United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-87/085 Jan. 1988
\vEPA Project Summary
Field Evaluation of the
Land-0-Matic Dry Pellet
Chlorination System
William T. Park
The effectiveness of dry pellet feeder
chlorinators to deliver a desired chlorine
dose in domestic water systems that
would normally receive only occasional
monitoring and adjustment was evalu-
ated at four wells near Tucson, AZ.
The Land-O-Matic Dry Pellet Chlori-
nator* was capable of providing an ac-
ceptable average chlorine dose in well
water supplied to domestic water sys-
tems. The chlorinator proved reliable
and easy to operate, but it required
regularly scheduled monitoring and
maintenance. Finally, data from the
three village water systems used in the
evaluation suggest that the construction
of the well and the configuration of the
water system are controlling factors in
selecting an appropriate chlorination
system.
This Protect Summary was developed
by EPA'a Water Engineering Research
Laboratory, Cincinnati, Ohio, to an-
nounce key findings of the research
project that Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
Disinfecting water in small domestic
water systems can be difficult. Such
systems typically operate with a minimum
of operator attention, and their intermit-
tent, on-and-off flow pattern complicates
the task of obtaining adequate disinfec-
tion. This project evaluated a chlorinator
(Land-0-Matic Dry Pellet Chlorinator,
* Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use.
Autotrol Corporation, Milwaukee, Wis-
consin) designed to dispense chlorine
pellets into a well during well pump
operation. The evaluation included deter-
mination of the equipment's ability to
dependably deliver the desired dose of
chlorine, as well as observation of equip-
ment operating capabilities in a desert
environment.
In a cooperative effort between the
U.S. Environmental Protection Agency,
the Indian Health Service (U.S. Public
Health Service), and the Papago Indian
Reservation, four chlorinators were in-
stalled at the villages of San Luis, Lower
Covered Wells, and Santa Rosa (Santa
Rose village well and Santa Rosa clinic
well) on the Papago reservation, west of
Tucson, Arizona. Information on the wells
is given in Table 1. The San Luis well was
located next to a stock corral, and water
in the well was subject to contamination
and had a variable chlorine demand. The
deep wells at the other two villages were
properly constructed and not subject to
surface contamination. During a 2-year
period before installation of the chlorina-
tors, coliforms were detected in 11 of 18
well water samples at San Luis, ranging
from 1 per 100 mL to 30 per 100 mL. One
of 19 samples at Lower Covered Wells
was positive (6 per 100 mL). Two of 23
Santa Rosa well water samples were
positive (2 per 100 mL and 22 per 100
mL) in the pre-test period.
The chlorinators used in this study
consisted of a modular designed thermo-
plastic device, with a storage bin and
motor-driven rotating pellet plate that
delivered dry chlorine pellets from the
storage bin to a drop tube. The pellets fell
through the drop tube into the well casing.
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Table 1. Water System Characteristics
Village
Component
San Luis
Lower Covered
Wells
Santa Rosa
Village Clinic
Well
Dug. with 8" drilled
8" steel casing
8" drilled
8" drilled
Depth
Pump
Capacity
Storage
Daily Water
Use Range
49ft
Jet
4-8 gpm
3.000 gal
3,200 to
6.500 gal
250ft
Submersible
12 gpm
20,000 gal
5,000 to
11. 000 gal
400ft
Submersible
55 gpm
150.000 gal
plus 3,000 gal
pressure tank
15,000 to 54.000
gal (combined)
500ft
Submersible
85 gpm
23.500 gal
Each chlorinator was fastened to the well
casing with a mounting bracket furnished
by the manufacturer. The chlorinators
were wired to operate when the well
pumps operated. The rate of pellet feed
was adjusted by changing the rotating
speed of the pellet plate and by opening
between 1 and 6 slots in the pellet plate.
A schematic diagram of the chlorinator is
shown in Figure 1.
The chlorinators were installed in 1983.
