Preliminary Results of 

Injecting Highly Treated 

Sewage-Plant Effluent 

Into a Deep Sand Aquifer at 

Bay Park, New York 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 751-A 

Prepared in cooperation with the Nassau County 

Department of Public Works 

Preliminary Results of 

Injecting Highly Treated 

Sewage-Plant Effiuent 

Into a Deep Sand Aquifer at 

Bay Park, New York 

By JOHN VECCHIOLI and HENRY F. H. KU 

DEEP-WELL ARTIFICIAL RECHARGE EXPERIMENTS 

AT BAY PARK, LONG ISLAND, NEW YORK 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 751-A 

Prepared in cooperation with the Nassau County 

Department of Public W arks 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1972 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress catalog-card No. 72-600146 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402- Price 30 cents (paper cover) 

Stock Number 2401-2181 
Abstract ___________________________________________ _ 

Introduction ________________________________________ _ 

Purpose and scope _______________________________ _ 

Previous work __________________________________ _ 

Acknowledgments _______________________________ _ 

Quality of the water injected _________________________ _ 

Effects of injection on well capacity ___________________ _ 

Changes in specific capacity ______ ~ _______________ _ 

Effect of turbidity on excessive head buildup _________ _ 

Effect of degasification on excessive head buildup _____ _ 

CONTENTS 

Page 

A1 

1 

1 

2 

2 

3 

4 

4 

7 

8 

Effects of injection on well capacity-Continued 

Biologic clogging of the well and aquifer ___________ _ 

Rate of excessive head buildup ____________________ _ 

Restoration of well capacity ______________________ _ 

Quality of initially repumped water ____________________ _ 

Movement of injected water through the aquifer ________ _ Dispersion of the front ___________________________ _ 

Changes in chemical quality ______________________ _ 

Migration of coliform bacteria ____________________ _ 

Summary of preliminary conclusions ___________________ _ 

References cited _____________________________________ _ 

ILLUSTRATIONS 

Page 

A9 

9 

9 

10 

10 

10 

11 

12 

13 

13 

Page 

FIGURE 1. Map of Long Island showing location of Bay Park injection site______________________________________________ A1 

2-6. Graph showing2. Turbidity of the water injected in tests RW1, RW2, and RW3_________________________________________ 4 

3. Head buildup and turbidity of water injected in tests RW4 and RW5__________________________________ 5 

4. Head buildup in tests RW1, RW2, and RW3 compared to drawdown observed during pumping test made before anyinjection____________________________________________________________________________ 7 

5. Conductivity of water from observation wells N7886 and N7890 during injection tests RW 4 and RW5_ _ _ _ _ _ 11 

6. Diagrammatic representation of the chemistry of the water injected (median) in tests RW 4 and RW5 and 

that recovered after 10 days of injection from observation wells N7886 and N7890 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 12 

TABLES 

Page 

TABLE 1. Injection-test statistics___________________________________________________________________________________ A2 

2. Selected chemical-quality characteristics of water injected in each test__________________________________________ 3 

3. Bacterial quality of water injected in each test______________________________________________________________ 6 

4. Unadjusted and adjusted 2-day specific capacities for each injection test________________________________________ 6 

5. Unadjusted and adjusted 10-day specific capacities for tests RW4 and RW5_ _ _ _ _ __ __ __ __ __ _ _ ____ _ _ _ _ _ ___ _ _____ _ 6 

6. Selected physical- and chemical-quality parameters of initially recovered water__________________________________ 10 

7. Bacterial quality of water recovered after test RW4 in 1969__________________________________________________ 11 

8. Selected chemical-quality characteristics of water recovered after 10 days of injection from observation wells N7886 

andN7890_________________________________________________________________________________________ 13 

III 

DEEP-WELL ARTIFICIAL RECHARGE EXPERIMENTS AT 

BAY PARK, LONG ISLAND, NEW YORK 

PRELIMINARY RESULTS OF INJECTING HIGHLY 

TREATED SEW AGE-PLANT EFFLUENT INTO A 

DEEP SAND AQUIFER AT BAY PARK, NEW YORK 

By JoHN VEcCHIOLI and HENRY F. H. Ku 

ABSTRACT 

Highly treated sewage-plant effluent is being injected into a sand 

aquifer at Bay Park, N.Y. Recharge is through a fiberglass-cased 

well finished with a gravel-packed 16-inch diameter stainless-steel 

screen set between 418 and 480 feet below land surface. The well is 

open to the Magothy aquifer of Late Cretaceous age. Maximum 

recharge rate thus far is 360 gallons per minute. 

Head buildup in the injection well (but not the aquifer) in each 

injection test has exceeded that predicted by pumping-test data 

even though the water injected had a physical and chemical quality 

acceptable for drinking water. In one test, the specific capacity of 

the injection well was reduced to half the preinjection value after 

10 days of injection. Excessive head buildup is strongly dependent 

upon the turbidity of the recharge water, even though turbidity 

levels are generally less than 2 milligrams per liter as Si02. The 

fine-grained nature of the aquifer probably accounts for the well's 

high sensitivity to small amounts of suspended matter. 

Redevelopment by pumping after each injection test has resulted 

in restoration of most of the specific capacity prevailing prior to 

each test. The first slug of water recovered during redevelopment 

is very turbid and the concentrations of iron, phosphate, and 

volatile solids are many times greater than those of the injected 

41° 

water. Bacterial content is also many times greater and this together with other evidence suggests that some deterioration in well 

capacity may be a result of biologic clogging. 

INTRODUCTION 

PURPOSE AND SCOPE 

Nassau County is a highly urbanized area on Long 

Island adjacent to New York City (fig. 1). Its population has grown from 672,765 in 1950 to almost 1.5 

million in 1965 (Peters and Rose, 1968, p. 627). With 

the growth of population has come a steady increase 

in ground-water pumpage for public supply-to nearly 

210 mgd (million gallons per day) in 1965 (Cohen and 

others, 1968, p. 70). Pumpage is expected to be almost 

300 mgd by 2010 (Peters and Rose, 1968, p. 627). Local 

ground water presently is the only source of publicsupply water, with most of the water being obtained 

from the Magothy aquifer of Late Cretaceous age. 

Intensive net withdrawals from that aquifer have 

730 

10 0 10 20 30MILES 

L-.~~~----~----~--~ 

FIGURE 1.-Location of Bay Park injection site. 

A1 
A2 DE.EP-WELL ARTIFICIAL RECHARGE EXPERIMENTS AT BAY PARK, LONG ISLAND, NEW YORK 

resulted in local landward movement of salty ground 

water (Lusczynski and Swarzenski, 1966; Cohen and 

Kimmel, 1970), and anticipated increased net withdrawals may accelerate the encroachment of salty 

ground water into Long Island's aquifers. 

A conservation method currently under study by 

Nassau County involves the reclamation of waste 

water and its return to the aquifer. Return might be 

through coastal injection wells intended to create a 

hydraulic pressure ridge and thus stabilize or retard 

movement of the salt-water front; or it might be through 

inland recharge basins or wells intended to augment 

natural recharge to the aquifers (Peters and Rose, 

1968, p. 625). 

As part of the water-reclamation study, the U.S. 

