Operations Manual
Stabilization
Ponds
by
CHUCK ZICKEFOOSE
R. B. JOE HAYES
PROJECT OFFICER
LEHN POTTER
MUNICIPAL OPERATIONS BRANCH
OFFICE OF WATER PROGRAM OPERATIONS
WASHINGTON, D.C.
for the
OFFICE OF WATER PROGRAM OPERATIONS
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
CONTRACT NO. 68-01-3547
AUGUST 1977
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Acknowledgements
This operations manual was prepared for the
Office of Water Program Operations of the
United States Environmental Protection Agen-
cy. Development and preparation of the man-
ual was carried out by the firm of Stevens,
Thompson & Runyan, Inc., Portland, Oregon.
Jim Scaief and R. B. Joe Hayes collected field
data and principle author was R. B. Joe Hayes
under the direction of Chuck Zickefoose.
Recognition is due to plant operators, Oregon
Department of Health and Environment, Cal-
ifornia Regional Water Quality Board, Colora-
do Department of Health, Minnesota Pollu-
tion Control Agency, Nebraska Department
of Environmental Control. EPA coordination
and review was carried out by Lehn Potter,
Office of Water Program Operations.
The mention of trade names of commercial
products in this publication is for illustration
purposes and does not constitute endorse-
ment or recommendation for use by the U.S.
Environmental Protection Agency.
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Introduction
BACKGROUND
Stabilization ponds were first used for waste-
water treatment in the midwest for remote
communities, but have since found extensive
use in various parts of the country. In addi-
tion to domestic uses, ponds are now treating
various types of industrial wastes including
vegetable, oil refinery, slaughterhouses, dairies
and rendering plants.
PURPOSE OF THIS MANUAL
Even though precise process control is not re-
quired, there are a number of factors to be
conscious of from an operation and mainte-
nance standpoint for the operator, plant own-
er and consulting engineer. This manual is
intended to serve several functions including:
. Supplement to the specific operation
and maintenance manual prepared for
municipal ponds.
. Provide basic information on pond
theory and features the beginning
operator should know.
. Provide tips on operation and mainte-
nance for experienced operators based
on information from various parts of
the nation.
. Outline troubleshooting tips for han-
dling various problems common to
ponds.
MANUAL ORGANIZATION
The manual is divided into six main parts:
. The Basics
. Control Information for Ponds
. Operation and Maintenance for Ponds
. Troubleshooting for Ponds
. Safety
. Appendices
USE OF THE MANUAL
The Basics For those wanting to brush
up on fundamentals or get aquainted
with types of ponds, terminology and
factors to consider in operation, this sec-
tion will be helpful.
Control Information for Ponds This
portion of the manual considers sam-
pling, flow control and use of informa-
tion gained from either visual, nasal or
laboratory investigation.
Operation and Maintenance for Ponds
After gathering information, some action
may be necessary and this subject is cov-
ered here. Housekeeping and day-to-day
activities are presented along with a sug-
gested checklist which can be adapted
for the individual plant.
Troubleshooting for Ponds This part
of the manual presents a number of po-
tential problems and gives solutions that
other operators have found to be
helpful.
Safety Many times only one person is
on site making it doubly important to
work safely. Major points are given here.
Appendices A glossary, sample calcula-
tions, flow measurement and references
are some of the inclusions. A sample
checklist which can be modified for the
individual plant is also included.
Ml
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PLANT MANAGEMENT
Operation of a wastewater treatment system
is a joint effort by a number of people, direct-
ly or indirectly. The two entities that are
most involved after the contractor moves off
site are the plant "owner" and operator. Each
have certain areas of responsibility.
Owner
The owner may be the private agency that
had the pond constructed, the governing
board of a sewerage agency, the city manager
or city council. It is the individual or group
of individuals that the operator is ultimately
responsible to and who have the authority to
make policy decisions in regard to pond
operation.
The owner of a pond has the responsibility of
providing an operator who is conscientious, in
good physical condition, and is capable of op-
erating and maintaining the facility after be-
ing provided proper instruction and orienta-
tion. The orientation period might initially
require the full-time duties of the operator.
If the current operator leaves the employ of
the owner, it is the owner's responsibility to
obtain immediate replacement. The replace-
ment should be provided with proper training
to make up any possible deficiency.
The owner should encourage opportunities
for plant personnel to expand their know-
ledge by attendance at meetings, short
schools, special training courses, and utilizing
other opportunities for increasing their tech-
nical competence.
The owner has the responsibility to establish
a salary level scale that encourages tenure of
trained and experienced personnel.
It is the responsibility of the owner to obtain
from the appropriate regulatory agency any
permit required for operation of the plant.
The owner is ultimately responsible for the
performance of the treatment facility. To
maintain such performance, the owner is re-.
sponsible for general supervision of the oper-
ator, in addition to supplying him or her with
all necessary tools, materials, and parts for
proper plant operation and maintenance. It is
also the responsibility of the owner to provide
adequate funds for plant expansion as needed.
Operator
The plant operator is responsible for the con-
scientious and proper operation and main--
tenance of the installation. This includes
maintenance of buildings, grounds, and
equipment.
The operator is responsible for maintaining a
safe working environment and being safety
conscious in his or her actions.
The operator is required to make those tests
and observations required for the proper op-
eration of the pond and to satisfy the appro-
priate reporting agency regulations. All re-
sults should be made known to the owner in
terms that can be easily understood.
The operator must have the ability to inter
pret laboratory tests and apply their results to
the operational control of the treatment
plant.
The operator is responsible in notifying the
owner as to the need for tools, parts, and sup-
plies. Sufficient notice should be given so
that such items will be available when needed.
The operator has the responsibility to become
fully acquainted with the plant and the treat-
ment process used. He should take advantage
of training offered by the regulatory agency,
manufacturer-supplier or local community
college.
IV
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Table of Contents
ACKNOWLEDGEMENTS i
INTRODUCTION iii
Background iii
Purpose of This Manual iii
Manual Organization iii
Use of the Manual iii
Plant Management iv
Owner iv
Operator- iv
TABLE OF CONTENTS v
1. THE BASICS 1-
Some Interesting Facts About Your Wastewater 1-'
Know Your Process 1-1
The Phenomenon of Pond Life.
The Role of Bacteria
The Role of Algae
How Are Wastes Treated
Types of Ponds
Stabilization Ponds
Oxidation Ponds
Facultative Ponds
Specialty Ponds.
What Natural Factors Affect the Process.
Wind Action___
Temperature-
Sunlight 1-11
How Physical Factors Affect Treatment 1-12
Surface Area 1-12
Water Depth 1-13
Short Circuiting 1-13
Series Operation 1-13
Parallel Operation.
Recirculation
How Chemical Factors Affect Treatment-
Oxygen
Nutrients.
