface. Only 2% of the total nitrogen applied over 30 years
was accounted for in the soil profile. This suggests the conversion of
nitrogen to mobile forms and movement from the soil profile either to the
atmosphere or the groundwater. Groundwater quality results indicate that 93%
of the total nitrogen in the applied wastewater was removed from solution.
Phosphorus
The fact that extractable phosphorus was so much higher at all sampling
depths in the treatment site suggests that availability for plant uptake was
high and that soil solution phosphorus may have passed through the soil
profile. Soil mass balance calculations further suggest significant
transport of phosphorus to the underlying groundwater.
Laboratory phosphorus isotherm studies revealed that after 30 years of
wastewater application, the soil profile at 0 to 16 cm (0 to 6 in.) is
retaining 68% of its experimentally determined sorption capacity. Existing
phosphorus sorption models were shown to underestimate the actual 30 year
phosphorus sorption capacity by factors of 4 to 15 based on measured
phosphorus in Hoi lister treatment site soils.
Boron
Boron was observed to increase fourfold in treatment site soils with the
most extensive accumulation near the surface.
CEC and Exchangeable Cations
1. Wastewater application caused a significant increase in CEC with respect
to depth and treatment in spite of the pH decrease which simultaneously
occurred. It is therefore presumed that the resulting loss of any pH
dependent charge was more than offset by the influx of organic matter
and mineral clays in the wastewater.
2. The data indicate that more exchangeable sodium is present than can be
predicted by the calculated ESR (exchangeable sodium ratio). One
explanation is concentration of sodium on the surface by evaporation
before transport through the soil profile. An alternative explanation
is that magnesium and calcium are ion-paired, complexed, or chelated to
a much greater extent than sodium. The result is a low SAR (sodium
adsorption ratio) value and therefore the calculated ESR underestimates
the exchange phase sodium.
3. High ESR values throughout the treatment site profile have not caused
any apparent decrease in infiltration capacity.
-------
4. The data indicate that magnesium was selectively replacing calcium in
the surface 100 cm (39 in.) of the soil. The newly mobilized calcium
traveled downward and then appeared to exchange with magnesium at 3UU cm
(10 ft).
Heavy Metals
1. The increase in extractable iron throughout the soil profile may result
from its accumulation by wastewater addition, or from its increased
extractability as a result of alternating periods of wetness and
dryness. There is no doubt, however, that iron was moving through the
soil profile.
2. In contrast to iron, manganese was leached by the wastewater from the
surface 30 cm (1 ft) with some redeposition at depth.
3. Nickel and cobalt did not accumulate at the surface 30 cm (1 ft) where
manganese was lost. However, extractable cobalt was six times higher in
treatment sites at 300 cm (10 ft) than in control sites at the same
depth. Similarly, extractable nickel values doubled at the 100 cm (39
in.) depth.
4. Wastewater application caused extractable cadmium to increase
significantly at 30 cm (1 ft).
5. The increase in extractable zinc to the 300 cm (10 ft) depth suggests
that some wastewater applied zinc has passed down to and perhaps through
this depth. The apparently higher mobility of zinc, as compared to
chemically similar cadmium, may be related to its higher input
concentration in the wastewater.
6. Significant extractable copper showed a pronounced accumulation in the
soil profile at 0 to 16 cm (0 to 6 in.).
7. The levels of soil DTPA-extractable metals will not adversely affect the
future agricultural potential of the Hollister rapid infiltration site.
GROUNDWATER QUALITY
1. On the basis of existing quality criteria for groundwater, there was no
evidence that toxic trace elements or potentially pathogenic bacteria
associated with municipal wastewater were entering the regional
groundwater supply, at harmful levels, as a result of wastewater
application to the land at Hollister, California.
2. Analysis of the wastewater and groundwater results indicates that the
soil filtration process has effectively reduced the COD, BOD, TOC, and
fecal coliform bacteria. After 30 years of continuous wastewater
application, COD, BOD, TOC, and fecal coliforms are reduced by 93, 96,
96, and 99%, respectively, after percolation through 7 m (22 ft) of
unsaturated gravelly and sandy loam soil.
-------
3. Almost complete nitrification and denitrification of the renovated
wastewater was indicated by the results after percolation to the shallow
groundwater. The favorable carbon to nitrogen ratio of 6:1 apparently
supplies sufficient energy to sustain denitrifying bacteria. No
significant nitrogen increase from land applied wastewater was observed
in the intermediate or deep observation wells.
4. Effective phosphorus removal required longer travel distances. Shallow
groundwater phosphorus concentrations indicated that 22 to 35% of the
wastewater phosphorus is currently being removed after 3U years of
wastewater application. This agreed closely with the accumulated mass
of phosphorus found in the treatment site and soil profile over the 3U
year operating history.
b. Trace element concentrations in the shallow groundwater were generally
the same as the applied effluent indicating little removal. However,
levels of all toxic trace elements, except lead, were below EPA drinking
water standards in the wastewater and shallow groundwater. Wastewater
lead concentrations were greater than drinking water limits, but were
less than concentrations in shallow observation wells. The indication
is that lead is being leached from the soil with the percolating
wastewater.
6. Manganese concentrations in the shallow groundwater were greater than
wastewater manganese concentrations. Manganese is being leached from
the soil with the percolating wastewater.
7. Comparison of wastewater and shallow groundwater iron concentrations
strongly suggested that applied iron is highly mobile and moving through
the soil profile.
8. Only slight boron removal (14%) was observed after percolation to the
shallow groundwater.
9. Fluoride concentrations increased slightly in the shallow groundwater
over the applied effluent.
-------
SECTION 3
RECOMMENDATIONS
1. The operating history, system operation, grounawater hydrology, and
pollutant removals determined in this study can be used in part to
design a rapid infiltration system that will not impair land resources
or groundwater resources.
2. Primary treatment should be considered adequate and preferred to
secondary level pretreatment for control of nitrogen. The carbon to
nitrogen ratio of primary effluent favored complete denitrification and
did not inhibit COD and BOD removal after relatively short underground
travel distance.
3. A study should be undertaken to determine the soil depth that is
necessary to achieve satisfactory wastewater treatment when primary
effluent is applied at moderate rates.
4. Monitoring of the Hoi lister rapid infiltration system should be expanded
to further define the preferred pathway of subsurface flow from the
site. This would provide the means to determine the underground travel
distance necessary to achieve a higher degree of treatment than
determined herein. Special emphasis should be given to phosphorus and
fecal coliform removals.
5. The greatest void of information remaining with respect to land
treatment systems is that of persistent or refractory organic compounds.
Uncertainties regarding health effects from transport of these materials
through the soil from land applied wastewater must be answered before
essential design criteria can be established. Quantification of basic
scientific data on organic substances of known or suspected toxicity and
determination of safe underground travel distances are major areas where
research is needed.
-------
- SECTION 4
PROJECT DESCRIPTION
Hoi lister is located in the San Juan Valley 35 km (22 miles) inland from
Monterey Bay, 144 km (90 miles) south of San Francisco (Figure 1).
Currently, the population served by sewers in and around Hoi lister is about
10,000. The rapid infiltration site is about 1.6 km (1 mile) west of the
city, 150 m (500 ft) south of the San Benito River bed. A summary of
important operating information for the Hoi lister wastewater management
system is shown in Table 1.
Table 1. OPERATING FACTORS,
HOLLISTER RAPID INFILTRATION SYSTEM
Preapplication treatment Primary
Groundwater level3, m 5.8-9.2
Infiltration area, ha 8.8
Total basins 20
Annual wastewater application, m/yr 15.4
Average daily flow, L/s 43.8
Length of operation, yr 30
Industrial influence Yes
a. Shallow water table created by infiltrating effluent.
b. Slaughterhouse * 0.9 L/s and paper recycler = 11.0 L/s,
about 27% of total flow.
m x 3.281 = ft
ha x 2.471 = acre
L/s x 0.0228 = Hgal/d
The facilities at the Hoi lister rapid infiltration site are shown in
Figure 2. Preapplication treatment consists of primary clarification of the
untreated influent wastewater. Sludge from the clarifier is regularly drawn
off and stored in a converted Imhoff tank before being applied to sludge
drying beds independent of the rapid infiltration area.
A portion of influent wastewater flow is equalized in an excavated
earthen reservoir before entering the head works and clarifier. Wastewater
is pumped from the equalizing reservoir each day when the flowrate is lowest
at 2 a.m.
10
-------
o
\
(
STOCKTON
SAN FRANCISCO
SANTA CLARA COUNTY
SANTA CRUZ COUNTY
SANTA CRUZ */
STUDY SITE
LOCATION
PACIFIC
OCEAN
SALINAS
IONTEREY COUNTY
HOLLISTER
SAN BEN I TO COUNTY \
Figure 1. Location of study site Hollister, California.
11
-------
Figure 2. Facilities plan of Hollister rapid infiltration system.
12
-------
The clarified effluent flows by gravity to the effluent treatment area,
which consists of 20 individually controlled infiltration basins. Basins are
controlled by a combination of alfalfa valves and manually prepared ditches.
One additional basin is kept in reserve for overflow effluent caused by
sporadic hydraulic overloading in the gravity distribution system.
The total basin area is 8.8 ha (21.7 acres) and the individual basins
range from 0.3 to 0.7 ha (0.6 to 1.8 acres). Normally, wastewater is applied
to a depth of 30 cm (12 in.), whereas time of application is controlled by
the area of the basin. Two basins are flooded simultaneously if the daily
flow exceeds the capacity of any individual basin. This situation occurs in
the smaller basins (<0.37 ha, <0.9 acres) during the wet winter months.
The interval between wastewater applications ranged from 14 to 21 days
during the study period. The length of time a basin was flooded and the
interval between applications decreased in the cooler and wet winter months
by 25 to 30%.
The initial effluent intake rate was much higher than the final intake
rate, because clogging of the soil surface by effluent solids reduced the
rate at which water entered the soil. The effluent was completely contained
within the basin it was applied to, leaving the site only as subsurface flow.
The average effluent intake rate was 10 cm/d (4 in./d) when basins are
flooded to a depth of 30 cm (12 in.).
Geologically, the site is located on alluvial deposits of the San Benito
River. The surface soil from which the basins are constructed is
characterized as Metz sandy loam [3]. According to the Soil Conservation
Service (SCS), soil permeability for Metz sandy loam ranges from 6.4 to 12.8
cm/h (2.5 to 5.0 in./h) in the upper 3 m (10 ft), and 12.8 to 25.4 cm/h (5.0
to 10.0 in./h) through the next 7.5 m (25 ft) [3].
The water table of the regional groundwater aquifer occurs at 20 m (65
ft) at the site. Eight observation wells were constructed to monitor
groundwater quality at the Hoi lister rapid infiltration site. The depth of
each well from the local ground surface is as follows:
Well Depth, m (ft)
1A 6 (20)
IB 24 (80)
1C 48 (160)
2A 54 (180)
3A 7.6 (25)
3B 21 (70)
4B 18.3 (61)
5A 10.5 (35)
13
-------
The wells are 5 cm (2 in.) in diameter constructed from PVC pipe
with a 0.6 m (2 ft) length of PVC well screen at the installed depth.
Existing offsite production wells were also monitored. Well 4C (City of
Hoi lister) serves as an upgradient control well with perforations beginning
at 56 m (185 ft). Four production wells (6C, 7C, 8C, and 9C) serve as
control wells downgradient of groundwater flow from the site. Observation
well locations are shown in Figure 3.
14
-------
EXISTING
OFFSITE WELLS
8C
LEGEND
A - SHALLOW WELLS
3-1D m (10-35 ft)
B - INTERMEDIATE WELLS
20-24 m (65-80 ft)
C - DEEP WELLS
> 48 m (> 160 ft)
RAPID
INFILTRATION
BASINS
METRES
Figure 3. Observation well locations at the Hollister rapid infiltration site.
-------
SECTION 5
RAPID INFILTRATION SYSTEM OPERATION
SYSTEM HISTORY
Wastewater was first applied to the site in 1922, when an outfall sewer
was constructed to convey the untreated wastewater away from the city. At
that time the site was in pasture, and the wastewater was allowed to flood
the general area in a more or less uncontrolled manner. During the 1920s,
1930s, and 1940s, 10 acres of walnuts were irrigated with a portion of the
wastewater until the orchards were abandoned. The wastewater could be
diverted from the pasture area easily and was used mainly because it was more
convenient than pumping from the native groundwater. Wastewater irrigation
of nursery stock was practiced successfully at the site from 1935 to 1946.
The practice was abandoned when the new infiltration basins were constructed.
In 1927, an Imhoff tank was constructed to remove settleable solids from
the wastewater before it was applied to the land. In about 1946, Basins 1
through 13 (north basins) covering 4.9 ha (12.2 acres) were constructed as
shown previously in Figure 2. Intermittent application of wastewater to the
infiltration basins was initiated at this time. No recovery or reuse of the
percolated effluent has ever been attempted.
In 1962, as a result of increased wastewater flow, a gravity clarifier
was constructed to increase solids removal before applying the effluent to
the infiltration basins. At that time, the original Imhoff tank was
converted to an unheated sludge digester by removing the interior partitions.
Seven additional basins (14 through 20) covering 4.0 ha (9.9 acres) were
constructed in the late 1960s when hydraulic loading began to exceed the
capacity of the original basins (see Figure 2).
In 1973, an equalizing reservoir was excavated to accept peak wastewater
flows before entering the clarifier. Even with the equalization reservoir,
however, hydraulic capacity of the clarifier was exceeded, resulting in high
concentrations of unsettled solids being applied to the basins. Construction
of the reservoir removed about 0.4 ha (1.0 acre) of infiltration basins from
service; however, Basins 14 through 20 were simultaneously expanded. The
total infiltration basin area including an overflow area is currently 9.1 ha
(22.6 acres). The net area used for infiltration is currently 8.8 ha (21.7
acres).
A slaughterhouse and a corrugated paper recycler were the only
significant industrial waste sources. The slaughterhouse waste had a high
BOD while the recycle operation added a significant solids load. The total
16
-------
flow from both sources of 0.9 L/s (0.02 Mgal/d) and 11.0 L/s (0.25 Mgal/d),
respectively, amounted to about 27% of the total flow.
CLIMATE
The climate in the Hollister area is marked by warm dry summers and cool
rainy winters, which is characteristic of the Central Coastal Region of
California. Although Hollister is separated from the Pacific Ocean by
coastal mountains, temperatures are moderated by the ocean influence. The
wet season is normally mid-November through mid-April. On the average,
little or no precipitation occurs from May through August. July is the month
with the highest average maximum temperature, while peak precipitation
usually occurs in January. The annual evaporation exceeds precipitation in
the Hollister area by several times; but the exact ratio will vary depending
on annual temperature, precipitation, and wind. Mean temperatures,
precipitation, and evaporation are compared to those for the 1962-1963
reporting period (only complete data available) in Table 2 [4]. The mean
annual "net evaporation" is approximately 150 cm (59 in.) according to one
report [5]. The net evaporation for 1962-1963 was 98 crn (39 in.) in which
below average temperatures but above average precipitation occurred. The
mean annual net evaporation is approximately 6% of the current annual
wastewater applied to the infiltration basins.
TABLE 2. HISTORICAL CLIMATIC DATA, HOLLISTER, CALIFORNIA
Month
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Annual
Mean
Avg temperature,
ar-tt
Temperature, Precipitation, Evaporatic
°C [6]b cm [6] cm [5]
20.0
19.5
20.0
17.0
13.0
10.0
9.5
11.0
13.0
14.5
16.5
18.5
15.0
0.03
0.05
0.46
1.24
3.30
6.78
6.53
6.30
4.75
2.87
0.89
0.20
33.40
27.56
25.98
20.57
14.96
8.38
3.81
2.36
4.98
9.45
16.00
23.62
25.91
183.59
in ,
Maximum
25.5
28.5
25.5
24.5
21.0
18.0
15.5
20.0
18.5
18.0
20.5
23.5
21.5
Minimum
8.0
9.0
8.0
6.0
3.5
1.0
-1.5
8.5
3.5
5.5
9.0
9.0
5.5
1962-1963 water year [4]b
recipitation, Evaporation,
cm cm
0
Trace
Trace
1.83
0.64
4.52
9.88
7.39
5.36
6.91
0.99
0.25
37.77
22.96
20.68
13.00
9.07
8.00
5.74
4.39
6.27
8.48
7.65
13.06
16.71
136.02
a. Temperatures reported to nearest 0.5°C.
b. Only available evaporation data for Hollister.
cm x 0.3937 - in.
(°C x 1.8) + 32 = °F
17
-------
Available climatic data for Hollister during the study period is shown
in Table 3. The weather pattern encountered was highly unusual with respect
to precipitation. Although the total annual rainfall was almost normal, the
monthly distribution was very unusual. The largest monthly rainfall occurred
in June 1976 which is normally precipitation free. Drought conditions
prevailed at Hollister and throughout northern California during this time
period. Based on available historical climatic data, it is estimated that
the net evaporation during the study period was slightly greater than normal.
TABLE 3. CLIMATIC DATA DURING STUDY PERIOD,
HOLLISTER, CALIFORNIA [7]
Month
Avg temperature, °Ca
Hours, Hours, Hours, Precipitation, Relative
Maximum Minimum >38°C <7°C <0°C cm humidity,*
May 1976
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan 1977
Feb
Mar .
Apr
May
Jun
Jul
Aug
24.0
31.0
27.0
27.0
26.0
25.0
20.0
17.5
14.5
19.5
18.0
24.0
21.0
27.0
30.5
28.5
6.5 1
9.5 14
11.0
12.0
11.0 1
8.5
5.1
-1.0
1.0
3.0
1.0
4.5
7.5
11.0
10.5
13.0 2
56
28
_.
43
168 22
414 83
418 61
250 9
279 21
195
59
..
0.0
6.45
0.0
3.07
7.72
1.27
2.29
3.15
2.13
1.14
2.21
0.79
2.21
0.43
0.0
0.0
37.5
32.6
41.4
41.9
41.0
40.8
44.0
31.5
47.2
34.9
28.5
26.9
35.9
38.0
30.5
37.2
a. Values reported to the nearest 0.5°C.
cm x 0.3937 = in.
(CC x 1.8} + 32 = °F
SURFACE WATER HYDROLOGY
The San Benito River is the only natural surface water source that
potentially has an effect on the Hollister rapid infiltration site. The San
Benito River is generally dry, except during unusually heavy rainfall
occurring below the point of the Hernandez Dam located some 80 km (50+ miles)
upstream of the study site. Regular releases from the Hernandez Reservoir
provide managed recharge of subsurface aquifers as well as flood control.
Surface flow does not generally occur as a result of water release from the
reservoir in the vicinity of the study site. However, groundwater levels of
18
-------
the main Hoi lister-San Juan groundwater basin in the site vicinity can be
affected by the releases from Hernandez Reservoir.
WATER AND WASTEWATER CHARACTERISTICS
The mineral content of the wastewater can be traced directly to the
quality of the domestic water supply. Potable water is derived solely from
wells and the quality varies from source to source. In general, the water
supply is relatively hard and high in total dissolved solids, sodium,
chloride, sulfate, and boron. A summary of available water supply quality
data for the City of Hoi lister is shown in Table 4. The effluent wastewater
quality results, in which three 24-hour composite samples were taken each
quarter for 1 year, are shown in Table 5. Data for each primary effluent
composite sample taken are shown in Appendix A.
TABLE 4. CITY OF HOLLISTER WATER SUPPLY QUALITY3
mg/L Unless Otherwise Noted
Item
Flow, L/s
General mineral analysis
Hardness (CaO>3)
Bicarbonate (CaCOj)
Carbonate (CaCOj)
Hydroxide
Alkalinity (CaC03)
Ca
Mg
Fe
Hn
Na
Cl
so4
F
N02-N and N03-N
pH, units
Conductivity, pmhos/cm
TDS
Trace elements
As
B
Cu
Pb
Se
Zn
General physical analysis
Color, units
Odor, threshold No.
Turbidity, JTU
Well No. 2
61.3
371
324
0
0
324
63
52
0.0
0.0
132
103
248
0.7
3
7.6
1380
870
0.00
0.6
<0.1
0.02
0.00
0.02
5
1
0.5
Well No. 4
100.7
374
328
0
0
328
61
54
0.0
0.0
130
101
264
0.7
2
7.7
1380
870
0.00
0.7
<0.1
0.02
0.00
0.02
5
1
0.3
Well No. 5
70.1
388
360
0
0
360
68
53
0.2
0.0
130
104
260
0.7
3
7.6
1490
940
0.00
0.6
<0.1
0.02
0.00
0.02
7
1
0.5
Cienega well
21.9
81
__
__
..
16
20
16
__
1.8
__
250
157
..
0.05
..
__
_
_
--
a. From City of Hollister Water Supply Monitoring data 1973.
L/s x 0.0228 = Mgal/d
19
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TABLE 5. CITY OF HOLLISTER EFFLUENT WASTEWATER QUALITY
mg/L Unless Otherwise Noted
Constituent
COD
BOD
TOC
Total N
NH3-N
N-organic
N03-N
Total P
PO/i-P
Total coliforms,
count/100 ml
Fecal conforms,
count/100 ml
pH, units
TDS
Conductivity,
umhos/cm
SS
Alkalinity
B
F
Na
Ca
Mg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Mn
N1
Pb
Se
Zn
SAR
Range a
546-1029
134-414
240-264
29.7-58.5
19.7-44.0
6.7-21.8
0.16-0.8
10.0-21.5
9.0-13.2
4.6x106
92x106-
3.5x106
24x106
7.0-8.1
1016-1593
1230-2480
206-438
416-465
0.95-1.8
0.33-1.08
196-391
31-71
27-76
10.9-16.0
185-490
161-250
<0. 005-0. 01 2
<0.1-0.24
<0. 001 -0.008
<0. 006-0. 008
<0. 004-0. 036
0.019-0.070
0.14-0.82
0.055-0.094
0.015-0.092
0.012-0.12
0.010-0.090
4.67-8.08
a. Range of twelve 24 h composite
b. Average of three 24 h composite
Jul 1976b
624
173
42.2
22.2
19.4
0.7
12.7
12.7
2.2xl06
7.0
1197
1847
--
--
1.1
0.6
246
59
62
11.3
258
176
0.007
<0.01
<0.1
0.004
0.008
<0.004
0.024
0.41
0.001
0.069
0.063
0.016
<0.001
0.015
5.33
samples.
samples.
Sep 1976b
593
208
--
46.7
33.5
12.9
0.34
10.7
9.0
ISxlO6
6.7xl06
7.3
1559
2400
--
«
1.8
0.57
377
71
57
12.1
471
219
<0.006
<0.01
<0.1
<0.001
0.011
O.004
0.011
0.17
<0.001
0.064
0.086
0.033
<0.001
0.032
8.08
Dec 1976b
659
153
30.9
22.3
8.1
0.5
16.2
10.6
69xl06
11.6xl06
7.8
1033
1620
221
433
1.4
0.37
230
53
75
12.6
192
243
0.011
<0.001
0.11
0.007
<0.006
0.015
0.068
0.34
cO.OOl
0.068
0.015
0.068
<0.001
0.053
4.76
Mar 1977b
946
346
248
40.9
23.2
17.5
0.18
10.2
9.8
21X106
19X106
7.2
1044
1293
327
459
1.3
1.08
197
31
63
15.6
216
215
<0.007
<0,01
0.21
0.003
<0.006
0.032
0.032
0.63
<0.001
0.080
0.040
6.10
<0.001
0.09
4.67
Average
706
220
248
40.2
25.3
14.5
0.43
12.4
10.5
27.6xl06
12.4xl06
7.3
1208
1790
274
446
1.4
0.66
262
54
64
12.9
284
213
<0.008
<0.01
<0.13
<0.004
<0.008
<0.014
0.034
0.39
<0.001
0.070
0.051
0.054
<0.001
0.048
5.71
20
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CONSTITUENT LOADING
Wastewater characteristics that can influence the amount of wastewater
that can be applied to a rapid infiltration site include organic matter,
nitrogen, and phosphorus. The current constituent loading rates at the
Hoi lister rapid infiltration site are shown in Table 6.
TABLE 6. WASTEWATER CONSTITUENT LOADING RATES
kg/ha
Constituent
COO
BOD
TOC
Total nitrogen
Total phosphorus
Daily
304
95
107
17.3
5.3
Annual
111,000
34,500
39,000
6,310
1,950
a. Based on 438 L/s applied to 8.8 ha.
kg/ha x 0.89 = Ib/acre
The mechanisms which cause removal and the fate of these and other
constituents during infiltration and percolation through the soil profile are
discussed in the soil and groundwater investigation sections.
21
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SECTION 6
METHODOLOGY
SITE SELECTION
The initial phase of the project involved the selection of a suitable
study site. The 1974 EPA Municipal Waste Facilities Inventory for California
was used to compile the initial list of candidate sites [8]. Listed in the
inventory were a total of 106 sites where some variation of the rapid
infiltration process was being used (see Table 7).
The candidate sites were screened according to criteria established by
the EPA and additional criteria developed during the screening procedure. To
be considered, a site must have been representative of the current state-of-
the-art for rapid infiltration treatment as defined by the site screening
criteria shown in Table 8.
The initial screening was performed using in-house information, an EPA
list of existing land application systems [2], and information obtained by
telephone. The most promising sites were identified for more detailed
screening, and the number of candidate sites was systematically reduced.
Detailed screening resulted in a list of the six most promising sites, shown
in Table 9. Three promising sites that currently pretreat to the primary
level and three that pretreat to the secondary level before land application
were selected.
Hoi lister was chosen as best representing the soil and groundwater
conditions for a typical site with potential for treatment by rapid
infiltration where primary effluent is applied. Fontana was rejected because
the depth to groundwater was very large and the direction of groundwater flow
was difficult to define. Gilroy was rejected because of shallow groundwater
and significant influence from a nearby industrial wastewater land
application system.
Of the systems applying secondary effluent, Santee was selected as
having a well-defined groundwater flow pattern. Santa Maria was rejected
because of operational changes in the last few years. Oakdale was rejected
because of shallow groundwater.
The final screening step included visits to the two most promising
sites--Hollister and Santee. It was concluded that the most suitable site
for the purposes of this study would be the one at Hoi lister, California.
The principal reasons for selection were that Hoi lister was more typical of
most rapid infiltration systems, had a longer history of operation, and was
applying primary effluent.
22
-------
TABLE 7. LIST OF CANDIDATE RAPID INFILTRATION SITES
IN CALIFORNIA, OCTOBER 1975 [8]
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
Community
Altaville
Anderson
Arden
Atascadero
Avenal
Big Bear Lake
Brea
Buellton
Buttonwillow
Calpella
Camarillo
Capistrano Beach
Cawelo
Ceres
Chester
Corona
Crescent! a
Dixon
Hemet
Escalon
Etna
Fillmore
Firebaugh
Fontana
Ft. Jones
Fresno Co. 1
Fresno Co. 2
Gilroy
Gridley
Gustine
Healdsburg
Hollister
Hughson
Irvine Ranch
Jamestown
Jurupa
King City
Lake Arrowhead
Lakeport 1
Lakeport 2
Lakeside
Laton
Lodi
Lone Pine
Lechuza
Malibu
Trancas (L.A. Co.)
Whittier Narrows (L.A. Co.)
L.A. Co. SD #22 Azuza
Manteca (Raymus Village)
Mariposa
Mendota
Mills-Cordova
Flowrate,
L/s
<3.1
33
298
11
20
8.8
2.2
3.5
<3.9
<0.9
114
17
<5.3
42
13
136
0.9
13
140
8.8
4.4
18
13
101
4.4
8.8
0.9
101
39
48
22
35
12
153
4.4
39
18
22
8.8
4.4
24
4.4
197
8.8
<4.4
<4.4
<4.4
661
31
0.4
2
4.4
8.8
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
92.
93.
94.
95.
96.
97.
98.
99.
100.
101.
102.
103.
104.
105.
106.
Community
Montalvo
Mount Shasta
Nevada City
Oakdale
Oceanside La Saline Plant
Oceanside Buena Vista Plant
Oceanside San Luis Rey Plant
Olivehurst
Orange Co. SD Plants 1 and 2
Moulton Miguel Plant 2A
Orange Cove
Palm Springs
Perris
Pinedale
Pixley
Sierra Lakes
Squaw Valley
Porterville
Rainbow A
Rainbow B
Rainbow C
Rancho Santa Fe
Redding (Clear Creek)
Redding (Paso Land Co.)