Geological Survey in cooperation with the Nassau 

County Department of Public Works is conducting a 

series of artificial-recharge experiments at Bay Park, 

N.Y. These tests are intended to obtain some of the 

scientific and economic data needed to evaluate the 

feasibility of injecting highly treated sewage-plant 

effluent into a proposed network of barrier-injection 

wells. 

The water-reclamation process, briefly, is as follows 

(Peters, 1968, p. 33). About 0.6 mgd of the effluent 

from an activated-sludge type sewage-treatment plant 

is given tertiary-stage treatment. This process consists of coagulation and sedimentation followed by 

filtration, first through a dual-media sand-anthracite 

filter and then through one to four activated carbon 

columns. Chlorination is the final step in the treatment. 

The reclaimed water produced by this process meets 

commonly accepted potable-water standards (Public 

Health Service, 1962). Additional treatment including 

degasification, pH adjustment, and dechlorination can 

be applied at the injection plant. 

Recharge takes place through a gravel-packed well 

consisting of an 18-inch diameter fiberglass casing 

above a 16-inch diameter stainless-steel screen, which 

is set 418 to 480 feet below land surface (Cohen and 

Durfor, 1966). Initially, the long-term pumping specific 

capacity of this well was about 33 gpm (gallons per 

minute) per foot of drawdown (G. D. Bennett, written 

commun., 1968). The injection stratum, which lies 

within the Magothy aquifer, consists mostly of slightly 

silty fine to medium sand with thin beds of coarse 

sand. The static water level of the injection stratum is 

about 5 feet below land surface, fluctuating generally 

between about 4 and 6 feet below the surface. 

This progress report presents preliminary conclusions 

reached from the testing done to date with the treated 

sewage-plant effluent. Experimental recharge with 

sewage-plant effluent has been underway since October 

1968. As of December 1969, three injection tests of 

2-days duration and two of 10-days duration have 

been made. The recharge rate has varied from 200 to 

360 gpm. The recharge water has been degasified in 

three of the tests. Table 1 summarizes significant 

features of the tests. 

PREVIOUS WORK 

The water-treatment and injection facilities at Bay 

Park have been described in several reports. Cohen 

and Durfor (1966) presented a detailed description of 

the injection well. In another paper, Cohen and Durfor 

(1967) discussed the objectives of the recharge study, 

and they briefly described the injection equipment. 

Peters and Rose (1968) reported extensively on the 

overall project with particular emphasis on the watertreatment facilities. Peters (1968) commented on the 

overall project, including some discussion of early 

operations of the treatment and injection plants. The 

geology and hydrology of the Bay Park site as well as 

the injection facilities and the nature of the experimentation were discussed briefly by Perlmutter, Pearson, and Bennett (1968). G. D. Bennett and others 

(written commun., 1969) described in detail the geohydrology, aquifer and well hydraulics, and the hydrochemistry of the injection site. F. J. Pearson, Jr. and 

G. D. Bennett (written commun., 1969) reported on 

results of early injection experiments that utilized 

public-supply water. 

ACKNOWLEDGMENTS 

The authors are especially grateful to John H. 

Peters, Commissioner, Nassau County Department of 

Public Works, for making available the physical and 

human resources of the Department throughout the 

course of this project. Particular thanks are given also 

to Francis J. Flood, Superintendent of Maintenance 

and Operations, Nassau County Department of Public 

Works, and to many others in that department for 

coordinating water-treatment operations with the injection experiments and for providing assistance in making 

modifications to the injection equipment. 

Maxim Lieber of the Nassau County Department of 

Health provided many of the chemical and all the 

bacteriologic analyses used in this study. Joseph H. 

Baier of the Nassau County Department of Health 

rendered much advice in planning the bacteriologic 

TABLE 1.-Injection-test statistics 

Test Date 

No. 

RW1I ___ Oct. 8-10, 1968 ____ _ RW2 ____ Dec. 10-12, 1968 ___ _ RW3 ____ Feb. 25-27, 1969 ___ _ RW4 ____ May 6-16, 1969 ____ _ RW5 ____ Sept. 15-25, 1969 ___ _ 

Approximate 

length 

(days) 

2 

2 

2 

10 

10 

1 RW signifies "renovated water.'' 

Injection 

rate 

(gpm) 

200 

350 

350 

360 

350 

Gallons Treatment at injected injection plant 

616,000 Degasification. 

1,063,000 Do. 

1,066,000 None. 

5,247,000 Do. 

5, 117, 000 Degasification. 
INJECTING HIGHLY TREATED SEWAGE-PLANT EFFLUENT INTO A DEEP SAND AQUIFER A3 

sampling program. John L. Rose and James Oliva of 

Burns and Roe, Inc., consulting engineers, participated 

in numerous helpful discussions. Louis S. Guaracin;i, 

Nassau County Department of Public Works, made 

some chemical analyses and also offered advice on 

numerous occasions regarding chemical problems. 

Wilbur D. Robichaux, Nassau County Department of 

Public Works, provided numerous suspended-solids 

analyses. Thanks are given also to Samuel D. Faust, 

Rutgers University, for his advice on chemical problems. 

U.S. Geological Survey, Water Resources Division, 

New York district. Philip Cohen, assistant district 

chief in charge of the Long Island program provided 

immediate supervision. Anthony A. Giaimo, Dennis 

Sulam, and Lillian B. Maclin, U.S. Geological Survey, 

and Lawrence A. Cerrillo, formerly with the U.S. 

Geological Survey, assisted in making test measurements and in reducing and compiling the data acquired. 

The authors are grateful for all this assistance. 

This phase of the study was under the general supervision of Garald G. Parker and Robert J. Dingman, 

respectively former and present district chiefs of the 

QUALITY OF THE WATER INJECTED 

The chemical quality of the water injected in each 

test is given in table 2. In general, the water varied 

TABLE 2.-Selected chemical-quality characteristics of water injected in each test 

[All constituents in milligrams per liter, except pH. Upper figures: Maximum observed-minimum observed. Lower figure: Median] 

Analyses by Nassau County Department of Health 

Test No ----------------------------------- RW1 RW2 RW3 RW4 RW5 

Number of samples _______________________ 3 3 4 21 10 

Total iron ________________________ 0.56-0.23 0.18-0.08 0.21-0.04 0.34-0.02 0 .58-o .14 

0.53 0.10 0.13 0.12 0.24 

Free C02- _____ -- ___ - ___ ------- _- _ 31-19 45-26 55-36 100-36 31-15 

20 34 43 65 21 Fluoride __________________________ 0.34-0.22- 0.32-0.16 0.39-0.29 0.44-0.24 0.45-0.16 

0.22 0.22 0.31 0.34 0.26 Ammonia nitrogen _________________ 26.5-22.5 29.5-25.5 24.5-21.5 30-21.5 29-23 

25 28 23.2 25 25 

Albuminoid nitrogen _______________ 0.53-0.46 0.60-0.52 0.54-0.33 0.52-0.27 0.56-0.32 

0.53 0.55 0.35 0.36 0.36 

Nitrite nitrogen ___________________ 0.003-0.001 0.003- <0 .001 <0 .001- <0 .001 0.001- <0 .001 0 .002-<0 .001 

0.001 0.001 <0.001 <0.001 <0.001 

Nitrate nitrogen ___________________ <0.05-<0.05 <0.05-<0.05 0.25-<0.05 1.55-<0.05 <0 .05- <0 .05 