pH
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2. CONTROL INFORMATION FOR PONDS
Sample Collection
Types of Samples
Automatic Samplers
Handling and Preservation nf Samples
Sample Point Locations
Pnnd Influent
Ponds
Pond Fffliifint
Tests and Measurements
Temperature
Flow
PH
Dissolved Oxygen
Chlorine Residual
Rnnr
D
Understanding ROD
Fff jrjenry of ROD Removal
Suspended Solids
Feral Coliform
Nitrogen
Important Visual Indicators
Color
Other Daily Data
Weather
Water Depth
Ice Cover
3. OPERATION AND MAINTENANCE FOR PONDS
2-1
2-1
2-1
2-2
2-2
2-2
2-2
2-3
2-3
2-3
2-3
2-4
2-4
2-5
2-5
9-5
7-R
2-7
2-7
2-7
2-7
2-8
2-8
2-9
2-9
2-9
2-9
3-1
Operation and Maintenance Goals for Stabilization Ponds 3-1
Operation and Maintenance Goals for Anaerobic Ponds 3-1
Operation and Maintenance Goals for Aerated Ponds 3-2
Plant Checklist 3-2
Hints to Improve Operation 3-6
Flow Regulation 3-6
Baffles and Screens 3-6
Pond Cleaning 3-7
Starting a Pond 3-7
Procedures 3-7
To Fill Successive Ponds 3-7
Discharge Control Program for Seasonal Discharges 3-8
Preparation 3-8
Discharge Procedures 3-8
VI
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4 TROURI ESHOOTINR FOR PONDS
How to Control Water Weeds
How to Control Burrowing Animals
How to Control Dike Vegetation
How to Control Scum
How to Control Odors
How to Control Blue-green Algae
How to Control Insects
How to Obtain Best Algae Removal in the Effluent
How to Correct Lightly Loaded Ponds
How to Correct a Low Dissolved Oxygen (DO)
How to Correct Overloading
How to Correct a Decreasing Trend in pH
How to Correct Short-circuiting
How to Correct an Anaerobic Condition
How to Correct a High BOD in the Effluent
How to Correct Problems in Aerated Ponds
How to Correct Problems in Anaerobic Ponds
5 SAFETY AROUND PONDS
Public Health Aspects
Personal Hygiene
Safety
Safety Fquipment
APPENDICES
A Glossary nf Terms
B Formulas and Problems
C F|nw Measuring Devices
D Design Considerations from an Operation
and Maintenance Viewpoint
E Pa^e Histories
F Metric Fqnjvalents
G References and Suggested Resource Material
H Plants Visited
.1 Checklist Form
4-1
4-1
4-1
4-2
4-2
4-3
4-3
4-4
4-4
4-4
4-5
4-5
4-5
4-fi
4-fi
4-7
4.7
d-7
5-1
5-1
5-1
5-7
5-3
A-1
B-1
C-1
D-1
E-1
F-1
G-1
H-1
J-1
VII
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1. The
Some interesting facts about
your wastewater
Know your process
The phenomenon of pond life
How are wastes treated
Types of ponds
Stabilization ponds
Oxidation ponds
Facultative ponds
Specialty ponds
What natural factors affect
the process
How physical factors affect
treatment
How chemical factors affect
treatment
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1. The Basics
SOME INTERESTING FACTS ABOUT
YOUR WASTEWATER
Water is used to carry man's waste products
from homes, schools, commercial establish-
ments and industrial enterprises. Water borne
wastes are classified as being domestic or
industrial.
The type of wastes discharged into the sew-
age collection system from industrial sources
varies widely and may bring on treatment
problems for the operator. In general, most
contribute a high concentration of organic
loading.
Domestic waste is pretty much the same
throughout the country. We all cook, eat and
clean up pretty much the same and during the
same hours. These general habits create a
pattern of loading throughout the day as
shown in the following diagrams.
N
Time of day
Variations in sewage flow
6
PM
Time of day
Variations in BOD
The average domestic sewage with well-
constructed sewers will provide flows of 75
to 100 gallons containing about 0.2 Ibs. or
240 mg/l of BOD per capita (person) per day.
Fresh domestic sewage is usually gray in
color, similar to dishwater, with a kind of
musty odor. If it becomes septic, it turns
black with a strong, foul odor and the pH
will be lower. The water temperature is
usually a few degrees warmer than pond
1-1
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temperature but will vary with time of year.
The solids are broken down according to
their physical characteristics.
Dissolved Solids make up about 40 percent
of the total solids and are dissolved in the
water like sugar is dissolved in coffee.
Suspended Solids are the remainder of the
total solids. Of these, some are settleable
when they enter the pond.
Common tests used to measure these solids
are the Imhoff Cone test for settleable solids
and a filtration-drying test for suspended
solids. Domestic sewage usually contains
about 0.2 Ib. (0.9 kg) of'suspended solids per
capita per day, or about the same as BOD.
Sewage can be described chemically in that it
contains both inorganic and organic
compounds.
The inorganic portion comes partly from the
original sources from infiltration and from
storm waters. Normal domestic sewage con-
tains about 50 percent inorganic and 50 per-
cent organic. The inorganic portion is rela-
tively stable and not easily subject to decay.
Inorganics consist of sand, grit, plastics, metal
etc. If stormwater is connected to a sewer sys-
tem or if infiltration occurs, the inorganic por-
tion increases sometimes to troublesome
proportions.
The organic portion is subject to decay (bac-
terial decomposition) containing proteins,
carbohydrates and fats. The principal chem-
ical elements are carbon, hydrogen, and oxy-
gen which are often combined with nitrogen,
sulfur and phosphorus.
As sewage ages, bacterial activity converts
more of the insoluble organics to soluble
organics which can then be used as food by
the bacteria. The food is then converted into
new growth and some by-products such as
carbon dioxide and water.
Pollution comes from the organic portion of
sewage. If it were to enter our waterways un-
treated, it would rob the stream of the oxy-
gen needed by primary life forms. Contamina-
tion occurs because polluted water carries dis-
ease causing germs and bacteria. Therefore,
from both an environmental and public health
standpoint, it is absolutely necessary to re-
duce both pollution and contamination to
acceptable levels. These levels are measured
in terms of biological oxygen demand
(BODg), dissolved oxygen (DO), pH, sus-
pended solids (SS) and fecal coliform which
are described in your Waste Discharge Permit.
KNOW YOUR PROCESS
Because it will provide better treatment
and fewer upsets. And when the process
becomes upset, you will know what cor-
rections to make and why.
1-2
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THE PHENOMENON OF POND LIFE
The process that takes place in a pond or
lagoon is an interesting one because it is a
natural cycle, continuous and a living
phenomenon. As with humans, conditions
and life are always changing. It is difficult
to predict, with certainty, what will be
happening. Changes may be due to tempera-
ture, weather, changes in the kinds of algae,
and other living organisms as well as changes
in the types of wastes.
Life in a pond is made up of billions of tiny
microscopic plants and animals co-existing
and depending on each other. In fact, it is
this relationship that makes a pond work.
The plant forms are the many different forms
of bacteria and algae which can use soluble
substances as food by absorbing it through
their skin or membrane. The animal forms
are higher species of free-swimming creatures
who use solid matter and bacteria and algae as
food by ingesting it through their mouth.
Vorticella
Paramoecium
The microbiology of a lagoon system is
important to its operation. An inexpensive
microscope can be used by the operator
to identify what is happening in the pond.
For example, most of the work is done by
microscopic bacteria which utilizes the
organic substances as food and under the
right conditions will come together, form
floe and become heavy enough to settle.
Other undesirable bacteria may also form
which are stringy (filamentous) and are
difficult to settle. These become more nu-
merous at low pH's, 6.5 or lower, or in a
carbohydrous waste. Green algae of the
Chlorella species are desirable because they
are mobile and stay near the surface. Fil-
amentous algae have a bluish-green color and
are undesirable. Various other algae with
different colors can be found in ponds, such
as:
Pyrrophyta - greenish tan to golden brown
Phaeophyta - brown
Rhodophyta - red
The last two are found in marine lagoons.
The color change is due to pigmentation.
The Role of Bacteria
Bacteria can be classified as those that must
have oxygen to live (aerobic) and those that
live in an environment without oxygen (an-
aerobic). Both types break down complex
organic substances into soluble matter which
passes through cell walls and is converted
into energy, protoplasm and end products
which diffuse out through the cell wall into
the surrounding liquid. While the intake and
conversion processes are much the same, the
end products are not. Typical products pro-
duced by the aerobic bacteria are carbon
dioxide, ammonia and phosphates. These
are essential food elements for the oxygen
producing algae. The anaerobic bacteria
which live in the oxygen starved bottom layer
of a pond produce carbon dioxide, hydrogen
sulfide, ammonia and other soluble material
which is diffused into the water as a gas or
is used by the aerobic bacteria as food.
Rotifers and crustaceans are often found in
ponds where they survive by feeding on the
bacteria and algae. One of the most common
forms are Daphnia. Oftentimes they can
clean a pond of the green algae.
1-3
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The Role of Algae
As stated earlier, the aerobic bacteria require
oxygen for their respiratory system in order
to stay alive. This use of oxygen is called
oxygen demand and any oxygen remaining
is measured as free dissolved oxygen (DO).
Water will hold only a certain amount of dis-
solved oxygen, at which point it becomes
saturated. Saturation is dependent upon water
temperature. When more than this given
amount is present in the water, the water is
said to be supersaturated. Cold water can
hold more oxygen than warm water per
cubic foot.
The demand for oxygen increases as the
bacteria and algae increase. And both the
bacteria and algae increase as the food supply
increases, i.e.: the organic loading.