Redlands
Reed ley
Rialto
Richvale
Rio-Dell
Ri pon
Riverbank
Salida
San Clemente
San Diego Co. (Brown Field)
San Miguel
Santa Maria
Santa Paula
Santee
Shasta Co.
Soledad
Spreckels
Tahoe City
Tranquillity
Tuolumne
Visalia
Waterford
Westwood
wheat! and
Winters
Winton
Woodbridge
Yreka
Yuba City
Flowrate,
L/s
4.8
22
31
48
140
18
22
33
6790
11
11
131
13
11
4.4
2
0.4
75
0.35
0.4
0.2
3.2
158
1.8
110
35
92
1.3
15
13
13
18
88
1.3
1 .3
188
74
44
0.09
13
3.5
5.2
2.2
4.4
210
8.7
8.7
5.7
8.8
15.0
8.8
44
66
L/s x 0.0228 = Mgal/d
23
-------
TABLE &. INITIAL SITE SCREENING CRITERIA
Item
Criteria
Period of operation
PreappHcation treatment
Wastewater sources
Wastewater flowrate
Uastewater application rate
Depth to groundwater
Control site
Availability of data
Operation practices
>10 years
Remain unmodified for at least 10 years
Domestic and commercial8
>4.3 L/s
>6 m/yr
>3 m and <30 m
Comparable geohydrologic characteristics
within 1.6 km of site
Historical Wastewater and groundwater
quality must be available for comparison
purposes
1. Wastewater application to the b
spreading basins must be Intermittent
2. Sludge must never have been applied
to the spreading bas1nsc
3. Soil conditions 1n the basins should
not have been altered drasticallyd
a. Industrial wastewater. in small amounts, resembling municipal
wastewater is acceptable.
b. Systematic flooding and drying over several days with
multiple independent basins.
c. .Constituents are generally much more concentrated in sludge
than in wastewater.
d. Surface disking or scarifying to restore infiltration is normal
and acceptable.
L/s x 0.0228 = Hgal/d
m x 3.281 = ft
km x 0.621 = mi
TABLE 9. SUMMARY OF DESIGN AND OPERATING
INFORMATION ON SIX CANDIDATE SITES
Site
location
Hoi lister
For) tana
Gllroy
Santee
Santa Maria
Oakdale
Level of
pretreatment
Primary
Primary
Primary
Secondary
Secondary
Secondary
Flowrate,
L/s
44
no
118
44
241
61
Application
rate, m/yr
15
21
24
58
46
67
Duration of
operations,
total number
of years
30
20
52
17
14
10
a. Average annual applied wastewater volume divided by the
Infiltration basin area.
L/s x 0.0228 * Hgal/d
»/yr x 3.281 « ft/yr
24
-------
STUDY PLAN
The method of approach was to characterize the applied effluent,
groundwater, and soil over a 1 year period. The concentration of
constituents in the effluent and groundwater were compared to determine the
current efficiency of the soil matrix in removing constituents contained in
the effluent. The constituents of concern in groundwater were those for
which drinking water standards have been set, and those that affect water
quality for irrigation and livestock watering. Observation wells
constructed for sampling groundwater were shown in Figure 3.
A mass balance of selected soil constituents was perfonned to determine
the effects of 30 years of effluent application to the land on the ability
of the soil to retain constituents in the applied effluent. For soils, the
important constituents were those that could restrict the use of the site to
grow crops if the current land use were changed. The soil sampling
locations are shown in Figure 4.
A sampling program was devised to quantify the constituents in the
effluent, groundwater, and soils. Certain constituents, specifically
organic pesticides and viruses, were not measured because of the inordinant
expense involved in the analyses. A summary of the sampling program is
given in Table 10.
TABLE 10. SUMMARY OF SAMPLING PROGRAM
Feature
Total No. of samples
No. of constituents
per sample
Timing of samples
Type of samples
Effluent Groundwater
12 52
38 37
6/76, 9/76, 6/76, 9/76,
12/76, 3/77 12/76, 3/77
Soil
20
25
6/76,
3/77
No. of sampling
locations 1 13 5
Type of samples 24 h Grab Multiple
composite composite
25
-------
INFILTRATION I
DRY
I SLUDGE \
STORAGE -J/
SLUDGE
BEOS
DIGESTER
CLARIFER
EQUALIZATION
RESERVOIR
INFILTRATION
BASINS
0 50 100 200 300 400 FEET
II I I
METRE
SOIL SAMPLING LOCATION - ONSITE
A SOIL SAMPLING LOCATION - CONTROL
Figure 4. Proposed soil sampling locations at the Ho "Mister
rapid infiltration site.
26
-------
Effluent Sampling
The primary effluent was sampled through the use of a 24 hour
refrigerated, composite sampler. The sampler was battery-powered and
installed to take samples from the effluent trough of the clarifier. Each
sampling day (3 consecutive days) produced 24 separate 1 hour samples that
were composited according to flow. The constituents analyzed for were:
Organic: COD, BOD, TOC
Bacterials: Total coliforms, fecal coliforms
Minerals: Suspended solids, IDS, pH, alkalinity, conductance, N organic,
N03-N, NH3-N, total N, total P, P04-P, Na, K, Ca, Mg, Cl, S04, B, F
Trace elements: Ag, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, In
Groundwater Sampling
Sampling of the groundwater took place in the specially constructed
series of observation wells and five existing offsite wells. Observation
wells at Sites 1, 2, and 3 were drilled to intercept the subsurface flow
leaving the site. Observation well No. 4 was drilled as an offsite control
well. Observation well No. 5 was drilled near the center of the site to
intercept the top of the groundwater mound created by the infiltrating
effluent.
At the peripheral well locations (Nos. 1 through 4), the first drilling
was to approximately 54 m (180 ft). At 1.5 m (5 ft) intervals the drilling
was stopped and a splitspoon sample of material was taken. This allowed the
profile to be plotted by the geologist. A well screen was established if
water bearing material existed near the 54 m (180 ft) level. A second well
was drilled to either an intermediate depth (24 m = 80 ft) or a shallow
depth (8 to 11 m = 25 to 35 ft) or both.
It was originally estimated that four shallow wells (noted as "A")
three intermediate wells (noted as "B"), and four deep wells (noted as "C")
would be drilled. The location of potential water bearing material in the
soil profile was determined at each site from a log of each boring.
Observation wells were established where potential water bearing material
was found. The locations of the shallow, intermediate, and deep wells
established from the geologic investigation were shown in Figure 3.
The wells were equipped with pumps to obtain groundwater samples from
specified depths. Sampling pumps were hand crank portable plunger pumps
with a flush cap cylinder, rod and couplings, and PVC carrier pipe. The
flush cap cylinder was smaller in diameter than the 5.1 cm (2 in.) inside
diameter of the observation wells. The pumps were able to obtain sufficient
water volume to flush out the standing water column in a relatively short
period of time. Samples were withdrawn in June 1976, September 1976
December 1976, and March 1977 (see Table 10).
27
-------
Five existing offsite wells were monitored at the same frequency. An
upstream well (No. 4C) owned by the City of Hoi lister served as a
supplementary control well. Four downstream wells (6C, 7C, 8C, 9C) 0.8 km
(0.5 mile) away were also utilized. These privately owned wells are used
for irrigation and domestic water production.
Suspended solids content was measured selectively in the groundwater
and carbon chloroform extract (CCE) was not measured in the primary
effluent. All other constituents measured in the groundwater were the same
as for the applied effluent. The methods of analyses for both effluent and
groundwater samples were from Standard Methods [9].
Soil Sampling and Analytical Procedures
The soil profile was sampled at three onsite locations and two offsite
control locations (Figure 4). The onsite locations were in a spreading
basin that has been in use since about 1946. Onsite and control samples
were taken in June 1976, and again in March 1977. To establish the extent
of vertical variation in soil chemistry within the soil profile, samples
were taken at the following depth increments:
Depth
increment
No. cm (ft)
1 0-2 0-0.07
2 2-4 0.07-0.13
3 4-16 0.13-0.52
4 25-35 0.8-1.2
5 95-105 3.1-3.4
6 295-305 9.7-10.0
Composite samples were taken at each sampling location to account for
the spatial variability of the soil. The basin selected for sampling was 18
by 180 m (60 by 600 ft); accordingly, grid nodes spaced 1.5 by 3 m (5 by 10
ft) were established at each sampling location. For the first three depth
increments, 20 subsamples were taken for compositing (one per grid node).
Preliminary analyses indicated that increments 1 through 3 were
indistinguishable and were finally analyzed as one composite whose mass was
proportional to its volume. For the fourth depth increment at the onsite
locations, 10 subsamples were composited. The fifth and sixth increments at
the onsite locations and the last three depth increments at the control site
were sampled from trenches excavated by backhoe. Three equally spaced
trenches were excavated over the original grid nodes. Samples were taken
from each face of a trench to duplicate as closely as possible the 10
subsample locations of the fourth depth increment. The high soil density at
the control site made it necessary to take subsamples from the excavated
trench sidewalls rather than sampling from the surface for the last three
increments.
28
-------
To determine if any significant quality changes have resulted from the
application of wastewater, 23 chemical and 3 physical soil parameters were
monitored at both control and treatment site locations. All laboratory
analyses were performed on air-dried soils. A listing of the constituents
and analytical procedures is shown in Table 11. The only field performed
measurements were bulk density and infiltration rate.
TABLE 11. SOIL CONSTITUENTS AND ANALYTICAL PROCEDURES
Procedure
Laboratory
pH [11]
Conductivity [11]
Organic Matter [12]
CaC03 [12]
Nitrogen [11]
B [11]
Total-P [11]
Extractable-P [11]
CEC [11]
Exchangeable cations [11]
Metals [13]
Particle Size [11]
Field
Infiltration Rate [11]
Bulk Density [11]
Description
1:1 paste
Saturation extract
K2Cr20?-H2S04
Gravimetric HC1 loss
Kjeldahl
Hot water extract
HC104-digest
0.5 m NaHCOj
NH4OAc - pH 7
NH4OAc - pH 7
DTPA-TEA extraction3
b
Sieve-hydrometer
Double cylinder
Core, excavation
Soil fraction
All
All
<0.6 mm
<2 mm
<2 mm
<2 mm
<2 mm
<2 mm
<2 mm
<2 mm
<2 mm
All
~
a. 0.005'M diethylenetriamine pentacetic acid - 0.1 M tri-
ethanolamine - 0.01 m CaCl2, 40 mL/20 g soil.
b. Clay analyses performed at discretion of laboratory
technician.
mm x 0.03937 = in.
m x 3.281 = ft.
Additionally, phosphorus sorption experiments were conducted in the
laboratory on both control and treatment site samples. Sorption isotherms
were determined using a "non-destructive" method developed by Enfield and
Bledsoe [10].
29
-------
SECTION 7
HYDROGEOLOGIC INVESTIGATION
The rapid infiltration site at Hoi lister is on the flood plain of the
San Benito River, approximately 150 m (500 ft) south of the river channel.
The flood plain is typically flat and has been used as a source for
commercial sand and gravel in the Hoi lister area. The site is protected
from flooding by fill materials.
REGIONAL HYDROGEOLOGY
The site is located in the San Juan subbasin of the Gilroy-Hollister
groundwater basin. The San Juan subbasin is defined within the larger basin
by geologic features that form relatively impermeable barriers to
groundwater movement. These boundaries include the Sargent anticline in the
Lomerias Muertos and Flint Hills on the north, the Calaveras fault and the
Bird Creek Hills on the east, and the San Andreas fault zone on the
southwest (Figure 5).
The San Juan subbasin is further divided into subunits. The boundaries
of these subunits are minor faults or zones of deformation that create
hydraulic discontinuities. The location of the Hollister site relative to
nearby subbasin and subunit boundaries is illustrated in Figure fa.
The major aquifer in the San Juan subbasin consists of unconsolldated
to weakly-cemented alluvium of Holocene Age and the upper member of the
Purisima formation of Pliocene age. These units are Indistinguishable on
drillers' or electric logs and are generally believed to form a single
hydrologic unit. Within these sediments, the most productive water-bearing
units are lenticular beds of sand and gravel that are interbedded with silt
and clay layers. Groundwater occurs mainly under artesian or semi-artesian
conditions in these units, although locally perched or semi-perched
conditions may exist.
The Holocene alluvium is broken by currently active faults 1n places,
such as the one that occurs approximately 600 m (2,000 ft) west of the
Hollister site. The Purisima formation and the older Tertiary and Jurassic
rocks that underlie the alluvium are highly folded and have been extensively
broken and tilted by faulting. Electric logs of gas production wells in the
Lomerias Muertos indicate that poor quality groundwater occurs to depths of
200 to 300 m (600 to 1,000 ft) in the older formation.
30
-------
SUBBASIN BOUNDARY
SUBUNIT BOUNDARY
0 1 2 3 4 5
5 MILES
KILOMETRES
Figure 5. Relation of groundwater subbasins and
subunits to geologic features [14].
31
-------
CO
ro
55 198S IATE»-LE»EL
CONTOURS ,
0 1000 2000 FEET
I I I < I I '
0 300 METRES
l>
Figure 6. Hydrogeology of the Hollister rapid infiltration site [14],
-------
Within the main groundwater body of the San Juan subbasin, groundwater
flow is toward a major pumping depression in the south-central part of the
valley. This depression has been caused by the withdrawal of groundwater
for irrigation in amounts that are in excess of the rate of recharge,
particularly since 1945. Throughout the valley, groundwater levels declined
up to 30 m (100 ft) between 1913-1968, and the San Benito River changed from
a gaining to a losing stream. Currently, all discharge from the San Juan
subbasin is by wells, and recharge consists of stream infiltration and
direct infiltration of precipitation. During the period 1946-1969,
discharge exceeded recharge by an average rate of 123 L/s (2.9 Mgal/d) [15].
However, even with current drought conditions, which began in 1975,
groundwater levels in the main aquifer did not decrease during the study
period, beneath the rapid infiltration site.
OBSERVATION WELLS
Existing information concerning the subsurface hydrology near the site
was reviewed and used as a basis for locating the groundwater monitoring
wells. This information included a U.S. Geological (USGS) survey report on
the regional subsurface hydrology [14], drillers' logs for wells near the
site, and the logs of two shallow test borings completed at the site [16].
Examination of these data sources indicated that the principal aquifer in
the vicinity of the Hoi lister site is alluvium and the upper member of the
Purisima formation. The principal aquifer is underlain by the middle member
of the Purisima formation, a less permeable unit that contains saline water at
depth and water with a high concentration of sulfate locally. The base of the
fresh water lies between 100 to 200 m (300 to 600 ft) below the surface in the
Hoi lister area.
The water level contours shown in Figure 6 indicate that groundwater
beneath the site moves in a westerly direction toward the subunit boundary
west of the site. These water level contours are based on wells screened at
depths between 30 to 100 m (100 to 300 ft).
Four peripheral sites and one site within the effluent treatment area
were chosen to monitor groundwater levels and quality. Monitoring sites were
located close to the infiltration basins so that extraneous effects on
groundwater quality, such as former or existing upgradient waste loadings,
irrigation, streamflow infiltration, etc., could be eliminated.
Observation well sites 1, 2, and 3 (see Figure 7) were located on the
downgradient side of the site to intercept the suspected path of groundwater
flow from the infiltration basins. It was proposed that a shallow, an
intermediate, and a deep observation well be constructed at each of these
three sites. The shallow wells would have a 0.6 m (2 ft) length of screen set
at a depth between 3 to 13 m ( 10 to 40 ft), and the intermediate and deep
wells would have similar screens set between 20 to 30 m (60 to 90 ft) and 45
to 60 m (135 to 180 ft), respectively. Available information indicated that
the movement of percolates through the unsaturated zone might be complex and
that perching conditions might be caused by apparently extensive clay deposits
which underlie the site at depths of less than 10 m (30 ft). The shallow
33
-------
RAPID INFILTRATION
BASINS
GROUND SURFACE
CONTOURS.
0 250 900
1000 FEET
I
100
T
200
300 METRES
Figure 7. Observation well sites.
-------
wells at each site were proposed to reveal possible perching in the
unsaturated zone, while the intermediate and deep wells were intended to
define the movement of the effluent in the saturated zone. The number of
wells that were actually placed at each site was limited by the availability
of permeable materials within the desired depth intervals.
At Site 4, the City of Hoi lister supply well was proposed as a deep
monitoring well upgradient from the treatment site. Therefore, only
intermediate and shallow wells were proposed at this site.
Site 5, located in infiltration basin 6, was proposed as a shallow
observation well that would intercept the groundwater mound created by
infiltration of the applied effluent.
The construction of the observation wells at Sites 1, 2, and 3 proceeded
as follows:
1. A 12.7 cm (5 in.) diameter uncased boring was drilled to the
maximum scheduled completion depth using a Failing 750 rotary
drilling rig. The completion depth depended on the depth at which
permeable materials were encountered in the 45 to 6U m (135 to 180
ft) interval.
2. During the drilling, 3.5 cm (1.4 in.) diameter splitspoon samples
were taken at 1.5 m (5 ft) intervals throughout the boring. The
location of permeable zones was observed by a geologist as the
samples were taken.
3. Upon completion of the boring, depths for observation wells were
selected based on availability of permeable zones. If feasible, a
deep observation well was installed in the borehole. The
observation wells were constructed with lengths of 5 cm (2 in.)
diameter PVC pipe with a 0.6 m (2 ft) length of 10-slot PVC screen
(0.03 cm, 0.01 in., openings) at the bottom. The space between
the well and the open hole was filled with sand at the screened
interval and with bentonite slurry from the top of the screen
to the surface.
4. Similar intermediate and shallow boreholes were then drilled to the
chosen depths for the installation. These wells were within 1.5 m
(5 ft) of the original boring, and splitspoon samples were
therefore not taken. A drawing of a typical completed observation
well and a photograph of a drilling rig are shown in Figure 8.
At Sites 4 and 5, borings were drilled only as far as the intermediate
and shallow zones, respectively. Similar observation wells were then
installed in the boreholes.
Pertinent information concerning observation well construction is
contained in Table 12. Shallow, intermediate, and deep wells are indicated
by the letters A, B, and C, respectively. Examination of the table shows
that, of the original 12 proposed observation wells, 4 could not be completed
due to the extensive clay layers beneath the site.
35
-------
3B 5ci
10P Of PIPE
BEN1DNIIE SUR«r
GROUND SUIMCE
TOP OF SAND FILTER
Pvt IELL ICKllK - NO. 10 1LOI
(CLOIEO IOTION)
Figure 8. Typical observation well construction and drilling rig,
36
-------
TABLE 12. OBSERVATION WELL CONSTRUCTION DATA
Well No.
1A
IB
1C
2C
3A
3B
4B
4Ca
5A
Screened
interval ,
m below
land surface
5.5-6.1
23.8-24.4
48.2-48.8
54.3-54.9
7.0-7.7
20.7-21.3
17.7-13.3
56.4-59.4
10.1-10.7
Elevation Elevation of
of land measuring point
surface, (top of casing),
m m
73.7
73.7
73.7
72.1
73.0
73.0
73.8
72.8
74.2
74.2
74.2
72.7
73.4
73.5
74.6
74.4
73.4
a. Existing City of Hoi lister well.
m x 3.281 = ft.
SITE HYDROGEOLOGY
Graphic logs of the borings at Sites 1 through 5, which are north-south
and east-west geologic cross-sections through the site area, are shown in
Figures 9 and 10. These graphic logs were based on the geologist's
description of the samples. The logs for two test borings that were done in
a previous investigation and a driller's log for the City of Hoi lister supply
well (observation well 4C) are also shown. Although it is evident that the
nature of subsurface materials was highly variable both horizontally and
vertically, several generalizations can be made.
A layer of permeable material generally occurs from the surface to a
depth of 10 to 20 m (30 to 60 ft). A clay layer separates this upper
permeable zone from an intermediate one which occurs at depths between 15 to
25 m (45 to 75 ft). All of the deep logs showed a thick zone of silt and clay
beneath the intermediate permeable zone. A deep zone of permeable material
also occurs below depths of 55 to 65 m (165 to 195 ft).
The depth to water in the observation wells that.were constructed at the
site varied from 10 to 20 m (30 to 60 ft) below the surface. The water level
elevations, on 4 selected days, in the six observation wells that were
screened in the saturated zone are shown in Figure 11. At each individual
site, the water level in the intermediate zone was higher than that in the
deep zone, indicating a net downward movement of water. This movement of
water may be in response to the pumping from the city well (4C) in the deep
aquifer.
37
-------
SITE 1 TB-1
SITE 5
SITE 3 TB-2
U>
00
14.2
19. g
22.0
21 .0
93. 1
INTERMEDIATE PERMEABLE ZONE
WELL-INDURATED CLAY AND SILT
20. 4 i
29.6
39.4
NOR IZONTAL SCALE : 1 c - 40 »
VERTICAL SCALE: AS SHOWN.
or 1 i n . - 330 It
LEGEND
13.7
1 4. e
SCREEN
GRAVEL
COARSE
SAND
MEDIUM
SAND
FINE
SAND
SILT
CLAY
MUCK.
PEAT
DEPTH OF
CON TACT.
Figure 9. North-south geologic section.
-------
SITE 2
SITE 4
2. 1
13.1
18.0
20. 7
..
LC
54.3
55.4
SHALLOW PERMEABLE ZONE
CLAY AND SILT
INTERMEDIATE PERMEABLE ZONE
ELL-INDURATED CLAY AND SILT
DEEP PERMEABLE ZONE
HORIZONTAL SCALE: 1 cm = 40 m
VERTICAL SCALE: AS SHORN m
8 . 2
-12.2
15.8
24.7
43.3
44.2
, 49. 1
53.1
56 . 4
59 . 9
or 1 in = 330 ft
6 5 . 0
6 . 7
l_2. 2
I 3 .
ii a.
It a. s
25.0
29.6
31.0
LEGEND
SCREEN
GRAVEL
COARSE
SAND
MEDIUM
SAND
FINE
SAND
= SILT
13.7
14.6
CLAY
MUCK .
PEAT
DEPTH OF
CON TACT.m
Figure 10. East-west geologic section.
-------
NOTE: PATUM GROUND SURFACE
ELEVATION= 73n
FOR ALL WELLS SHOWN
1 2
© ©
0 0
1 S
IS
$ *
©
J
6/28/76
11/22/78 1/28/77 4/1/77
Figure 11. Water levels in intermediate and
deep observation wells on four selected days.
40
-------
Within the intermediate zone, the water levels indicated a movement of
water toward the northeast. This trend may have been caused by greater
leakage from the intermediate to the deep aquifer in the vicinity of Site 3,
since the impermeable clay between the two zones appeared to be thinner to the
north.
WATER LEVEL RESPONSE
Shallow Wells
The shallow observation wells at Sites 1, 3, and 5 were installed to
determine if perching conditions occurred as effluent percolated down to the
clay layers that underlie the upper permeable zone, as well as for monitoring
water quality. Early in the 1 year study period it was discovered that Wells
3A and 5A had rapid water level responses to effluent application. Continuous
water level recorders were installed to more accurately define these responses
(Figure 12). Well 1A remained dry throughout the study, except when the berni
around Basin 20 was breached and the field adjacent to Site 1 was flooded.
The response of Wells 3A and 5A to wastewater application is shown in
Figure 13. The water level in Well 3A rose at a greater rate and to a higher
elevation than that in Well 5A. This difference was most likely a result of
higher permeabilities in the upper layer in the vicinity of Site 3 which
created a preferred path for infiltration. After the peak water level was
reached, the perched water table dropped at a greater rate in Well 3A than in
Well 5A, again indicating a higher aquifer permeability at Site 3.
Both of these wells responded noticeably to flooding in Basins 3 through
8 since these basins were closest to the two wells. The effects of flooding
in other basins were not evident on the hydrographs of Wells 5A or 3A.
It was also observed, during the study, that the rise of water levels in
Wells 3A and 5A was related to the depth of the effluent applied in the
infiltration basins. A specific relationship between these phenomena was
beyond the scope of the project, however.
Intermediate and Deep Wells
The intermediate depth observation wells constructed at Sites 3 and 4
showed no discernable response to effluent application. The wells did show a
yearly water level fluctuation of 0.7 to 1.0 m (2 to 3 ft) , with high water
levels occurring during the winter when natural recharge is greatest (Figure
The intermediate well at Site 1 showed a 1 m (3 ft) rise in water level
at the same time that the water level in Well 1A rose. This occurred when
the adjacent field was flooded following a breach in the Basin 20 berm. The
boring log from Site 1 showed 15 m (50 ft) of clay and silt between the upper
and intermediate permeable zones. The most probable explanation for the
response of Well IB is that there were zones of permeable material nearby
that allowed the effluent to pass down to the intermediate zone.
41
-------
Figure 12. Continuous water level recorders,
42
-------
1 . 5
4 . 5
6 . D
7 . 5
9 . 0
, 54 ~- BASIH(S) BEING FLOODED
DRY
LEGEND
WELL 3 A
WELL 5 A
20 24 28
All G
^ ^/
' 4 8 12 18 20 24 28 4 8 12 IB 20
SEP 0 C T
TIME. DAYS (1976)
4. 5
8. 0
7. 5
9.0
10. 5
1 3 5 7
i.ViVi
3 5 e
.J
I 1 1
20 24 21
0 C T
4 8 12 1620 24 28
N 0 V
4 8 12 18 20
DEC
4. 5
C" 8.0
ui g . o
u. 10. 9
24 28
DEC
(1978)
TIME. CAYS (1976)
> 12 16 20 24 28 |
1 AN
(1977)
TIME. DAYS
I 12 18 20
f I I
24 28
Figure 13. Water level response to basin flooding in
observation wells 5A and 3A.
43
-------
JUL
APR HAY
TIME. Months
1977
Figure 14. Water level response of intermediate and deep wells.
-------
The deep observation wells, at Sites 1, 2, and 4, did not show any
response to effluent application (Figure 14). The lower permeable zone in
which these wells were screened is overlain by a 20 to 35 m (60 to 110 ft)
layer of clay and silt that is probably continuous beneath the treatment site
and is an effective barrier to vertical groundwater movement.
SUMMARY AND DISCUSSION
The data collected during the observation well drilling and the water
level monitoring indicated that the movement of the effluent through the
ground is complex and controlled by highly variable subsurface conditions.
The intermediate and deep observation wells showed no response to effluent
application in the infiltration basins. The infiltrating effluent apparently
formed a mound which is perched on top of the clay layer that underlies the
upper permeable zone. When infiltration ceased, the mound subsided mainly by
lateral outflow from the site.
The mound that resulted from the flooding of Basins 3 through 8 was
dissipated by lateral outflow to the north. The hydrograph of Well 3A
indicates that Site 3 is in a more permeable part of the upper zone, which is
probably a preferred path for infiltration and outflow. The exit paths for
mounds created by flooding other basins are not known, although it is
probable that the outflow was to the north for Basins 1 through 13 and toward
the south or southeast for Basins 14 through 20. No lateral outflow was
observed at Site 1, southwest of the treatment facility.
Some vertical leakage may be occurring also, especially near Site 3
where the clay and silt between the upper and intermediate permeable zones is
the thinest. A comparison of iron and manganese concentration in effluent
and groundwater indicates that vertical leakage from the upper to the
intermediate permeable zone is taking place (see Section 9).
45
-------
SECTION B
SOIL INVESTIGATION
INTRODUCTION
The Hoi lister rapid infiltration site is located in an area mapped as a
Metz sandy loam [3], though the terms gravelly sand or gravelly sandy loam
appear more appropriate. The soil is alluvial, currently classified as a
Typic Xerorthent [3]. A representative profile is shown below [3]:
Ap 0 to 20 cm (0 to 8 in.), grayish-brown (2.5 Y 5/2) sandy loam, very
dark grayish-brown (2.5 Y 3/2) when moist; weak, fine granular
structure; soft when dry, very friable when moist, nonsticky and
nonplastic when wet; few very fine and fine roots; few very fine
and fine tubular pores; mildly alkaline; slightly effervescent;
clear, smooth boundary.
Al 20 to 35 cm (8 to 14 in.), grayish-brown (2.5 Y 5/2) sandy loam,
very dark grayish-brown (2.5 Y 3/2) when moist; weak, fine
subangular blocky structure; soft when dry, very friable when
moist, nonsticky ana nonplastic when wet; few very fine and fine
roots; few very fine and fine interstitial pores; moderately
alkaline, slightly effervescent; clear, wavy boundary.