<0.05 <0.05 <0.05 <0.05 <0.05 

Oxygen consumed __________________ 13-6.8 4.8-4.4 4.6-3.1 3.9-2.1 3.4-2 

10 4.6 3.8 3.3 3 Chloride __________________________ 75-69 74-72 86-76 70-62 77-63 

70 72 78 64 73 Total hardness ____________________ 80-66 70-64 70-66 106-54 92-64 

72 68 69 62 72 

Total alkalinity ____________________ 87-84 82-76 86-78 86-33 91-68 

86 81 85 73 77 pH _______________________________ 7.0-6.7 6.8-6.6 6.7-6.5 6.6-6.2 7.1-6.9 

6.9 6.7 6.6 6.4 7.0 Total solids _______________________ 364-355 376-370 380-364 418-259 377-338 

357 373 377 377 357 

Methylene blue active substances _____ 0.41-0.28 0.59-0.18 0.14-0.07 0 .18-<0 .02 0.04-0.02 

0.39 0.24 0.13 <0.02 0.02 

Calcium hardness __________________ 42-36 44-34 38-34 44-28 50-40 

38 38 35 34 42 

Total phosphate ___________________ 3. 60-1.90 3.08-1.0 2.40-1.74 4.20-0.90 6.20-1.44 

3.40 2.32 2.32 1.56 3.56 

Orthophosphate ___________________ 3. 60-1.90 2.80-0.90 1.92-1.44 3.50-0.81 4.80-1.40 

3.40 1.92 1.91 1.52 3.10 Sulfate ___________________________ 125-115 147-132 144-132 185-118 144-127 

118 144 135 147 137 

Analyses by U.S. Geological Survey 

Test No ___________________________________ RW1 RW2 RW3 RW4 RW5 

Number of samples _________________________ 6 6 7 11 9 

Silica _____________________________ 14-13 14-14 14-13 15-12 14-10 

14 14 14 14 14 Calcium __________________________ 16-15 18-16 16-15 18-15 18-16 

16 16.5 16 16 18 M agnesi urn _______________________ 6.3-5.2 5.6-5.3 5.1-4.7 4.4-2.7 5.7-5.0 

5.7 5.4 4.9 4.1 5.2 Sodium ___________________________ 81-71 68-66 86-76 77-63 74-64 

76.5 67.5 80 69 69 Potassium ________________________ 13-12 13-12 13-12 13-12 12-11 

12.5 12 12 12 11 
A4 DEEP-WELL ARTIFICIAL RECHARGE EXPERIMENTS AT BAY PARK, LONG ISLAND, NEW YORK 

little, chemically, from test to test, and what variations did occur did not appear to be significant controlling factors in the head buildup observed in each 

test; an exception is the phosphate content of the water 

injected in test R W5, as discussed in a later section. 

The physical quality of the water injected varied to a 

greater extent than the chemical quality and significantly so, as discussed beyond. Temperature ranged 

from 14°C (Celsius) in test RW3 to 23°C in RW5 (table 

4). Turbidity also showed considerable variation from 

test to test and during individual tests. Temperature, 

of course, is largely dependent on the time of year. 

The turbidity of the recharge water depends upon 

several factors in the treatment process including 

influent load, effectiveness of the operation of the 

clarifier, and backwashing of the filters. 

Turbidity of the water injected during the first 

three tests, as measured by an automatic continuousrecording turbidimeter, is shown in figure 2. Because of 

questionable operation of this unit during tests RW4 

and R W5, it was necessary to measure turbidity by 

other means. A manually operated turbidimeter was 

used in the latter tests as well as during test RW3. 

Comparison of the two methods during test RW3, as 

en 

fz 

2.0 

1.0 ---...... 

0 

3.0 

well as on a few other occasions, indicates that the 

turbidity determinations are not identical quantitatively; hence direct comparison of turbidity during 

tests RW4 and RW5 with turbidity during the earlier 

tests is not possible. 

Turbidity determinations made during tests R W 4 

and RW5 are plotted in figure 3. During test RW4, the 

mean turbidity of the injected water was 0.90 mg/ I 

(milligrams per liter) as Si02 and the standard deviation was 0.42 mg/1 as Si02. For test RW5, the mean 

was 0.57 mg/ 1 as Si02 and the standard !deviation was 

0.33 mg/1 as Si02. Test of significance at the 95-percent 

confidence limit showed the means to be significantly 

different. (See p. A9.) 

With the exception of test RWl, bacterial quality of 

the water injected showed little variation from test to 

test. Table 3 gives summary data on the bacterial 

quality of water for each test, as measured by coliform 

counts. 

EFFECTS OF INJECTION ON WELL CAPACITY 

CHANGES IN SPECIFIC CAPACITY 

The effect of injecting the reclaimed water on the 

capacity of the injection well can be evaluated in terms 

TEST RW3 

- -----

TEST RW2 

::::) 2.0 ~ 

z 

~ ~ 

(.) / ~ ~ J ~ ~ 

--- / ~ 1.0 

3.0 

2.0 

1.0 

0 

0 

-- 400 

I ~ TEST RWl 

__/ ~ 

~ 

800 1200 1600 2000 2400 2800 3200 

TIME, IN MINUTES, SINCE INJECTION BEGAN 

FIGURE 2.-Turbidity of the water injected in tests RWl, RW2, and RW3. 
INJECTING HIGHLY TREATED SEWAGE-PLANT EFFLUENT INTO A DEEP SAND AQUIFER A5 

of the specific capacity of the well. When water is 

withdrawn from a well, the specific capacity of the 

well is the rate of yield, in gallons per minute, per foot 

of drawdown; when water is injected into a well, the 

specific capacity of the well is the rate of injection per 

foot of head buildup. If no well clogging occurs, the 

head buildup observed in the well during injection 

should theoretically equal the drawdown that would 

occur if the well were pumped at the same rate, other 

1-

LU 

LU 

I.&.. 

22 

20 

TEST RW4 

things being equal. Head buildup in excess of that 

amount is an indication of clogging of the well and 

(or) the aquifer, and the excess buildup is reflected in 

a decrease in the injecting specific capacity of the well. 

Before any injection, the long-term (2 days) pumping specific capacity of the well was 32.8 gpm per foot 

(G. D. Bennett, written commun., 1968). However, 

the pumping specific capacity decreased as a result of 

the recharge operations, and the pumping specific 

_/'~ ------

---- 5 

a: 

~ 

_J 

18 

16 

~ 

5 

IDCl 14 <( 

LU 

:::c 

1-

LU 

12 

22 

~:!:! 20 

~ 18 Cl 

_J 

5 

ID 16 

Cl 

<( 

LU 

:::c 14 

12 

/ 

v 

/ 

~ 

471-718 0- 72 - 2 

~ v 

v 

TEST RW5 ... -.. 

~ ....---

r _____......... ~ 

~ ~~ ~ t:'ump off 2 hours Pump surging J 

~ II I 

./ 

~ ~ 

v 

FIGURE 3.-Head buildup and turbidity of water injected in tests RW4 and RW5. 
A6 DEEP-WELL ARTIFICIAL RECHARGE EXPERIMENTS AT BAY PARK, LONG ISLAND, NEW YORK 

capacity before each injection test has, in general, 

been slightly less than the pumping specific capacity 

before the preceding test (table 4). 