There are two sources for oxygen. One
source is diffusion of air into the water from
the atmosphere. The other source is from
algae.
CHLAMYDOMONAS
Algae are microscopic plants and live in much
the same manner as grass or your garden vege-
tables. They contain chlorophyll which con-
verts sunlight into energy to degrade complex
compounds into simpler products and for
growth. This phenomenon is called photo-
synthesis. Other basic requirements are nut-
rients, principally carbon, nitrogen and
phosphorus. And, like your garden vege-
tables, they grow best under warm tempera-
tures and die off with cold temperatures.
The most important role that algae perform
in a pond is the production of the major por-
tion of the oxygen.
Since algae need sunlight, they will be found
near the surface of a pond. This is called the
aerobic layer. The depth of this layer is de-
pendent upon climate and density of algae.
It is normally between 6 and 18 inches (15-46
cm), but this layer may extend down to 4 ft.
(125 cm) in a well mixed pond. At night,
algae will require oxygen in their respiratory
system. Thus, when the sun goes down, the
algae do not die, but continue to function and
consume oxygen, although they have stopped
oxygen production. This explains why the
dissolved oxygen level will be at its lowest
point immediately after sunrise.
There are many forms of algae to be found
in ponds, however, two important classifica-
tions appear which can be related to the qual-
ity of the pond.
1. One is the so-called green algae which
gives a pond a green color and indicates
a good healthy condition. They are asso-
ciated with a high pH and with a waste
high in nutritional value.
2. The blue-green algae are filamentous and
appear when the nutrient and pH levels
are low or survive when the higher ani-
mal forms such as protozoa devour the
green algae. Therefore, the appearance of
blue-green algae in a pond is an indica-
tion of poor conditions.
1-4
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Pond loading has a direct bearing on micro-
bial (bacteria and algae) life within a pond.
A.The microbial population will be greatest
near the influent and decreases toward
the outer edge of a pond.
B. At low organic loadings, various proto-
zoa (predators) will appear such as Daph-
nia and Paramecium, which utilize the
algae and bacteria as food. Operationally
you would not expect to see any of
these forms in a primary cell but, would
see them in the polishing pond. There
have been cases where the predators have
caused a pond to clear up and other
cases where predators are found, the
pond remains green. This is because
blue-green filamentous algae is present,
which the predators do not touch.
C. Overloaded ponds create a rapid growth
by both bacteria and algae, which in
turn creates an oxygen demand that
cannot be satisfied by either the algae
or wind action. This results in algae
die off as seen by floating mats of algae
and a decrease in dissolved oxygen. It
can easily reach a state where the entire
pond will become anaerobic.
One of the biggest problems or deficiencies
of oxidation and stabilization ponds is the
amount of algae contained in the pond dis-
charge. Algae, in this case, contributes signifi-
cantly to the suspended solids being dis-
charged to a receiving stream. The most com-
mon method used to reduce the amount of
algae is to use a draw off point below the al-
gae layer. In the mid-part of the nation, dis-
charge is limited to twice per year when algal
content is low and effluent is in the best
condition.
There are several other methods available to
reduce the algae concentration; rapid sand fil-
tration, submerged rock filters, alum coagula-
tion, mixed media filters, and chlorination.
Of the listed methods, all except chlorination-
will add considerable cost and man-hours for
algae removal. Chlorination can effectively
kill the algae but, the dead algae cells will
release stored organics and thus contribute to
the BOD load being discharged. It is true that
this BOD is quite stable and inoffensive, but it
will decrease the oxygen in the receiving
stream.
When wastewater is discharged into a pond,
the heavy solids settle out near the inlet
where two types of anaerobic bacteria stabil-
ize the organic matter. This is shown in the
following simple diagram.
Acid,
Anaerobic
Bacteria
Acid Former Methane Former
Waste stabilization occurs in two steps:
1. Acid bacteria break down the complex
organics and use the soluble matter
as food which is converted into organic
acid.
2. The organic acid is used as food by the
methane bacteria which convert the
acid into carbon dioxide (C02>, am-
monia (CH^), hydrogen sulfide
and methane gas.
1-5
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The byproducts of anaerobic decomposition
are soluble in water and become food material
for the aerobic bacteria and algae. Algae
require carbon, nitrogen, nutrients and
sunlight. Sufficient sunlight energy may be
available in depths from 12 to 18 inches (30
to 46 cm), hence, algae are only found near
the surface. When these are available the algae
produce free oxygen which is required by
the aerobic bacteria. When light energy
is not available, such as nighttime or when
the surface is covered with ice or duckweed,
the algae do not convert the carbon dioxide,
therefore no oxygen is produced. The aerobic
bacteria in the surface layer, using the free
oxygen, feed on the soluble organics in
the raw waste as well as the soluble by-
products of anaerobic decomposition. In
turn they produce some inert material, which
settles to the bottom, and dissolved sulfate,
nitrate, phosphate and carbonate compounds
required as the source of energy by the
anaerobic bacteria. Thus, in most ponds the
treatment process is a complex interaction
between two separate bacterial communities
and algae. Each is doing something useful for
the other. This is shown below.
Soluble
Organics
Aerobic
"Zone
Aerobic
Bacteria
Algae
Anaerobic
Zone
Acid
Formers
Methane
Formers
HOW ARE WASTES TREATED
Regardless of the treatment devices used,
treatment usually proceeds along similar
lines. Settleable solids are removed first
either in a pond or in separate primary clari-
fiers. If the solids are removed from the flow
by settling in a primary clarifier, the solids
will be handled in separate facilities such as
anaerobic digesters. If raw solids enter a
pond, the settleable solids will settle out
near the inlet and undergo anaerobic de-
composition as in an anaerobic digester.
This is one reason why the first cell in a
series is called a primary cell.
The next step in treatment of wastes is called
secondary treatment. This is a biological
reaction step in which organic dissolved and
suspended matter is oxidized (converted) by
bacteria into stable end products, thus
reducing the BOD and suspended solids. In
ponds, this step is usually accomplished in
both the primary and secondary cells. A third
step in treatment is often designed into a
treatment system which involves polishing
treated wastewater. These ponds are lightly
loaded and used to remove additional BOD
and suspended solids. They are referred to as
tertiary or polishing ponds and can be the last
cell in a system or as a single pond following
conventional secondary treatment.
1-6
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TYPES OF PONDS
Oxygen demand determines the type of ponds
required. Aerobic types have oxygen distri-
buted throughout the water. Anaerobic ponds
are devoid of oxygen. Facultative systems
have an aerobic surface layer and an an-
aerobic bottom layer.
AEROBIC
ANAEROBIC
FACULTATIVE
Wastewater is treated in various types of ponds
or lagoons which are named according to the
type of treatment involved. Lagoons are bod-
ies of water confined within natural boundar-
ies, while ponds are shallow and manmade.
Treatment usually occurs in two or more
ponds called cells. These cells are arranged in
series with water flowing from one cell into
another. For example, in a stabilization pond,
influent enters a primary cell, then flows into
a secondary cell, then into the polishing cell.
Raw
Waste
SER
Primary
Cell
ES
Second-
ary
Cell
Tertiary
Cell
-1
Many systems are arranged so that two or
more primary cells can receive the plant
flow. In these cases, the plant flow enters a
distribution manhole or a box which is gated
or valved to divide and direct the flow into
the primary cells. This is called parallel opera-
tion. Effluent from these cells then follows
the usual series pattern to obtain the maxi-
mum solids and algae removal prior to dis-
charge. From an operational viewpoint,
series operation normally will provide the
best treatment if the actual loading is below
the design loading. This is because of the
detention time. Parallel operation for the
primary cells is most often practiced when
loadings exceed the design and for winter
operation.
Second-
ary
Tertiary
PARALLEL
Ponds and lagoons are designed as continuous
discharge, controlled discharge, or no dis-
charge. Ponds designed and operated as con-
tinuous discharge must usually disinfect the
plant effluent with chlorine in order to des-
troy the pathogenic (disease causing)
organisms.
Controlled discharge is used when the waste-
water is held for long periods of time before
discharging. The discharge periods are usually
twice a year. The selected period is based on
two factors: the condition of the pond con-
tents and the condition of the receiving
stream. In general, these ponds discharge
1-7
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shortly after the ice break up in the spring
and shortly after the first frost in the fall. One
reason these periods are selected is that the
algae mass is at its lowest concentration.