Cl 35 to 108 cm (14 to 43 in.), light brownish-gray (2.5 Y b/2) sand,
grayish-brown (2.5 Y 5/2) when moist; single grain; loose when dry
or moist; nonsticky and nonplastic when wet; mildly alkaline,
slightly effervescent; abrupt, smooth boundary.
C2 108 to 150 cm (43 to 60 in.), light brownish-gray (2.5 Y 6/2)
stratified coarse sand and gravel, grayish brown (2.5 Y 5/2) when
moist; single grain; loose when dry or moist, nonsticky and
nonplastic when wet; contains small lenses of silt and clay; mildly
alkaline, slightly effervescent.
The site surface profile was modified by surface disking operations that
were practiced to restore infiltration capacity. In addition, the soil
contained more gravel and gravel lenses and generally less clay than the
typical profile.
Other soil types (Nacimiento clay loam, Metz gravelly sandy loam, sandy
alluvial land, river wash) are located nearby and adjacent to the site.
Because soil forming processes generally do not create distinct boundaries
between soil classification units and because soil properties vary within
46
-------
units, it was not possible to find control sites with characteristics
identical to the treatment sites. The control sites finally chosen were
reasonably similar to the treatment sites.
The results of physical and chemical analyses are presented separately
in the following sections. The methods of analyses were discussed previously
in Section 6.
PHYSICAL PROPERTIES
Particle Size
A mixture of inorganic and organic particles making up a mineral soil
can be texturally classified by determining the proportions of the three
major soil separatessand, silt, and clay. An exponential rise in surface
area, adsorption capacity, swelling, plasticity, cohesion, and heat of
wetting occurs when soil particle size decreases from sand to colloidal clay
The effect of soil texture on the direction of change of soil physico-
1 properties is summarized in Figure 15.
[17].
chemical
Soil Property
Surface Area
Molecular
adsorption
CEC
Swelling
Plasticity
Heat of wetting
Water holding
capacity3
Infiltration3
Percolation*
Permeability*
External
drainage3
Aeration*
Organic matter
content3
Structure*
Bulk density*
Porosity (total)*
Soil Texture
Sand Silt Clay
Sand, loamy sand, Loam, silt loam, Sandy clay, silty
sandy loam silt, sandy clay clay, clay
loam, clay loam,
silty clay loam
^-
>
- -M-
' -<
-^
-^
- -->-
-< -
-V-
^-
a. Colllgatlve properties.
Note: Arrow Indicates direction of magnitude Increase.
Figure 15. Physico-chemical properties of soils
as related to textural classification [18].
47
-------
The particle size distribution of the five sampling sites is given in
Table 13. The size limits of the soil separates are identical to those used
by the U.S. Department of Agriculture.
TABLE 13. PARTICLE SIZE DISTRIBUTION IN SOIL SAMPLE FROM THE
HOLLISTER RAPID INFILTRATION SITE
Depth, cm
USDA textural classification3 Gravel
Control No.l
0-16
25-35
95-105
295-305
Gravelly sandy loam
Gravelly sand
Gravelly sand
Gravelly sand
6
16
30
42
Sand
Silt
Clayb
63
81
69
52
26
3
1
6
5
--
--
Control No. 2
0-16
25-35
95-105
295-305
Treatment
0-16
25-35
95-105
295-305
Treatment
0-16
25-35
95-105
295-305
Treatment
0-16
25-35
95-105
295-305
Gravelly sandy loam
Gravelly sand
Gravelly sand
Gravelly sand
site No.l
Gravelly loamy sand
Gravelly sand
Gravelly loamy sand
Gravelly sandy loam
site No. 2
Sandy loam
Gravelly loamy sand
Gravelly sand
Sandy loam
site No. 3
Gravelly sandy loam
Gravelly sand
Gravelly sand
Gravelly sand
4
24
56
15
20
10
38
6
2
10
30
1
6
8
29
15
66
71
43
84
67
86
54
70
64
70
69
67
64
88
70
82
23
5
1
1
13
4
8
17
28
20
1
26
26
4
1
3
7
--
--
7
6
6
4
-
~~
a.
>2 mm = gravel; 0.05-2 mm « sand; 0.002-0.05 mm » silt; <0.002 mm clay.
b. Clay fractional on (by hydrometer) was performed only when the analyst had
reason to believe that clay was present in the pan sieve sample. When clay
analysis was not performed, the soil was assumed to be all silt.
mm x 0.03937 = in.
48
-------
Control sites are either gravelly sands or gravelly sandy loams while
the treatment site textures range from gravelly sand to gravelly sandy loam.
In all cases, sand is more than 50% of the less than 2 mm size fraction.
Because soils in this textural class have large spaces between particles,
they are expected to have a high percolation rate, low water holding
capacity, and high aeration capacity [18]. Field inspection of the sand
fractions from both control and treatment site locations indicated that they
consisted largely of quartz, feldspar, and shale fragments.
Surface Area
It has been shown that for a specialized set of conditions and spherical
particles, an estimate of soil surface area can be obtained using the
relationship [19]:
- =
M pr
where A = surface area
M = mass of soil
p = particle density
r = particle radius
To calculate rough values of surface area per unit mass, a particle
density of 2.65 g/cm3 was selected, while particle radii for each size
fraction were calculated from the average particle diameters given in Table
14.
TABLE 14. SURFACE AREA PER UNIT SOIL MASS
Size fraction
Average diameter, cm
A/M = 3/pr, cm2/g
Gravel
0.30
8
Sand
0.0102
22
Silt
0.0026
870
Clay
0.0001
22,600
cm x 0.3937 = in.
cm2/g x 70 = in.2/lb
Estimates of surface area distribution for a hypothetical 100 g soil
sample are presented in Table 15. While the numbers are gross estimates
only, they are qualitatively important because many soil-solution
interactions, especially heavy metal sorption, are surface area dependent.
Surface area estimates range from a low of 2,264 cm2 (351 in.2) to a
high of 179,694 cm^ (27,853 in.2) with surface soil horizons generally having
the highest surface area. Treatment site 1, however, has its surface area
maximum at 300 cm (118 in.). (Clay analysis was not performed on the surface
depth fraction; a small amount of clay would significantly alter this
estimate.) A similar subsurface maximum exists for treatment site 2.
49
-------
TABLE 15. ESTIMATED SURFACE AREA DISTRIBUTION (cm*) FOR A
100 g SAMPLE OF SOIL
Depth, cm
Control No. 1
0-16
25-35
95-105
295-305
Control No. 2
0-16
25-35
95-105
295-305
Treatment site No. 1
0-16
25-35
95-105
295-305
Gravel
48
128
240
336
32
192
448
120
160
80
304
48
Sand
1,386
1,782
1,518
1,144
1,452
1,562
946
1,848
1,474
1,892
1,188
1,540
Silt
22,620
2,610
870
5,220
20,010
4,350
870
870
11,310
3,480
6,960
14,790
Clay
113,000
158,200
158,200
Total
137,054
4,520
2,628
6,700
179,694
6,104
2,264
2,838
15,782
5,452
8,452
174,578
Treatment site No. 2
0-16 16
25-35 80
95-105 240
295-305 8
1,408 24,360 135,600 161,384
1,540 17,400 19,020
1,518 870 2,628
1,474 22,620 135,600 159,702
Treatment site No. 3
1
0-16
25-35
95-105
295-305
cm2 = 0.155 in.2
48
64
232
120
1,408
1,936
1,540
1,804
22,620
3,480
870
2,610
90,400 114,476
5,480
2,642
4,534
Bulk Density
Bulk density measurements reflect the status of soil structure, which 1n
turn affects water movement, aeration, and porosity. It is a measure of
total soil space not occupied by solid matter and is affected by texture,
organic matter content, aggregation, root penetration, and compaction. Bulk
density measurements were performed at selected locations throughout the
study area using the methods described previously. The results are presented
in Table. 16.
3
Average measurements ranged from 1.27 to 1.72 g/cm , but there were not
sufficient data to determine if conclusive differences existed between
control and treatment sites or among depths.
50
-------
TABLE 16. SOIL BULK DEMSITY MEASUREMENTS (g/cm3)
AND CALCULATED SOIL POROSITIES
Site
Control No. 1
Control No. 2
Depth, cm
0-8
25-33
0-8
25-33
95-103
Db
Core method
1.59
1.65
1.41
1.27
1.57
Excavation D[j
method Average
1.84 1.72
1.65
1.41
1.27
1.57
%
Porosity
35
38
47
52
41
Treatment
site No. 3
4
0-8
4-12
25-33
95-103
1.25
1.38
1.57
1.48
1.33
~
1.29
1.38
1.50
1.48
51
48
42
44
g/cm3 x 27.8 = lb/in.3
Soil porosity can be calculated from bulk density as follows:
%? = (1 - ^.) 100 (2)
where %P = percent pore volume
05 = bulk density
P = particle density, assumed as 2.65 g/cm3
The results of such calculations are also presented in Table 16.
Control site 2 and treatment site 3 are similar, having porosities in
the range 42 to 52%. Control site 1 is slightly lower with an average
porosity of 37%. The lower than average bulk densities of the near-surface
measurements at the treatment site may have been the result of diskina
operation. ^my
Infiltration Studies
Water intake rates were measured for several basins where wastewater had
been applied for 30 years. The results of the basin flooding infiltration
studies are presented in Table 17. nwauiun
The average infiltration rate for the basins was 17.7 cm/d (0.58 ft/d)
which s over twice the average daily application rate of 8 cm/d (0.27 ft/d)
Basin 11 was tested without prior disking, and may have caused larger than
normal pore clogging and the subsequent low infiltration rate.
51
-------
TABLE 17. BASIN FLOODING
INFILTRATION RATES
Location
Basin 3
Basin 4
Basin 5
Basin 6
Basin 7
Basin 9
Basin 10
Basin 11
Basin 12
Basin 13
Average
Infiltration
rate, cm/d
17.7
17.7
20.4
14.6
20.7
18.3
8.8
4.6
22.0
31.7
17.7
cm/d x 0.3937 = in./d
Infiltration rates are generally thought to be a function of many
factors, including initial water content and temperature which were not
controlled in the measurement of the infiltration rate. Nonetheless, at this
rapid infiltration site, infiltration rates were apparently related to soil
porosity, being highest where porosity was greatest.
Cylinder infiltrometer tests were also conducted in an infiltration
basin to determine the effect of wastewater solids and surface scarification
on infiltration rate. Tests were conducted using clear water (SS = 0 mg/L)
and primary effluent (SS = 275 mg/L) on the soil of infiltration Basin 6,
which had not been disked since the last wastewater application. Tests were
repeated on the same soil after disking. The testing procedure is described
in reference [20] where buffer cylinders approximately 90 cm (3b in.) in
diameter were continuously flooded in an attempt to approximate the true
vertical infiltration rate. Inner test cylinders were 55 gal drum sections
46 cm (18 in.) in diameter. A typical test cylinder is shown in Figure 16.
The infiltration rate was measured until steady state conditions were
established (generally in less than 2 hours).
A one-way analysis of variance was performed on the infiltrometer data
to determine if mean infiltration rates were statistically equal for the nine
treatments considered (Table 18). The hypothesis of equality was rejected at
the a = 0.01 level.*
a = 0.01 level is the probability of rejecting a true hypothesis.
52
-------
Figure 16. Cylinder infiltrometers.
53
-------
Mean infiltration rates, standard deviations, and coefficients of
variation are listed in Table 18.
TABLE 18. CYLINDER INFILTROMETER IMFILTRATION RATES
Rank order
of
treatments
1
2
3
4
5b
6
7
8
9
Location
Basin 6
Basin 6
Basin 6
Basin 6
Basin 6
Control site
Basin 6
Basin 6
Control site
Soil
condition
Undisturbed
Undisturbed
Undisturbed
Undisturbed
Undisturbed
Undisturbed
Disked
Disked
Disked
Fluid
Clear water
Clear water
Clear water
Effluent
Clear water
Clear water
Clear water
Effluent
Clear water
Buffer
pond
Yes
Yes
Noa
Yes
Yes
Yes
Yes
Yes
Yes
Repli-
cates
5
5
5
6
6
2
6
6
4
Mean Infil-
tration rate,
cm/d
110
116
146
152
177
177
268
287
311
Standard
deviation,
cm/d
24
49
30
73
104
55
85
98
159
Coefficient of
variation,
X
22
42
21
48
59
31
32
34
51
a. Cylinders were tested (1n place) after treatment No.2 without a buffer pond.
b. Cylinders were tested (1n place) after treatment No.4 with clear water.
cm x 0.3937 * in.
Duncan's multiple range test, a = 0.05 (probability of rejecting a true
hypothesis), indicated significant differences between the following
treatment means referred to in Table 18: 7-6, 7-5, 7-4, 7-3, 7-2, 9-6, 9-5,
9-3, 9-2, 9-1, 8-6, 8-5, 8-3, 8-2, and 8-1.
Final infiltration rates in all cases were several times the rates
determined by flooding the entire basin with wastewater (see Table 17). This
phenomenon was predicted by Bouwer [21] who suggested that a small buffer
area in relation to inner test cylinder area may result in an overestimation
of infiltration rate by cylinder infiltrometers. On the other hand, Burgy
and Luthin [22] reported single cylinder infiltrometer results within 30% of
the mean infiltration rate determined by flooding 12 m by 27 m (40 ft by 90
ft) plots. No difference was reported when buffer ponds were used. In the
second case, test cylinders were small, (15 cm [6 in.]) and buffer cylinders
were not large, (30 cm [12 in.]), relative to inner cylinder diameters.
The coarse texture of the Hoi lister soil may account for the high
measured infiltration rates. The relatively small cylinder area as compared
to that of the infiltration basin tends to decrease the effect of gas binding
and soil pore clogging by wastewater solids. In addition, there was no
significant difference between tests conducted with and without buffer
cylinders at Hoi lister. This suggests that radial movement of water below
the infiltrometers was occurring.
54
-------
Infiltrometer results did not show a significant difference (a = 0 05)
between tests using clear Water and tests with wastewater. This relation
held for both undisturbed or disked soil conditions. The documented pore
clogging effect of wastewater solids [23] was somehow masked by infil trometer
us s u conQi ui ons
u °f diskin9 on infiltration velocity is clearly
indicated by the data. Although the solids mat, which characteristically
forms during flooding at Hollister, had dried and formed large cracks the
infiltration capacity was not as great as tests conducted on disked soil.
Also, under similar test conditions, there was no significant difference
between the control site, where wastewater had never been applied, and Basin
6 where wastewater has been applied for 30 years
SOIL CHEMISTRY
Introduction
The soil chemistry program at the Hollister rapid infiltration site
ipin H^r h rlyS1S °,f 23 so11 V*r<*^' The methods of analyse have
been described previously. A summary of the results is presented in Table
,1 Pa^fierS dr< dis9ussed separately or in natural groups. The data were
also plotted as a function of sampling depth. For the purposes of plotting
the means are bracketed by an error bar of plus or minus one standard
To fjd.litate plotting, treatment site points were depressed 6 cm
(22 in.) from their true location. In all cases, squares represent control
sites, and circles represent treatment sites. control
rm nq°^nS?VhInLPdr?U?terS' concentration " pseudo-mi nimums" occurred at 100
cm (39 in.) depth. This occurred because the data were calculated on a
whole soil basis, though the analytical measurements were performed on the
ess than 2 mm size fraction. The larger concentrations of gravel at 100 cm
(39 in.) caused the "whole soil" concentrations to appear small.
NN *nHe/Had4r iS ?dvl!?d that the sum of the exchangeable cations Ca, Mg
Na and K differs significantly from the cation exchange capacity (CEC
This was probably due to analytical error. Chapman [24] notes that in
calcareous soils, CEC tends to be underestimated, while exchangeable Ca is
overestimated. The U.S. Salinity Laboratory [12 recommends that Ca not
50115 While ^ ^ ^ cautfolt
55
-------
TABLE 19. RESULTS OF SOIL CHEMICAL ANALYSES
Depth, cm
Control
No. 1
0-16
25-35
95-105
295-305
Control
No. 2
0-16
25-35
95-105
295-305
Treatment
Site No. 1
0-16
25-35
95-105
295-305
Treatment
Site NO. 2
0-16
25-35
95-105
295-305
Treatment
Site No. 3
0-16
25-35
95-105
295-305
CaCOs Conductivity,
pH equiv, % fimhos/cm
8.5
9.2
9.4
9.4
7.8
8.4
8.9
9.1
6.3
6.8
7.9
8.8
6.4
6.5
7.8
8.8
6.7
7.6
8.0
8.6
1.55
2.27
2.47
2.51
1.08
2.06
2.27
3.04
0.28
0.27
1.17
1.42
0.36
0.29
2.01
1.39
Nm
Nm
Nm
2.32
740
100
100
400
770
500
330
500
2940
2400
1800
700
2620
1280
1260
880
2470
770
500
600
Organic
matter, %
0.76
0.08
0.02
0.01
1.35
0.15
0.02
0.02
1.20
0.20
0.06
0.11
2.19
0.12
0.03
0.08
2.02
0.28
0.05
0.03
Nitrogen, PP"1
Total
560
76
64
45
840
110
34
180
1200
370
120
180
1720
350
93
190
1600
200
104
77
Organic
550
62
45
34
818
98
30
167
1100
330
99
140
1600
290
74
150
1500
174
86
65
Phosphorus
Extractable,
ppm
13
0.67
0.56
3.7
8.4
0.15
0.09
0.17
57
61
42
54
109
73
39
32
110
63
3)
21
Total -P,
ppm
710
610
390
330
790
460
360
470
1600
1200
720
960
2000
1400
790
840
2800
1400
920
850
Boron,
ppm
<0.19*
<0.17
<0.14
0.13
0.22
<0.15
<0.09
<0.17
0.66
0.36
0.18
0.38
1.08
0.35
0.17
0.47
0.70
0.34
0.16
0.20
CONTINUED
56
-------
TABLE 19 (CONTINUED)
Depth, cm
Control
No. 1
0-16
25-35
95-105
295-305
Control
No. 2
0-16
25-35
95-105
295-305
Treatment
Site No. 1
0-16
25-35
95-105
295-305
Treatment
Site No. 2
0-16
25-35
95-105
295-305
Treatment
Site No. 3
0-16
25-35
95-105
295-305
CEC,
meq/100 g
7.2
2.8
1.9
2.3
8.6
3.3
1.2
2.6
4.8
4.1
3.2
6.9
11.
6.2
2.7
7.5
11.
4.2
2.0
3.2
Exchangeable cations,
meq/100 g
Na
0.93
0.11
Nm
0.12
0.41
0.07
0.02
0.05
1.2
0.77
0.39
0.91
3.4
0.59
0.22
0.74
1.2
0.48
0.26
0.14
K
0.26
0.02
Nm
0.01
0.30
0.05
NOT
Nm
0.22
0.13
0.06
0.16
0.34
0.16
0.01
0.16
0.38
0.10
0.09
0.02
Ca
5.6
3.0
1.8
1.5
5.7
1.8
0.88
3.2
0.64
Nm
2.8
4.5
1.7
0.09
2.3
6.2
0.94
0.18
0.57
2.7
Mg
1.8
1.1
1.3
1.5
1.8
1.1
0.70
7.6
3.3
2.9
2.2
4.2
7.0
4.0
1.3
4.2
6.3
2.6
1.4
1.9
Cd
0.08
0.01
0.01
0.01
0.12
0.02
0
0.01
0.14
0.07
0.02
0.03
0.24
0.05
0.01
0.01
0.18
0.04
0.01
0.01
Co
0.08
0.07
Nm
0.01
0.04
Nm
Nm
Nm
0.10
0.07 '
0.05
0.09
0.14
0.05
0.03
0.04
0.04
0.04
0.03
0.05
DTPA extractable
heavy metals, ppm
Cr
<0.08
<0.07
<0.06
<0.05
<0.08
<0.06
<0.04
<0.07
<0.06
<0.07
<0.05
<0.08
<0.08
<0.07
<0.06
<0.08
<0.08
<0.07
<0.06
<0.07
Cu
2.4
0.35
0.71
0.24
4.0
0.36
0.17
0.37
6.7
2.7
1.5
2.3
8.2
2.2
0.87
1.2
6.2
1.4
0.50
0.60
Fe
19
7.6
6.3
7.0
23
7.0
3.7
8.0
120
104
41
26
270
160
53
32
170
140
28
14
Hn
5.4
2.5
1.7
2.1
5.2
2.6
1.2
2.4
2.2
1.0
1.3
2.2
3.1
0.54
2.1
4.4
2.1
0.66
2.0
4.6
Ni
0.62
0.24
0.20
0.19
0.73
0.27
0.14
0.24
0.74
0.54
0.50
0.28
2.4
1.0
0.39
0.32
1.3
0.33
0.31
0.44
Pb
5.1
0.17
<0.14
<0.12
10.
0.36
<0.09
<0.17
3.5
0.59
0.35
0.41
5.7
0.67
0.29
0.36
6.6
0.28
0.17
0.17
Zn
0.98
0.12
0.04
0.05
1.6
0.21
0.03
0.07
11.
3.4
0.21
0.23
8.0
1.1
0.24
0.18
7.5
1.4
0.27
0.32
a. Below detectable limits
Note: Nm = not measurable.
cm x 0.3937 - 1n.
57
-------
Statistical Analysis of Soil Data
Three types of statistical analyses were performed for each soil species.
The tests and corresponding hypotheses are presented below.
Two-way analysis
of variance (ANOVA)
t-test (at each
depth increment)
Duncan's multiple
range test
H0:
Her
H0:
^controls = ^treatment site
^depth 1 = ydepth 2 = ydepth 3 = ydepth 4
Depth-treatment interaction = 0
^controls = ^treatment site
H0: paired treatment means are equal
H0: paired depth means are equal
In all cases, y equals the mean of the subscripted soil variable.
The tneory and assumptions underlying these statistical analyses are
presented in several texts [26, 27]. Briefly, it is assumed that the
hypothesis to be tested is true. Then the consequences of this assumption
are examined in terms of a sampling distribution. If, as determined from the
sampling distribution, observed data have a relatively high probability of
occurring, the decision is made that the data do not contradict the
hypothesis. On the other hand, if the probability of an observed set of data
is relatively low when the hypothesis is true, the decision is that the data
tend to contradict the hypothesis, ana the hypothesis is rejected.
The level of significance a, of a statistical test defines the
probability level that is to be considered too low to warrant support of the
hypothesis being tested, that is, a is the probability of rejecting a true
hypothesis. If the probability of observed data, p, is smaller than the
level of significance a, then the data are said to contradict the hypothesis
being tested, and a decision is made to reject the hypothesis.
The value of a was arbitrarily set at 0.10 for the two-way ANOVA, and
depth increment t-test, and ata= 0.05 for Duncan's multiple range test.
Thus when the calculated value of p was less than ot, the above hypotheses
were rejected [28].
58
-------
For the two-way analysis of variance, measurements for both control
treatment sites were given the following symbolic designations for
statistical treatment.
and
D2
D4
xm
X112
X211
X212
X311
X312
X411
X412
X121
X122
X123
X221
X222
X223
X321
X322
X323
X421
X422
X423
where D]
D£
DS
04
depth increment, 0-16 cm (0-6 in.)
depth increment, 25-35 cm (10-14 in.)
depth increment, 95-105 cm (37-41 in.)
depth increment, 295-305 cm (116-120 in )
control site treatment
application site treatment
k observations for DjTj
Once coded, Biomedical Computer Program BMDP2V, was used to generate
ANOVA tables for each of the 23 soil chemical species [29]. With the aid of
such a table it was then determined if significant differences in observation
magnitude existed among depths, between treatments, and/or resulted from a
depth-treatment interaction.
59
-------
The physical significance of such a statistical treatment is illustrated
by three hypothetical situations presented below. Two curves presented in
each graph represent control and treatment sites.
CONCENTRATION
SITUATION A
CONCENTRATION
CONCENTRATION
Q
SITUATION B
Q - CONTROL SITE
6 - TREATMENT SITES
SITUATION C
In Situation A, both control and treatment sites have concentrations
that are uniform with respect to depth, but the treatment site exhibits a
statistically significant increase in concentration relative to the control
site. In contrast, Situation B shows that control and treatment sites not
only exhibit a statistically significant difference due to wastewater
treatment, but also shows that depth introduces a significant source of
variation. Situation C introduces a third source of variation, a depth-
treatment interaction. In this case, the concentration for the treatment
site has increased at all depths relative to the control site. However, a
selective enrichment is observed where the values of depth are low (i.e., at
the surface). A statistical summary including chemical species, source of
variation (D, T, DT) calculated F-statistic, and P-value, is presented in
Table 20. Test statistics were deemed significant when the condition P< ct=
0.10 was satisfied.
60
-------
TABLE 20. ANALYSIS OF VARIANCE FOR SELECTED SOIL PARAMETERS
Species
CEC
Na
K
Ca
Mg
Cd
Co
Cr
Cu
Fe
Mn
Ni
Source
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
F
10.02
4.70
0:46
4.23
6.51
0.73
25.93
9.09
0.53
6.10
4.99
10.68
2.89
3.20
1.89
33.98
10.43
2.97
3.39
7.04
0.31
6.35
1.99
1.54
39.94
28.56
4.69
7.14
30.47
5.30
14.17
5.80
11.16
4.66
4.88
0.73
P
0.001
0.051
0.718
0.029
0.025
0.552
0.000
0.011
0.669
0.009
0.045
0.001
0.079
0.099
0.185
0.000
0.007
0.074
0.054
0.021
0.817
0.008
0.184
0.253
0.000
0.000
0.022
0.005
0.000
0.015
0.000
0.033
0.001
0.022
0.047
0.552
Species
Pb
Zn
PH
CaCO-
J
Conduc-
tivity
Organic
Matter
Total -N
Organic-
N
Extrac-
table-P
Total -P
Boron
Source
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
D
T
DT
F
29.22
0.68
1.33
35.61
38.55
19.58
20.60
66.33
3.31
7.91
35.54
0.86
5.97
27.16
2.63
35.11
4.03
2.29
57.82
18.62
7.89
66.70
17.95
8.24
5.31
66.46
2.91
9.30
37.63
2.86
9.40
26.92
5.56
P
0.000
0.427
0.310
0.000
0.000
0.000
0.000
0.000
0.057
0.004
0.000
0.489
0.010
0.000
0.098
0.000
0.068
0.130
0.000
0.001
0.004
0.000
0.001
0.003
0.015
0.000
0.078
0.002
0.000
0.080
0.002
0.000
0.013
In addition to the two-way ANOVA, a t-test for each depth increment and
a Duncan s multiple range test were performed. These analyses helped isolate
the location(s) of heterogeneity" within the soil profile. The analyses
were performed using a Hewlett-Packard combination desktop calculator-
plotter. Sample output is given in Table 21. Outputs for all soil data are
shown in Appendix B.
61
-------
TABLE 21. SAMPLE OUTPUT FOR STATISTICAL
ANALYSIS OF SOIL DATA
pH, Units
Depth, cm
1. 0-16
2. 25-35
3. 95-105
4. 295-305
Control 1
(1)
8.500
9.200
9.400
9.400
Control 2
(2)
7.800
8.400
8.900
9.100
Treatment
site 1
(3)
6.300
6.800
7.900
8.800
Treatment
site 2
(4)
6.400
6.500
7.800
8.800
Treatment
site 3
(5)
6.700
7.600
8.000
8.600
Mean
(6)
7.140
7.700
8.400
8.940
8.045
RSDa
(7)
13.528
14.520
8.460
3.502
5. TOTAL
6. MEAN
7. RSDa
0-16
25-35
95-105
295-305
36.500
9.125
4.682
34.200
8.550
6.786
Control Average
8.150
8.800
9.150
9.250
GROUPS OF NONHETEROGENEOUS MEANS"
DUNCAN'S MULTIPLE RANGE TEST.
8.940
8.400
7.700
7.140
8.400
29.800
7.450
15.047
29.500
7.375
84.333
30.900
7.725
55.285
Treatment Site Average
6.467
6.967
7.900
8.733
160.900
"t"
-5.545880
-3.537971
-6.228411
-3.661871
9.125
8.550
7.725
8.550
7.450
7.375
a. Relative Standard Deviation.
b. Numbers on same horizontal line are nonheterogenous.
Mean column (6); second set refers to Mean line 6.