The injecting specific capacities observed in each 

injection test were lower than the corresponding pumping specific capacities obtained before each test. This 

indicates that some clogging of the well and (or) the 

contiguous part of the aquifer occurred in each injection test. Specific capacity data are summarized in 

tables 4 and 5. 

Head buildup distribution in the aquifer at distances 

of 20 to 200 feet from the injection well was virtually 

equal, in each injection test, to the drawdown distribution observed during the original pumping test. Hence 

clogging of the aquifer, if any occurred, probably was 

restricted to the immediate vicinity of the injection 

well. 

Temperature of the water injected varied from 

test to test. Because (1) the viscosity of the water is 

inversely related to temperature, (2) the hydraulic 

conductivity is inversely related to the viscosity of 

the water, and (3) the specific capacity of the well is 

TABLE 3.-Bacterial quality of water injected in each test 

[Bacterial analyses by Nassau County Department of Health] 

Test No____________________ RW1 

Total chlorine, residual 

(mg/1): 

Maximum observed 

Minimum observed_ Median __________ _ 

Number of samples_ 

Coliform confirmed 

(MPN1 /1 OOml): 

Maximum observed 

Minimum observed_ Median __________ _ 

Number of samples_ 

Standard plate count at 

35°C (number/ 

ml): 

Maximum observed 

Minimum observed_ Median __________ _ 

Number of samples_ 

t Most probable number. 

>240 

2.2 

93 

23 

>300 

<30 

>300 

23 

RW2 RW3 RW4 RW5 

2.2 

0 

1.2 

25 

38 

<2.2 

2.2 

25 

64 

<30 

<30 

25 

3 

0 

2.5 

14 

2.2 

<2.2 

<2.2 

15 

<30 

<30 

<30 

15 

3.5 

2 

2.5 

33 

5 

<2.2 

<2.2 

33 

35 

<30 

<30 

33 

3 

2 

2.5 

30 

38 

<2.2 

<2.2 

31 

<30 

<30 

<30 

31 

TABLE 4.-Unadjusted and adjusted 2-day specific capacities for 

each injection test 

(1) 1 (2) 

Pretest Unad2-day justed Test pumping 2-day No. specific injecting capacity specific 

(gpm/ft) capacity 

(gpm/ft) 

RWL_ 31.7 

RW2__ 30.4 

RW3__ 30.5 

RW4__ 30.3 

RW5__ 28.9 

28.6 

27.4 

30.3 

25.6 

22.9 

(3) 

Apparent 

decrease 

in specific 

capacity; 

co1.1 - col. 2 (gpm/ft) 

3.1 

3 

.2 

4.7 

6 

(4) 

Temperature 

(oC) 

22 

16 

14 

18 

23 

(5) 

Headbuildup 

correction 

(ft) 

+0.50 

+ .14 - .14 

+ .44 +1.01 

(6) 

Adjusted 

2-day 

injecting 

specific 

capacity 

(gpm/ft) 

26.7 

27.1 

30.6 

24.8 

21.5 

(7) 

Adjusted 

decrease 

in specific 

capacity; 

col. 1 - col. 6 (gpm/ft) 

5.0 

3.3 

5~5 

7.4 

1 Column 2 represents specific capacity based on head buildup unadjusted for 

differences in temperature of the injected water and the native aquifer water (15°); 

column 5 is adjustment for temperature difference; and column 6 is specific capacity based on adjusted head buildup. 

TABLE 5.-U nadjusted and adjusted 1 0-day specific capacities for 

tests RW4 and RW5 

(1) 1(2) (3) (4) (5) (6) (7) 

Pretest Unad- Apparent Adjusted Adjusted 

10-day jus ted. decrease Tern- Head- 10-day decrease 

Test pumping 10-day in specific per a- buildup injecting in specific 

No. specific injecting capacity; ture correction specific capacity; 

capacity specific col.1 - (OC) (ft) capacity co1.1 - (gpm/ft) capacity col. 2 (gpm/ft) col. 6 (gpm/ft) (gpm/ft) (gpm/ft) 

RW4 __ 30.3 17.7 12.6 18 +0.53 17.2 13.1 

RW5 __ 28.9 14.7 14.2 23 +1.21 14 14.9 

1 Column 2 represents specific capacity based on head buildup unadjusted for 

difference in temperature of the injected water and the native aquifer water; column 

5 is adjustment for temperature difference; and column 6 is specific capacity based on adjusted head buildup. 

closely related to the hydraulic conductivity of the 

aquifer, adjustments need to be made in the specific 

capacity to account for the temperature differences. 

These adjustments were made by a method described 

by G. D. Bennett (written commun., 1969) in which 

the extent of the cylinder of injected water of temperature different from that of the aquifer water is taken 

into consideration. Bennett's method is as follows. 

The head-buildup correction at any time caused by 

the temperature difference is calculated from the 

equation 

SwTt - Swt = (;LT - ~J ;·:~log G:') (1) 

where SwTt - Swt = head buildup in the injection well 

for injection water of temperature T, at time t, minus head 

buildup in injection well for 

formation water at time t, in feet. 

K LT lateral hydraulic conductivity to 

injection water of temperature 

T; in feet per day. 

K L lateral hydraulic conductivity to 

formation water, in feet per day. 

Q injection rate in cubic feet per day. 

D thickness of injection stratum, in 

feet. 

TTt radius of cylinder of injection water 

of temperature T, at a time t 

after the start of injection, in 

feet., and 

r w = radius of injection well, in feet. 

The lateral hydraulic conductivity of the formation to 

injection water at temperature T, K LT, is obtained by 

multiplying the hydraulic conductivity to formation 

water, KL, by~where J.L is the viscosity of the formaJ.LT 

tion water and J.LT is the viscosity of the injection water. 

In applying the temperature adjustments, several 

simplifying assumptions must be made that are known 

not to be entirely valid. Hence the adjustments to the 

specific capacities as given in tables 4 and 5 represent 

extreme values, and the actual adjustments probably 
INJECTING HIGHLY TREATED SEWAGE-PLANT EFFLUENT INTO A DEEP SAND AQUIFER A7 

should be somewhat less. Accordingly, the true specific 

capacity probably lies somewhere between the observed 

value and the adjusted value. 

EFFECT OF TURBIDITY ON EXCESSIVE HEAD BUILDUP 

A causal relation has been observed between the 

turbidity of the injected water and the excessive head 

buildup in the injection well. The excessive head buildup 

is simply an expression of the clogging of the well. 

Without clogging, the head buildup should virtually 

stabilize at the end of about 1 day owing to the leaky 

artesian character of the aquifer (G.D. Bennett, written 

commun., 1969). (See fig. 4.) After adjustments are 

made for temperature differences, any increase in head 

buildup beyond that predicted by the pumping test 

curve represents a decrease in the injecting specific 

capacity of the well caused by clogging. 

It was noted that turbidity varied from test to test 

and within individual tests; however, directly comparable data are available for only the first three tests. 

Recalling figure 2, it is seen that turbidity during test 

RW3 was lowest and comparatively uniform throughout the test. During test RW1, a treatment-plant malfunction resulted in the injection of high-turbidity 

water for several hours of the test. Turbidity of the 

water during the second test was generally greater, 

although the peak concentration was less than the peak 

concentration of the first test. 