Deep ponds often experience a "spring
turnover" problem when the ice melts and the
pond warms'up. This is due to increased bio-
logical activity and bottom sludge floating to
the surface causing temporary odor problems.
Most of the time, this will last between
2 to 15 days.
No discharge ponds are those designed to take
advantage of an area's evaporation rate and/
or ground percolation. In these cases the rate
of evaporation and/or percolation equals or
exceeds the inflow rate. Often one of the
most difficult operating problems associated
with these ponds is controlling water depth
to discourage weed growth. This can be
helped by deliberately adding water to the
pond.
Regardless of type of pond, best operation is
only achieved when the entire pond is used.
When no water movement occurs in a portion
of a pond, a condition called short-circuiting
results. Short-circuiting can be caused by poor
design of inlet and outlet piping arrangements
or by uncontrolled growth of water weeds.
If either of these conditions occur, they must
be corrected.
As mentioned previously, the three major
categories of ponds are aerobic, anaerobic,
and facultative, other ways of describing
them are found in textbooks or are in com-
mon use in different parts of the nation.
Some of these definitions are given below.
The reader should remember that these are
examples of one or more of the above major
types.
STABILIZATION PONDS
Receive raw untreated wastes and usually
consist of two or more cells (individual
ponds). The first cell which receives the
untreated waste is called a primary cell.
The following cell is a secondary cell which
is often followed by a polishing cell (or ter-
tiary cell). Stabilization ponds are often
designed with two or more primary cells
so that they can be operated in parallel
to prevent overloading problems.
XN,
OXIDATION PONDS
Ponds receiving treated waste and operated
in series are called oxidation ponds. These
may serve as secondary treatment following
a standard primary plant.
Secondary
hen
Pond
Pond
1-8
-------
Most stabilization and oxidation ponds
stabilize organic wastes through a complex
natural process involving sunlight, oxygen,
water currents, algae and bacterial action.
Stabilization and oxidation ponds require
large surface areas, shallow depths and long
detention times for natural stabilization
to occur.
FACULTATIVE PONDS
Facultative ponds are the most common
type of ponds used for stabilization and
oxidation lagoons. They have two zones
of treatment: an aerobic surface layer and
an anaerobic bottom layer. Facultative
ponds operate with 3 to 8 feet (1 to 2.4 m)
of water depth and are usually loaded be-
tween 15 and 80 Ibs. BOD per acre (17 and
90 kg per ha) per day. Oxygen for aerobic
stabilization in the surface layer is provided
by algae and wind action. Decomposition of
the sludge in the bottom zone takes place an-
aerobically. The lagoons are usually designed
to provide sufficient waste dilution and natu-
ral aeration to insure that the surface liquid
will remain aerobic.
FACULATIVE
An existing stabilization or oxidation pond
can be upgraded by either increasing its
detention time or decreasing its surface BOD
loading or both. Another method is to
deepen the pond and install mechanical
aeration. Generally speaking, cold climates
may favor the use of compressed air. Inter-
mittent seasonal operation or high oxygen
requirements usually favor mechanical
aerators or diffused aeration pipelines.
Other ponds are built to serve special pur-
poses.
SPECIALTY PONDS
These include high rate aerobic ponds, anaer-
obic ponds, tertiary ponds, and aerated
lagoons.
High Rate Aerobic Ponds are usually limited
to applications where a high algal mass is de-
sired for harvesting. The algae is then used
as food for cattle. These ponds are shallow
(about 12-18 inches [30-46 cm] ) and usually
loaded from 60 to 200 Ibs. of BOD per acre
(67 to 224 kg per ha) per day.
SHALLOW AEROBIC
SCUM LAYER
ANAEROBIC
Anaerobic Lagoons are ponds designed
to treat high oxygen demand wastes such
as slaughterhouse wastes. The organic loads
are so high in these ponds that anaerobic
conditions prevail throughout..These ponds
are similar to anaerobic digesters or septic
tanks.
1-9
-------
Tertiary Ponds are used for polishing efflu-
ents from conventional secondary treatment
processes. They are also often used as the
last pond of a stabilization or oxidation pond
system to remove algae before the effluent
is discharged. These ponds are similar to
facultative ponds except that they are very
lightly loaded, usually less than 15 Ibs BOD
per acre (17 kg per ha) per day.
Second-
ary
Plant
Tertiary
Pond
->
Aerated Ponds are employed in those cases
where supplemental oxygen is needed due to
high organic loadings. For example, when a
facultative pond becomes overloaded it uses
more oxygen than it produces and turns
anaerobic. One method to increase oxygen
is to install powered aeration equipment.
Many ponds are being designed and operated
with aeration systems to permit higher load-
ings in smaller spaces. These ponds then
get essentially all of their oxygen by mechani-
cal means and very little algal mass is formed.
WHAT NATURAL FACTORS AFFECT
THE PROCESS
Wind Action
Wind action creates surface mixing on ponds
increasing with surface area. Large ponds
need riprap on dikes for protection. Wind
also tends to remove oxygen from the water
when the pond is supersaturated. When the
dissolved oxygen is less than saturation, wind
action helps to drive oxygen into the water.
Temperature
Water will hold more oxygen per cubic foot
at a cold temperature than at a warm temper-
ature. As an example, water in the winter
time will hold almost twice as much oxygen
as in the summertime. However, in colder
climates, ice cover prevents adding DO by
wind and snow cover prevents algal action
for DO production.
Biological activity decreases with temperature,
a 10-degree drop in temperature will reduce
microbial activity by one-half.
Best conditions are when it is warm with
good sunlight and a moderate breeze. This
produces the greatest bacterial activity and
hence the highest BOD removals from the
raw waste.
1-10
-------
Normal slow changes in temperature pro-
duce long-term seasonal effects such as
changes from spring to summer.
Abrupt or sudden temperature changes
bring about short-term problems. For ex-
ample, a sudden rise in temperature causes
the bacteria to multiply at a rapid rate causing
the oxygen demand rate to increase faster
than the slower algae can supply the neces-
sary oxygen. This may result in a more
turbid effluent than is normal. A sudden
drop in temperature can cause a pond to
clear up. This occurs because the algae activ-
ity slows down and they settle out. An ex-
ample of this is a sudden frost in the spring
or fall. This is normally the time when ponds
with controlled discharge are lowered.
Wind
Temperature
(Hot, Cold,
Freezing)
Sunlight
Rain
As the weather gets colder and daylight
becomes shorter, bacterial and algae activ-
ity gradually gets slower. In northern freezing
climates during extended cold periods the
rate of biological activity becomes quite
slow. Ponds located in areas where they
are covered with ice may experience a "spring
turnover" when the weather warms enough to
melt the ice if drastic changes occur. This
condition is accompanied by rising chunks of
sludge and unpleasant odors which may per-
sist for a month or so. Cold weather also
brings about an increase in the concentration
of ammonia nitrogen as compared to the
warm months.
Example: Jan. 6-10 mg/l
May 3.0-0.1 mg/l
The concentration of phosphorus is greatest
during cold weather. On the other hand,
suspended solids is lowest during cold weather-
due to decreased algae activity.
Warm weather brings about a great increase
in algae growth. Operators can expect to see
clouds of "algae blooms" which stops light
penetration and reduces oxygen production.
The increase in algae growth also causes an
increase in suspended solids plus an increase
in oxygen demand (BOD) in the effluent of
flow through ponds.
Warm weather increases evaporation rates
which will change the detention time and
may affect the amount of effluent that is
discharged.
The arrival of spring also brings on heavy
growth of water weeds which may change
the pattern of water movement. Scum mats
also form on the surface. Both scum and
water weeds form excellent breeding grounds
for mosquitoes and other insects.
Periods of heavy rainfall affect pond opera-
tions as the increased volume of water com-
ing into the pond dilutes the organic waste, it
may change pond temperature, will cause a
sudden increase in water depth and may
shorten detention time.
Sunlight
Sunlight is indispensable to effective opera-
tion of stablization ponds through photo-
synthesis of algae in producing oxygen.