First set of numbers refers to
For an a = 0.10, the computed, absolute value of t must exceed 2.353
before the hypothesis of equality of means can be rejected. So for the case
presented, treatment site and control site values of pH are significantly
different at all depth increments.
pH and Calcium Carbonate
The pH of the soil-water system is critical, since it serves as a
"master variable" controlling the solubility of many elements and influences
microbial activity. It is important to know both the initial pH of a soil
system and the expected changes in pH as the system is manipulated over time.
In a "natural system," soil pH change is affected by biological
activity, organic matter, alkaline-earth carbonates, and by hydrous oxides of
62
-------
aluminum and iron. For an arid-zone, nonsaline soil, such as the Metz,
calcium carbonate undoubtedly exhibits a major pH control.
The addition of wastewater to the treatment site has significantly
decreased soil pH (Table 20). This pH reduction was apparent at all depths
(Table 21). The pH differences between control and treatment sites ranged
from 0.5 to 1.6 units depending on the depth below the surface. The highest
average pH values were found at depths of 300 cm (118 in.), while mildly
acidic conditions (pH 6.5) were found in samples from the surface of the
treatment sites (Figure 17).
Simultaneously, calcium carbonate concentrations have been depleted at
the treatment site. The buffering capacity of the soil was thereby
diminished, permitting a pH reduction. The effect was most pronounced in the
surface 30 cm (12 in.) where the difference was statistically significant.
The ultimate fate of Ca, dissolved from calcium carbonate, is uncertain
as there had been no noticeable accumulation of CaCO, at depths through 300
cm (Figure 18). Although there was a slight increase in exchangeable Ca at
300 cm, it was not statistically significant. Therefore, it is possible that
Ca was passing through to the underlying groundwater.
PH
6. 00 7. 00 8.00 9. 00
so
I 00
I 50
200
250
300
1
,,
k 4-
. 150
200
250
300
0-5 1.0 1.5 2.0 2.5 3.0
1 - ' - I IT-, I - 1 - 1 - 1 - 1 - 1 - 1 - 1
LE8END
0= CONTROL SITES
0= TREATMENT SITES
Figure 17. Vertical distribution
of soil pH.
Figure 18. Vertical distribution
of soil calcium carbonate.
63
-------
Interestingly, the average surface soil pH at the treatment site (pH =
6.5) was less than the average pH of the applied wastewater (pH = 7.3). This
suggests an additional mechanism(s) for pH reduction. One possibility is the
nitrification of wastewater ammonium to nitrate according to the following
reaction:
NHj + 202 = N03" + H20 + 2H+ (3)
The creation of 2 moles of hydrogen for every mole of NH4 oxidized
would further reduce the pH of the soil system. In addition, it can be
postulated that the species CaN03 would form, accelerating the leaching of Ca
from the soil profile.
It should be noted as well that the pH at the control site was often in
excess of that which would be predicted by equilibrating CaCO- with water (pH
= 8.2). Therefore, the presence of a more soluble carbonate or bicarbonate
species (NaC03, MgHCOo) is suggested.
Conductivity of the Saturated Extract
Conductivity serves as a quick estimate of the amount of soluble salts
in the soil system. The measured value is a function of both temperature and
soil water content at the time of measurement. The USDA salinity laboratory
has published several graphs and tables that allow conversion of conductivity
measurements to soluble salt concentration. Input of salts at a rate greater
than that removed by leaching will increase the measured conductivity. It is
a valuable parameter for monitoring soil salinity and predicting plant
toxicity.
A plot of average conductivity versus depth is presented in Figure 19.
Both treatment and control sites show the same general trend, that is,
highest extract conductivity at the surface which decreases with depth.
Treatment site values are significantly higher than the controls, rising to
nearly 2,700 ^mhos/cm at the surface (see Table 20), reflecting the input of
soluble salts in the wastewater. The interaction between depth and treatment
is also significant (p = 0.098), as exhibited by the larger differences
between surface conductivity values and those at depth.
The lack of significant difference between treatments at 30 and 100 cm
(12 and 39 in.) resulted from the large standard deviations at these depths.
Though not statistically significant, salinity increases may be occurring at
these depths as well. At this level of soil extract conductivity, these
soils could successfully grow any crop although the most salt sensitive crops
might suffer some yield diminution.
64
-------
ELECTRICAL CONDUCTIVITY, mmhos/cm
LEGEND
O CONTROL SITES
O TREATMENT SITES
Figure 19. Vertical distribution
of saturated paste, soil conductivity,
Organic Matter
Soil organic matter influences soil water holding capacity, the
stability of soil structure, pH, the exchange capacity, the retention of
trace metals by chelation, and the cycling of carbon, nitrogen, and
phosphorus [17, 30]. It has a much higher gravimetric cation exchange
capacity than any clay mineral and has a surface area comparable to that of
expandable clays [18]. Its exchange capacity is highly pH dependent, being
very low at pH values less than 5, but rising to over 300 meq/lOOg at pH
values of 8.5. Of some interest is the fact that organic matter tends to
counteract the unfavorable effects of high exchangeable sodium percentage on
soils by stabilizing aggregates of clay minerals, thus diminishing dispersion
and pore clogging. It serves as an energy material for microorganisms which
in turn form humates, fulvates, and other polymers which form and stabilize
aggregates.
The balance between input and decay of organic matter is modified by
such factors as composition of the input material, type of microorganisms
present, temperature, pH, availability of moisture, and the oxygen content in
the immediate environment [17].
An analysis-of-variance (Table 20) of the Hoi lister soil data revealed a
significant increase in soil organic matter resulting from wastewater
application. Control site values range from 1.35% at the surface to 0.01% at
300 cm (Figure 20). Treatment site values range from 2.19% to 0.03% for the
same depth increments.
65
-------
ORGANIC MATTER, »
O.S 1.0 1.5 2.0
100
1 SO
200
290
300
LEGEND
CONTROL SITES
O TREATMENT SITES
Figure 20. Vertical distribution
of soil organic matter.
In contrast to the analysis-of-variance, the t-statistic revealed no
contrasts between control and treatment site locations at any depth
increment. This apparent discrepancy may have resulted from the smaller
number of degrees of freedom used in the t-test or the assumptions implicit
in the analysis-of-variance may have been violated.
Because of the above anomalies, the buildup of organic matter, if any,
must be considered small. This would suggest that the soil microbial
population existed in sufficient numbers to bio-oxidize most of the incoming
organic matter. It should be noted, as well, that the BOD of the shallow
treatment site wells was not significantly different (t-test,a = 0.10) than
the offsite control wells, further suggesting that degradation of bio-
oxidizable material was occurring. The fact that COD and TOC values showed
significant increases relative to the control wells suggests that some
"refractory" organics were passing through the soil profile.
Nitrogen
The nitrogen cycle in soils is quite complex. When presented in a
grossly simplified manner, it can be viewed as follows: plants acquire
nitrogen as ammonium or nitrate ions and form organic nitrogen; after death,
the organic nitrogen is mineralized into ammonium ion which in turn may be
acquired by living plants or nitrified to nitrate. Nitrate may be acquired
by plants or denitrified to either nitrous oxide or nitrogen gases.
66
-------
Nitrogen accumulation can be expected to occur when organic forms of
nitrogen are introduced into the soil system, or when the dominant form of
nitrogen is the ammonium cation [18]. In contrast, nitrogen losses are
expected when nitrogen is in a mobile anionic form (N0o~, NO ~) or when it is
converted to a gaseous species (N2, N20). The former Toss i$ by leaching,
while the latter loss is by atmospherTc escape and leaching [23].
The rates of nitrogen conversion, and therefore rates of accumulation
and losses, are influenced by pH, temperature, aeration, moisture,
availability of a carbon source, and the presence of the appropriate
microorganisms. The rate and magnitude of nitrate loss to the underlying
grounawater is of some importance because it has been one of several
associated causes of methemoglobinemia in infants. The USPHS has recommended
that domestic water supplies contain less than 10 ppm nitrate-N.
Significant concentration increases resulting from wastewater treatment
were observed at the Hoi lister site for the two nitrogen species measured--
total and organic-N. Differences were significant for the first three depth
increments, but nonsignificant at 300 cm (118 in.). The results are plotted
in Figures 21 and 22, respectively.
TOTAL-N. ppm
ORGANIC-N. ppm
so
100
130
zoo
250
300
400 800 1200 1800
-I r-=-l 1 1 1 H-
50
100
ISO
ui 200
250
300
400 BOO 1200 1600
-I r-^r-l ' 1 i 1
LEGEND
O CONTROL SITES
O TREATMENT SITES
Figure 21. Vertical
distribution of soil
total-nitrogen.
Figure 22. Vertical
distribution of soil
organic-nitrogen.
67
-------
Total-N and organic-N were seen to be closely related in both trend with
depth and magnitude. The highest concentrations of total-N occurred at the
surface where values of nearly 1500 and 700 ppm were observed for treatment
and control sites respectively. The values decreased by factors of one-fifth
and one-tenth at 300 cm depth. Organic-N accounted for 80% or more of the
total-N throughout the soil profile, though it accounted for only 40% of the
total-N in the wastewater. This suggests that organic-N was being
preferentially bound by the soil.
A comparision of total-N input with the mass of total soil nitrogen
currently in excess of background levels (mass balance) revealed that the
surface 300 cm of soil can account for only 2% of the total-N applied over
the 30 year period. This implies that much of the nitrogen had been
converted to mobile forms and no longer exists within the sampled soil
profile. Conversion to N? or N20 would result in atmospheric losses, while
conversion to NO," would result in losses to the underlying groundwater.
Evidence for botn processes is presented in the following paragraphs.
Nitrate-N levels in the shallow groundwater were higher than input
levels (Section 9, Table 28 ) and suggest that some nitrification was
occurring. However, the high background nitrate-N levels in the offsite
control wells, especially at 9C, make this conclusion tentative.
The case for denitrification is presented as follows:
Organic-N is generally coverted to N03-N without much change in absolute
concentration. If nitrification and subsequent loss to the underlying
groundwater were occurring, total-N levels in the shallow aquifer would be
expected to approach input total-N levels. Examination of the groundwater
and effluent data (Table 28) reveals that input levels of total-N are
significantly greater (t-test, p = 0.00) than total-N levels in the shallow
groundwater. This suggests that denitrification and subsequent atmospheric
nitrogen loss was occurring. In addition, the necessary pH, carbon source,
and anaerobic conditions (when flooded) for such a conversion exist at the
treatment site. Further evidence for the reducing conditions necessary for
denitri
reduction
ification are given in the heavy metals section where evidence for
ion of Mn09 to Mn+2 is presented.
Phosphorus
Soil phosphorus is known to occur both in organic and inorganic forms.
The chemistry and thermodynamic relationships of the organic forms, however,
are less well understood.
In general, the major controls exerted by the soil system on Inorganic
phosphorus availability are adsorption onto clay minerals and hydrous oxides
of iron, aluminum, and manganese as well as the formation of
cryptocrystalline precipitates with calcium, iron, and aluminum. Organic
forms are thought to be adsorbed in a manner similar to inorganic forms [18].
Because the removal mechanisms are still not fully understood, the term
sorption is increasingly used to describe any loss of soluble phosphorus from
the system [17, 23, 31]. The extent of sorption is modified by soil type,
68
-------
particle size pH redox potential, temperature, organic matter content, and
reaction time LloJ.
Classical adsorption isotherm expressions have been used to describe
phosphorus sorption. The two most common are the Langmuir and Freundlich
expressions; though the slow mineralization of phosphorus in organic matter
as well as the slow migration of adsorbed P to interfacial precipitation
^^r'oon1'65^ imP°sslble *> determine the precise sorption capacity of a
soil [32]. Theoretical and empirical equations have been used to describe
the kinetics of phosphorus uptake by soils [31].
At the Hoi lister rapid infiltration site, significant differences
between control and treatment sites were observed (p = 0.002) for both total
and bicarbonate extractable phosphorus at every depth increment The
9\gn*!S$inCCnSlh%dJP?h-^eat"!ent interaction is easily observed in Figures
23 and 24. Both total and extractable P show a greater accumulation in the
surface 100 cm (39 in.) of the soil profile than shown at depth. At the
surface, treatment site total-P increased from 750 to 2,100 pom while
extractable-P increased from 9 to 92 ppm.
TOTAL-P. ppm
500 1000 1900 2000 2100
SO
100
I 30
200
230
300
-i h
90
100
190
200
290
300
BICARBONATE-P. ppn
70 *o go 10 100
* i I .t rI ,«.
LEGEND
D CONTROL SITES
O TREATMENT SITES
Figure 23. Vertical distribution of
soil total phosphorus.
Figure 24. Vertical distribution
of soil bicarbonate
extractable phosphorus,
69
-------
The fact that extractable-P was so much higher at all sampling depths in
the treatment sites not only suggests that biological availability was high,
but also that soil solution P may have been passing through the soil profile.
The latter is verified by noting that shallow groundwater concentrations of
total P were dramatically larger (8 and 10 mg/L) than baseline concentrations
of about 0.1 mg/L. In addition, shallow well levels of total-P were
approaching input levels.
Mass balance calculations, performed by comparing total-P input over the
30 year period to measured soil sorbed phosphorus, revealed that only 30% of
the total P applied had been retained within the upper 300 cm (118 in.) of
soil. Again, this suggests significant transport of P to the groundwater
bel ow.
In addition to the field studies, phosphorus isotherms for both surface
control and surface treatment sites were generated using the nondestructive
technique of Enfield and Bledsoe [10]. Freundlich isotherms were used to
describe the shape of the sorption curves. In Table 22, the values K, n, and
multiple -r2 terms are presented for the following equation:
S = KCn (4)
where S = sorbed P, ppm
C = equilibrium P concentration, mg/L
K,n = constants related to the energy of sorption
TABLE 22. CALCULATED FREUNDLICH COEFFICIENTS
FROM PHOSPHORUS SORPTION ISOTHERMS
Location
Control, 0-16 cm
Treatment site,
0-16 cm
Time,
h
1
3
53
120
288
1
53
288
K
6.82
14.7
22.2
28.6
33.1
3.64
7.25
16.0
n
0.661
0.576
0.459
0.478
0.470
G.868
0.729
0.579
r2
0.99
0.99
0.97
0.93
0.98
0.92
0.91
0.85
cm x 0.3937 = in.
The corresponding sorption curves are plotted in Figures 25 and 26. The
extent of sorption is a function of time and is observed to increase as the
equilibration time increases. Of particular interest, however, is the extent
of sorption at the treatment site. After 288 hours, an equilibrium
concentration of 20 mg/L will yield 92 ppm sorbed P at the treatment site,
which compares with 135 ppm at the control site for an equivalent
concentration. Thus, even after 30 years of wastewater application, the
surface soil is retaining 68% of its experimentally determined sorption
capacity.
70
-------
411
300
111
111
9
II
II
I
SI
3 h
l_h-
o.i i
1.1
LEgENC
IT
3 h
93 h
A 120 h
211 h
2 3 4 I I 7 I III 21 31 41 91
EtUILIRRlUN CONCENTRATION, C, I/L
NOTE:
PREDICTED 30 yr ISOTHERH
ir ENFIELOS APPROACH.
Figure 25. Logarithmic plot of Freundlich
regression equation to the experimental
data for sorbed phosphorus as a function
of time and equilibrium concentration.
Control site composite, 0-16 cm depth.
100
10
70
10
211 h
53 h
1 h
I liitltllt II tl 40 50
EQUILIIIIUI CONCENIItTION, f,mt/l
LE8END
1 h
A 53 h
Figure 26. Logarithmic plot of Freundlich
regression equation to the experimental
data for sorbed phosphorus as a function
of time and equilibrium concentration.
Treatment site composite, 0-16 cm depth.
-------
Sawhney and Hill [33] found equivalent behavior for Connecticut soils
and suggested that alternating periods of wetting and drying may bring fresh
mineral surfaces into equilibrium with the soil solution, creating new sites
for P sorption. Enfield [32] notes that there is a balance between sorption
and conversion of adsorbed P to more insoluble forms. He suggests that
sorption is initially rapid onto mineral surfaces, but as time increases,
reactions occur which utilize adsorbed orthophosphate to form phosphate
minerals that have solubilities that are somewhat less than the adsorbed
forms. This regenerates some sites for adsorption. Therefore, short-term
laboratory P isotherm studies represent minimum estimates of field P
sorption.
Tofflemire [34] approached the problem of relating laboratory P
isotherms to field studies in an empirical manner. He noted that at Lake
George, New York, a "mineralization factor" of 6 could be used to relate
actual field P removal after 36 years of wastewater application to that
predicted by a 120 hour isotherm. Further, he indicated that a factor of at
least 2 would be appropriate for most rapid infiltration systems. Using the
Hoi lister soils data and Tofflemire1 s approach, a "mineralization factor" of
15 is obtained (1,367/91 = 15, where 91 ppm is the amount of P sorbed after
120 hours at 12 mg/L equilibrium concentration [the average total -P input
level] and 1,367 ppm is the average difference between control and treatment
site total-P concentrations).
Enfield [31] and Enfield, et al . [32] took a more quantitative approach
to relating laboratory studies to actual field P removal. They noted that P
removal is a function of solution P concentration in the surrounding solution
(C), and the amount of P already sorbed by the soil (S). Three functions are
presented below:
Model Model integrated
differential form form (S - 0, at t - 0)
1. ff-a(KC-S) S=K
2. ff- 30.cn. s) S - .C" -
3. -aCbsd S =
(1 - d)at]
If values of 3.S/3t, C, and S are known (from isothermal plots) the
constants a, K, 3, m, n, a, b, and d can be evaluated using multiple
regression techniques. The results of such an exercise are presented in
Table 23, for t in hours, C in mg/L, and S in ppm. Because concentrations
greater than 20 mg/L are generally not encountered in domestic wastewater,
only points below this equilibrium concentration were included when
evaluating these coefficients.
72
-------
TABLE 23. EVALUATION OF THREE
DYNAMIC PHOSPHORUS SORPTION MODELS
Mode]
1
2
3
Coefficient
a
K
0
m
n
a
b
d
Value
0.369
6.64
0.45
22.47
0.53
4490
2.24
-3.48
r2
0.75
0.77
Plots of dynamically predicted versus equilibrium observed values of
are presented in Figures 27 through 29, respectively. Models 1 and 2
are adequate when values of as/3t are greater than 5 ppm/h (i.e., when
equilibration times are short), but fail when as/3t is small. Model 3
appears to be the least satisfactory model, and is inadequate throughout the
range of 3S/3t. Order of magnitude differences are observed.
As with most models, they should not be extrapolated beyond the
experimental equilibrium times. Models 1 and 2 approach KC and mCh
respectively, as t increases, while S approaches infinity as t increases in
Model 3. Therefore in their present form, these models cannot be used as a
predictive tool for land treatment operations.
In an effort to overcome this problem, Enfield [32] introduced a
graphical interpolation technique. Underlying this empirical technique is
the assumption that phosphorus removal is a function of C, S, and t.
Using Enfield1s approach, a predicted 30 year isotherm was constructed
and graphed in Figure 25 (previously mentioned). As is observed Ehe amount
of sorption is shown to increase markedly over that recorded at 120 hoSrs
Previously it was shown that the actual amount of P removal at the Hollister
site was 1 367 pprn. This compares to a predicted value of 325 ppm that would
be expected to be removed at an equilibrium concentration of 12 Sg/L Hence
this method underestimates the soil's removal capacity by a factor of 4
More research is necessary to relate laboratory P sorption to field studies
Factors such as PH and Ca concentration are factors that should be accounted
for in any future models. Both the models of Tofflemire and EnfilldSave
been shown to be conservative, and therefore still useful for design
D u i \J\J jC o
purposes
73
-------
IODEL 2
IODEL 1
49.0-
JC
1 "-^
D.
0.00
-7.50 a
5. 39
O.
J »«
IS>
fO J 4
12 ^
« 9-10192029303940
3S/3t, ppm/hr
45 50
i 9 I o 19 ;g » 11 11 « is tg
3S/3t, ppm/hr
Figure 27. Dynamically predicted values Figure 28. Dynamically predicted
versus equilibrium observed values of values versus equilibrium observed
sorption rates (aS/9t). Model 1. values of sorption rates (3S/9t).
Model 2.
MODEL 3
§. i. 40
O-
.700
.350
0.00
- . 3 50
-.710
-1.15 -
& DYNAMICALLY MEOICTED
EOVILIBRIUM memo
NOTE: I0«£ »OINTt tVITTID F0» CLARITY
3S/3t, ppm/hr
Figure 29. Dynamically predicted values
versus equilibrium observed values of
log sorption rates (3S/8t). Model 3
74
-------
Boron
Boron is an agriculturally important species because small amounts are
essential for plant growth, while even a slight excess can be toxic to some
plants L36J. Boron concentrations in irrigation waters in excess of 0.5 mq/L
are considered undesirable for boron sensitive crops such as citrus stone
and pome fruit trees as well as grapes [36]. ' '
The increased use of boron compounds in certain household laundry
products has tended to aggravate the problem [37]. Bingham reports that in
the Santa Ana River system in California as much as 50% of the 0 75 to 1 50
mg/L boron in the sewage effluent comes from household sources [36]. Purves
and Mackenzie also showed that boron in sludges and municipal waters is
largely in a water soluble form [38].
It is generally assumed that the orthoboric acid species exists in
nature. Since the pK of the first dissociation constant is 9.2 the
undissociated form, H3B03, is thought to be the dominant species in natural
systems L39J.
Many soils are capable of immobilizing boron. Boron adsorption occurs
mainly onto the mineral fraction of the soil, though organo-boron
combinations do occur [17]. Boron can be adsorbed onto iron and aluminum
hydroxy compounds present as coatings on, or associated with, clay minerals
[40, 41]; onto iron or aluminum oxides in the soil [42]; and onto micaceous
clays although all clay minerals show some capacity for boron retention [431
Rhoades, et a! . [44] concluded that in arid soils boron adsorption is
associated with magnesium hydroxy clusters or coatings on the weatherinq
surfaces of ferromagnesium minerals such as olivine, enstatite, oiopside
auguite, tremolite, and hornblende, as well as the micaceous layer silicates.
Boron adsorption occurs over a wide range of PH. Such results suggest
that boron is adsorbed as boric acid under acid conditions and borate ion as
the PH approaches 9.0 [41]. Boron adsorption also takes place independently
of concomitant adsorption of other anions. Studies by Schalscha et al F451
revealed no effect from the simultaneous adsorption of sul fate oJ ffiofftate
on boron adsorption. Griffin and Burau [46] found evidence for th?ee
tnterfacially adsorbed
depth-treatment interaction was observed as well, caused by the
an in the control soil is nearly unifonn with depth, havinq a
. 5f °'16 ppm' the ° to 16 cm <° to 6 in.) treatment site sSoles
had approximately four times more boron than the control samples S1^esamples
differences were much less at 30 and 100 cm, but are statistically
significant. Boron may be passing through to underground waters thouah a
significant increase in boron was not observed at 300 cm. s' OU9h a
75
-------
BORON, Ppm
zoo
250 .
300
LEGEND
D CONTROL SITES
O TREATMENT SITES
Figure 30. Vertical distribution of
soil boron.
CEC and Exchangeable Cations
Electrostatic charges at soil surfaces arise from atom-proxying in
aluminosilicate minerals, proton-hydroxide reactions at the aqueous-solid
interface, and specific adsorption of weak acids or bases [47,48]. These
negative charges create electromagnetic force fields which attract cations
and repel anions. The exchanged ions near the charged surfaces are in dynamic
equilibrium with the cations of dissolved salts in an outer solution. If the
composition of the salt solution changes, it is reflected by a corresponding
change of composition in the inner exchange phase.
The soil cation exchange capacity (CEC) is a property of paramount
importance for it is associated with nutrient availability, soil
permeability, and the ability of the soil to desorb cations from a wastewater
influent.
Numerous equations have been developed for describing exchange reactions
[48]. Most appear to have been derived from classical mass-action
expressions or Donnan theory [49]. In general, the final form of these
equations takes the form:
AX + B+ - BX + A*
for the reaction
(5)
where the quantities in brackets represent activities of solution Ions and
the quantities in parentheses are exchanger concentrations [50].
76
-------
The selectivity coefficient, KAB, is generally not constant over a wide
range of exchange compositions. Therefore, models using single-valued
coefficients can only be used semi quantitatively over limited concentration
ranges. This is largely due to the existence of nonequivalent bonding sites
on the soil surface [47, 50]. More quantitative approaches treat the
coefficient as a function of exchange composition.
The actual soil CEC is a function of pH, presence of organic matter
surface area, type of clay mineral, and the analytical method used [24] '
Generally, that portion of the soil that hydroxylates or deprotonates easily
as the pH is increased (amorphous hydrous oxides and organic colloids) will
show a corresponding CEC increase. That fraction of the CEC due to atomic
proxying will remain relatively unaffected by changes in pH. Soil surface
area can be correlated with the CEC. »un Mg+2> K+> Na+
when the ions are of comparable concentrations.
Empirical relationships exist [12] that relate solution equilibrium
concentrations of soluble cations to the concentration of exchangeable
cations. The most widely used are: manseauie
ESR « -0.0126 + 0.01475 (SAR) ,&\
EPR = 0.0360 + 0.1051 (PAR) tj\
where ESR = exchangeable sodium ratio
* exchangeable sodium
CEC - exchangeable sodium
EPR * exchangeable potassium ratio
exchangeable potassium
ttt - exchangeaoie potassium
where Na+, K+, Mg+2, Ca+2 refer to concentrations in meq/L.
77
-------
The older SAR-ESR relationships have been modified to include additional
water quality parameters. Certain combinations of water soluble salts will
result in the deposition or dissolution of calcium carbonate, thereby
affecting the SAR. Rhoades [51] presents the equation:
ESR = SAR [1 + (8.4 - pHc)]2 (8)
soil irrigation
surface water
Tables for calculating pHc are presented in Ayers and Westcot [52].
In arid fine grained soils, an ESR greater than 0.15 is generally
considered serious, though susceptibility to permeability degradation is a
function of mineralogy, cementing materials, and other factors. Highly
hydrated Na replaces less hydrated Ca+^ and Mg+2, resulting in increased
dispersion of clay. This in turn adversely affects soil penneability.
Soils in the application site showed a significant increase in CEC with
respect to depth and treatment. However, no depth-treatment interaction was
observed. Because of the smaller number of degrees of freedom, the more
specific t-statistic did not show significant CEC increases due to treatment
at any depth (Figure 31). Duncan's range test indicated that CEC increases
were significant only for treatment Site 2 over control Sites 1 and 2.
Control site CEC value averages ranged from 1.5 to 7.9 meq/100 g, while
treatment site values ranged from 2.6 to 8.9 meq/100 g. Highest values were
at the surface with lower values at depth. In spite of the pH decrease
resulting from wastewater application, CEC increased. It is therefore
presumed that the resulting loss of any pH dependent charge was more than
offset by the influx of organic matter and mineral clays in the wastewater.
As a general rule, a 1% increase in soil organic matter or clay content can
result in a CEC increase of 3 or 0.8 meq/100 g, respectively.
Three exchangeable cations (Na, K, and Mg) showed significant increases
in concentration after wastewater treatment. Significant differences
occurred for Mg at the surface and at 30 cm (1 ft), for Na at 30 cm (1 ft)
and 100 cm (39 in.), and for K at 30 cm only. No significant depth-treatment
interactions were observed for any of these cations (Figures 32 through 34).
This is especially apparent for Na and K whose increases appeared nearly
uniform throughout the soil profile. The effect of wastewater addition on Ca
(Figure 35) is confounded by the possibility of analytical error and chemical
interactions and is discussed subsequently. The interpretation of Mg
behavior is complicated by the inclusion of a 300 cm (10 ft) control value
that appears to be anomolous (7.6 meq/100 g). Laboratory contamination
appears to be the cause of this high value.
As was described previously, SAR and PAR are often used to predict ESR
and EPR [48, 51]. This exercise was performed for Hollister soils. The
results are presented in Table 24.
78
-------
so
100
ISO
UJ 200
230
300
CEC , maq/IOOg
2.0 4.0 S.O 1.0 10.0
-,I,I,Ii A iI
SODIUM, meq/IOOg
Figure 31. Vertical
distribution of cation
exchange capacity.
200
250
300
POTASSIUM , meq/IOOg
01 0.2 0.3
Figure 32. Vertical
distribution of
exchangeable sodium.