1.1.1 

1-

:::1 

z 

~ 

Q: 

0.040 

~ 0.035 

z 

0 

...J 

...J 

~ 

Q: 

1.1.1 

a.. 0.030 

ti 

The unit head buildup (head buildup divided by rate 

of recharge) observed in the 2-day tests is shown in 

figure 4. Also shown is the pumping-test curve representing the unit drawdown ( drawdown divided by rate 

of discharge) observed during pumping of the well prior 

to any injection; this drawdown curve serves as a 

reference curve against which to compare the headbuildup curves. If clogging had not occurred during 

injection, the head-buildup curves should resemble the 

pumping-test curve, and they do for the first few hours 

of each test. The later parts of the curves, from about 

300 minutes on, depart distinctly from the pumpingtest curve. The excessive head buildup shown by the 

later parts of the curves seems to reflect the turbidity of 

the injected water closely. The least turbid water injected was that during test RW3, and this test had the 

least excessive head buildup. The most turbid water 

injected was that during test RW2 and, correspondingly, this test had the greatest excessive head buildup. 

These data are not adjusted to reflect differences in 

temperature between the injected water and the native 

aquifer water. However, the only test in which the 

temperature of the injected water differed significantly 

was test RW1, in which the injected water was 7°C 

warmer than the aquifer water. If the final head buildup 

in test R W1 is adjusted for temperature, the head 

buildup is raised to about that in test RW2. 

Mention should be made also of the initial higher 

position of the curve for test RW3; this probably rei 

I 

I 

I 

RW2y• / 

'/ rRw1 // 

~~l ........... 

~~ ~~ RW 

~---- .:::::- ~...,~ 

~-'"'"" -I- ~- [..,* ....... 

... -· -- -- 1.1.1 --- ·-- LL. 

~ ~ .... .. I-- .. 1---' 

~~ 

........ ~ ~-I-• 

~ ~-

~-

z 

3:1.1.1 

g ~ 0.025 

3:..: 

<I(J: 

It:() 

ocn 

ct:O 

Oct: 

a..O 

:::lw 

~ ~ 0.020 

::I<( 

COJ: () 

01.1.1 

<I(Q: 

1.1.1 

J: 

0.015 

0.1 

,... j,.' ....... ~~ ~ ~w~, .. .......: ~ 

v ~ V' 