The percentage of available annual sunlight
varies throughout the country which is
governed by latitude (which governs seasons),
elevation and cloud cover. The amount of
available sunlight helps to determine how well
1-11
-------
the pond operates and the area and depth
needed for proper operation.
The depth of sunlight penetration determines
the extent to which the pond volume partici-
pates in oxygen production and hence, the
optimum pond operating depth. Loss of
light by reflection increases up to 30 percent
when the surface is roughened by the wind.
Algal density, which varies from season to
season and pond to pond, determines the
depth of light penetration and intensity. In
general, with good algal growth and disper-
sion, oxygen production will be good up to
about 24 inches (60 cm) in depth. Oxygen
production does not meet the oxygen demand
beyond this depth without vertical mixing
by wave action. The pond operator can do
much to maintain optimum oxygen produc-
tion by removing duckweed or other materials
that reduce light exposure.
All of the preceding remarks can be related
to operation by the following summary.
A. Do not decrease water depth to less
than three feet (1 m) for warm weather
operation.
B. Keep algal blooms dispersed.
C. Keep pond free from duckweed
hyacinth or similar weeds.
HOW PHYSICAL FACTORS AFFECT
TREATMENT
Surface Area
Surface area is determined by organic loading
(Ibs. of BOD per acre per day) and is called
the surface loading rate. Surface loading deter-
mines the type of pond. For example:
. Aerobic Ponds 60-200 Ibs. BOD/Acre/
Day (67-224 kg per ha)
. Facultative Ponds 15-30 Ibs. BOD/
Acre/Day (17-35 kg per ha)
. Anaerobic Ponds 200-1000 Ibs. BOD/
Acre/Day (224-1120 kg per ha)
. Tertiary Ponds 5-15 Ibs. BOD/Acre/Day
(6-17 kg per ha)
Sometimes surface loading is related to the
connected population such as 100 persons
per acre per day for facultative systems, but
the'type of pond will determine the exact
figure.
As an example of surface loading, if the
organic load is 300 Ibs./day, (336 kg/day) on a
facultative pond, a minimum of 10 acres (4
hectares) may be required.
1-12
-------
Water Depth
Water depth will vary, particularly in ponds
that are being filled for the first time or in
systems that operate on a seasonal cycle for
controlled discharge.
To start a new pond, two feet (0.6 m) of water
should be added prior to fresh starting waste-
water feed. In controlled discharge systems,
primary cell should not drop below three feet
(0.9m).
Maintaining a minimum level is necessary to
prevent exposing sludge blankets on the bot-
tom to atmosphere thus preventing odors and
also to prevent allowing the pond bottom to
dry out and crack.
Short Circuiting
Regardless of type of pond, best operation
is only achieved when the entire pond is used.
When no water movement occurs in a portion
of a pond, a condition called short circuiting
results. Short circuiting can be caused by
poor design of inlet and outlet piping arrange-
Square Feet
or Acres
Surface
Area
Series
Short
Circuiting
Series
Parallel
ments, unlevel bottoms, shape o'f cells, pre-
dominant wind direction, or by uncontrolled
growth of water weeds. If any of these condi-
tions occur, they must be corrected. Methods
of correction are described in the trouble-
shooting section. Short circuiting in ponds
leads to many problems, including dead spots
which reduce the area of effective treatment
and also contribute to odor problems and
sludge mats.
Series Operation
Series operation, particularly when three or
more ponds are used, tends to minimize the
amount of algae in the last cell and should
result in better quality effluent. As a result,
ponds are often operated in series during the
warmer months, when algae production is
highest.
Series operation during winter leads to special
problems when ponds are under an ice cover.
The first cell can become overloaded and,
when warm weather returns, the cell may be
septic and produce unwanted odors and
sludge which has floated to the surface.
Plants that are designed with at least three
cells have the ability to operate the first two
as primary cells and during summer months
run these in series to minimize algae growth
when the flow reaches the secondary cell.
Those plants that use controlled discharge
during spring and fall find the best results by
allowing the first cell to fill to at least three
feet (9 m) or more then transfer to the next
cell in succession in increments of 6 inches
(0.15 m) until the ponds are at maximum or
time for discharge arrives.
SE
f
I
»
*
iRIES WITH 2 PRIMARY CELLS
1-13
-------
Parallel Operation
Parallel operation is used to reduce organic
loading in the primary cells. Parallel opera-
tion is especially advantageous during winter
months so that sewage solids can be distri-
buted over a wider area.
Winter month operation in parallel has the
advantage of distributing the load over more
surface pond area and this is particularly
important when ice covers develop and activ-
ity is low. Again, for plants with three cells,
the first two should be used in parallel and if
the system operates on a controlled discharge,
primary cells should be filled at the same time
once both are at the 3-foot (9 m) depth and
then alternately discharge 6 inches (0.15 m)
at a time into the secondary cell until it
reaches the same depth as both primaries.
Pf
vRA
*
»
-+
LLELWITH 2 PRIMARY CELLS
Recirculation
Recirculation is a means of improving pond
conditions. This allows oxygen that has been
produced by the algae in one pond, or part of
the pond, to. be mixed with low oxygen areas
of the system. Other advantages include a
mixing to help prevent odors and anaerobic
conditions in the feed zone.
The most common method of recirculation
is to recycle effluent from a secondary cell
to the effluent of the primary cell. This
method obtains the greatest amount of dis-
solved oxygen.
HOW CHEMICAL FACTORS AFFECT
TREATMENT
Oxygen
Oxygen is necessary for maintaining the life
forms in an aerobic pond. It is used by the
bacteria to stay alive. Oxygen combines with
many substances to form oxides and break up
many complex organic molecules into simpler
molecules making them more available to the
bacteria. Since oxygen is used to oxidize
these organics, the DO (dissolved oxygen)
will decrease in proportion to the amount of
organic material present. This is known as
the oxygen demand of the waste.
Water will only hold a certain amount of dis-
solved oxygen. When the amount of air/
oxygen entering the water equals the amount
leaving the water, it is said to be saturated. In
ponds containing algae, the water can become
super-saturated with oxygen (more oxygen
enters water than is used).
Wind also tends to remove oxygen from the
water when the pond is super-saturated.
When the dissolved oxygen is less than satura-
tion, wind action helps to drive oxygen into
the water.
The strength of the waste can be indirectly
measured by the biochemical oxygen demand
1-14
-------
(BOD) test. The test measures the amount of
oxygen used by the bacteria over a 5-day
period. If the demand for oxygen is greater
than the supply, the aerobic bacteria will die
off and anaerobic conditions will develop
along with operational problems. Low dis-
solved oxygen concentrations result in turbid
effluents, bad odors, and the growth of fila-
mentous type of bacteria.
Nutrients
Without a sufficient supply of nutrients
(nourishment), the bacteria will not be able to
grow and multiply. Although several
elements are needed, nitrogen and phos-
phorus are the principal elements required.
Domestic wastes usually contain enough of
both. Nitrogen is in the form of ammonia
(NH3).
pH
This test indicates whether a pond is acid or
alkaline. Both the aerobic and anaerobic sys-
tems require an alkaline environment for best
operation. Operators should check pH of the
pond effluent to determine if any toxic
materials are entering the pond. The pond
color is related to pond pH and should help
operators to forecast any impending prob-
lems. Green shows a high pH (alkaline).
Yellowish-green indicates a lowering pH
(acidic). Color may not relate to pH when a
strong wind stirs up silt from the bottom or
highly colored industrial wastes influence the
pond's color.
A lowering pH can be corrected by letting the
cell rest for a few days. The pH will change
throughout the day and will usually be at its
lowest in the early morning and highest in the
late afternoon, because algae are most active
during daylight and cause chemical reactions
that drive pH upward. (C02 produced by
bacteria at night causes the pH to be lowered.)
1-15
-------
2. Control Information for Ponds
Sample collection
Types of samples
Sample point locations
Tests and measurements
Important visual indicators
Other daily data
-------
2. Control Information
for Ponds
Adequate control of the process is necessary
to meet assigned discharge requirements.
It is necessary to know the quantity, con-
centration, and type of waste entering the
plant. It is also necessary to know what is
happening in the pond and what is going
out of the pond. Therefore, there are three
major points of measurements: The plant
influent, the pond and the plant effluent.