After an initial 6-month period of opera-
tion for break-in and adjustment, a weekly
program of sampling was conducted in
1984 and 1985. Chlorine samples were
collected on Monday, Wednesday, and
Friday. Bacteriological samples were col-
lected on Monday and Wednesday. When
samples were taken, the operation of the
units was observed, and notes were made
on any problems encountered or adjust-
ments made. Chlorine pellets were added
as needed. Free and total chlorine residual
determinations were made with a DPD
test kit. Coliform analysis by the mem-
brane filter method was performed at the
Papago Tribal Utility Authority Water
Quality Laboratory on the same day that
samples were collected
Results
The results of coliform tests at the four
wells indicated that the dry pellet feeder
chlorinators are most effective when
water of uniform quality is treated. Water
from the San Luis well, subject to
transient contamination, was not easy'to
treat using a chlorinator that could not
automatically change dose in response to
changes in chlorine demand. At San Luis,
44 of 150 coliform samples were positive.
In contrast, at Lower Covered Wells and
Santa Rosa, only one positive coliform
test was observed in the 300 tests per-
formed. The wells at Santa Rosa and
Lower Covered Wells were designed and
constructed to provide a sanitary water
supply, and the ground water there was
not subject to contamination. Chlorinators
at these wells could operate at a steady
rate of feed, without requiring frequent
adjustment. This situation proved the
most appropriate for operation of the
chlorinators.
Variability of chlorine dose was also
evaluated during the study. The mecha-
nism of chlorination involves dropping
solid, 1 -gram pellets into the well casing.
Wells at San Luis and Lower Covered
Wells had stainless-steel pellet catch
screens installed in the casing. These
caught the pellets and allowed water to
flow by as the pellet dissolved. At Santa
Rosa, neither well had a catch screen, so
pellets dropped to the bottom of the well
and dissolved.
In wells having catch screens, chlorine
concentrations were above average when
pumping began. Pellets that had dropped
into the casing near the end of the
previous pumping cycle dissolved while
the pump was off. Then with a resumption
of pumping, the water in the well casing
had a chlorine residual higher than
desired. In wells lacking catch screens,
pellets fell to the bottom of the well. In
this situation, chlorine concentrations
were lower than desired upon start-up of
the pump. When catch screens were
used, the high chlorine concentration
quickly declined, indicating that the
standing water in the well casing had
been pumped out. When no screen was
used, however, the chlorine concentration
increase occurred slowly.
A pumping test was performed at the
Santa Rosa Village well (no catch screen
used here) after a 24-hour period with no
pumping. Chlorine dosing began when
pumping started, but the equilibrium
chlorine concentration was not reached
until pumping had continued for 90
minutes.
The results of this study demonstrate
the importance of having adequate stor-
age capacity for pumped water. The
storage can provide contact time for dis-
infection, and it can also provide for
equalization of the disinfectant residual.
Contact time is best provided in a plug
flow regime, whereas dose equalization
is best in a complete mixing regime.
Accomplishing both purposes in a single
tank would involve an ingenious approach
to baffle design and hydraulics, but if
engineers are aware of the treatment
goals desired and of the characteristics of
the dry pellet feed chlorinator, they can
attempt to meet those goals. The least
desirable situation, both in terms of short
contact time and wide fluctuations of
chlorine residual, was the system with
only a small storage volume. When
chlorination facilities of this type are
designed for small systems, regulatory
guidance should be sought to ensure that
adequate disinfection is attained when
the system is placed in use.
Operating problems were observed
during the test period and were associated
with the pellet drop tube, the metal pellet
plate, metal parts related to the plate
drive, and the amount of pellets stored in
the chlorinator.
The clear-plastic pellet drop tube sup-
plied originally became dark, and the
inside became sticky. Pellets stuck to the
drop tube and eventually clogged it. This
situation was corrected by use of a gray-
plastic drop tube provided by the manu-
facturer.
The rotating circular plate controlling
the rate that pellets dropped into the well
sometimes encountered excessive resis-
tance and did not function as intended.
Pellets jammed between the housing and
the plate, and caused operating difficul-
ties. In 1985, the manufacturer rede-
signed the pellet plate and fabricated it
from a much harder, more rigid, non-
metallic material. The new plate was not
tested in this study, but it is expected to
be effective in reducing these operating
problems.
Chlorine is a very corrosive chemical,
and corrosion of metal parts in the pellet
housing assembly and the clutch as-
sembly occurred. The significance of the
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Pellet plate
Slots automatically
pick up and feed
1 gram pellets.
Slot adjustable to
feed from 1 to 6
pellets per revolu-
tion - 1 RPM max.
Mounting
Bracket
Feed rate adjustment
Wide range of settings
to assure the exact rate
of chlorination required.