jRwr 

~~~ 

II 

ll 

111Trtr ... curvi 

10 100 1000 3000 

TIME, IN MINUTES, SINCE PUMPING OR INJECTION BEGAN 

FIGURE 4.-Head buildup in tests RWl, RW2, and RW3 compared to drawdown observed during pumping test made before any injection. 
A8 DEEP-WELL ARTIFICIAL RECHARGE EXPERIMENTS AT BAY PARK, LONG ISLAND, NEW YORK 

fleets, in part, residual deterioration of specific capacity 

from previous injection tests (table 4). 

Another demonstration of the control of turbidity on 

excessive head buildup is shown by the records for 

the first 10-day test, RW4 (fig. 3). The pumping-test 

curve in figure 4 shows that without clogging the head 

buildup in the injection well should virtually level off 

by the end of the first day. However, the head buildup 

in test RW4 (fig. 3) continued to rise irregularly 

throughout the 10-day period. Comparing the headbuildup curve with the turbidity of the water injected, 

it is seen that the rate of excessive head buildup (that 

beyond the first day) is steepest for those periods of 

injection with relatively high turbidity water, whereas 

the rate of excessive head buildup diminishes greatly 

during periods of injection of low-turbidity water. 

Head buildup and turbidity data for test RW5 also 

are shown in figure 3. The control of turbidity on excessive head buildup is not obvious in this test. Apparently another factor was operative in controlling excessive head huildup during this test. (See following 

discussion on p. A9 .) 

Turbidity, of course, is a rough measure of the 

suspended-solids content of the water. For test RW3, 

the test in which turbidity was lowest (0.3-0.8 mg/1 

as Si02),. the suspended-solids content ranged from 

2 to 4 mg/1 and averaged 3 mg/1; during test RW4, in 

which the turbidity was as high or higher (0.3-1.85 

mg/1 as Si02) than in any other. test except for the 

peak turbidity in test RW1, the suspended-solids content ranged from 3 to 10 mg/1 and averaged 5 mg/l. 

These suspended-solids contents are very low values, 

and yet a change of only a few milligrams per liter of 

suspended matter seems to have an appreciable effect 

on the excessive head buildup in the injection well. 

After each injection test, the well was redeveloped 

by pumping. The first slug of water recovered each 

time was very turbid, which probably indicates that 

most of the injected particulate matter was retained in 

the immediate vicinity of the well. Turbidity dropped 

off sharply with continued pumping. Head measurements made in an observation well screened within the 

gravel pack were virtually identical to those in the injection well, suggesting that the filtration and deposition of the suspended matter was taking place beyond 

the gravel pack. Presumably, the suspended matter in 

the injected water was being filtered out at or near the 

gravel pack-aquifer interface. The fine- to mediumgrained character of the injection stratum seemingly is 

very effective in filtering particulate matter from the 

injected water. The fineness of the bed probably also 

accounts for the well's high sensitivity to small amounts 

of suspended matter. 

EFFECT OF DEGASIFICA TION ON EXCESSIVE 

HEAD BUILDUP 

Well-clogging problems caused by the release of 

entrained air or dissolved gases from the injected 

water have been reported by several investigators 

(Price, 1961, p. 28; Foxworthy and Bryant, 1967, p. 18; 

Sniegocki, 1963, p. 4; and California State Wat~r 

Pollution Control Board, 1954, p. 165). Release of a1r 

or gases can cause clogging of the aquifer. Also, excessive amounts of free oxygen can cause precipitation of 

solutes, such as iron, by changing the oxidation-reduction conditions prevailing in the aquifer. 

Of the five tests described in this report, the recharge 

water was degasified in two of the short tests and in 

one of the longer tests. Contrary to expectations, the 

excessive head buildup in those tests was higher than 

in those tests in which the water was not degasified. 

Of course, other parameters, such as turbidity, varied 

from test to test, and this probably was one ,of the 

major controls on the excessive head buildup. Hence, 

if degasification played a role in reducing excessive 

head buildup it was very minor and not discernible 

because of masking by the other variables. 

Degasification was effective in removing most of the 

dissolved oxygen and much of the dissolved carbon 

dioxide from the recharge water and, presumably, any 

other gases that it contained. For example, in test 

R W5, prior to being degasified the recharge water ~ontained 4.8 mg/1 dissolved oxygen; after it was degas1fied 

the dissolved-oxygen content dropped to about 1 mg/1 

or less. No other significant change in the chemistry of 

the injection water due to degasification was noted 

except for an increase in pH, which resulted from the 

reduction in carbon dioxide content of the water. 

Degasification may reduce excessive head buildup 

over longer periods of injection. However, the short 

testing accomplished thus far suggests that any such 

reduction might be small compared to effects of other 

parameters, contrary to what has been reported from 

the studies cited above. Apparently the Bay Park system permits little air entrainment when the water is 

injected under pressure through a pipe which opens into 

the well crusing at a depth of 192 feet (Cohen and 

Durfor, 1966), as has been done in all the tests thus far. 

Also because the temperature of the recharge water 

has been about equal to or warmer than the aquifer 

water, any gases dissolved in the recharge water would 

tend to remain in solution within the higher pressurecolder temperature aquifer environment. 

The amount of dissolved oxygen contained in the 

recharge water is well below saturation. Moreover, the 

injection water has an organic oxygen demand that 

probably consumes most if not all the free dissolved 

oxygen. Hence, the oxidation-reduction regimen within 
INJECTING HIGHLY TREATED SEWAGE-PLANT EFFLUENT IN:TO A DEEP SAND AQUIFER A9 

the aquifer is probably not changed sufficiently to 

cause oxidation of ferrous iron to ferric iron and subsequent precipitation within the aquifer. In fact, the 

converse appears to be true in that the dissolved ferrous iron content of the injected water increases within 

the aquifer suggesting a dissolution of iron rather than 

a precipitation. (See p. A12.) 

Facilities at Bay Park allow for the injection of water 

into the well casing at land surface. Some entrainment 

of air and (or) an increase in dissolved-oxygen content 

may result from such a procedure, to the point where 

well clogging could be affected by those two factors; 

however, this premise must await future testing. 

BIOLOGIC CLOGGING OF THE WELL AND AQUIFER 

Clogging of wells by growths of iron bacteria and 

other slime-producing organisms is a well-known 

phenomena (anonymous, 1966, p. 196). Direct evidence of such phenomena at Bay Park is not available, 

but several lines of indirect evidence suggest the possibility of such occurrences. For example, the recharge 

water, being treated sewage, contains abundant biotasustaining nutrients. Proliferation of at least coliform 

bacteria around the injection well has been observed. 

High concentrations of iron, phosphate, and organic 

material in the immediate vicinity of the injection well 

also have been observed. Head buildup in test RW5 is 

not readily explained by other factors, such as turbidity. 

In test R W5 the water had the warmest temperature--

230C, dissolved oxygen was removed, the pH was close 

to neutral, and the phosphate content was highest; all 

of which provide for favorable environmental conditions for growth of anaerobic organisms. Moreover, 

treatment of the injection well after test RW4 with a 

compound designed to control growth of nuisance 

organisms resulted in a small improvement in well 

capacity. This treatment suggests that some of the 

loss in capacity observed during this injection test 

was a result of biologic clogging. 

In most of the tests, a total chlorine residual of 2.5 

mg/1 was maintained in the injection water. Seemingly, 

this high residual-chlorine content should have minimized biologic clogging, and perhaps it did. However, 

because of the high ammonia nitrogen content of the 

injection water, most of the available chlorine is combined rather than free and, hence, it is a much less 

efficient: col~cidal agent (Fair and Geyer, 1954, p. 808). 

In addition, no chlorine residual has been observed in 

water from an observation well 20 feet away from the 

injection well, which indicates that the available 

chlorine does not persist for long within the aquifer. 

Besides the organic material injected, the aquifer contains carbonaceous matter, such as lignite, which would 

readily absorb chlorine. 

In summary, clogging of the well and the adjacent 

aquifer by bacterial growths is an unanswered problem 

at this time, but certainly the importance of the problem warrants continued, more detailed bacterial 

studies. 

RATE OF EXCESSIVE HEAD BUILDUP 

It is somewhat premature to comment on the longterm rate of excessive head buildup because the injection tests thus far have not exceeded 10 days. However, 