Several tests must be run on samples of
wastewater taken at each of the major points.
These are: Flow, temperature, pH, dissolved
oxygen (DO), BOD, suspended solids (SS),
fecal coliform, and also chlorine residual
when disinfecting with chlorine.
The results of these control tests are often re-
ferred to as control parameters and are used
to determine how well treatment is progress-
ing to predict operational changes and to
assess the results of treatment. For contin-
uous flow through systems the following
tests, flow, temperature, pH, and chlorine
residual, can be easily performed by the oper-
ator on a daily basis with simple equipment
such as a glass electrode pH meter, DO meter
or DO kits, and a colorimetric comparator.
BOD, SS, and fecal coliform tests require
more time, costly equipment, and techni-
cal know-how. A small, part-time operation
may therefore elect to collect samples for
these tests, but send them to local chemical
laboratories for analysis.
Systems that operate on a controlled dis-
charge basis will need to concentrate testing
during the period prior to and during dis-
charge as required by their regulatory agency.
Weather is one of the most important factors
affecting pond operation. Knowledge of
weather conditions will help to explain many
things about pond operation.
SAMPLE COLLECTION
The collection of test samples of wastewater
is the basis for obtaining accurate test results.
TEST RESULTS ARE ONLY AS GOOD AS
THE SAMPLE. Test samples must be
REPRESENTATIVE of the waters being
sampled. This requires selecting a point
that will give a uniform sample. If the
sample is to be stored before testing, it must
be refrigerated. Sample containers must
always be clean before sampling to avoid
getting the wrong results. Temperature, pH,
residual chlorine, and DO should always be
taken immediately to avoid deterioration and
should be taken at the same time each day.
Occasionally though, it is a good idea to
check these parameters at other times during
the day to get a feel for the daily changes that
occur. For example, if tests are normally run
at 8:00 a.m. each morning, then perhaps
every two months, take additional tests at
10 a.m., 2 and 4 p.m.
TYPES OF SAMPLES
A grab sample is a single sample taken at no
set time or flow. Grab samples are used to
measure temperature, pH, DO, fecal coliforms
and chlorine residual.
Chosing the correct time to sample may be a
problem because grab samples are only repre-
sentative of conditions at the moment. Raw
sewage flow varies in content, as well as
2-1
-------
volume, during a typical day. One sample
at any time of day cannot possibly be used
for compiling data on a whole day's opera-
tion. For that matter, neither can three, four,
or five samples. It remains for a decision to
be made as to how many samples can con-
veniently be taken in a 24-hour period.
Samples of the pond will yield the most infor-
mation if taken at sunrise and in mid-after-
noon, with separate analyses run on the two
samples.
Samples of effluent from controlled discharge
ponds should be taken during discharge -
perhaps one sample every two hours and com-
bined into one composite sample. Each indi-
vidual state has guidelines that are specific
for their particular situation and should be
consulted by the operator.
Composite samples are taken by gathering in-
dividual samples at regular intervals over a
selected period of time. The individual sam-
ples are then mixed together proportionally
to the flow at the time of sampling. For
example, a composite sample might be made
for Tuesday covering the period from 8 a.m.
with a sample collected at 8 a.m., 10 a.m., 12,
2 p.m., and 4 p.m. Each individual sample
must be refrigerated immediately to avoid
deterioration.
At each sampling time the flow must be re-
corded for use at the end of the sampling
period. At the end of the sampling period,
remove the samples from the refrigerator.
Then, stir each one and pour an amount of
the samples proportional to the flow at the
time the sample was taken.
Composite samples are needed to test and
measure for BOD and suspended solids.
See Appendix B for a sample calculation on
compositing.
Automatic Samplers. There are a number of
kinds of automatic samplers on the market.
Some are battery-powered and self-contained;
others must have an external power source.
All offer sampling at chosen intervals, some as
frequently as every 10 minutes, and composit-
ing of samples on the spot. This equipment
is most valuable for sampling raw sewage flow
but can be used for effluent as well. Whether
this type of equipment should be purchased
for waste stabilization ponds would depend,
somewhat, on the loading and the ease of
getting representative composite samples by
hand.
Handling and Preservation of Samples.
Sewage samples deteriorate rapidly if sub-
jected to summer temperatures and to some
extent, freezing. Exclusion of sunlight is also
recommended. For these reasons, collected
samples should be transferred to a refrigerator
where they can be stored until removed for
analysis. A temperature of 40 degrees Fah-
renheit (4° Celcius) will prevent deteriora-
tion for 24 hours.
Containers used for sample storage need to be
kept as clean as possible. Stoppered glass
bottles or wide-mouth jars are preferred and
are easiest to use for mixing and cleaning.
SAMPLE POINT LOCATIONS
Pond Influent
Samples of the raw wastewater can be
obtained from several points:
1. The wet well of the influent pump
station. One method is to use a
bucket or container attached to a
rod. The sample must be taken
from a turbulent well-mixed point.
2. A manhole at the inlet diversion
control structure.
2-2
-------
Ponds
Pond samples should be composited consist-
ing of four equal portions from four corners
of the pond.
The sample should be taken eight feet (2.5
meters) out from waters edge and one foot
(0.3 meter) below the water surface. This
should be done carefully to avoid stirring
up material from the pond bottom.
Pond samples should not be taken during or
immediately after high winds or storms since
solids will be stirred up after such activity.
Pond Effluent
Samples of pond effluent should be taken
from the outlet control structure, or a
well-mixed point in the outfall channel.
SAMPLING
DEVICES
CANON
A STICK
BOD BOTTLE
ON A STICK
COFFEE CAN
ON A ROPE
WEIGHT
PUMP
INSULATED
SAMPLE
CONTAINER
TESTS AND MEASUREMENTS
Test results along with visual indicators are
used to operate the lagoon to keep it alive
and healthy. Following is a description of the
important tests and measurements and what
they do.
Temperature
The temperature of the raw wastewater can
be used to detect infiltration and some indus-
trial wastes. A sudden decrease in tempera-
ture may indicate warm industrial wastes.
Since dissolved oxygen varies with tempera-
ture, it is often necessary to know how close
to saturation the DO test is when it is run.
This can be determined by the following
oxygen saturation table.
SOLUBILITY OF OXYGEN
°C
0
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
°F
32.0
33.8
35.6
37.4
39.2
41.0
42.8
44.6
40.4
48.2
50.0
51.8
53.6
55.4
57.1
59.0
60.8
61.6
64.4
66.2
68.0
69.8
71.6
73.4
75.2
77.0
02
(PPM)
14.6
14.1
13.8
13.5
13.1
12.8
12.5
12.2
11.9
11.6
11.3
11.1
10.8
10.6
10.4
10.2
10.0
9.7
9.5
9.4
9.2
9.0
8.8
8.7
8.5
8.4
°C
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
IN FRESHWATER
°F
78.8
80.6
82.4
84.2
86.0
87.8
89.6
91.4
93.2
95.0
96.8
98.6
100.4
102.2
104.0
105.8
107.6
109.4
111.2
113.0
114.8
116.6
118.4
120.2
122.0
123.8
02
(PPM)
8.2
8.1
7.9
7.9
7.6
7.5
7.4
7.3
7.2
7.1
7.0
6.9
6.8
6.7
6.6
6.5
6.4
6.3
6.2
6.1
6.0
5.9
5.8
5.7
5.6
5.5
2-3
-------
Flow
Flow measurement is necessary for all ponds.
Measuring the influent flow tells the operator
many things about the operation.
1. It determines hydraulic loading and
tells when a pond has reached or
exceeded its hydraulic capacity. A
hydraulically overloaded pond may
not provide complete treatment
because the biological activity may
not be complete before water leaves
the pond.
2. It is the only clue to describing the
extent of infiltration.
3. When related to BOD and SS re-
ductions, it describes its effect
on overall treatment.
4. It provides the basic data for deter-
mining mode of operation (when
the operator has these options)
such as use of series or parallel op-
eration, retention time, and what
operating depth to use.
Use series operation when flows are
below design. Compute hydraulic
loadings on basis of gallons per acre
per day (Appendix B) or popula-
tion equivalent.
Storage capacity and operating
depth should be calculated to deter-
mine the amount of discharge for
intermittent discharge ponds.