100
1 50
200
250
300
Figure 33. Vertical
distribution of
exchangeable potassium.
MAGNESIUM, neq/IOOg
CALCIUM, miq/IOOg
1.02.0 4.05.08.0
Figure 34. Vertical
distribution of
exchangeable magnesium.
50
100
I 50
200
250
300
1.0 2.0 3.0 4.0 5.0
LEGEND
O CONTROL SITES
O TREATMENT SITES
Figure 35. Vertical
distribution of
exchangeable calcium
79
-------
TABLE 24. MEASURED AND CALCULATED EXCHANGE RATIOS FOR
SOILS AT THE HOLLISTER RAPID INFILTRATION SITE
ESR ^ -« EPR
-< calculated > measured -^ calculated ^- measured
Location
Treatment site
Control site
0.15a
0.07b
0.30
0.10
0.02b
0.04
0.04
a. Reference [51]
b. Reference [12]
While the results for predicted and calculated EPR are in close
agreement, the data in Table 24 indicate that more exchangeable Na is present
than can be predicted using either of the previously discussed functional
relationships. One explanation is that the salts of Na, Ca, and Mg have been
concentrated by evaporation before transport down the profile. As the
absolute solution concentrations of Na, Ca, and Mg increase, the colloid
preference for Na would increase. An alternative explanation is that Mg and
Ca are ion-paired, complexed, or chelated to a much greater extent than Na.
Sulfate, present in inorganic or organic forms (ABS, LAS), and soluble
orthophosphates and organic polyphosphates are known to form complexes with
both Ca and Mg. Since the composition of the exchange phase is regulated by
the concentration of free ions, an SAR calculated using total concentrations
would be expected to be low. Therefore, the calculated ESR underestimates
the exchange phase composition when the irrigation water contains complex!ng
species. Though ESR values are high throughout the treatment site, no
apparent infiltration rate decreases have been observed.
Complications are apparent when discussing the fate of applied calcium.
As mentioned previously, analytical inaccuracies arise when measuring
exchangeable Ca in a calcareous soil. For this reason, the U.S. Salinity
Laboratory [12] recommends that exchangeable Ca not be reported in calcareous
soils. With this limitation in mind, the following discussion can only be
viewed as preliminary.
Control and treatment site values for Ca are significantly different.
Unlike the previous exchangeable cations, calcium decreased after wastewater
addition, though the decrease was significant through the surface 30 cm (1
ft) only. A decrease of 4.5 meq/100 g Ca was observed at the surface.
The relationship of Ca to Mg is puzzling. The applied wastewater had a
molar Mg/Ca ratio of approximately 2. Given that most soil colloids have
nearly equal exchange affinity for Ca and Mg, it would be expected that the
ionic ratio of exchangeable Mg/Ca would be approximately the same as that in
the wastewater. As is observed in Table 25, the addition of wastewater
increased the Mg/Ca ratio in the surface 100 cm (39 in.) to values greater
80
-------
than 1, but reduced the ratio at 300 cm (10 ft). This suggests that Mg was
selectively replacing Ca in the surface 100 cm (39 in.) of the soil. The
newly mobilized Ca traveled downward and then appeared to exchange with Mg at
300 crn (10 ft) resulting in a lower Mg/Ca ratio at 300 cm.
TABLE 25. EXCHANGEABLE Mg/Ca RATIO
Control Treatment
Depth, cm sites sites
0-16
25-35
95-105
295-3905
0.3
0.5
0.8
1.7
5.4
115.7
1.3
0.8
cm x 0.3937 = in.
Several hypotheses can be advanced to explain this ion-selective
behavior. A partial list of hypotheses is presented below. A combination of
several is not ruled out.
1. Analytical discrepancies
a. When calcium carbonate is present in a sample, reported CEC
values may be too low, and exchangeable Ca too high.
b. In treatment site samples, reported values for exchangeable Ca
may be too low because orthophosphate in the acetate extract
was not compensated for in flame atomic absorption
spectrophotometry. Releasing agents such as Lanthanum or
Strontium were not added.
2. Chemical interactions
a. Loss of Ca in the effluent by precipitation of a calcium
phosphate species in the upper regions of the profile.
b. Selective adsorption of Mg in the upper regions of the soil
profile by ligand combination. The amino-carboxylate of ami no
acids shows selectivity for Mg. A significant amount of this
ligand would be present only if there is a sufficient amount
of decomposing protein with exposed peptide linkages.
c. Differential chelation, complexing, or ion-pairing of Ca and
Mg in the solution phase. This requires a ligand(s) of high
concentration that selectively chelates to or is selectively
coordinated by Ca. Mg would then remain as a free ion able
to compete with Ma and K for a position on the exchange phase.
Organic phosphates might be one such ligand, though it is
questionable whether they exist in concentrations that are
sufficient to make this a complete explanation.
81
-------
3. Historical
a. Effluent composition has fluctuated over time and effluent
samples are not representative.
Heavy Metals
Several sorption mechanisms have been proposed to describe soil uptake
of heavy metals from a percolating solution. Specific adsorption and
interfacial precipitation are thought to be the controlling mechanisms at
lower or trace amounts in the soil-water system.
Bulk or noninterfacial precipitation of hydroxides, hydroxy-carbonates,
sulfides, or phosphates can be a controlling mechanism at any level of a
particular metal, depending on the activity or concentration of the nonmetal
precipitant. At very high metal levels, cation exchange may be a controlling
mechanism [35, 47, 53-57]. In some cases several processes may be operating
simultaneously.
The extent of heavy metal sorption can be modified by several factors
including surface area of the sorbent, charge per unit area of sorbate, pH,
temperature, concentration of metals, and the presence of ion-pair complex
and chelate formers [47, 49, 57]. Iron and manganese are metals that also
undergo oxidation-reduction reactions and are greatly affected by biological
activity [58].
The potential hazards of the heavy metals to man make them a critically
important variable to monitor in any land treatment system. Where domestic
wastewater is applied [59] in rapid infiltration systems, accumulation in the
soil and leaching to groundwater should be assessed.
The method of heavy metal analysis was a DTPA-extraction. This
procedure is thought to vary in extraction efficiency, ranging from only a
few percent for iron and manganese up to 50 to 60% of the labile Cd.
Therefore, unlike "total-metal" analyses, DTPA-extractable metals cannot be
used for mass balance calculations, unless the efficiency of extraction for
each metal is known. The DTPA method is more sensitive to changes in metal
status in soil, and was therefore used for the following qualitative
interpretations.
Seven of the nine monitored metals showed significant increases after
wastewater treatment, with p values ranging from 0.047 to 0.000. Only lead
failed to show any significant differences between treatments. Chromium was
not included in any ANOVA because its concentration was below the detection
limit in all cases. Depth-treatment interactions were not observed for
copper, nickel, and lead.
After wastewater application, DTPA-Fe increased by nearly a factor of 9
at the surface, and was also significantly greater at other sampling depths
throughout the profile (Figure 36). There 1s a question of whether this
increase is a result of accumulation of iron by wastewater addition or the
result of alternating periods of wetness and dryness, resulting 1n both
82
-------
reducing and oxidizing conditions. Reduction of ferric iron to ferrous,
followed by oxidation of ferrous to ferric and subsequent precipitation'as a
hydrous oxide could lead to a less crystalline oxide, more soluble and more
extractable by DTPA. There is no doubt, however, that iron was moving
through the soil profile as shown by a relatively high iron concentration in
the shallow and intermediate groundwater. There was no indication from the
data whether iron was moving in the ferric or ferrous oxidation states or as
complexed, chelated, or stable soil forms.
In contrast to iron, manganese was leached by the wastewater from the
surface 30 cm (1 ft) (Figure 37). Surface manganese concentrations decreased
from 5.3 to 2.5 ppm. Though the average increase is not significant there
seems to be some redeposition at depth, expecially in treatment Sites 2 and
3. In addition, there is evidence to suggest that manganese entered the
shallow and intermediate depth wells (see Section 9). Preliminary soil
analyses (using "total-Mn") indicated that not only was there a diminution in
extractable manganese, but there was also significant loss of "total-Mn" in
the 0 to 16 and 25 to 35 cm (0 to 6 and 10 to 14 in.) samples at the
treatment sites.
so
100 ?
1 90
in 200
290
300
DTPA-IRON, ppm
90 100 190 200 290
I 1 1 1 1i 1 1 1
DTPA-MANGANESE, ppm
LEGEND
D CONTROL SITES
O TREATMENT SITES
too
190
u 200
290
300
1.0 2.0 3.0 4.0 3.0
Figure 36. Vertical distribution
of DTPA-extractable iron.
Figure 37. Vertical distribution
of DTPA-extractable manganese.
83
-------
One explanation of this behavior is that the influx of carbon (248 mg/L
as TOO and its subsequent oxidative metabolism by microorganisms could have
created local anaerobic regions. Within these regions, there is a demand for
alternative electron acceptors. Nitrate ion, if available, represents a
suitable alternative to oxygen. Tetravalent manganese in soil oxides can
also serve as an electron acceptor for oxidative microbiological metabolism
of organic matter. The result is reduction of manganese to the more soluble
divalent form, which can be lost from the surface by leaching. Redeposition
would occur when and if a more oxidizing environment is encountered. Because
many heavy metals are sorbed by manganese oxides, loss of these oxides from
the profile may have serious consequences. Increased manganese
solubilization could lead to the mobilization of formerly sorbed metals and
could diminish the capacity of the soil to sorb metals entering the
wastewater. Lehman and Wilson [60] and Ng and Bloomfield [61] reported
similar behavior and attributed heavy metal mobilization to reducing
conditions caused by fermenting organic matter.
Nickel and cobalt have similar geochemical behavior. Both tend to
associate with the hydrous oxides of manganese and iron. Manganese oxides
are thought to be the major control, regulating cobalt in some soils [57].
It is interesting to note that both cobalt and nickel did not increase in the
surface 30 cm (1 ft) of the treatment site where manganese was lost, but did
increase at 100 and 300 cm where Mn accumulated (the relationship is not
statistically significant). Average DTPA-extractable cobalt was six times
higher in treatment plots at 300 cm (10 ft) than in control plots at the same
depth, 0.01 ppm versus 0.06 ppm (Figure 38). Similarly, average nickel
values doubled from 0.17 ppm to 0.40 ppm at the 100 cm (39 in.) depth (Figure
39). Shallow groundwater concentrations of both nickel and cobalt were
statistically greater than background levels measured in the offsite control
wells, and suggests that both metals were passing through the soil profile.
DTPA-extractable cadmium and zinc values are summarized in Figures 40
and 41, respectively. For cadmium, wastewater application caused a
significant increase only at the 30 cm (1 ft) depth where its average
concentration increased from 0.015 ppm in controls to 0.053 ppm in treatment
sites. The apparent increase at the surface is not significant.
DTPA-extractable zinc significantly increased in wastewater treatment
profiles even at 300 cm (10 ft), where the average control value was 0.06
ppm, compared to an average treatment site value of 0.24 ppm. This suggests
that some zinc passed down to and perhaps through the 300 cm (10 ft) depth.
Groundwater zinc concentrations (Section 9, Table 26) were also high, further
suggesting that zinc was moving downward. The relatively higher mobility of
zinc contrasts with the behavior of cadmium, even though many aspects of the
chemistry of zinc and cadmium are similar [62]. This apparently higher
mobility of zinc may be related to its higher input concentration in the
wastewater.
DTPA-extractable copper behaved in a manner similar to cadmium, showing
a most pronounced accumulation at the surface, where average values increased
84
-------
DTPA-COBALT, Ppm
0.0*3 0.06 0.09 0.12
' ' '
1 00
1 50 -
iu 200
250
300
LE6END
O CONTROL SITES
O TREATMENT SITES
Figure 38. Vertical distribution
of DTPA-extractable cobalt.
DTPA-NICKEL, ppm
0.5 1.0 1.5 2.0
90
100
1 50
uj 200
250
300
n 39' Vertical distribution
of DTPA-extractable nickel.
DTPACADMIUM, ppm
0.05 0.10 0.19 0.20
100
19.0
ui 200
290
300
LEGEND
O CONTROL SITES
O TREATMENT SITES
90
toot
150
*
3:
»-
u 200
O
290
300
DTPA-ZINC, ppm
2.0 4.0 6.0 t.O 10.0
Figure 40. Vertical distribution
of DTPA-extractable cadmium.
Fl9nTn«41' Vertical distribution
of DTPA-extractable zinc.
85
-------
significantly from 3 ppm in controls to 7 ppm in treatment sites (Figure 42).
Although treatment site values were larger than controls below 30 cm (1 ft),
the increase is not significant. Copper concentrations in the shallow and
intermediate depth groundwater samples were nearly equal to input values.
This may indicate that copper was moving unimpeded through the profile,
possibly as a metal chelate or an ion pair. It may also indicate that
effluent copper concentrations were not greatly different from levels in the
soil-water controls.
The behavior of lead is different than any of the other metals discussed
previously. Wastewater application did not cause any significant differences
(Figure 43) in concentration. This may reflect the small imput of lead or it
might indicate that lead is passing through the profile to the groundwater
below.
50
15*
288
258
DTPA-COPPER , ppm
1.02.83.84.05.88.07.0
-I 1 1=I 1 1 1
OTPA-LEAD, pp>
90
tao
150
ui 200
290
300
LEGEND
O CONTROL SITES
O TREATMENT SITES
Figure 42. Vertical distribution
of DTPA-extractable copper.
Figure 43. Vertical distribution
of DTPA-extractable lead.
86
-------
Agricultural Potential of Soils Treated with Heavy Metals
Monitoring the potential for accumulation of heavy metals within the
food chain involves an evaluation of the ionic activities at the plant root
surface, the amount of labile metals relative to both total composition and
solution activities, and relative intensity effects in which the availability
of one ion is affected by that of other ions. Plant uptake of an ion from
soils is affected by inherent differences among species and varieties within
species, ion interactions, and soil-plant interactions [63].
Copper, cadmium, and zinc have been the metals of primary concern in
most wastewater disposal systems [64]. However, copper and zinc do not
usually approach toxic levels in the ultimate food chain as a result of
wastewater disposal since plant toxicities occur before these metals reach
levels that would be harmful to animals and humans. Cadmium poses the
greatest concern to the ultimate food chain since it is readily taken up by
plants and accumulates in the vital organs of animals ana humans eating these
plants [64]. One way to offset this potential problem is to have in solution
metals whose chemistries are similar to that of cadmium and can successfully
compete for plant uptake. a^i.«aiui iy
Research has shown that at low cadmium levels, increasing the relative
i±nh! nil
-------
TABLE 26. COMPARISON OF SOIL MICROELEMENT CONTENT AFTER
LONG-TERM SLUDGE AND WASTEWATER APPLICATION
Range of DTPA - extractable metals, ppm
Source
Chaney [65 ]
Hollister
(Surface 35 cm)
Condition
Sludge treated
Control
Wastewater treated
Control
Zn
1.3-95
2.7-7
1.1-11
0.12-1.6
Cd
0.10-27
0.08-0.16
0.04-0.24
0.01-0.12
Cu
1.4-100
1-4
1.4-8.2
0.35-4.0
Ni
0.2-88
0.2-0.6
0.33-2.4
0.24-0.62
TABLE 27. COMPARISON OF SOIL DTPA-EXTRACTABLE HEAVY
METAL WITH HEAVY METAL CONTENTS OF SELECTED CROPS [65]
Location
F-0416
F-0418
F-0420
F-0422
F-0424
Sc
F
6.
6.
6.
6.
6.
n i
iH
9
6
4
2
1
Soil
DTPA-extractable, air dry soil
Zn
8.0
6.8
61.8
36.6
25.8
Cd
1.36
1.06
8.4
5.8
3.8
Cu
4.6
5.1
25.3
15.6
10.1
N1
0.8
0.9
4.1
3.0
2.0
Zn
30.3
32.8
49.8
46.0
45.6
Crop
Grains, dry crop
Cd
0.22
0.10
2.13
1.32
1.68
Pd
Oat
0.71
0.61
0.56
0.56
0.50
Cu
4.0
4.2
4.7
4.3
4.8
N1
2.1
1.5
7.5
5.6
5.8
Red Clover
F-1681
F-1682
F-1683
F-1684
F-0749
F-0750
F-0751
F-0752
F-0753
F-0754
F-0758
F-0759
F-0760
6.
6.
6.
5.
6.
5.
5.
6.
6.
6.
5.
5.
5.
6
6
1
9
4
5
9
2
3
4
2
0
0
62.8
30.1
24.6
24.6
8.8
13.6
9.6
5.9
3.7
3.9
7.1
6.4
10.2
8.9
4.5
3.4
3.0
0.22
0.33
0.23
0.17
0.11
0.11
0.13
0.17
0.22
29.0
10.8
8.6
7.4
5.3
8.1
5.2
4.2
2.3
3.0
3.8
4.1
7.1
4.2
2.3
2.2
2.2
0.8
1.2
0.6
0.5
0.4
0.5
1.2
0.9
O.B
43.4
57.6
45.5
50.6
48
67
56
51
45
44
19
18
16
0.88
0.92
0.60
0.66
0.30
0.19
0.23
0.23
0.18
0.37
0.23
0.56
0.43
2.3
2.4
1.6
2.6
Soybean
0.50
0.84
0.74
0.60
0.89
0.57
Corn
0.87
0.78
0.77
7.7
10.8
7.9
7.2
12.0
14.3
12.8
13.9
11.8
12.7
1.8
2.0
1.7
2.2
1.6
1.8
2.3
1.8
2.4
2.8
2.0
1.5
1.4
0.7
0.4
0.4
Heavy metal uptake by plants appears to be a function of available
metal, pH, and plant species. Uptake tends to increase as available metal
increases and decreases with a rise in pH. Metal enrichment will vary from
crop to crop. Though conclusions are confounded by these interacting
factors, Chaney et a].. [65] found from these and other data that the uptake
of zinc) cadmium, and nickel was accelerated by sludge incorporation
especially at low soil pH, and that copper and lead uptake generally was
unaffected by sludge addition. Most importantly, no phytotoxicity was
observed in crops ordinarily grown on farms where sludge had been used.
-------
In light of these findings, it seems reasonable to conclude that the
levels of DTPA-extractable metals will not adversely affect the future
agricultural potential of the Hoi lister rapid infiltration site. Surface
soil pH values of 6.3 to 7.6 will favor reduced metal uptake and soil DTPA-
extractable metal concentrations are low relative to soils having higher
metal loading rates without observed plant toxicity. Any crops grown on the
site should be monitored for heavy metal uptake, however.
89
-------
SECTION 9
GROUNDWATER QUALITY INVESTIGATION
INTRODUCTION
The hydrogeologic investigation determined that the shallow groundwater
table beneath the rapid infiltration basins was hydraulically responsive to
percolating wastewater. The shallow groundwater was sampled when underground
detention time was at a minimum by taking samples at the maximum water level
(See Figure 13). The results from Wells 3A and bA, in the shallow groundwater
aquifer, represent renovated water quality after 7 m (22 ft) of percolation
through the unsaturated soil matrix.
The onsite intermediate wells (IB and 3B) did not show a definite water
table response to effluent application (Figure 14), and groundwater quality
did not convincingly indicate movement of effluent to this level. The onsite
deep wells (1C and 2C), similarly, did not indicate any influence of applied
wastewater on deep groundwater as observed from water table fluctuations and
groundwater quality data. All results were compared to offsite control
wells, upgradient and downgradient of groundwater movement in the regional
groundwater aquifer.
The results of the groundwater sampling program are shown in Table 28.
The values represent the arithmetic average of four grab samples taken, over
the study period, according to the procedures stated in Section 6. The
range, standard deviation and coefficient of variation for the individual
samples are listed in Appendix C. Chemical and bacterial analyses were
performed according to Standard Methods [9]. The results of effluent
sampling accompany the groundwater quality results for comparison.
STATISTICAL ANALYSIS OF GROUNDWATER DATA
For purposes of analyses, well samples were grouped into four categories-
shallow (A), intermediate (B), deep (C), and controls. Well 4C was
originally established as an upgradient control well. The validity of this
assumption was tested for every parameter. Unless there was a significant
difference between Well 4C and the downgradient control wells, (at thea =
0.10 level), it was considered to be a control well for that particular
chemical parameter. Data collected over time were viewed as replicate
samples.
Once properly grouped, a one-way analysis of variance (ANOVA) was
performed using the SPSS statistical package [67]. Data reported as "less
90
-------
TABLE 28. AVERAGE EFFLUENT AND GROUNDWATER QUALITY RESULTS
mg/L Except as Noted
Groundwater'
Effluent
Constituent Range Av
COO 546-1.029
BOD.' 134-414
TOC 240-264
CCE
Total N 29.7-58.5
NH4- - H 19.7-44.0
M org. 6.7-21.8
NO, - N 0.16-0.6
Total P 10.0-21.5
P04 - P 9.0-13.2
Total conforms, 4.6 x 10'- -,
count/100 BL 92 x 10' "
Fecal Conforms, 3.5 x 10'- .,
count/100 ml 24 x 10' "'
pH, units 7.0-8.1
TDS 1,016-1,593
Conductivity, J>H0.Zi480
Alkalinity 416-465
B 0.95-1.8
F 0.3-1.1
55 206-328
N« 196-391
Ca 31-71
Kg 27-76
K 10.9-16.0
Cl 185-490
S04 161-250
Ag <0. 005-0. 012
As
Ba <0.1-0.24
Cd <0. 001-0. 008
Co <0. 006-0.008
Cr <0. 004-0. 036
Cu 0.019-0.070
Fe 0.14-0.82
Hg
Hn 0.055-0.094
N1 0.015-0.092
Pb 0.012-0.12
Se
In 0.010-0.090
SAR 4.67-8.08
a. Average of 4 grab samples.
b. Depth of xell screen 7.5-10.6
c. Depth of Mil screen 19.5-24.0
d. Dtpth of Mil screen 48 .
e. Average of twelve 24 h composite
f. Average of three 24 h composite
g. Single grab sample.
Shillo»b
erege*
706
220
248f
"
40.2
25.3
14.5
0.43
12.4
10.5
6 x 10*
4 x 10*
7.3
1,208
1,790
446f
1.4
0.7
274n
262
54
64
12.9
284
213
<0.008
<0.01
<0.13
<0.004
<0.008
<0.014
0.034
0.39
<0.001
0.070
0.051
0.054
<0.001
0.048
5.71
*.
».
samples
temples.
3A
46
6
10'
2.2
3.8
<0.4
2.2
1.2
8.0
6.8
1.1 x 10'
156,000
7.5
1,282
1,710
538
1.2
1.1
15
249
100
71
13.0
281
164
<0.006
<0.01
<0.11
0.007
<0.008
1.281 ft
91
-------
than x" were input as x. The option used was "ONEWAY," which tested the
hypothesis:
Ho: Ul=y2=u3=p4=y5
where y-|_4 are the means of the four groundwater groups, and yg is the
effluent mean.
If the hypothesis could not be rejected at the a = 0.10 level, no
further statistical analyses were performed. If rejection was warranted,
pairwise contrasts (t-test) were performed to isolate the sample(s) whose
mean was different. The t-statistic was computed using both pooled and
separate estimates of variance. Only if Cochran's "C" statistic proved
significant (ct= 0.10), indicating nonhomogeneous variance, was the latter t-
statistic used. Sample output from SPSS ONEWAY is shown in Table 29.
COD, BOD, AND TOC
COD, BOD, and TOC are indicators of the strength of organic compounds
present in wastewater and groundwater. The chemical oxygen demand (COD) is a
measure of the oxygen equivalent of that portion of organic matter that is
susceptible to oxidation by a strong chemical oxidant. The biochemical
oxygen demand (BOD) test measures the oxygen uptake in the microbial
oxidation of organic matter. TOC is a measure of total organic carbon.
Bouwer and Chaney [68] stated that for land treatment, TOC may be a more
appropriate parameter than BOD and COD, since the latter two were developed
primarily for oxygen requirements in aquatic environments. TOC can also be
used as a gross indicator of persistant organic compounds that remain when
BOD and COD are completely removed [69]. In addition, TOC can be used as a
measure of the energy (carbon) available for denitrification. Actual
observed carbon requirements for effective denitrification vary in the
reported literature [70, 71].
In a rapid infiltration system, the reduction of BOD, COD, and TOC is
accomplished largely by the adsorption and subsequent biodegradation of
organic compounds. Lance et al. demonstrated that anaerobic biological
decomposition can be as effective as aerobic reactions for soil columns under
conditions of continuous flooding [72] or long periods of flooding (9 days)
followed by a shorter recovery period of 5 days [71].
The COD of the Hoi lister primary effluent ranged from 546 to 1,029 mg/L
with an average concentration of 706 mg/L. The average COD concentrations in
shallow Wells 3A and 5A were 46 and 50 mg/L, respectively. These values
correspond to a 93% COD reduction after vertical percolation through 7 m (22
ft) of soil.
Relative to the other deep wells, COD levels in Well 2C were higher by a
factor of 5 to 8 throughout the study period. This resulted from well
contamination. An organic mud which was used to maintain the borehole during
well construction was observed in each groundwater sample from Well 2C. When
Well 2C is excluded, significant differences between intermediate, deep, and
offsite control wells are not observed. This supports the contention that
92
-------
TABLE 29. SAMPLE OUTPUT FROM SPSS ONEWAY
VARIABLE: TOTAL NITROGEN
ANALYSIS OF VARIANCE
SOURCE D.F. SUM Of SQUARES MEAN SQUARES
BETWEEN GROUPS 4 11661.1698 2915.2922
WITHIN GROUPS 46 1123.6402 24.4270
TOTAL 50 12784.8086
GROUP
GRPOl
GRP02
GRP03
GRP04
GRP05
TOTAL
STANDARD
COUNT MEAN DEVIATION
10 3.3500 2.3538
9 7.2889 4.2040
8 2.3000 2.3821
12 4.5250 4.3650
12 39.8666 7.8803
51 12.7490 15.9905
FIXED EFFECTS MODEL 4.9424
RANDOM EFFECTS MODEL 16.0494
STANDARD
ERROR
0.7443
1.4013
0.8422
1.2601
2.2748
2.2391
0.6921
7.1775
MINIMUM
0.
1.
0.
0.
29.
0.
2000
3000
4000
2000
7000
2000
F RATIO
119.347
MAXIMUM
8.
14.
7.
12.
58.
58.
7000
5000
9000
2000
3000
3000
95
1.
4.
0.
1.
34.
B.
11.
-7.
PCT
6662
0574
3085
7516
8697
2516
3559
1786
F PROB.
0.0000
CONF
TO
TO
TO
TO
TO
TO
TO
TO
INT FOR
5
10
4
7
44
17
14
32
MEAN
.0338
.5204
.2915
.2984
.8735
.2464
.1421
.6766
CONTRAST COEFFICIENTS MATRIX
CONTRAST
CONTRAST
CONTRAST
CONTRAST
CONTRAST
CONTRAST
CONTRAST
CONTRAST
CONTRAST
CONTRAST 10
CONTRAST 1
CONTRAST 2
CONTRAST 3
CONTRAST 4
CONTRAST 5
CONTRAST 6
CONTRAST 7
CONTRAST 8
CONTRAST 9
CONTRAST 10
GRPOl
1.0
1.0
1.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
GRP02
-1.0
0.0
0.0
0.0
1.0
1.0
1.0
0.0
0.0
0.0
GRP03
GRP05
0.0
-1.0
0.0
0.0
-1.0
0.0
0.0
1.0
1.0
0.0
GRP04
0.0
0.0
-1.0
0.0
0.0
-1.0
0.0
-1.0
0.0
1.0
0.0
0.0
0.0
-1.0
0.0
0.0
-1.0
0.0
-1.0
-1.0
VALUE S.
-3.9389
1.0500
-1.1750
-36.5166
4.9889
2.7639
-32.5777
-2.2250
-37.5666
-35.3416
POOLED VARIANCE ESTIMATE
ERROR T VALUE D.F. T
2.2709
2.3444
2.1162
2.1162
2.4016
1794
1794
2559
2559
2.0177
-1.735
0.446
-0.555
-17.256
2.077
1.268
-14.948
-0.986
-16.653
-17.516
46.0
46.0
46.0
46.0
46.0
46.0
46.0
46.0
46.0
46.0
PROB.