from figure 3, it is seen that the rate of excessive head 

buildup insofar as has been observed, appears to be 

roughly linear on an arithmetic scale. For test R W 4, 

the average rate over the 10-day period was about 0.75 

of a foot per day. In test RW5, a rate of 1.5 feet per 

day prevailed for the first 5 days and a rate of slightly 

more than 1 foot per day prevailed for the latter 5 days. 

The change in rate may in part be due to a 2-hour 

unscheduled shutdown of the pump on the sixth day. 

If one assumes that the rate of excessive head buildup 

will remain roughly linear over longer periods of time, 

and if an excessive head buildup of 100 feet is taken as 

an arbitrary allowable limit, then, at a rate of about 

1 foot per day, periods of uninterrupted injection 

could extend for only 100 days. At that time, injection 

would have to be halted temporarily and the well 

redeveloped. Of course, if higher excessive injection 

heads were allowed, continuous injection could proceed for longer periods. The amount of allowable excessive head buildup would depend upon, among other 

things, the nature and thickness of material overlying 

the injection zone immediately adjacent to the well 

and the design of the injection well and appurtenances. 

Future injection experiments of up to several months 

duration are planned to test the long-term rate of 

excessive head buildup. 

RESTORATION OF WELL CAPACITY 

After each injection test the well was redeveloped by 

pumping. Thus far, the specific capacity that prevailed 

prior to each test was largely but not entirely restored. 

Residual deterioration that occurred, particularly after 

tests RW1, RW4, and RW5, has resulted in a 20-percent 

cumulative decline of the pumping specific capacity of 

the well from that prior to any injection with treated 

sewage. 

Most of the well-capacity restoration occurred within 

the first hour or so of pumping, when the bulk of the 

suspended solids that had been injected were removed. 

Additional restoration doubtlessly occurred whenever 

the pumping rate was increased abruptly, or pumping 

was stopped and restarted, owing to the removal of 

additional particulate matter with each surge. After the 
A10 DEEP-WELL ARTIFICIAL RECHARGE EXPERIMENTS AT BAY PARK, LONG ISLAND, NEW YORK 

first few surges, the well capacity restored with each 

successive surge was small. 

After test R W 4, redevelopment by continuous pumping at varying rates was carried out for 5 days. The 

well was then surged 10 times by pumping it at 1,000 

gpm, the maximum capacity of the equipment, for 10-

minute intervals followed by 5-minute shutdown 

periods. No improvement in specific capacity was 

noted. This procedure was repeated after 2 days of 

continuous pumping; this time 20 surge-cycles were 

applied. Again no noticeable improvement occurred. 

Another 10 surge-cycles were applied 2 days later, 

again with no apparent improvement. 

After redevelopment by pumping was considered 

complete, the well was dosed with a solution of a commercial ammonium compound designed to control the 

growth of nuisance organisms in wells. The well was 

then pumped and a carefully controlled specificcapacity test was made. The test indicated an improvement of about 7 percent in the specific capacity over 

that prevailing before the treatment. 

QUALITY OF INITIALLY REPUMPED WATER 

After each recharge test, the injection well was 

pumped to remove the water injected and, also, to 

attempt to restore the specific capacity of the well. 

With the exception of test R W3, the first water recovered was invariably highly turbid and contained 

concentrations of suspended solids, iron, and phosphate 

many times greater than those of the injected water. 

(See table 6.) Much of the suspended solids were volatile solids and this, coupled with the high oxygen 

demand of the water, indicates that much of the 

material that accumulated around the well was organic. 

Moreover, after at least three of the tests, the first 

water pumped was slightly higher in ammonia nitrogen 

and albuminoid nitrogen than the injected water. 

Also, the water at first was unpleasantly odorous, sugTABLE 6.-Selected physical- and chemical-quality parameters of 

initially recovered water 

[Analyses by Nassau County Department of Health. All constituents in milligrams per liter] 

Test No _____________________ RWl RW2 RW3 RW4 RW5 

Turbidity______________ 225 78 5 80 1163 Total phosphate ________ 30 26 1.44 19.6 43.5 Total iron ______________ 45.5 7.55 .08 15.1 50.5 Total solids ____________ 672 513 532 686 

Total suspended solids ___ 328 136 6 84 248 

Total dissolved solids ____ 344 377 381 448 438 

Total volatile solids__ _ _ _ 171 146 132 232 

Volatile suspended solids_ 116 50 37 82 

Volatile dissolved solids __ 55 96 95 150 

Total fixed solids ________ 501 367 400 454 

Fixed suspended solids ___ 212 86 47 166 

Fixed dissolved solids__ _ _ 289 281 353 288 

Oxygen consumed_ _ _ _ _ _ _ 2 48 35 15 36 1 21 

1 Sample collected 5 minutes later than others. 2 Analysis for total organic carbon. 

gesting the presence of dissolved gases, which may be 

a result of organic decomposition. 

The turbidity and associated high values of suspended 

solids, phosphate, and iron content prevailed during the 

first few tens of minutes of pumping. With continued 

pumping, they gradually diminished to low values, but, 

upon an abrupt increase in pumping rate or upon a 

shutdown and subsequent renewal of pumpage, turbidity increased once again. In other words, everytime the velocity of the water moving into the well was 

increased abruptly, the resulting agitation dislodged 

particles that had been filtered or adsorbed onto the 

aquifer face during injection. Each succeeding agitation resulted in a lesser amount of material being dislodged than in the previous one until virtually no more 

injected material was dislodged. 

Much the same can be said for the bacterial content 

of the recovered water. After each test, the injection 

well was left idle for 4 to 20 days. The well was then 

pumped intermittently until practically all the recharge water was extracted and the well was once again 

producing virtually native ground water. In each 

instance, high counts of coliform bacteria were observed in the first water recovered. Continued pumping 

resulted in lower counts. However, whenever the well 

was idled, the water that was initially recovered upon 

resumption of pumping, after the casing was cleared, 

contained a higher bacterial count than before the end 

of the previous pumping period. This may have been 

due in part to a growth of organisms during the idle 

periods, to a dislodging of a greater number of organisms owing to the surging action at the start of pumping, or to a combination of both. Data for test RW4 is· 

given in table 7; the trend shown typifies that observed 

after each of the tests. 

MOVEMENT OF INJECTED WATER 

THROUGH THE AQUIFER 

DISPERSION OF THE FRONT 

Because the dissolved-solids content of the injected 

water is about 10 times greater than that of the native 

aquifer water, specific conductance provides a convenient parameter for monitoring the movement of the 

injected water within the aquifer. Conductivity of the 

injected water ranged from about 700 to 800 micromhos, 

whereas the conductivity of the native aquifer water 

was about 40 micromhos. Conductivity of water from 

an observation well 20 feet away (N7886) from the 

injection well and a well100 feet away (N7890) during 

injection tests RW4 and RW5 are plotted in figure 5. 

Conductivity of the water from well N7886 was determined from pumped samples and, because this 

observation well is screened the full thickness of the 
INJECTING HIGHLY TREATED SEWAGE-PLANT EFFLUENT INTO A DEEP SAND AQUIFER All 

TABLE 7.-Bacterial quality of water recovered after test RW4 in 1969 

[Analyses by Nassau County Department of Health. Intermittent pumping from 

6-5 to 6-23; pauses.from 6-27 to 7-1, 7-1 to 7-15, 7-16 to 8-6] 

Cumulative Date gallons Standard plate Coliform 

withdrawn count at 35°C confirmed 

(thousands) (number /ml) (MPN 1/100 ml) 

6-2 __________ 2 >300 >240 

6 >300 >240 

24 >300 >240 

86 >300 >240 6-3 __________ 576 >300 >240 

883 44 240 6-4 __________ 1,483 <30 240 

1,699 <30 240 6-5 __________ 2,299 <30 38 6-23 _________ 7,207 >300 >240 

7,327 <30 38 6-27 _________ 10,580 <30 5 7-L _________ 10,586 >300 >240 

10,676 <30 8.8 7-15 _________ 10,682 >300 >240 

10,778 88 2.2 7-16 _________ 11,253 <30 <2.2 8-6 __________ 11,346 38 

11,438 <2.2 8-7 __________ 11,918 <2.2 

1 Most probable number. 

injection stratum, the conductivity represents an average for the water throughout the 60-foot injection zone. 

For well N7890, conductivity was determined by a 

down-hole probe throughout most of the test and by 

pumped samples once per day for the last 3 days of 

the test. This well is screened roughly in the middle 10 

feet of the injection stratum and, hence, the conductivity observed represents more of a point sample 

than that from well N7886. 

The conductivity curves for well N7886 indicate a 

sharp rise in conductivity once the first change is observed. This suggests that little dispersion of the injected slug is occurring within the first 20 feet of travel. 