Drawdown of the pond should not
exceed the minimum pond depth
of approximately three feet re-
quired for weed control. Sample
calculations are given in Appen-
dix B.
5. Flows are required to translate
BOD and SS test results into
pounds per day. These should then
also be calculated into loading of
pounds per acre per day. Appendix
B contains sample calculations.
This information is then used with
hydraulic loading to determine
which operational mode to use, and
with DO to determine the need for
supplemental aeration.
6. Flow information is required for
calculating chemical dosages.
Effluent flows are measured as part
of the tests for NPDES permit re-
quirements indicating the effect of
effluent on receiving waters.
Periodic checks between influent
and effluent flows should be made
to determine the extent of either
evaporation or exfiltration (loss
of water by seepage into soil).
Some examples of flow measuring
devices are Parshall Flumes, V-
notch weirs, floats, irrigation flume
with markings, and using a pump
station wet well with a known
depth and recording pumping time
multiplied by pump capacity.
See Appendix C for a more com-
plete discussion of flow measure-
ment, determining the flow,
devices.
pH
The pH of the influent and effluent will vary
throughout the country among neighboring
lagoons, and throughout the day on a given
pond. This pH variability is due to several
causes: the natural alkalinity and hardness of
the water, the type and volumes of commer-
cial and industrial wastes and the pond itself.
2-4
-------
The pH of incoming domestic sewage normal-
ly is between 6.8 and 7.6. Algal reactions in
lagoons can be expected to raise the pH to as
high as 9.5 or above. pH is closely tied to the
production of oxygen by the algae as they
convert inorganic carbon to organic carbon.
The combination of organic metabolism, alka-
linity and time are needed to produce oxygen.
This means that there must be food for the
bacteria, enough natural alkalinity and
enough detention time. If any of these are
missing within the lagoon the pH will start to
decrease toward the acid side with a possible
drop in DO. Other changes may also occur,
such as the disappearance of the green algae
and the color of the pond changing to a blue-
green.
The pH can be a good indicator of the pond's
condition. Some of the abnormal causes for a
decreasing pH are septic wastes coming in as a
result of low flows, or it may be due to an
acid industrial waste. Fluctuations may also
be due to normal activity. The pH may be re-
duced during the night as a result of increased
bacterial action and lower algal activity. This
will cause the values to be lower at the pond
bottom than at the top.
Dissolved Oxygen
Dissolved Oxygen (DO) is a good indicator of
the activity of an aerobic lagoon. By watching
trends in oxygen levels of the influent the op-
erator can tell something about the strength of
the waste load coming in. If the average DO
concentration in the pond drops when measur-
ed under the same day-to-day conditions, it is
an indication that the BOD loading may be in-
creasing and corrective action should be taken.
This might include distributing the influent to
other ponds, mechanical aeration or the addi-
tion of sodium nitrate. The DO level in the cell
may be used to determine when a discharge
can occur from controlled discharge ponds.
This level should be at or near saturation. Use
a grab sample and test immediately.
Chlorine Residual
Chlorine residual is a test to determine the
amount of chlorine present after the neces-
sary detention time for disinfection (destroy
fecal coliform bacteria). The general rule of
thumb is to have 0.5 milligrams per liter
(mg/L) after a contact time of 1 hour. Use a
grab sample and test immediately. The op-
erator should check the NPDES permit for
the exact requirement as some states may not
require disinfection, others designate a pre-
scribed coliform minimum and others may
require dechlorination.
BOD5
BOD (5-Day Biochemical Oxygen Demand) is
a measurement of the amount of oxygen re-
quired in a 5-day period by the microorgan-
isms in consuming the organic material in the
wastewater.
Basically, BOD indirectly measures the or-
ganic strength of the wastewater. It is im-
portant to measure the strength of wastewater
in coming to determine pond loading in terms
of pounds of BOD per acre per day and com-
pare this with the pond design for operational
changes such as series or parallel operation.
Another use is to measure the impact of the
organic strength on the receiving stream and
also the amount of BOD reduction received
from treatment.
Normal domestic sewage varies from between
150 and 250 milligrams per liter (mg/L) per
day and treatment must reduce this to less
than the level defined in the plant waste
discharge permit.
Understanding BOD
The BOD test has been defined as a method
of measuring the amount of dissolved oxygen
consumed by living aerobic organisms while
feeding on the organic materials in the sam-
ple. The test requires:
2-5
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1. 300 ml of sample to be tested.
This may be a diluted or undiluted
sample.
2. Controlled temperature at 68 de-
grees Fahrenheit (20 degrees C).
3. Exclusion of all sunlight.
4. Exclusion of air (stoppered).
5. An initial DO supply, enough to
last 5 days, plus 40 to 60 percent
excess.
6. A representative group of aerobic
organisms.
The test attempts to measure the dissolved
oxygen demand on the receiving stream were
the raw sewage discharged without treatment
or the demand of the treated effluent. From
the test results, the effectiveness of treatment
in the pond can be determined.
As an example, it is assumed that two BOD
tests have been completed. Results on the
raw sewage are 200 mg/L and the pond ef-
fluent 27 mg/L. What do these results tell
the operator and what can be done with the
results.
First, observe what happened during the 5
days the tests were being incubated and what
the numbers 200 and 27 really stand for.
200 mg/L BOD indicates that the raw sewage
carries a potential oxygen demand of 200
pounds of oxygen for every 1,000,000
pounds of raw sewage, the effluent 27
pounds. The question now becomes: What
was the difference in the raw and effluent
samples to produce the wide difference in
oxygen demand? If the requirements for the
test are checked it is seen that all 6 of the pre-
viously mentioned items were controlled
equally, so the difference in the numbers
must be associated with an unknown. That
unknown is the organic material (food) in the
2 samples. The organisms grew, lived and re-
produced in proportion to their food supply.
They also used dissolved oxygen in the pro-
cess - in direct proportion to their numbers
and rate of activity.
Since their rate of growth was apparently
limited by their food supply, it is noted that
BOD is in proportion to the organic mate-
rials (food) contained in the sample. Waste
treatment in the pond becomes a method of
reduction of organic materials (food) which
leaves the effluent with a lower biochemical
oxygen demand (BOD).
Next, consider the receiving stream. Each
plant has been issued a discharge permit
stating maximum pounds BOD to be dis-
charged per day. How was this figure arrived
at? Each plant places an oxygen demand on
the stream by discharging effluent and as the
stream follows its course, others are also con-
tributing wastes. The limit says that if the
stream is to be given a fair chance to recover
before reaching the next known contributor,
no more than the stated pounds of BOD can
be added from an individual upstream plant.
To fully comprehend the effect of even a low,
BOD discharge, requires computation of total
pounds BOD discharged.
Example:
Flow: 49,000 gpd
BOD Effluent: 27 mg/L
1. 49,000 gpd x 8.34 Ibs/gal = 0.4
million Ibs. flow
2. 0.4 million Ibs. flow x 27 mg/L
BOD = 11 Ibs. BOD discharged
2-6
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The effect on the receiving stream may be
illustrated by the following example:
Ibs. BOD discharged 11 Ibs.
mg/L DO in stream 7.5 mg/L DO
7.5 mg/L DO means 7.5 Ibs. DO/1
million Ibs. stream flow
11 Ibs. BOD divided by 7.5 = 1.5 million
Ibs. stream flow
1.5 million Ibs., divided by 8.34 Ibs/gal =
180,000 gal. stream flow
This means there are 11 pounds BOD dis-
charged to a stream carrying 7.5 mg/L DO
could entirely strip 180,000 gallons of stream
flow of all dissolved oxygen. Actually, the
stream, by wave and ripple action, plus algae,
is continually replacing the oxygen used, but
at a limited rate.
Efficiency of BOD Removal
Last, it is of value to compute the efficiency
of removal of BOD by the pond.
Example:
Raw BOD: 200 mg/L
BOD Effluent: 27 mg/L
ppm BOD Removed: 173 mg/L
173 ppm divided by 200 mg/L = .865 x
100 = 86.5% removal of BOD
The pond has reduced the BOD of the raw
sewage flow 86.5 percent.