0.090
0.656
0.581
0.000
0.043
0.211
0.000
0.329
0.000
0.000
SEPARATE VARIANCE ESTIMATE
S. ERROR T VALUE D.F. T PROB.
1.5868
1.1240
1.4635
3935
6349
8845
6718
5156
4257
2.6005
-2.482
0.934
-0.803
-15.256
3.051
1.467
-12.193
-1.468
-15.487
-13.590
12.3
15.1
17.4
13.3
12.9
17.7
17.5
17.5
13.8
17.2
0.029
0.365
0.433
0.000
0.009
0.160
0.000
0.159
0.000
0.000
93
-------
COD concentrations in both the intermediate and deep aquifers are not the
result of wastewater application.
The BOD of the effluent ranged from 134 to 414 mg/L and averaged 220
mg/L. The average BOD concentrations in Wells 3A and 5A were 6 and 13 mg/L,
respectively. A 96% reduction in BOD was achieved. BOD levels in all
aquifers were not statistically different. Shallow aquifer concentrations
were indistinguishable from background concentrations. Anomolous BOD
behavior was not observed for Well 2C.
The TOC was measured only during the last sampling period. The range of
240 to 264 mg/L and average of 248 mg/L was for three composite effluent
samples. The TX concentrations of Wells 3A and 5A were 10 and 11 mg/L,
respectively, for one grab sample in March 1977. A 96% reduction of TX in
the shallow groundwater is indicated. All wells have statistically equal TOC
concentrations suggesting that even "refractory" organic compounds have been
removed to background levels. More data on the movement of refractory
organic compounds are needed, however, to base any conclusions.
The COD, BOD, and TOC results indicate that effective aerobic
decomposition of organic matter was occurring. The wastewater application
cycle allowed for the reduction of organic constituents to background levels.
Hoi lister removal efficiencies compare favorably with those reported for the
Fort Devens, Massachusetts, rapid infiltration site having 31 years of
continuous operation. At Fort Devens, primary effluent COD and BOD
concentrations of 192 and 112 mg/L were reduced to 27 and 5.9 mg/L,
respectively [73]. Wastewater percolates approximately 5.4 m (18 ft) through
soils with physical and hydraulic characteristics similar to those at
Hoi lister.
RESIDUAL ORGANICS (CARBON CHLOROFORM EXTRACT)
Organic compounds present in groundwater were adsorbed onto activated
carbon and extracted with chloroform [74]. This procedure was developed for
high quality water and the effluent was not analyzed. The large sample
volume (55 litres), time consuming adsorption procedure, and costly solvent
extraction limited the number of samples tested. Carbon chloroform extract
(CCE) values are expressed as mg/L, based on the total weight adsorbed onto
the carbon divided by the volume of water passed through the carbon sample.
While no determination of removal efficiency was possible, it can be inferred
from the COD, BOD, and TX results that wastewater application has no
influence on the intermediate or deep groundwater. The CCE levels of onsite
and offsite intermediate and deep wells were comparable; however, inadequate
sample replicates prevented statistical relationships between CCE and other
organic pollution indicators.
NITROGEN
Typical, medium strength domestic wastewater may contain 40 mg/L of
nitrogen of which 25 mg/L is in the form of NH.-N and 15 mg/L is 1n the
organic form [75]. A review of several rapid infiltration projects indicates
that the concentration and form of nitrogen being applied to the soil is the
94
-------
same after primary or secondary treatment [69, 76-78]. Ammonium and organic
nitrogen applied to soils at rapid infiltration sites are almost completely
converted to the nitrate form [69, 76-78]. The availability of oxygen is
critical to the conversion process. Short and frequent application cycles
from 0.5 to 3 days flooding followed by 5 to 14 days before reapplication '
maximize nitrification [69, 77, 78]. '
In addition to nitrification, denitrification is an important conversion
process. Organic carbon is needed to supply energy to denitrifying bacteria
The level of organic carbon in the supplied wastewater is critical to the
removal of the highly mobile nitrate ion. Lance and Whisler observed that
nitrate from a percolating wastewater was removed by denitrification [79]
The denitrifying bacteria are facultative anaerobes which use nitrate-
nitrogen as an electron acceptor when oxygen concentrations become very low.
In the denitrification reaction, where glucose is used as a caroon
source, 3.2 grams are required for each gram of nitrogen denitrified (C-N «
~1'^1 h?3CSnJn?«l!!!1?ler obsSrved that stabilized municipal wastewater (C:N
* 1.2.3) did not contain enough unstabilized organic matter to denitrify
wastewater applied to soil columns [71]. These laboratory results were
verified at the Flushing Meadows rapid infiltration project [69] On the
other hand, it is very probable that a high BOD wastewater does denitrify
rapidly when applied to soil. Law et aK reported 83 to 90% removal of total
nitrogen from overland flow treatment of high BOD cannery wastes [80] Lance
also demonstrated that with the addition of 150 mg/L glucose (C-N * 5*n
soil columns intermittently flooded with secondary sewage water'realized'a
90% nitrogen reduction [71]. Nitrogen removal decreased to 60% when the
carbon concentration was 80 ppm (C:N * 2.7:1) [71]. At Hoi lister the C N
ratio was approximately 6 to 1, a condition favoring denitrification.
In addition to the C:N ratio in wastewater, the distribution of carbon
in the soil profi e influences the location where denitrification might take
place. At the Hollister rapid infiltration site, soil organic matte? was
highest near the surface and declined progressively with depth (See Table
19). Gilmore et_al_. showed that a flooded surface soil containing 0 9% total
carbon denitrified added nitrate readily without organic amendments, but thl
subsoil containing 0.48% total organic carbon failed to denitrify unless an
available organic substrate was supplied [81]. Therefore, the zone of most
active denitrification is likely to be near the soil surface in spite of its
proximity to the atmosphere. This has been demonstrated in field experiments
by Rolston et a . who observed maximum rates of production of NO and N
within the WTO cm (4 in.) [82]. Lance et al. [83] a sS observed thai
denltrf cation takes place near the soil luTfTce. By monUorin reSSx
potentials versus depth in sewage flooded soil columns It was Sown SL+
denitrification zone was established in the top 20 S (8 ?n ) or less [83]
At Hollister, a 93% reduction in total nitrogen was achieved as thP
wastewater passed from the surface to the shallow water table NTtrate-N
levels in the shallow water table are approximately 1 ppm and therefore Led
no immediate contamination problem to permanent groundwater supplies
95
-------
Denitrification is believed to be the primary removal mechanism.
Favorable conditions for conversion exist at the infiltration site, including
availability of an energy source, temporary anaerobism due to soil flooding,
adequate detention time due to moderate infiltration rate, and a near neutral
pH. The infiltration rate at Hoi lister was in the range reported by Lance
and Whisler for good nitrogen removal [79].
Concentrations of all nitrogen species in the shallow water table were
statistically indistinguishable (t-test, a = 0.10) from the corresponding
nitrogen levels in the offsite control wells.
Higher concentrations of nitrate-N and total-N were observed in the
intermediate wells and were comparable to offsite control wells. This
suggests that the nitrogen in the intermediate aquifer was derived from a
source other than the surface applied wastewater.
PHOSPHORUS
Concentrations of phosphorus in municipal wastewater§3can range from 1
to 40 mg/L, occurring mostly as inorganic phosphorus (PO. ) [84, 85]. The
effluent concentration will be a function of influent concentration and the
degree of removal during treatment. Primary and secondary effluents may have
similar concentrations. For example, the secondary effluent applied at
Flushing Meadows ranged from 10 to 15 mg/L P04-P [69]while the inorganic
phosphorus concentration for Hoi lister's primary effluent averaged 10.5 mg/L
P04-P.
Phosphorus removal in rapid infiltration systems has been studied in the
Flushing Meadows project [23, 69, 76]. The phosphorus concentration in the
wastewater averaged 15 mg/L in 1969, but decreased to about 10 mg/L for the
period 1970 to 1972. Phosphorus removal increased with an increase in travel
distance and residence time in the soil profile. A travel distance of 9 m
(30 ft) removed about 70% of the phosphorus in 1969, but removal efficiency
was reduced to about 30% in 1970 when a substantial increase in flowrate
occurred. With a flow distance of 100 m (330 ft), phosphorus removal
increased to about 90% and was greater with an even longer travel distance.
After 5 years of operation and phosphorus additions of nearly 48.0QO kg/ha
(43,000 lb/acre) the removal efficiency was rather stable.
Pratt [23] points out that rapid infiltration systems require sandy
soils that can sustain high water intake rates and high transmissivity in the
subsurface environment. Therefore, no layers with high sorptive capacity for
phosphorus are likely to be encountered. What little capacity there 1s may
soon be saturated, and the retention will then depend on mineralization and
precipitation reactions. One logical precipitant is the calcium supply 1n
the wastewater.
The coarse gravelly soil at Flushing Meadows [69, 76] is calcareous and
contains little or no iron and aluminum oxides. Therefore, 1t was concluded
that P removal resulted from the precipitation of calcium phosphate species,
ammonium magnesium phosphates, and other insoluble compounds [69].
96
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At the Calumet, Michigan, rapid infiltration system, phosphorus removal
continues to be from 89 to 97% efficient, though the system has operated for
over 88 years. The influent concentrations of a raw municipal wastewater
were reduced from 3.5 mg/L total -P to 0.4 to 0.1 mg/L after 3.1 to 9 2 m (10
to 30 ft) of vertical percolation, respectively. The soil is a poorly sorted
gravel having an annual hydraulic loading of 34 m/yr (112 ft/yr) [86],
At Fort Devens, Massachusetts, [73] where a primary effluent has been
a?PlleJ ^n^101 1njiltration basins for over 30 years, removal efficiencies
of 86 to 90% were observed in observation wells located 80 to 150 m (262 to
492 ft) from the infiltration basins. Only 18% of the input phosporus
remained after 1.5 m (5 ft) of vertical percolation [73]. The total
h*draulic loadi"9 ^s 27.1
At the Lake George Village rapid infiltration site, total phosphorus in
an observation well 4.9 m (16 ft) below the surface averaged 0.9 mq/L as
compared to an input level of 2.1 mg/L. Unchlorinated secondary effluent is
43Pl1?140°ft)fUr SaPd bedS dt dn annUal hydraulic aPPHcation rate of
nn cAL5,0!l1sJf!> 85% °Vh(: influent Phosphorus is inorganic orthophosphate
(10.5 mg/L). After percolation through 6.7 m (22 ft) of soil to the shallow
groundwater, 23 to 35% of the input P was removed. This figure is in c?ose
agreement with the 30% removal ratio calculated for the upper 300 cm of soil
pK*OT 1 I 6»
There is no statistical evidence of phosphorus contamination in the
intermediate and deep water-bearing strati. Intermediate, deep and offsite
contro we is indicate that average P concentrations were statistical ly
indistinguishable at the o- 0.1 level. Only the shallow water table
responded to wastewater addition.
The ratio of P04-P/total P in the wastewater is comparable to the same
ratio in the shall ow\ater table. This suggests that there was St Elective
removal of morgamc-P relative to organic-P in the soil profile Both forml
were entering the shallow groundwater. t»uiiie. eotn terms
FECAL COLIFORM AND TOTAL COLIFORM BACTERIA
exrlhrfL^^^
water and groundwater. The presence of fecal coliforms is indic
«^frg^%t ss^s.'ff^1B
associated with domestic wastewater. H»«*«uiai neaitn risks
The relative health risks from pathogens at rapid infiitrati
be greater than other land treatment techniques bemuse ?he sol I J
highly transmissive and thus has less chance to retain
Chaney [68] point out that fecal col iformblcteri fare ne
after water has traveled 5 to 7 cm (2 to 3 in.) througth! !
97
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the coarse soils at rapid infiltration systems, which are necessary to
maintain infiltration and transmissivity, may require on the order of 30 m
(100 ft) to completely remove fecal coliform bacteria. With adequate travel
distance, effective removal of fecal coliforms has been demonstrated [69,
73].
Bacterial removal efficiency within the soil profile is a function of
wastewater application rate, subsurface travel distance, solids buildup on
the soil surface, the type of organism, soil type, moisture-retention
capacity, soil organic content, pH, temperature, sunlight, rain, degree of
wastewater contamination, and antagonism from the resident microbial flora.
Under certain favorable conditions, applied organisms may actually multiply
and increase in numbers. In general, land treatment using intermittent
application and drying periods results in die-off of enteric bacteria
retained in the soil [23].
Bouwer et al. [69] found deeper penetration of fecal coliforms below
rapid-infiltration basins after the basins were flooded following an extended
drying or resting period. This was probably due to reduced entrapment of E.
coli on the surface of the soil. The clogging layer of organic fines that
had accumulated on the soil during flooding, forming an effective filter,
partially decomposed after drying. A more open surface was created,
resulting in a less effective filter when flooding was resumed. In addition,
the bacterial population in the soil undoubtedly declined during drying
because the nutrient supply was discontinued. Consequently, there was less
competition from the native soil bacteria, and hence greater survival of the
fecal coliforms when flooding was resumed. As flooding continued, however,
fine suspended solids accumulated again on the soil surface. The native soil
bacterial population also increased. This resulted in increased retention of
E. coli and a return to fecal coliform levels of essentially zero in
renovated water sampled from a depth of 9 m (29 ft). Almost all fecal
coliform removal took place in the first 1 m (3 ft) of soil.
At the Fort Devens, Massachusetts rapid infiltration system, analysis of
groundwater samples for fecal coliform bacteria proved negative in
observation wells located 60 to 100 m (197 to 328 ft) from the application
area [73]. Total coliform densities in the unchlorinated effluent ranged
from 18 to 53 x 10^ per 100 ml.
At Hoi lister, fecal coliform removal approached 99% consistently in the
shallow groundwater Wells 5A and 3A after a total percolation distance of 7 m
(22 ft). Although fecal coliform densities were substantially reduced from
levels in the applied effluent, they were significantly higher than levels in
the intermediate and deep wells. In general, fecal coliforms were absent in
intermediate and deep wells. The exception was intermediate depth Well 3B
which averaged 11 per 100 mL for two samples, with three negative samples.
This could have resulted from "short-circuiting" into the intermediate
aquifer from either the shallow water table or direct surface contamination.
No fecal coliforms were detected in intermediate Well IB. Total coliform
bacteria, which includes fecal coliforms plus coliforms orginating from other
sources, were also monitored.
98
-------
The relationship between fecal and total coliform counts gave some
indication of bacteria originating from other than human sources. Total
coliform bacteria removal ranged from 96% in Well 5A to 99+% in Well 3A after
7 m (22 ft) of percolation. The uncharacteristically high total coliform
densities in Well 2C are believed to be the result of residuals from the
drilling operation which were not completely flushed from the well during
construction. This material was present in each sample withdrawn from Well
2C over the sampling period, but was not present in samples from other wells.
High fecal coliform counts in Well 9C, an offsite control well, were noticed
in one sample out of two taken during the study period.
The large heterogeneity of variances in the coliform data made standard
statistical comparisons meaningless.
pH
The pH of wastewater can be modified by the soil's buffering capacity
and by the chemical and biological reactions which take place within the soil
profile at a rapid infiltration site. Wastewater which contains organic
acids can show an increase in pH as it moves through the soil because the
acids are biodegraded and lost from the system [68]. On the other hand, for
biodegradable material, pH may decrease because soil microbial activity'
produces CC^ and organic acids [68].
At the Flushing Meadows project, the pH of sewage effluent was about 8
whereas that of the renovated water was approximately 7. This pH drop was
attributed to the bacterial production of C02 and organic acids.
Nitrification and removal of carbonates would also reduce the pH [69].
At the Lake George Village, New York, rapid infiltration site, secondary
effluent pH was 6.94 while that of the renovated water in a well 4.9 m (16
ft) directly beneath an infiltration basin was slightly lower at 6.37 [87]
Production of organic acids and carbon dioxide by soil bacteria and
nitrification of ammonium were thought to be responsible for the slight oH
drop [88]. 3 p
At Fort Devens, Massachusetts, the pH of soil water extracted by suction
lysimeters at 1.5 m (5 ft) increased slightly in one lysimeter and stayed the
same in another [73]. Control site soil pH ranged from 4.6 to 5.2 whereas
the treatment bed pH ranged from 5.7 to 6.2 [73]. Comparison of effluent and
groundwater pH directly beneath spreading basins at a depth of 24.4 m (80 1
ft) showed a drop from 7.0 to 6.8 standard units [73].
At the Whittier Narrows and Rio Hondo test basins, surface applied
secondary effluent had pH values of 8.0 and 8.30, respectively After
percolation through 1.8 m (6 ft) of soil previously used for groundwater
recharge of stormwater runoff, the pH had dropped to 7.78 and 7 90
respectively. The pH reduction was attributed to carbon-dioxide production
and/or nitrification in the soil matrix [89]. K
At Hoi lister, a significant difference between the average pH of the
primary effluent (7.3) and the pH of the shallow groundwater (7.6) was
observed. However, the pH of the shallow groundwater was indistinguishable
99
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(t-test, a= 0.10) from that of the offsite control wells (7.7). This
suggests that wastewater dissolution of soil calcium carbonate is increasing
the pH of the percolating solution, offsetting the production of hydrogen
ions from nitrification reactions and organic acid formation.
DISSOLVED SOLIDS
Total Dissolved Solids and Electrical Conductivity
The total dissolved solids (TDS) concentration of municipal wastewater
is comprised of several ions including sodium (Na+), calcium (Ca ^),
magnesium (Mg+2), potassium (K+), chloride (Cl~), sulfate (SO/f2), and
others. Effluent TDS of several primary treatment plants in California range
from 935 to 1,898 mg/L [84]. The secondary effluent at Flushing Meadows
ranged from 1,000 to 1,200 mg/L [69].
TDS concentrations can vary widely depending on the industrial mix of
the community, the proportion of commercial to residential development, ana
the nature of the residential community. Wide variations can be encountered
from drainage areas having selected land development characteristics yet
having the same water supply [84].
The effluent and shallow groundwater TDS concentrations at Hoi lister
were both generally in the 1,200 to 1,300 mg/L range. The salt concentration
of the renovated water is approximately equal to that of the applied
effluent. Electrical conductivity (EC) measurements bear this out. TDS and
EC measurements in the intermediate and deep observation wells were highly
variable. Constrasts using the t-statistic revealed that TDS and EC
measurements in the effluent, shallow groundwater, and offsite control wells
were generally indistinguishable.
Exchangeable Cations and Sodium Adsorption Ratio
Though all four of the major cations (Na+, K+, Ca+ , Mg+ ) found in+
wastewater undergo exchange reactions with soils, the fate of applied Na is
generally of greatest concern. When the wastewater ratio of sodium to
calcium and magnesium is large, highly hydrated sodium cations replace less
hydrated Ca and Mg on the soil. This process causes the dispersion of soil
clay particles, resulting in a decrease in soil permeability. The nature of
rapid infiltration systems is such that the sodium hazard is generally
considered minimal, because the clay percentage is usually so small that the
effect is not noticed.
If the reuse of renovated water for irrigation purposes is an objective,
sodium hazard must be considered. In most cases soil permeability becomes a
hazard before direct sodium toxicity is noticed. In a few plants this is not
strictly true, notably avocados [52]. To determine the sodium hazard, the
sodium adsorption ratio (SAR) was developed by the U.S. Department of
Agriculture Salinity Laboratory. SAR is defined as follows:
SAR = Na/[l/2 (Ca + Mg)] 1/2
where Na, Ca, and Mg are concentrations of the respective ions in meq/L of
100
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water. Ratios less than 4 are generally acceptable on almost all soils
though higher values are suitable for water of higher conductivity A '
detailed description of the SAR and sodium hazard is found in reference [12].
At Hoi lister, concentrations of sodium and potassium in the shallow
aquifer were not statistically different (
-------
human consumption. Sulfates are also important, primarily in industrial
reuse applications, because of their tendency to form scales in boilers and
heat exchangers.
The sulfate concentration in the effluent and shallow groundwater at
Hoi lister was less than that contained in the majority of potable water wells
serving the City of Hoi lister. The sulfate concentration of Well 3A was
noticeably less than the effluent, while Well 5A was somewhat higher than the
effluent sulfate measured. An analysis-of-variance reveals that the sulfate
levels in the effluent, treatment site aquifers, and off site control wells
are indistinguishable (p= 0.78). Sulfate contamination resulting from
wastewater application has not occurred.
SUSPENDED SOLIDS
The suspended solids (SS) concentration of untreated municipal
wastewater can range from 100 to 350 mg/L [85]. Municipal effluent from
several primary treatment plants indicates that the suspended solids are
completely removed in most cases [85], if the facility is not overloaded.
The SS in the primary effluent at Hoi lister averages 274 mg/L, indicating the
lack of treatment efficiency by the pretreatment facility.
The average removal indicated by total SS levels in Wells 3A and 5A was
95%. Effective filtering of input solids occurred although complete removal
was not indicated after percolation through 7.7 m (22 ft) of soil. Improper
well development is probably the cause of inorganic SS levels, which were
also detected in several intermediate and deep observation wells.
Complete evaluation of removal effectiveness cannot be made because SS
levels in the offsite control wells were not measured. However, the general
appearance of these samples indicated that no SS were present.
ALKALINITY
Bicarbonate accounted for all of the alkalinity in the Hollister public
water supply (see Table 4) with additional pickup during domestic water use.
Biological activity, during wastewater percolation through the soil profile,
can produce carbon dioxide and organic acids. The resulting action of C02
solubilizes soil carbonate materials and can cause an additional increase in
the alkalinity of the percolate.
Results at Lake George Village, New York, showed seasonal increases in
alkalinity in shallow observation wells during the summer months [88]. The
well was located 5 m (16 ft) below the surface. Natural dilution and
biological slowdown are given as reasons for decreases in alkalinity during
winter months [88].
Alkalinity in the primary effluent at Hollister averaged 446 mg/L, which
is roughly 110 mg/L greater than the domestic water supply. In the shallow
observation wells, alkalinity increases were observed relative to input
levels, though the increases were not significant. The simultaneous
102
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reduction in BOD during percolation implies considerable biological activity
and CO- production. The resulting attack on soil carbonate material would
tend to increase alkalinity.
Alkalinity measurements from the intermediate and deep observation wells
do not indicate any influence from application of wastewater to the soil
system. In fact, all measurements are statistically indistinguishable.
BORON
The primary environmental concern with boron in renovated watPr ic -itc
potential toxicity to plants. Accumulation of excessive boron In^lal?
tissue results in reduced production Toxicitv iJmJJc * k 1n.Plant
c
concentration in domestic wastewater significantly Bouwer S %i roi * A
mineral pickup during domestic and commercial use, wastewater boron
concentrations are twice that of the raw water supply, averaging 1.4 mg/L.
Very few results on boron removal at rapid infiltration sites have been
reported. Bouwer et al_. [69] found essentially no boron riSSvI In the sandJ
and grave ly soils below infiltration basins at Flushing Meadows The lack
perco^^Wm1^^
concentrations, only 14% of the applied boron is retained in the ove??vina
soil. The absence of a significant amount of clay is believed to be the
reason for low boron removal. tne
^ x,,,,v.i wells are
FLUORIDE
Fluoride is significant in public drinking water supplies due to it,
well recognized effects on human teeth [90]. Evidence from nuhiir h iH
studies has shown that fluoride-ion concentration?^? aPpximaie?y fo mo/.
are optimum for the prevention of dental fluorosis and cavities [90] 9
irrigation water. A maximum limit of
Academy of Science and National Academy
103
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of Engineering for continuous use on all soils [66]. Applications of soluble
fluoride salts to acid soils can produce toxicity to plants [91]. Soil type,
calcium and phosphorus content, and pH seem to be the major factors
controlling plant uptake of fluoride [92]. The adsorption of wastewater
fluoride by soil and its subsequent equilibration with fluorite (CaF2) and
fluorapatite (Cas [P04]3 F) leads to both retention of fluoride in the soil
and the control of ion-specific injury to plants. The Ca"1^ added with
wastewater generally maintains the soil Ca level high enough to prevent
fluoride injury. Injury from added NaF has been demonstrated in acidic soils
low in Ca, but not in well-limed soils [93]. Crops raised on fluoride-
enriched soils show little increased fluoride uptake as long as the soil is
near neutral pH.
Very little information on the fate of fluoride at operating rapid
infiltration systems is available. At Flushing Meadows, Arizona, the
fluoride content of secondary effluent was reduced from 4.1 to 2.6 mg/L after
movement through 9 m (30 ft) of sandy soil in a high rate application system.
Increased removal was noted with further movement through the coarse textured
soil [69]. The fluoride removal somewhat paralleled the phosphate removal
suggesting precipitation of fluorapatite.
At Hollister, apparently no fluoride is added to the municipal
wastewater from domestic or other water use since concentrations in potable
water and primary effluent are relatively equal. The fluoride concentrations
in Wells 3A and 5A increased after 7 m (22 ft) of movement through the soil
profile. This suggests that F~ is currently passing through the soil profile
without treatment, causing concentration levels to rise relative to baseline
levels. It may also be possible that the decrease in soil pH resulting from
wastewater addition may cause the dissolution of any fluorapatite species
present in the soil profile.
It should be noted that even the average fluoride concentration of 1.0
mg/L in Well 3A is below the irrigation water limit set for use on all soils
[66].
TRACE ELEMENTS
The greatest concern regarding trace elements has been their potential
health and plant toxicity hazard [68]. Soil has been shown to be effective
in reducing the concentration of trace elements in percolating effluent over
limited periods of time. However, their long term ability to remove metals
is questioned because of their ineffectiveness after sorption saturation
[60]. This concern would be especially true if the creation of new soil
sorption sites (influx of wastewater clays and organic material) did not keep
pace with the influx of metals.
Regulations regarding the recommended maximum concentrations of trace
elements in irrigation waters and maximum allowable concentrations of trace
elements in drinking water have been established. These are tabulated in
Table 30, together with the average effluent concentrations of the Hollister
wastewater. Except for lead, all average effluent concentrations of trace
elements are below both of these limits. Effluent lead slightly exceeds
drinking water standards.
104
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TABLE 30. COMPARISON OF TRACE ELEMENT LEVELS
TO IRRIGATION AND DRINKING WATER LIMITS
mg/L
Maximum
Recommended maximum concentration
in irrigation in drinking
Element waters [66] waters [94]
Ag (silver)
As (arsenic)
Ba (barium)
Cd (cadmium)
Co (cobalt)
Cr (chromium)
Cu (copper)
Fe (iron)
Hg (mercury)
Mn (manganese)
Ni (nickel)
Pb (lead)
Se (selenium)
Zn (zinc)
__a
0.1
__a
0.01
0.1
0.05
0.2
5.0
__a
0.2
0.2
5.0
0.02
2.0
0.05
0.05
1.0
0.010
~a
0.05
~a
--a
0.002
a
a
0.05
0.01
--a
Average
wastewater
concentration
<0.008
<0.01
<0.13
<0.004
<0.008
<0.014
0.034
0.39
<0.001
0.070
0.051
0.054
<0.001
0.048
Average
shallow
groundwater
concentration
<0.006
<0.01
<0. 13
0.028
0.010
O.014
0.038
0.36
<0.001
0.96
0.13
0.09
<0.001
0.081
a. None set.
Most studies investigating solution heavy metal-solid phase interactions
have found that specify adsorption, interfacial precipitation bulk
precipitation, and cation exchange can reduce influent heavy metal
concentrations. Mobility potentials of heavy metals are increased in acidic
soils, having low ion-exchange capacities and organic matter.
Several studies have reported on the fate of trace metals at ooeratina
rapid infiltration projects. Metal concentrations in the secondary^??lent
and in the renovated water from a well 27 m (86 ft) from the basing of th«
Flushing Meadows project showed considerable removal o? copper and z?nc but
?f f!f CfdTm 3n? I6ad C69L Metals d1d not ^cumulate in the surf ace'l 5m
(5 ft) of the sen because of the low organic matter and clay content of the
basin soils the low retention times of the water in the surface Mils and
the low metal concentrations in the effluent. ^rrace soils, and
A study of metal accumulation in infiltration basins at Fn^t n*»«nf
Massachusetts, revealed a peak of heavy metals wMch ci?nclSed witS an '
organic matter accumulation zone at 45 cm (18 in.). The SrganlS tXr in
this zone and its metal content appeared to increase during winter
decrease during summer [95]. 9 wirrter
105
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The soils at Hollister are low in organic matter with a cation exchange
capacity typical of sandy and gravelly soils. The soil pH is generally
alkaline favoring heavy metal sorption.