The curves for well N7890 indicate a more gradual rise 

800 

u 700 

~ N 

!;;;: 600 

(/) 

0 

~ 500 

0 

0::: 

u 

~ 400 

~ 

~ 300 

> 

i= 

g 200 

Cl 

z 

8 100 

/ 

I 

/, 

tl 

/ / 

// 

1// 

/ 

TEST RW4.>- ~----

-- ----- ..,...-

Well N7886 

--- <;:;ST RW5 

Well N7890 

1TEST RW5 

in conductivity, presumably reflecting a greater amount 

of dispersion of the water-quality front as it moves out 

greater distances from the injection well. Permeability 

stratification within the injection zone is known to 

exist, based on geologic observation of core samples 

and on current-meter observations of flow within the 

screened part of the well (G. D. Bennett, written 

commun., 1969). Conductivity profiles in well N7886 

suggest that much of the dispersion of the injected 

slug results from unequal rates of travel of the front 

through various layers of the injection stratum, as 

described theoretically by Mercado (1967, p. 23). 

Diffusion and (or) dilution most likely also account 

for part of the dispersion observed. 

CHANGES IN CHEMICAL QUALITY 

In gross aspect, little change occurred in the chemistry of the injected water as it moved through the 

aquifer, based on present information. In detail, however, some noteworthy changes were observed. The 

chemical character of the injected water and of water 

from observation wells N7886 and N7890 is depicted 

diagrammatically in figure 6. Comparison of the characterization of the injection water with that from 

N7886 for tests RW4 and RW5 indicates that calcium and bicarbonate are the only major constituents 

to show much change; both decrease with movement 

through the aquifer. According to F. J. Pearson, Jr. 

(written commun., 1969), the most likely cause for this 

decrease is the exchange of calcium for hydrogen, in 

addition to other cations, on the clay minerals contained in the Magothy aquifer. The liberated hydrogen 

ions would react with bicarbonate in solution to produce nonionized H2C0 3, which does not appear in the 

f------ -----.-....-- - -!-----

~ ----- / -- ...... --- ~ ---- 4-------lEST RW4 ,._.-.:::: =--

~-- - ~~ 

,_ 

2 3 4 5 6 7 8 9 10 

TIME. IN DAYS, SINCE INJECTION BEGAN 

FIGURE 5.-Conductivity of water from observation wells N7886 and N7890 during injection tests RW4 and RW5. 
Al2 DEEP-WELL ARTIFICIAL RECHARGE EXPERIMENTS AT BAY PARK, LONG ISLAND, NEW YORK 

TEST RW4 

Injection water 

I 

Observation well N7886 

EXPLANATION 

TEST RW5 

Injection water 

Observation well N7886 

Ca --+---- HC03 

Mg--

NH4 --• -•-- N03 

Observation well N7890 CATIONS ANIONS Observation well N7890 

(Native aquifer water shown by hachures) 

1 0 1 2 3 3 2 1 0 1 2 3 

MILLIEQUIVALENTS PER LITER MILLIEQUIVALENTS PER LITER 

CATIONS ANIONS CATIONS ANIONS 

FIGURE G.-Diagrammatic representation of the chemistry of the water injected (median) in tests RW4 and RW5 and that recovered 

after 10 days of injection from observations wells N7886 and N7890. 

analysis, and therefore, results in an apparent loss of 

bicarbonate ion. Table 8 lists more complete analyses 

of water obtained from the observation wells. 

In conjunction with the reduction in calcium and 

bicarbonate content, the water from well N7886 

showed a decrease in total and calcium hardness, 

alkalinity, and pH, and an increase in carbon dioxide. 

Other noteworthy changes include a large loss in phosphate content, which presumably reflected a concentration of phosphate around the injection well. Iron 

content increased considerably, most likely as a result 

of dissolution of pyrite and (or) other iron-bearing 

minerals contained within the injection stratum. Dissolved-solids content of the water was about 10 percent less than that of the injected water, but, with 

continued injection and more complete flushing of 

native aquifer water, together with the establishment 

of a new equilibrium between the injected water and 

the aquifer framework, the dissolved-solids content of 

the water from well N7886 may approach that of the 

injected water. 

The chemical character of the water from well N7890, 

as shown in figure 6 and table 8, indicates that this 

water was a mixture of aquifer water and injection 

water even after 10 days of injection. The iron content, 

as in water from well N7886, was considerably higher 

than both the injected water and the native aquifer 

water. 

MIGRATION OF COLIFORM BACTERIA 

Although the water injected is relatively free of 

coliform bacteria, a proliferation of coliform bacteria 

has been noted in the immediate area of the injection 

well upon cessation of injection. Sparse evidence thus 

far suggests that coliform bacteria may be migrating 

through the aquifer along with the injected water, at 

least as far as well N7886, 20 feet away from the injection well. Movement of bacteria is slower than that of 
INJECTING HIGHLY TREATED SEWAGE-PLANT EFFLUENT INTO A DEEP SAND AQUIFER A13 

TABLE B.-Selected chemical-quality characteristics of water recovered 

after 10 days of injection from observation wells N7886 and N7890 

[All constituents in milligrams per liter except pH. Analyses by Nassau County 

Department of Health, except for Si02, Ca, Mg, N a and K which were made by U.S. Geological Survey. MBAS, methylene blue active substances] 

N7886 

Test No_____________________ RW4 

Total iron_____________ 0. 58 

Free C02-------------- 80 Fluoride______________ . 29 

Ammonia nitrogen_____ 25 

Albuminoid nitrogen___ .36 

Nitrite nitrogen_ _ _ _ _ _ _ < . 001 

Nitrate nitrogen_______ < .05 

Oxygen consumed______ 1 . 8 

Chloride_ _ _ _ _ _ _ _ _ _ _ _ _ _ 67 

Total hardness_________ 44 

Total alkalinity________ 41 

pH___________________ 6 

Total solids ____________ 342 

MBAS________________ < .02 

Calcium hardness_ _ _ _ _ _ 26 

Total phosphate_______ .14 

Orthophosphate________ .13 

Sulfate ________________ 132 

Silica _________________ 12 

Calcium_______________ 10 

Magnesium____________ 3. 5 

Sodium _______________ 67 

Potassium_____________ 10· 

RWS 

0.91 

105 

.23 

18.5 

.24 

< .001 

< .05 

2 

74 

42 

33 

5.8 

321 

<.02 

22 

.60 

.50 

138 

10 

8.2 

4.2 

67 

9 

N7890 

RW4 

0.64 

55 

.18 

1.30 

.018 

< .001 

<.05 

.9 

28 

44 

7 

5.4 

120 

<.02 

40 

.02 

.02 

60 

8.2 

7.8 

3.1 

23 

2 

RWS 

1.30 

100 

< .10 

1.38 

.04 

< .001 

<.05 

1 

24 

34 

6 

5.1 

123 

<.02 

16 

.02 

<.01 

54 

8.0 

7.2 

3.3 

22 

1.6 

the water itself, perhaps because of the time necessary 

for regrowth around the injection well. However, much 

more study is necessary to define the rate and distance 

of migration. 

SUMMARY OF PRELIMINARY CONCLUSIONS 

Recharge with highly treated sewage-plant effluent 

has been conducted intermittently at Bay Park since 

October 1968. Preliminary findings to date are: 

1. Head buildup in the injection well (but not the 

aquifer) in each test thus far has exceeded that 

predicted by pumping-test data, even though the 

water injected was of potable quality. In one test, 

the specific capacity of the injection well was 

reduced to about 50 percent of the preinjection 

value after 10 days of injection. 

2. The amount of excessive head buildup in the injection well was strongly dependent upon the turbidity of the recharge water, even though turbidity levels were less than a few milligrams per 

liter as Si02. A small increase in suspended matter 

had an appreciable effect on the excessive head 

buildup. 

3. Most of the particulate matter injected was filtered 

out and retained at or near the aquifer-gravel pack 

interface. 

4. Degasification of the injection water has not resulted in a measurable reduction of clogging of the 

injection well. 

5. Specific capacity of the injection well, which was 

reduced during injection, was largely restored by 

pumping. 

6. Water recovered from the injection well after each 

test initially was very turbid and contained high 

concentrations of iron, phosphate, and volatile 

suspended solids. It was also high in bacterial 

content. 

7. Little change occurred in the chemistry of the injected water as it moved through the aquifer for 

distances of 20 feet. Changes noted include a 

decrease in calcium and bicarbonate content, and 

conjunctively, a decrease in hardness, alkalinity, 

and pH. Phosphate content also decreased, but 

iron content increased. 

REFERENCES CITED 

Anonymous, 1966, Ground water and wells: St. Paul, Minn., Edward E. Johnson, Inc., 440 p. 

California State Water Pollution Control Board, 1954, Report on 

the investigation of travel of pollution: Sacramento, Calif., 

Pub. no. 11, 218 p. 

Cohen, Philip, and Durfor, C. N., 1966, Design and construction 

of a unique injection well on Long Island, New York, in 

Geological Survey research 1966: U.S. Geol. Survey Prof. 

Paper 550-D, p. D253-D257. 

--- 1967, Artificial-recharge experiments utilizing renovated 

sewage-plant effluent-a feasibility study at Bay Park, New 

York, U.S.A., in Symposium of Haifa, Artificial recharge and 

management of aquifers: Internat. Assoc. Sci. Hydrology Pub. 

no. 72, p. 193-199. 

Cohen, Philip, and Kimmel, G. E., 1970, Status of salt-water encroachment in 1969 in southern Nassau and southeastern 

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