Electric Cable
Figure 1. Typical ch/orinator system schematic
Well Pump
corrosion was observed when equipment
maintenance was carried out. Some
screws were so corroded that disassembly
of the motor and clutch assembly resulted
in damage to screwheads.
Early in the study, investigators noted
that the drive motor seemed to labor
when the pellet housing was full. This
was attributed to flexing of the pellet
plate under the weight of a full load of
pellets. During the study, the pellet
volume was kept about one-quarter full
and no more problems were encountered.
Changing to a more rigid pellet plate is
expected to aHeviate this problem.
All four chlorinators were exposed to a
desert environment with no shelter or
protection. After 2 years, the only weather-
ing problems observed were those of
clear-plastic drop tube deterioration and
metal parts corrosion. The equipment was
not harmed by very high air temperatures
or bright sunshine.
Because of the modular design, the
units were easy to disassemble and re-
assemble. No special tools were needed.
Except for the oxidized metal parts, no
major problems were encountered when
repairs were made.
Conclusions
1. The Land-0-Matic Dry Pellet Chlori-
nator produced an acceptable average
chlorine dosage in three water systems
of varied configurations.
2. Although the chlorinators produced
acceptable average chlorine dosages
in the pumped water, they could also
produce undesirable high and/or low
chlorine levels for short periods of
time.
3. High daily temperature and intense
sunshine had no apparent effects on
the dry pellet chlorinator assembly.
However, the clear-plastic pellet drop
tubes that conveyed the chlorine pel-
lets from the chlorinator to the well
deteriorated rapidly and resulted in
improper chlorinator operation.
4. Chlorinator operation was labored
when the storage bin was filled to
capacity with dry chlorine pellets.
5. The interior metal parts in all the nest
and clutch assemblies and 25% of the
pellet housing assemblies became
badly oxidized and, therefore, difficult
to disassemble.
6. The openings in the pellet plates would
occasionally plug up with chlorine
pellets and/or pellet fragments, which
would then cause the pellet plate to
bind inside the retainer funnel while
the motor continued to turn. This pre-
vented the pellets from entering the
well and caused accelerated wearing
in or between the clutch assembly
and shank of the pellet plate.
7. Operation, maintenance, and repair of
the chlorinators was very simple and
required no special training or tools.
8. The combination of pellet plate open-
ings, rotation speed adjustments, and
drive motor speeds allowed the chlori-
nators to operate over a wide range of
pumping rates.
R ecommendations
1. Well construction is an important
consideration in the effective operation
of dry pellet chlorinators and should
be given considerable weight in select-
ing the proper chlorination system.
2. The dry pellet chlorinators are most
effective when used in well water
systems that pump directly to large
storage tanks, which in turn act to
equalize variations in chlorine dosages.
Thus, the physical attributes of the
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water system should be a considera-
tion in selecting the type of chlorinator
used.
3. Dry pellet chlorinators in operation
should be put on a maintenance
schedule that would allow cleaning of
the pellet housing of chlorine dust
and pellet fragments on a semimonthly
basis.
4. The dry pellet chlorinators should be
disassembled at least annually and
inspected for signs of excessive wear,
oxidation, and/or other associated
problems, and questionable operating
parts should be replaced.
5. A clear-plastic pellet drop tube was a
desirable feature on the chlorinators
as it allowed for easy verification of
chlorinator operation. A non-deterior-
ating transparent tube should be sub-
stituted for the original tubes or some
other means of observing pellet de-
livery should be incorporated into the
chlorinators.
6. The Land-0-Matic Dry Pellet Chlori-
nator should be evaluated in an area
that has both high relative humidities
and periods of extreme low tempera-
tures. These factors could influence
the effective operation of the
chlorinators.
The full report was submitted in ful-
fillment of Interagency Agreement
AD75F2A210 by the U.S. Public Health
Service under the sponsorship of the
U.S. Environmental Protection Agency.
William T. Park is with the Indian Health Service, U.S. Public Health Service,
Tucson. AZ 85746.
Gary S. Logsdon is the EPA Project Officer (see below).
The complete report, entitled "Field Evaluation of the Land-0-Matic Dry Pellet
Chlorination System," (Order No. PB 88-113 667/AS; Cost: $14.95, subject
to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use S300
EPA/600/S2-87/085
0000329 PS
U S €KV1R PROtECTION
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