Of the 14 trace elements monitored in the Hollister groundwater, five
showed no significant increases in groundwater concentrations relative to
offsite control wells; three had concentrations that averaged below the
limits of detection; and six showed significant increases in at least one
aquifer relative to background levels in the control wells.
Groundwater concentrations of Ag, Ba, Cd, Co, and Cr in all three
aquifers below the treatment site have been unaffected by wastewater
addition. No statistical differences were observed between treatment site
aquifers and offsite control wells. Concentrations, of Ag, Ba, Cd, Co, and
Cr in the offsite control wells are not significantly different from
concentrations in the primary effluent.
The F ratio for Cd is nearly significant (p = 0.11). This suggests that
the shallow aquifer may be exhibiting the first signs of Cd "breakthrough."
The average concentration of Cd in the shallow wells exceeds maximum
allowable concentrations in drinking water, but because of its variability,
is not significantly different from the offsite control site wells. There is
no soil evidence that suggests Cd mobilization through the upper 300 cm of
soil (see Figure 41).
Analyses-of-variance could not be performed for As, Hg, and Se because
all reported values were below the limit of flame atomic absorption
detection. While no conclusive statement regarding the transport and removal
of these elements through the soil profile can be made, it is apparent that
groundwater contamination by these metals is not occurring.
Treatment site aquifer concentrations of Mn, Ni, Fe, Zn, Pb, and Cu were
significantly different than control well values. Significant shallow
groundwater-control well contrasts were observed for all six metals. Average
control well values of 0.006, 0.041, 0.003, 0.021, 0.016 and 0.015 mg/L were
observed for Mn, Ni, Fe, Zn, Pb, and Cu, respectively. This compares with
average treatment site shallow groundwater values of 0.961, 0.125, 0.356,
0.081, 0.074, and 0.038 mg/L for the same metals. Intermediate well-control
well contrasts were observed for all of these metals except Ni. Deep well-
control well contrasts were significant for Cu, Mg, Pb, and Zn.
Average shallow and intermediate groundwater concentrations of Pb
exceeded those limits set by the EPA for drinking water. The concentration
of Mn in the same groundwaters exceeded the recommended maximum concentration
for irrigation waters used continuously on all soils.
Metal concentrations in some wells were greater than that input by
wastewater. This is particularly apparent for Mn. Input Mn concentrations
averaged 0.070 mg/L, as compared to average values of 0.961, 0.357, 0.154
mg/L for shallow^ intermediate, and deep groundwater, respectively. Lehman
and Wilson [60] observed similar behavior in a continuously flooded,
lysimeter-equipped soil column. In their study, more solution Mn was
106
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observed in soil-water at depths of 15 and 23 cm (6 and 9 in.), than at 8 cm
(3 in.). They concluded that Mn originated from within the soil profile In
addition, Ng and Bloomfield [61, 96] studied trace metal mobilization in soil
media and found that Mn was mobilized by continuous flooding in the presence
of organic matter. Mn mobilization can occur if pH-Eh conditions are
modified to favor the conversions of tetravalent, insoluble manganic forms to
divalent, soluble manganous species. Hem [35] has shown that the solubility
of Mnr<1 is enhanced when both pH and Eh are lowered. The solubility of iron
also increases when conditions become more acidic and more anaerobic zones
are created..
At Hollister, a significant decrease in soil pH was observed after
wastewater addition. In addition, the input of an organic rich wastewater
can create anaerobic environments in the soil. Immediately after flooding
the soil surface becomes saturated; oxygen transfer is diminished- and a
decrease in redox potential results. Both the lowered pH and Eh conditions
favor the solubility of soil Mn and Fe. This is substantiated by the
significant loss of soil Mn from the upper 30 cm of soil. Significant
deposition was not detected through 300 cm, suggesting that Mn is travelling
to the underlying groundwater. In contrast, soil Fe showed significant
increases throughout the soil profile. However, the reduction of ferrous
iron to ferric, followed by re-oxidation (after drying) to ferric and
subsequent precipitation as a hydrous oxide, could lead to a less crystalline
oxide, more amenable to DTPA extraction. Therefore, mobilization of soil Fe
cannot be ruled out.
In addition to the mobilization of Mn and Fe, the possibility exists
that the wastewater addition has resulted in the mobilization of soil Ni Zn
Pb and Cu. Ng and Bloomfield [61, 96] noted that these metals were
mobilized by continuous flooding in the presence of organic matter While
the formation of metal chelates may be an important factor in the transport
of these metals, the more likely possibility is that mobilization has
occurred in response to the dissolution of iron and manganese oxides It has
often been suggested that these oxides furnish the principal control on the
fixation of heavy metals in soils. Consequently, their loss from the soil
profile could decrease the ability of the soil to retain input heavy
and dissolve existing sorbed metals.
s
s,
107
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Jour. WPCF 45:1476-1484. July 1973.
2. Sullivan, R. H., et al. Survey of Facilities Using Land
Application of Wastewater. Environmental Protection Agency, Office
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3. Soil Survey, San Benito County, California. U. S. Department of
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Bulletin No. 130-63. State of California. The Resources Agency,
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Department of Commerce, National Oceanic and Atmospheric
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7. San Benito County Weather Station at Mansfield Road.
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9. Standard Methods for the Examination of Water and Wastewater, 14th
Edition. American Public Health Association, New York. 1976.
10. Enfield, C. G., and B. E. Bledsoe. Kinetic Model for
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S. Government Printing Office, Washington, D. C. 1975.
11. Black, C. A. (ed.). Methods of Soil Analysis, Parts 1 and 2.
American Society of Agronomy, Inc., Madison, Wisconsin. 1965.
12. Diagnosis and Improvement of Saline and Alkali Soils. Agriculture
Handbook No. 60, USDA, Washington, D. C. 1969.
13. Lindsay, W. L. and W. A. Norvell. New DTPA-TEA Soil Test for Zn
and Fe. Agron. Abstr. 1969.
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14. Kilburn, C. Groundwater Hydrology of the Hoi lister and San Juan
Valleys. U.S. Geological Survey, Water Resources Division. August
31 , 1972.
15. Faye, R.E. Mathematical Model of the San Juan Valley Groundwater
Basin, San Benito County, California. U.S. Geological Survey
Water Resources Division. August 1974. '
16. Reynolds Soil and Foundation Engineers. Soil Investigation
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56. Zqsoski, R. J. Sorption and Sorptive Interactions of Cd and Zn on
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114
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94. Federal Register EPA National Interim Primary Drinking Water
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16, 108-135. 1962.
115
-------
TABLE A-l. WASTEWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Parameter
COO
BOO
TOC
Total Kjeldahl
Nitrogen
NH3-h
N-Organ1c
H03-N
Total P
P04-P
Total Conforms,
count/100 ml
Fecal Collforns,
count/100 ml
pH. units
TOS
Conductivity.
mhos/on
SS
Alkalinity
1
F
Na
Ca
Kg
K
Cl
50«
*9
As
Ba
U
Co
Cr
CM
Ft
Hg
Hn
N1
Pb
Se
In
6/21/76
680
ISO
46.2
24.4
21.8
0.68
19.5
13.2
1.3 x 106
--
7.0
1,256
1.890
1.3
0.79
253
56
60
11.7
260
161
0.008
<0.01
<0.1
0.004
0.008
<0.004
0.024
0.34
<0.001
0.056
0.06S
0.012
<0.001
0.016
6/23/76
546
151
38.9
22.4
16.50
0.64
22.0
12.8
5.4 x 106
--
7.0
1.184
1.790
1.0
0.50
244
64
61
11.3
266
180
0.008
<0.01
<0.1
0.005
0.008
<0.004
0.028
0.50
<0.001
0.058
0.065
0.025
<0.001
0.020
6/24/76
647
219
39.5
19.7
19.8
0.76
24.0
12.0
49,000
--
7.0
1.152
1,860
1.1
0.45
242
S3
64
10.9
248
186
0.006
<0.01
<0.1
0.004
0.007
<0.004
0.019
0.38
<0.001
0.094
0.060
0.012
<0.001
0.010
9/15/76
572
211
35.3
23.0
12.3
0.17
10
9
46 x 106
11 x ID*
7.2
1.500
2,320
1.8
0.55
363
70
76
11.7
434
218
0.008
<0.01
<0.1
<0.001
0.014
<0.004
0.031
0.15
<0.001
0.070
0.092
0.045
<0.001
0.035
9/16/76
625
214
..
58.3
44.0
14.3
0.19
12
9
4.6 x 106
4.6 x 106
7.3
1,593
2,400
1.8
0.6
377
71
69
12.5
488
228
< 0.005
<0.01
<0.1
<0.001
0.009
<0.004
0.021
0.22
<0.001
0.067
0.087
0.033
<0.001
0.030
9/17/76
581
202
-_
45.6
33.6
12.0
0.67
10
9
4.6 x 106
4.6 x 106
7.3
1,585
2,480
..
1.7
0.55
391
71
27
12.1
490
210
< 0.005
<0.01
<0.1
<0.001
0.010
<0.004
0.020
0.14
<0.001
O.OS5
0.080
0.022
<0.001
0.030
12/6/76
656
134
30.8
21.7
9.1
0.46
21.5
8.5
92 x 106
9.2 x 10^
7.5
1,032
1,600
234
447
1.2
0.37
230
55
74
12.5
185
250
0.010
<0.01
0.11
0.007
<0.006
0.012
0.070
0.35
<0.001
0.067
0.016
0.070
<0.001
0.052
12/7/77
722
145
..
29.2
22.5
6.7
0.44
11.3
11.3
92 x 106
2.2 x 10*
7.8
1,042
1,640
222
437
1.6
0.41
230
52
75
12.9
200
228
0.011
<0.01
0.10
0.007
<0.006
0.018
0.070
0.32
<0.001
0.067
0.015
0.068
<0.001
0.051
12/8/76
598
180
--
31.2
22.8
8.4
0.52
IS. 9
12.2
24 x 106
3.5 x Ifl6
8.1
1,024
1,620
206
416
1.4
0.33
230
53
75
12.5
190
250
0.012
<0.01
0.12
0.008
<0.006
0.015
0.065
0.34
<0.001
0.071
0.015
0.065
<0.001
0.057
2/22/76
840
414
240
40.2
22.6
17.6
0.2
10.0
9.2
16 x 106
16 x 106
7.3
1,072
1,230
328
454
1.4
1.1
196
32
62
16.0
220
225
0.011
<0.01
0.24
0.003
<0.006
0.030
0.030
0.52
<0.001
0.080
0.048
0.120
<0.001
0.090
2/23/77
969
359
240
40.2
23.9
16.3
0.16
10.0
9.9
24 x 106
16 x 1C6
7.1
1,044
1.330
327
465
1.3
1.1
196
31
62
14.8
205
210
4.005
<0.01
0.22
0.003
<0.006
0.036
0.032
0.82
<0.001
0.084
0.038
0.110
<0.001
0.090
2/24/77
1.029
266
264
41.6
23.0
18.6
0.18
10.5
10.4
24 x 10*
24 x 106
7.1
1,016
1.320
327
459
1.3
1.1
200
31
64
16.0
224
210
O.005
<0.01
0.18
0.002
<0.006
0.031
0.035
0.54
<0.001
0.075
0.033
0.070
<0.001
0.080
-------
TABLE B-l. pH
Units
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-3U5
TOTAL
MEAN
RSD
CONTROL SITES
(1)
8.500
9.200
9.400
9.400
36.500
9.125
4.6S2
(2)
7.800
3.400
8.900
9.100
34.200
8.550
6.786
TREATMENT SITES
(3)
6.300
6.800
7.900
8.300
29.800
7.450
15.047
(4)
6.400
6.500
7.800
8.800
29.500
7.375
34.333
(5)
6.700
7.600
a. ooo
8.600
30.900
7.725
55.285
MEAN
(6)
7.140
7.700
8.400
8.940
8.045
160.900
RSD3
(7)
13.528
14.520
3.460
3.502
CONTROL SITE AVERAGE
0-16 8.150
25-35 8.800
35-105 9.150
295-305 9.250
TREATMENT SITE AVERAGE
6.467
6.967
7.900
8.733
-5.545880
-3.537971
-6.228411
-3.661871
GROUPS OP NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
8.940
8.400
7.700
7.140
8.400
********
9.125
8.550
7.725
8.550
7.450
7.375
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-2.
CALCIUM CARBONATE
Percent
00
1.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
BSD
0-16
25-35
95-105
295-305
CONTROL SITES
(1) (2)
1.550 1.080
2.270 2.060
2.470 2.270
2. 510 3.040
3.300 3.450
2.200 2.113
20.267 38.202
CONTROL SITE AVERAGE
1.315
2.165
2.370
2.775
TREATMENT SITES
(3) (4) (5)
0.230 0.360 0.000
0.270 0.290 0.000
1.170 2.010 0.000
1.420 1.390 2.320
3.140 1.050 2.320
0.785 1.013 0.580
76.139 227.059 427.675
TREATMENT SITE AVERAGE
0.213
0.187
1.060
1.710
MEAN
(6)
0.654
0.978
1.584
2.136
1.338
26.760
"t"
-4.900730
-13.750675
-1.732522
-2.416334
RSDa
(7)
97.857
111.671
64.052
33.598
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST."
2.
1.
0.
136 1.534
534 0.978
978 0.654
* *******
2.
2.
1.
200 2.113
113
013 0.705 0.580
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-3. ELECTRICAL CONDUCTIVITY SOIL EXTRACT
mmhos/cm
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
0.740
0.100
0.100
0.400
1.340
0.335
90.984
(2)
0.770
0. 500
0.330
0.500
2.100
0.525
34.654
TREATMENT SITES
(3)
2.943
2.400
1.800
0.700
7.843
1.961
49.034
(4)
2.623
1.230
1.260
0.830
6.043
1.511
110.773
(5)
2.467
0.770
0.500
0.600
4.337
1.084
99.628
MEAN
(6)
1.909
1.010
0.738
0.616
1.083
21. 663
RSDa
(7)
55.906
87.d74
88.086
30.057
CONTROL SITE AVERAGE
0-16 0.755
25-35 0.300
95-105 0.215
295-305 0.450
TREATMENT SITE AVERAGE
2.678
1.483
1.187
0.727
10.609333
1.851530
1.965833
2.467282
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
1.909
1.010
0.798
0.616
1.961
1.511
1.084
0.525
1.511
1.084
0.525
0.335
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-4. ORGANIC MATTER
Percent
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
0.76U
0.080
0.020
0.010
0.870
0.218
166.890
(2)
1.350
0.150
0.020
0.020
1.540
0. 385
167.856
TREATMENT SITES
(3)
1.200
0.200
0.060
0.110
1.570
0.393
137.947
(4)
2.190
0.120
0.030
0.080
2.420
0.605
89.501
(5)
2.020
0.280
0.050
0.030
2.380
0.595
63.607
MEAN
(6)
1.504
0.166
0.036
0.050
0.439
3.780
RSD3
(7)
39.427
46.585
50.461
86.023
ro
o
CONTROL SITE AVERAGE
0-16 1.055
25-35 0.115
95-105 0.020
295-305 0.015
TREATMENT SITE AVERAGE
1.803
0.200
0.047
0.073
't"
1.656706
1.305976
2.342160
1.921840
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST."
1.504
0.166
0.050
0.036
********
0.605 0.595
0.393
0.385
0.218
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-5.
TOTAL NITROGEN
ppm
CONTROL SITES
TREATMENT SITES
MEAN
RSD°
1.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSO
(1)
559.000
76.000
64.000
45.000
744.000
186.000
133.868
(2)
840. 000
112.000
34.000
184.000
1170.000
292.500
126.531
(3)
1182.000
372.000
117.000
178.000
1849.000
462.250
106/435
(4)
1722.000
347.000
93.000
187.000
2349.000
587.250
100.985
(5)
1586.000
200.000
104.000
77.000
1967.000
491.750
54.328
(6)
1177.800
221.400
82.400
134.200
403.950
8079.000
(7)
41.590
60.608
40.511
50.559
ro
CONTROL SITE AVERAGE
0-16 699.500
25-35 94.000
95-105 49.000
295-305 114.500
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.*3
TREATMENT SITE AVERAGE
1496.667
306.333
104.667
147.333
t"
3.405576
3.009486
3.886174
0.476101
1177.800
221.400
134.200
82.400
********
587.250
491.750
491.750
462.250
462.250
292.500
292.500
186.000
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-6.
ORGANIC NITROGEN
ppm
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSO
CONTROL
(1)
545.000
62.000
45.000
34.000
686.000
171.500
145.345
SITES
(2)
818.000
98.000
30.000
173.000
1119.000
279.750
129.957
TREATMENT SITES
(3)
1122.000
326.000
99.000
137.000
1684.000
421.000
113.482
(4)
1592.000
290.000
74.000
150.000
2106.000
526.500
98.373
(5)
1491.000
174.000
86.000
65.000
1816.000
454.000
43.108
MEAN
(6)
1113.600
190.000
66.800
111.800
370.550
7411.000
RSDa
(7)
39.706
60.925
42.912
53.073
ro
ro
CONTROL SITE AVERAGE
0-16 681.500
25-35 80.000
95-105 37.500
295-305 103.500
TREATMENT SITE AVERAGE
1401.667
263.333
86.333
117.333
t"
3.419416
3.020034
4.493534
0.222999
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
1113.600
190.000
111.800
66.800
* *******
526.500
454.000
454.000
421.000
421.000
279.750
279 .750
171.500
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-7.
TOTAL PHOSPHORUS
ppm
i.
2.
3.
4.
5.
6.
7.
ro
CO
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSO
CONTROL SITES
(1)
705
609
385
334
2033
508
34
.UOO
.000
.000
.QUO
.000
.250
.905
CONTROL
748
532
374
401
(2)
792.
456.
363.
468.
2079.
519.
36.
000
000
000
000
000
750
069
TREATMENT SITES
(3)
1560
1192
719
964
4435
HOB
32
SITE AVERAGE
.500
.500
.000
.000
.000
.000
.000
.000
.000
.750
.243
(4)
1965.
1440.
788.
842.
5035.
1258.
104.
000
000
000
000
000
750
694
(5)
2820
1403
923
850
5996
1499
107
.000
.000
.000
.000
.000
.000
.582
TREATMENT SITE AVERAGE
2115.
1345.
810.
885.
000
000
000
333
MEAN
(6)
1568 .400
1020.000
635.600
691.600
97U.900
19578.000
"t"
2.843629
7.073207
5.605943
6.794494
RSDa
(7)
55.877
44.919
39.324
39.584
0-16
25-35
95-105
295-305
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
1568.400
1020.000
691.600
635.600
********
1499.000
1258.750
1108.750
519.750
1258.750
1108.750
508.250
1108.750
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-8. BICARBONATE EXTRACTABLE
PHOSPHORUS, ppm
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
13.000
0.670
0.560
3.700
17.930
4.483
130.770
(2)
8.400
0.150
0.090
0.170
8.810
2.203
187.596
TREATMENT SITES
(3)
57.000
61.000
42.000
54.000
214.000
53.500
15.300
(4)
109.000
73.000
39.000
32.000
253.000
63.250
114.806
(5)
111.000
63.000
33.000
21.000
228.000
57.000
115.156
MEAN
(6)
59.680
39.564
22.930
22.174
36.087
721.740
RSD3
(7)
83.285
91.070
91.099
99.223
ro
CONTROL SITE AVERAGE
0-16 10.700
25-35 0.410
95-105 0.325
295-305 1.935
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST."
59.680
39.564
39.564
22.930
TREATMENT SITE AVERAGE
92.333
65.667
38.000
35.667
t"
3.567259
13.606802
11.015636
2.678614
22.174
********
63.250
57.000
53.500
4.483
57.000
53.500
2.203
53.500
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-9. BORON
ppm
1.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
0.190
0.170
0.140
0.130
0.630
0.158
17.484
(2)
0.220
0.150
0.090
0.170
0.630
0.158
34.142
TREATMENT SITES
(3)
0.660
0.360
0.180
0.380
1.580
0.395
50.188
(4)
1.080
0.350
0.170
0.470
2.070
0.518
109.863
(5)
0.700
0.340
0.160
0.200
1.400
0.350
101.967
MEAN
(6)
0.570
0.274
0.148
0.270
0.316
6.310
RSDa
(7)
65.173
38.156
24.079
54.496
ro
en
0-16
25-35
95-105
295-305
CONTROL SITE AVERAGE
0.205
0.160
0.115
0.150
TREATMENT SITE AVERAGE
0.813
0.350
0.170
0.350
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
3.513570
18.024983
2.740501
1.931468
0.570
0.274
0.270
0.143
****** **
0.518
0.395
0.395
0.350
0.350
0.158
0.158
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
ro
1.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
TABLE B-10. CATION EXCHANGE CAPACITY
meq/100 g
CONTROL SITES
7
2
1
2
14
3
53
(1)
.170
.790
.910
.310
.180
.545
.025
CONTROL
7
3
1
2
8
3
1
2
15
3
63
SITE
.905
.020
.575
.445
(2)
.640
.250
.240
.580
.710
.928
.681
AVERAGE
4
4
3
6
19
4
25
TREATMENT SITES
(3)
.820
.140
.190
.930
.080
.770
.606
(4)
11.170
6.210
2.700
7.500
27.580
6.395
71.152
TREATMENT SITE
8.910
4.837
2.623
5.887
10
4
1
3
20
5
24
AVERAGE
(5)
.740
.160
.930
.230
.110
.028
.511
8
4
2
4
4
MEAN
(6)
.508
.110
.204
.510
.333
RSDa
(7)
30.805
31.945
34.286
55.432
96.660
0
2
2
1
It . II
.372073
.011952
.024490
.988362
0-16
25-35
95-105
295-305
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
8.508
4.510
4.110
2.204
********
6.895
5.028
5.028
4.770
4.770
3.928
3.545
a.
b.
Relative standard deviation
Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
1.
2.
3.
4.
5.
6.
7.
PO
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
TABLE B-ll. EXCHANGEABLE
SODIUM, meq/100 g
CONTROL SITES
(1)
0.930
0.110
0.001
0.120
1.161
0.290
148.111
CONTROL
0
0
0
0
(2)
0.410
0.070
0.020
0.050
0.550
0.138
132.964
SITE AVERAGE
.670
.090
.011
.085
TREATMENT SITES
(3)
1.210
0.770
0.390
0.910
3.280
0.820
41.511
(4)
3.410
0.590
0.220
0.740
4.960
1.240
106.775
(5)
1.230
0.480
0.260
0.140
2.110
0.528
105.954
TREATMENT SITE AVERAGE
1.950
0.613
0.290
0.597
MEAN
(6)
1.438
0.404
0.178
0.392
0.603
12.061
It A. tl
1.330321
4.751761
4.195057
1.690705
RSD3
(7)
80.039
75.517
92.943
102.350
0-16
25-35
95-105
295-305
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
1.433
0.404
0.392
0.178
********
1.240
0.820
0.820
0.528
0.528
0.290
0.138
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-12. EXCHANGEABLE
POTASSIUM, meq/100 g
1.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
0.260
0.020
0.001
0.010
0.231
0.073
171.923
0
0
0
0
0
0
162
(2)
.300
.050
.001
.001
.352
.088
.737
0
0
0
0
0
0
46
TREATMENT SITES
(3)
.220
.130
.060
.160
.570
.143
.681
0
0
0
0
0
0
72
(4)
.340
.160
.010
.160
.670
.168
.404
0
0
0
0
0
0
28
(5)
.380
.100
.090
.020
.590
.148
.968
MEAN
0
0
0
0
0
2
(6)
.300
.092
.032
.070
.124
.473
RSDa
(7)
21.082
62. 156
124.926
117.166
00
0-16
25-35
95-105
295-305
CONTROL SITE AVERAGE
0.280
0.035
0.001
0.006
TREATMENT SITE AVERAGE
0.313
0.130
0 .053
0.113
111"
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
0.522233
3.800000
1.737310
1.787104
0.300
0.092
0.070
0.032
-********
0.168
0.148
0.148
0.143
0.143
0.038
0.088
0.073
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-13. EXCHANGEABLE
MAGNESIUM, meq/100 g
1.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
1.840
1.120
1.250
1.480
5.690
1.423
22.189
1
1
0
7
11
2
114
(2)
.810
.140
.700
.590
.240
.810
.562
3
2
2
4
12
3
25
TREATMENT SITES
(3)
.300
.880
.240
.180
.600
.150
.819
6
4
1
4
16
4
108
(4)
.970
.020
.310
.210
.510
.128
.126
6
2
1
1
12
3
95
(5)
.320
.590
.430
.880
.220
.055
.136
MEAN
4
2
1
3
2
58
(6)
.048
.350
.386
.868
.913
.260
RSD3
(7)
60.692
52.568
39.946
62.960
ro
0-16
25-35
95-105
295-305
CONTROL SITE AVERAGE
1.825
1.130
0.975
4.535
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST."
TREATMENT SITE AVERAGE
5.530
3.163
1.660
3.423
2.538119
3.608478
1.596132
-0.447265
4.043
3.368
2.350
1.386
********
4.128 3.150
3.055
2.810
1.423
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous. First set of numbers refers to Mean
column (6); second set refers to Mean line 6.
-------
TABLE B-14. EXCHANGEABLE
CALCIUM, meq/100 g
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL
(1)
5.550
3.020
1.750
1.450
11.770
2.943
63.442
SITES
5
1
0
3
11
2
72
(2)
.660
.820
.830
.150
.510
.878
.134
0
0
2
4
7
1
103
TREATMENT SITES
(3)
.640
.010
.790
.510
.950
.988
.658
1
0
2
6
10
2
96
(4)
.670
.090
.310
.240
.310
.578
.381
0
0
0
2
4
1
336
(5)
.940
.180
.570
. 720
.410
.103
.062
MEAN
2
1
1
3
2
45
(6)
.892
.024
.660
.614
.298
.950
RSDa
(7)
86.621
131.297
56.382
50.637
CO
o
0-16
25-35
95-105
295-305
CONTROL SITE AVERAGE
5.605
2.420
1.315
2.300
TREATMENT SITE AVERAGE
1.083
0.093
1.890
4.490
t"
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
-11.390349
-5.151093
0.618915
1.503232
3.614
2.892
1.660
1.024
********
2.943 2.878 2.578
1.988
1.103
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-15. DTPA-IRON
ppm
CONTROL SITES
1.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSO
(1)
19.000
7.560
6.300
7.000
39.860
9.965
60 .666
(2)
23.
6.
3.
7.
41.
10.
32.
000
990
700
990
630
420
386
CONTROL SITE AVERAGE
0-16
25-35
95-105
295-305
21.000
7.275
5.000
7.495
TREATMENT SITES
(3) (4) (5)
122.000 274.
104.000 160.
41.000 53.
26.000 32.
293.000 519.
73.250 129.
64.008 115.
000 169.000
000 140.000
000 28.000
000 14.000
000 351.000
750 67.750
035 114.235
TREATMENT SITE AVERAGE
188
134
40
24
.333
.667
.667
.000
MEAN
(6)
121.400
33.710
26.400
17.398
&2.227
1244.540
"t"
2.883835
6.022371
3.806608
2.412568
RSD3
(7)
88.066
86.732
81.298
63.965
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
121.
83.
400 83
710 26
.710
.400
17.393
********
129.
87.
73.
750 37
750 73
250 10
.750
.250
.420
73.250
10.420
9.965
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-16.
DTPA-MANGANESE
ppm
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
5.450
2.520
1.680
2.090
11.740
2.935
58.309
(2)
5.180
2.580
1.230
2.380
11.370
2.843
58.681
TREATMENT SITES
(3)
2.240
1.040
1.290
2.160
6.730
1.683
36.083
(4)
3.140
0.540
2.100
4.360
10.140
2.535
95.380
(5)
2.070
0.660
1.990
4.590
9.310
2.328
108.117
MEAN
(6)
3.616
1.468
1.658
3.116
2.465
49.290
RSD3
(7)
44.420
68.464
23.d35
40.047
CONTROL SITE AVERAGE
0-16 5.315
25-35 2.550
35-105 1.455
295-305 2.235
GROUPS OP NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
TREATMENT SITE AVERAGE
2.483
0.747
1.793
3.703
t"
-6.432115
-9.2J8372
0.919582
1.459979
3.616
3.116
3.116
1.658
1.468
******* *
2.935
2.843
2.535
2.328
1.683
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-17. DTPA-NICKEL
ppm
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
0.620
0.240
0.200
0.190
1.250
0.313
65.363
(2)
0.730
0.270
0.140
0.240
1.380
0.345
76.120
TREATMENT SITES
(3)
0.740
0.540
0.500
0.280
2.060
0.515
36.620
(4)
2.430
1.040
0.390
0.320
4.180
1.045
108.406
(5)
1.300
0.330
0.310
0.440
2.380
0.595
83.081
MEAN
(6)
1.164
0.484
0.308
0.294
0.563
11.250
RSD3
(7)
64.937
68.628
46.904
32.232
GO
GO
CONTROL SITE AVERAGE
0-16 0.675
25-35 0.255
95-105 0.170
295-305 0.215
TREATMENT SITE AVERAGE
1.490
0.637
0.400
0.347
"t"
1.267567
1.402727
3.085774
2.031885
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
1.164
0.484
0.308
0.294
***** ***
1.045
0.595
0.595
0.515
0.515
0.345
0.313
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-18. DTPA-COBALT
ppm
CA>
1.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
0-16
25-35
95-105
295-305
CONTROL SITES
(1) (2)
0.080 0.040
0.070 0.010
0.010 0.010
0.010 0.010
0.170 0.070
0.043 0.018
88.822 85.714
CONTROL SITE AVERAGE
0.060
0.040
0.010
0.010
TREATMENT SITES
(3) (4) (5)
0.100 0.140 0.040
0.070 0.050 0.040
0.050 0.030 0.030
0.090 0.040 0.050
0.310 0.260 0.160
0.078 0.065 0.040
28.611 65.271 96.825
TREATMENT SITE AVERAGE
0.093
0.053
0.037
0.060
MEAN
(6)
0.080
0.048
0.026
0.040
0.049
0.970
11 1"
0.825723
0.531369
3.098387
2.535463
RSDa
(7)
53.033
51.875
64.358
82.916
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
0
0
0
0
0
.080 0.048
.048 0.040 0.026
********
.078 0.065 0.043
.065 0.043 0.040
.043 0.040 0.018
0.040
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-iy. DTPA-ZINC
ppm
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
0.980
0.120
0.040
0.050
1.190
0.298
153.408
(2)
1.590
0.210
0.030
0.070
1.900
0.475
157.332
TREATMENT SITES
(3)
10.560
3.420
0.210
0.230
14.420
3.605
135.254
(4)
8.040
1.100
0.240
0.180
9.560
2.390
112.969
(5)
7.520
1.420
0.270
0.320
9.530
2.383
108.717
MEAN
(6)
5.738
1.254
0.158
0.170
1.830
36.600
RSDa
(7)
73.719
106.383
72.357
66.160
CO
in
CONTROL SITE AVERAGE
0-16 1.285
25-35 0.165
95-105 0.035
295-305 0.060
TREATMENT SITE AVERAGE
8.707
1.980
0.240
0.243
6.018932
1.935515
9.043140
3.433033
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
5.738
1.254
0.170
0.158
********
3.605
2.390
2.383
0.475
0.298
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous. First set of numbers refers to Mean
column (6); second set refers to Mean line 6.
-------
TABLE B-20. DTPA-CADMIUM
ppm
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSD
CONTROL SITES
(1)
0.080
0.010
0.010
0.010
0.110
0.028
127.273
(2)
0.120
0.020
0.010
0.010
0.160
0.040
133.853
TREATMENT SITES
(3)
0.140
0.070
0.020
0.030
0.260
0.065
83.796
(4)
0.240
0.050
0.010
0.010
0.310
0.078
98.056
(5)
0.180
0.040
0.010
0.010
0.240
0.060
23.570
MEAN
(6)
0.152
0.038
0.012
0.014
0.054
1.080
RSDa
(7)
40.126
62.828
37.268
63.888
en
CONTROL SITE AVERAGE
0-16 0.100
25-35 0.015
95-105 0.010
295-305 0.010
TREATMENT SITE AVERAGE
0.187
0.053
0.013
0.017
2.146879
3.199798
0.774597
0.774597
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST."
0.152
0.038
0.014
0.012
********
0.078
0.065
0.060
0.040
0.028
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-21. DTPA-COPPER
ppm
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
RSO
CONTROL SITES
(1)
2.410
0.350
0.710
0.240
3.710
0.928
108.734
(2)
4.030
0.360
0.170
0.370
4.930
1.233
151.503
TREATMENT SITES
(3)
6.720
2.700
1.490
2.290
13.200
3.300
70.749
(4)
8.230
2.230
0.370
1.190
12.520
3.130
105.472
(5)
6.200
1.440
0.500
0.600
8.740
2.185
42.282
MEAN
(6)
5.518
1.416
0.748
0.938
2.155
43.100
RSDa
(7)
41.661
75.431
65.579
89.442
CO
I
CONTROL SITE AVERAGE
0-16 3.220
25-35 0.355
95-105 0.440
295-305 0.305
TREATMENT SITE AVERAGE
7.050
2.123
0.953
1.360
3.864505
3.725866
1.211560
1.645489
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
5.518
1.416
0.938
0.748
***** ***
3.300
3.130
2.185
3.130
2.185
1.233
2.185
0.928
a. Relative standard deviation
b. Numbers on same horizontal line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of numbers refers to Mean
-------
TABLE B-22. DTPA-LEAD
ppm
i.
2.
3.
4.
5.
6.
7.
0-16
25-35
95-105
295-305
TOTAL
MEAN
BSD
CONTROL SITES
(1)
5.080
0.170
0.140
0.120
5.510
1.378
179.196
(2)
10.370
0.360
0.090
0.170
10.990
2.748
185.002
TREATMENT SITES
(3)
3.520
0.590
0.350
0.410
4.870
1.218
126.356
(4)
5.680
0.670
0.290
0.360
7.000
1.750
121.753
(5)
6.580
0.280
0.170
0.170
7.200
1.800
312.206
MEAN
(6)
6.246
0.414
0.208
0.246
1.779
35.570
RSDa
(7)
40.998
50.799
52.048
52.736
CO
CO
CONTROL SITE AVERAGE
0-16 7.725
25-35 0.265
95-105 0.115
295-305 0.145
GROUPS OF NONHETEROGENEOUS MEANS.
DUNCAN'S MULTIPLE RANGE TEST.b
TREATMENT SITE AVERAGE
5.260
0.513
0.270
0.313
-1.074722
1.468735
2.188993
1.749809
6.246
0.414
0.246
0.208
********
2.748
1.800
1.750
1.378
1.218
a. Relative standard deviation
b. Numbers on same horizontal Line are nonheterogenous.
column (6); second set refers to Mean line 6.
First set of .numbers refers to Mean
-------
TABLE C-l. WELL 3A GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOD
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total collform ,
count/ 100 ml
Fecal collform ,
count/100 ml
pH, units
TDS
Conductivity,
wnhos/cm
SS
Alkalinity
B
F
Na
Ca
Mg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Hn
N1
Pb
Se
Zn
SAR
July
60
3
4.1
<0.2
3.8
0.14
6.5
5.6
>2.4 x 105
>2.4 x 105
7.5
1,285
1,620
--
1.0
1.5
230
119
57
12.5
258
65
0.006
<0.01
<0.1
0.003
0.008
<0.004
0.030
0.49
<0.001
1.65
0.075
0.009
<0.001
0.066
4.34
1976
Sept
27
<6
3.5
1.6
1.0
0.9
7.9
5.8
4.6 x 106
430,000
7.4
1,504
2,220
1.7
1.4
327
106
78
16.0
402
228
<0.005
<0.01
<0.1
0.010
0.012
<0.004
0.094
0.12
<0.001
0.81
0.115
0.10
<0.001
0.084
5.88
Dec
71
16
--
2.7
0.1
0.9
1.8
11.4
9.4
35,000
35,000
7.7
1.200
1,580
521
1.2
0.4
239
82
78
12.1
250
194
0.005
0.01
<0.02
0.010
<0.006
<0.004
0.038
<0.01
<0.001
1.8
0.04
0.11
<0.001
0.021
4.53
Mar
1
39
5
10
2.2
3.7
0
1.1
2.6
7.4
7.4
350.000
24,000
7 c
' . 3
1.138
1,420
..
514
1.0
0.9
219
68
74
11.3
215
168
<0.005
<0.01
0.23
0.003
<0.006
0.032
0.04
0.20
<0.001
0.94
0.16
0.06
<0.001
0.13
4.37
1977
2
32
<2
..
4.9
4.3
0.6
6.6
240.000
49.000
--
15
580
..
230
126
70
12.9
..
--
-_
..
--
..
..
__
..
4.07
Average
46
6
3.8
<0.4
2.2
1.2
8.0
6.8
1.1 x 106
156,000
7.5
1,282
1,710
..
538
1.2
1.1
249
100
71
13.0
281
164
<0.006
<0.01
<0.11
0.007
<0.008
<0.011
0.041
0.21
O.001
1.30
0.10
0.10
<0.001
0.073
4.64
Standard
deviation
19
5.6
0.8
<0.8
1.7
1.0
2.0
1.8
2.0 x 106
177,000
0.1
160
351
36
0.3
0.5
44
25
9.0
1.8
83
70
<0.001
<0.09
0.004
<0.003
<0.014
0.010
0.21
0.50
0.05
0.06
0.041
0.71
Coefficient
of variation
0.41
0.93
0.21
? n
t . u
0.77
0.83
0.25
0.26
1.82
1.13
0.01
0.12
0.21
0.07
0.25
0.45
0.18
0.25
0.13
0.14
0.3
0.43
0.17
0.82
0.57
0.38
1.27
0.24
1.0
0.38
0.5
0.6
0.56
0.15
139
-------
TABLE C-2. WELL 5A GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOD
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total collform,
count/100 ml
Fecal coHfonn,
count/100 ml
pH, units
TDS
Conductivity,
umhos/cm
SS
Alkalinity
B
F
Na
Ca
Hg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Mn
N1
Pb
Se
Zn
SAR
July
10
--
<0.2
<0.2
<0.2
0.05
0.13
0.13
54,000
<2
7.9
1,090
1,810
--
0.7
0.75
248
133
75
13.6
280
280
0.008
<0.01
<0.1
0.005
0.018
<0.004
0.014
0.55
<0.001
0.70
0.115
<0.005
O.001
0.118
4.26
1976
Sept
56
<6
--
1.4
<0.1
<1.3
0.11
19
13
1.1 x 106
930,000
7.6
1,462
2,020
--
1.7
--
308
101
70
16.4
342
280
<0.005
<0.01
<0.1
0.085
0.019
<0.004
0.058
0.19
<0.001
0.81
0.115
0.10
<0.001
0.073
5.76
Mar 1977
Dec
78
43
--
2.8
<0.1
1.0
1.8
11.2
9.9
<2
0
7.5
1,388
2,000
--
516
1.3
0.4
285
120
85
17.6
315
218
0.003
<0.01
O.02
0.10
<0.006
O.004
0.052
0.04
<0.001
0.8
0.04
0.16
<0.001
0.037
4.86
1
33
5
11
1.7
2.8
0.5
1.4
0.9
10.2
10.2
1,600
1,600
7.7
1,160
1,480
519
1.1
1.2
223
71
66
13.3
230
210
<0.005
<0.01
0.38
0.008
0.006
0.055
0.02
1.25
<0.001
0.18
0.38
0.04
<0.001
0.13
4.44
2
32
2
--
1.4
--
1.3
0.1
7.3
1.300
790
~
--
10
530
--
242
112
«
-.
--
..
..
«
..
..
..
4.48
Average
50
13
--
1.7
<0.2
<1.0
0.6
9.6
8.3
231,000
186,000
7.7
1,275
1,828
~
522
1.2
0.80
261
107
74
14.9
292
247
<0.007
<0.01
<0.15
0.050
<0.012
<0.017
0.036
0.51
-------
TABLE C-3. WELL IB GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOO
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total coif form ,
count/100 ml
Fecal coHform,
count/ 100 ml
pH, units
TOS
Conductivity,
ymhos/cm
SS
Alkalinity
e
F
Na
Ca
Mg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Mn
N1
t>b
Se
Zn
SAR
July
25
3
--
0.72
7.1
<0.2
0.2
6.9
0.06
0.06
<2
0
8.1
846
1,170
0.5
0.4
115
57
77
3.5
88
210
<0.004
<0.01
<0.1
0.002
0.010
<0.004
0.04
1.25
<0.001
0.40
0.04
0.04
<0.001
0.16
2.33
1976
Sept
10
0
--
-
4.0
<0.1
<0.1
4.0
0.13
0.11
<2
0
7.8
817
1,210
..
0.7
0.4
143
30
76
3.5
82
228
<0.005
<0.01
<0.1
<0.0"01
<0.006
<0.004
0.039
0.14
<0.001
0.083
0.055
0.015
<0.001
0.14
3.16
Dec
32
5
5.4
0.4
0.6
4.4
0.08
0.04
<2
0
8.7
748
1,090
..
341
0.7
0.2
133
57
84
4.7
60
200
0.003
<0.01
0.08
0.008
<0.006
0.01
0.09
0.07
<0.001
0.22
0.02
0.085
--O.C01
0.70
2.62
Mar 1977
18
<2
9
10.1
0.0
1.1
9.0
0.3
0.3
<2
0
8.3
804
1,000
__
470
0.8
0.4
166
38
87
3.9
92
186
<0.005
<0.01
0.16
0.004
<0.006
<0.004
0.07
0.38
<0.001
0.18
0.028
0.06
cO.COl
0.14
3.39
Average
21
<3
9
0.72
6.7
<0.2
<0.5
6.1
0.14
0.13
<2
0
8.2
804
1,118
..
406
0.7
0.35
139
46
81
3.9
80
206
<0.004
<0.01
<0.11
0.004
<0.007
<0.006
0.06
0.46
<0.001
0.22
0.04
0.05
-------
TABLE C-4. WELL 3B GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOO
TOC
CCE
Total N
NHa-N
N org
N03-N
Total P
P04-P
Total coll form,
count/100 ml
Fecal coll form,
count/100 ml
pH, units
JDS
Conductivity,
inhos/cm
SS
Alkalinity
B
F
Na
Ca
Hg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Hn
N1
Pb
Se
Zn
SAR
July
22
<6
--
1.3
<0.2
1.2
<0.05
--
<2
-------
TABLE C-5. WELL 1C GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOO
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total coli form,
count/100 ml
Fecal coli form.
count/100 ml
pH, units
TDS
Conductivity,
gmhos/cm
SS
Alkalinity
B
F
Na
Ca
Mg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Mn
Ni
Pb
Se
Zn
SAR
July
11
<6.0
0.54
7.9
<0.2
7.9
<0.05
<0.03
<0.03
<2
<2
8.1
1,277
1,700
--
0.5
0.4
214
69
115
4.7
136
375
0.006
<0.01
<0.1
0.004
0.012
<0.004
0.009
0.030
<0.001
0.360
0.080
0.011
<0.001
0.110
3.66
1976
Sept
10
3.0
--
0.78
1.1
0.5
0.5
0.15
0.27
0.22
23
<2
7.7
1.376
1,890
0.2
0.3
207
26
109
5.1
144
400
<0.005
<0.01
<0.1
<0.001
0.009
<0.004
0.066
0.010
<0.001
0.18
0.080
0.010
<0.001
0.138
3.97
Dec
32
5.5
--
1.2
0.9
0.2
0.1
0.12
0.05
8
<2
7.9
1,266
1,800
..
485
0.6
0.2
212
77
112
5.9
110
398
0.032
<0.01
0.08
0.008
<0.006
<0.004
0.10
0.08
<0.001
0.14
0.02
0.055
O.001
0.70
3.61
Mar 1977
18
5.0
13
--
1.2
0.0
1.1
0.1
0.06
<0.02
<2
<2
8.4
1,334
1,500
553
0.4
0.4
193
50
135
5.1
143
295
0.008
<0.01
0.15
0.002
<0.006
0.008
<0.004
<0.04
<0.001
0.15
0.010
0.10
<0.001
0.14
3.22
Average
18
<4.9
13
0.66
2.9
<0.4
2.4
0.1
0.12
<0.08
<9
<2
8.0
1.313
1,723
__
519
0.4
D.3
207
56
118
5.2
133
367
<0.013
<0.01
<0.11
<0.004
<0.008
<0.005
0.045
<0.04
<0.001
0.21
0.048
0.044
<0.001
0.27
3.61
Standard
deviation
10
<1.3
__
0.17
3.4
<0.4
3.7
0.04
0.11
<0.09
<10
0
0.3
51
167
48
0.2
0.1
9
23
12
0.5
16
49
<0.013
<0.03
<0.003
<0.003
<0.002
0.046
<0.029
0.10
0.038
0.043
0.29
0.31
Coefficient
of variation
0.56
0.27
..
0.26
1.17
1.0
1.5
0.4
0.92
1.1
1.1
1.0
0.38
0.04
0.10
0.09
0.5
0.33
0.04
0.95
0.10
0.10
0.12
0.13
1.0
0.27
0.75
0.33
0.40
1.0
0.73
0.48
0.79
0.98
1.1
0.09
143
-------
TABLE C-6. WELL ZC GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOD
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total collform,
count/100 ml
Fecal conform,
count/100
pH, units
TDS
Conductivity,
ymhos/cm
SS
Alkalinity
B
F
Na
Ca
Mg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Hn
N1
Pb
Se
Zn
SAR
July
140
<6
0.4
<0.2
0.3
0.08
0.06
0.06
540
<2
8.0
830
1,210
--
0.3
0.4
120
63
79
5.5
94
186
<0.004
<0.01
<0.1
0.003
<0.006
<0.004
0.032
0.30
<0.001
0.130
0.055
0.010
<0.001
0.137
2.38
1976
Sept
199
46
--
1.6
<0.1
1.6
O.OS
0.07
<0.02
4,600 3
1,100
7.6
790
1.200 1
0.8
0.3
129
240
75
5.1
50
180
<0.005
<0.01
<0.1
<0.001
0.008
<0.004
0.008
0.007
<0.001
0.068
0.060
0.036
<0.001
0.047
1.86
Dec
86
6
2.9
<0.1
1.5
1.4
0.14
0.02
,500
<2
8.0
718
.110
440
0.6
0.2
133
47
80
5.9
70
103
0.007
<0.01
0.09
0.014
<0.006
0.08
0.12
0.50
<0.001
0.084
0.015
0.07
<0.001
0.041
2.74
Mar 1977
81
5
20
2.1
0.7
1.0
0.4
0.06
<0.02
<2
<2
7.9
702
907
420
0.5
0.2
156
30
68
5.5
109
108
<0.005
<0.01
0.15
0.004
<0.006
<0.004
0.09
<0.04
<0.001
0.12
0.024
0.15
<0.001
0.16
3.60
Average
127
<16
20
1.8
<0.3
1.1
0.5
0.08
<0.03
2,161
276
7.9
760
1,107
430
0.6
0.3
135
95
76
5.5
81
144
<0.006
<0.01
<0.11
0.006
<0.007
<0.03
0.063
0.21
<0.001
0.101
0.039
0.067
<0.001
0.10
2.65
Standard
deviation
55
<20
--
1.1
<0.3
0.6
0.6
0.04
<0.02
2,238
549
0.2
60
141
.-
14
0.2
0.1
15
98
5
0.3
26
45
<0.002
--
<0.03
0.006
<0.001
<0.040
0.052
0.23
--
0.029
0.022
0.061
--
0.06
0.73
Coefficient
of variation
0.43
1.25
--
0.61
1.0
0.55
1.2
0.5
0.67
1.0
1.99
0.03
0.08
0.13
--
0.03
0.33
0.33
0.11
1.0
0.07
0.05
.0.32
0.31
0,33
--
0.27
1.0
0.14
1.33
0.83
1.1
--
0.29
0.56
0.91
0.6
0.28
144
-------
TABLE C-7. WELL 4C GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOO
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total col 1 form,
count/ 100 ml
Fecsl collform,
count/100 ml
pH, units
TDS
Conductivity,
umhos/cm
SS
Alkalinity
B
F
Na
Ca
Mg
K
Cl
S04
Ag
AS
Ba
Cd
Co
Cr
Cu
Fe
Hg
Mn
Ni
Pb
Se
Zn
SAR
July
10
2
--
1.7
<0.2
<0.2
1.7
0.05
0.05
<2
<2
8.0
855
1.190
--
0.5
0.5
101
61
87
3.5
88
194
<0.004
<0.01
<0.1
0.003
<0.006
<0.004
0.012
0.030
<0.001
<0.003
0.050
0.008
<0.001
0.050
1.94
1976
Sept
10
2
--
1.6
<0. 1
<0.1
1.6
0.06
0.03
<2
<2
7.7
857
1,230
..
0.8
0.5
110
27
83
3.5
82
193
<0.005
<0.01
<0.1
<0.001
<0.006
<0.004
0.04
<0.04
<0.001
0.007
0.055
0.008
<0.001
0.068
2.37
Dec
28
4
0.65
2.1
<0.1
0.5
1.6
0.07
0.01
<2
<2
7.7
740
1,170
__
411
0.7
0.4
106
65
95
4.7
50
180
0.004
<0.01
0.03
0.007
<0.006
0.09
0.042
<0.01
<0.001
0.003
0.045
0.012
<0.001
0.041
1.96
Mar 1977
15
<2
-------
TABLE C-8. WELL 6C GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOD
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total conform,
count/100 ml
Fecal coHform,
count/100 ml
pH, units
TDS
Conductivity,
pmhos/cm
ss
Alkalinity
B
F
Na
Ca
Hg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Mn
N1
Pb
Se
Zn
SAR
July 1976*
14
6
<0.2
<0.2
<0.2
<0.05
0.04
0.04
<2
<2
7.2
855
1,950
1.4
0.3
230
217
103
4.5
250
280
0.008
<0.01
<0.1
0.003
0.008
< 0.004
0.008
0.020
<0.001
< 0.003
0.070
< 0.005
< 0.001
0.002
3.22
"Only date sampled.
146
-------
TABLE C-9. WELL 7C GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOD
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total collform,
count/ 100 ml
Fecal conform,
count/100 ml
pH, units
TDS
Conductivity,
umhos/cm
ss
Alkalinity
B
F
Na
Ca
Mg
K
Cl
S04
*9
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Hn
N1
Pb
Se
Zn
SAR
July
<10
<6
..
<0.2
<0.2
<0.2
<0.05
0.04
0.04
<2
<2
7.5
951
1,400 1
1.1
0.6
120
62
85
2.7
138
280
<0.004
<0.01
<0.1
0.002
<0.006
<0.004
0.006
0.125
<0.001
0.003
0.055
<0.005
<0.001
0.002
2.32
1976
Sept
<10
<6
..
5.6
<0.2
<0.2
5.6
0.01
<0.01
<2
<2
7.8
962
,590
..
..
0.8
0.6
147
230
91
2.7
156
200
<0.005
<0.01
<0.l
0.002
<0.006
<0.004
<0.004
<0.04
<0.001
<0.003
<0.005
<0.005
<0.001
0.003
2.08
Dec
--
_.
«
--
--
--
--
--
--
--
w_
..
<*
«
--
-
«
--
«
..
..
«
-
..
--
<
-
--
Mar 1977
22
3
6
12.2
0.0
1.2
11.0
0.05
<0.02
23
<2
7.8
1.260
1,580
<
556
1.0
0.4
219
54
108
4.7
284
194
<0.005
<0.01
0.20
0.06
<0.006
<0.004
<0.004
0.24
<0.001
0.015
0.022
0.02
<0.001
0.06
3.96
Standard Coefficient
Average deviation of variation
<14
<5
»»
<6.0
<0.2
-------
TABLE C-10. WELL 8C GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise Noted
Constituent
COD
BOD
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total coli form,
count/100 ml
Fecal coli form,
count/100 ml
pH, units
TDS
Conductivity,
umhos/cm
SS
Alkalinity
B
F
Ma
Ca
Hg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Mn
N1
Pb
Se
Zn
SAR
1976
July Sept
18
<6
..
<0.2
<0.2
<0.2
<0.1
0.1
0.1
-------
TABLE C-ll. WELL 9C GROUNDWATER QUALITY RESULTS
mg/L Unless Otherwise, No ted
Constituent
COD
BOD
TOC
CCE
Total N
NH3-N
N org
N03-N
Total P
P04-P
Total conform,
count/100 ml
Fecal collform,
count/100 ml
pH, units
TDS
Conductivity,
umnos/cm
SS
Alkalinity
B
F
Na
Ca
Mg
K
Cl
S04
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
rig
Mn
N1
Pb
C*»
Se
Zn
SAR
1976
July Sept Dec
52
0.3
0.71
10.2
<0.1
0.3
9.9
0.13
0.0
33
8
8.3
1.274
1,940
- -- . ..
579
1.1
0.25
230
-- -- loo
107
5.5
265
16
0.005
<0.01
<0.02
0.007
<0.006
<0.004
0.032
<0.01
<0.001
<0.003
-- 0.035
<0.05
<0.001
0.076
-- 3.81
Mar 1977
<8
<2
5
9.5
0
0.4
9.1
<0.02
<0.02
540
540
7.5
1,312
1,510
568
1.0
0.4
219
59
111
5.1
267
194
<0.005
<0.01
0.06
<0.001
<0.006
<0.004
<0.004
<0.04
<0.001
0.018
0.016
0.015
<0.001
0.004
3.88
Standard Coefficient
Average deviation of variation
30
1.2
0.71
9.9
<0.05
0.4
9.5
<0.08
<0.01
287
274
7.9
1.293
1,725
574
1.1
0.3
225
80
109
5.3
266
105
<0.005
<0.01
<0.04
<0.004
<0.006
<0.004
<0.018
<0.03
<0.001
<0.03
<0.005
mm
^^
<0.020
<0.03
<0.011
0.013
0.025
0.051
0.05
1.0
1.0
__
0.05
..
0.18
0.06
1.0
*
1.3
14
0.08
0.02
0.18
0.01
0.06
0.33
0.04
0.36
0.03
0.06
0.004
0.83
0.75
1.3
1.1
1.0
1.0
0.5
0.76
1.3
0.01
149
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-78-084
4. TITLE AND SUBTITLE
LONG TERM EFFECTS OF L/
DOMESTIC WASTEWATER H
Infiltration Site
2.
iND APPLICATIO
ollister , Californ
7. AUTHOR(S)
Charles E. Pound, Ronald W. Crites, James
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Metcalf & Eddy, Inc.
Palo Alto, California 94303
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Lab-
Office of Research and Development
U. S. Environmental Protection Agency
Ada, Oklahoma 74820
3. RECIPIENT'S ACCESSION1 NO.
5. REPORT DATE
N OF Aoril 1978 issuine date
tia Ranid 6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
V. Olson
10. PROGRAM ELEMENT NO.
1BC611
1 1 . CONTRACT/GRANT NO.
68-03-2361
13. TYPE OF REPORT AND PERIOD COVERED
.Ada. OK
14. SPONSORING AGENCY CODE
EPA-600/15
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The objective of this study was to evaluate the long-term effects of applying
municipal wastewater after primary treatment to the land using the rapid infiltration
technique. This was accomplished by analyzing groundwater quality and soil
chemistry at a site with a long operating history.
Primary municipal effluent has been applied continuously to rapid infiltration
basins at Hollister, California, for more than 30 years. The current daily flow is
43.8 L/s (1.0 Mgal/d) . Annual wastewater application equals 15.4 m (51 ft) to 20
infiltration basins intermittently flooded for 1 to 2 days every 14 to 21 days, dependin
on basin size and season of year.
Infiltration rates were determined, subsurface hydrology was logged, and
water table response to wastewater application was monitored. A sampling and
analysis program covering a 1 year period included samples from (1) primary
effluent, (2) onsite and control site soil profiles, (3) groundwater at the site and
upgradient and downgradient of groundwater movement from the site.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
groundwater recharge
soil properties
trace elements
water chemistry
13. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
b.lDENTIFIERS/OPEN ENDED TERMS
rapid infiltration systems
jrimary pre-treatment
(wastewater)
and application
municipal wastes
wastewater treatment
19. SECURITY CLASS (This Report)
TTNCTfASPTFTF.n
20. SECURITY CLASS (This page)
TTMf T A SfJTpTp-n
c. COSATI Field/Group
43F
91A
21. NO. OF PAGES
166
22. PRICE
EPA Form 2220-1 (9-73)
150
» u.». «OVB«HBIT muraia omcii H7i7 57.140/682 7
------- |