(The preceding illustration was taken from
the publication Operating Waste Stabilization
Ponds, EPA Region VII produced by
Kirkwood Community College.)
Suspended Solids
Suspended solids (SS) test measures the dry
weight of solids retained on an asbestos or
glass fiber or millipore filter and is expressed
in milligrams per liter.
Suspended solids removal is as important as
BOD removal for preventing stream pollution.
In normal domestic sewage the concentration
of SS and BOD are nearly the same. Suspend-
ed solids are difficult to remove from lagoon
effluents due to the high concentration of al-
gae. Equipment required for this test includes
a drying oven, a dessicator and a weighing
balance.
Tests must always be run on composited sam-
ples from both the influent and effluent.
Fecal Coliform
Fecal coliform test indicates the possible pres-
ence or absence of pathogens (disease causing
organisms). The source of this group of or-
ganisms are man, mammals, and birds.
Tests are always run on grab samples collected
in a sterile container and must be run within 6
hours of sampling.
Nitrogen
Nitrogen testing may be required of those
plants discharging into a lake, reservoir or
large body of water. Wastewater contains or-
ganic nitrogen which is an essential nutrient
for algae. Organic nitrogen is converted to
ammonia nitrogen by bacteria as protein is
broken down. The ammonia nitrogen is fur-
ther oxidized to nitrites and then to nitrates
by nitrifying bacteria. This latter step is
known as nitrification. In some cases, it is
necessary to remove nitrate in order to con-
trol algae growth. Oxygen is removed under
anaerobic conditions (the nitrate is a source
of oxygen for the anaerobic bacteria), and the
nitrate is reduced to nitrogen gas. This step is
called denitrification.
2-7
-------
As an indicator of pollution the presence of
ammonia nitrogen indicates polluted waters,
the presence of nitrites still shows pollution
but nitrates indicate that nitrification has pro-
ceeded sufficiently to produce a stable nitro-
gen compound.
The following diagram illustrates the steps in
nitrification.
Anaerobic
or Aerobic
Bacteria
Nitrosomas
Bacteria
(Aerobic)
Nitrobacter
Bacteria
(Aerobic)
In most oxidation ponds, nitrification does
not appear, at least on a continuing level. The
reason for this is explained by the fact that
the nitrifying bacteria tend to settle or need
to cling to some surface. Therefore, they are
not exposed to compounds in solution.
It has been found that concentrations of more
than 20 mg/L of nitrogen can be harmful to
fish life, therefore, many pond discharges are
required to test for total nitrogen.
Some plants are also required to test for ni-
trates and ammonia. The significance of these
tests are:
A. If nitrification is occurring, there
will be an increase in nitrate with
a corresponding decrease in
ammonia-nitrogen.
B. In well-nitrified effluent all of the
ammonia nitrogen will be converted
to nitrates.
IMPORTANT VISUAL INDICATORS
Color
The color of the pond is directly related to
pH and DO. Below are listed the usual gen-
eral color characteristics.
Dark sparkling green - good; high pH
and DO
Dull green to yellow - not so good, pH
and DO are dropping; blue-green
type algae are becoming predom-
inant
Gray to black - very bad; pond is septic
with anaerobic conditions pre-
vailing
Tan to brown - OK if due to a predomi-
nance of a type of brown algae.
Not good if due to silt or bank
erosion.
2-8
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OTHER DAILY DATA
Weather
Weather has a great influence on the pond's
activity as discussed in Chapter I. Records
showing such factors as periods of sunshine,
cloudiness, weather temperature, period and
extent of rainfall and percent of ice cover,
often explain what has happened in the pond,
the quality of effluent and/or expected stor-
age. For example, in continuous flow sys-
tems, for extended cloudy periods of two
weeks the operator could expect to see an in-
crease in BOD in the final effluent and a re-
duction in suspended solids. Weather fore-
casts are important too, especially for a pond
that is near the design loading limit. Increas-
ing BOD in the effluent could indicate to the
operator that it is time to change flow pat-
terns; such as to parallel operation for the
winter season.
Water Depth
Water depth in continuous flow systems plays
an important role in pond operations. Abrupt
decreasing changes in water depth can signal a
leak or excessive percolation, while a sudden
increase may foretell a large spill into the sys-
tem by a user, or that the collection system is
experiencing storm water infiltration. Water
depth that remains unchanged can indicate
that pipelines are plugged. Water depth
changes in controlled discharge systems are
normally a part of regular operation and rapid
changes are part of the operation procedures.
Ice Cover
Ice cover is important to record as it relates
the extent of biological activity and which
one is predominant, aerobic or anaerobic.
The usual reporting shows percent of pond
area covered and how long the ice cover lasts.
2-9
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3. Operation and Maintenance
for Ponds
Operation and maintenance
goals for stabilization ponds
Operation and maintenance
goals for anaerobic ponds
Operation and maintenance
goals for aerated ponds
Plant checklist
Hints to improve operation
Pond cleaning
Starting a pond
Discharge control program
for seasonal discharges
-------
3. Operation and
Maintenance
for Ponds
OPERATION AND MAINTENANCE GOALS
FOR STABILIZATION PONDS
1. The pond effluent should:
a. Meet the NPDES or other regulatory
permit levels for BOD and SS for
continuous flow systems.
b. Discharge when it has the best qual-
ity and will effect the receiving
stream the least.
2. The primary cells should have a deep
green sparkling color which indicates
high pH and DO.
3. Secondary or final cells should be high in
DO and provide an effluent that will
meet discharge limits.
4. The surface water should have wave
action when wind is blowing. The ab-
sence of good wave action may indicate
anaerobic conditions or an oily surface.
5. A good pond has no weeds growing in
the water nor tall weeds on the bank to
stop wave action.
6. Dikes are well seeded above the water
line with grasses and kept mowed. This
prevents soil erosion and insect prob-
lems.
7. Erosion of dikes is prevented at water's
edge by the use of riprap, broken con-
crete rubble or a poured concrete
erosion pad.
8. Inlet and outlet structures are clean. No
floating debris, caked scum, or other
trash that might produce odors or be
unsightly.
9. Mechanical equipment is well maintained
with the help of a written schedule and
records are kept on lubrication and
maintenance.
10. A good pond operation includes a sched-
ule for getting things done. An available
plant record shows weather data and
basic test results such as pH, DO, BOD,
SS, and chlorine residuals.
OPERATION AND MAINTENANCE GOALS
FOR ANAEROBIC PONDS
1. Anaerobic ponds operate with no DO.
2. A well-operating anaerobic pond is cov-
ered entirely with a dense scum blanket
which helps to keep the pond anaerobic
and minimizes foul odors.
3. Two important operation considera-
tions:
a. Keep the pond pH at or near neutral
(7.0) to keep the bacteria in balance.
b. Control of odors by maintaining no
DO and a heavy scum blanket.
4. Normally, the anaerobic pond is fol-
lowed by additional treatment, such as
3-1
-------
an aerated pond and polishing cells or a
discharge to a separate municipal waste-
water treatment plant. Records should
be kept on:
a. Detention time
b. Load (BOD and SS)
c. Effluent quality (BOD, SS and pH)
d. Pond content information (pH, SS,
alkalinity, volatile acids, scum and
sludge depth)
5. The major on-site attendance will be
needed mostly in:
a. Maintaining mechanical equipment
b. Keeping pipelines, diversion boxes
and screens clean
c. Collecting samples
d. Running lab tests
e. Performing housekeeping
OPERATION AND MAINTENANCE GOALS
FOR AERATED PONDS
1. Aerated ponds will require the same
daily inspections and maintenance used
for stabilization ponds plus special atten-
tion to the aeration equipment.
2. Maintain a minimum of 1 mg/L DO
throughout the pond at heaviest loading
periods.
3. Surface mechanical aerators should pro-
duce good turbulence and a light amount
of froth.
a. Monitor DO at aerated cell outlet
daily.
b. Keep logs and large pieces of wood
out of the pond to prevent damage
to the aerator.
4. For diffused air systems that use a blow-
er and pipelines to diffuse air over entire
bottom of pond:
a. Check blower daily
b. Visually inspect aeration pattern for
"dead spots" or line ruptures. Re-
pair if necessary to maintain even
distribution of air.
c. Measure DO at several points in the
pond weekly and adjust air to main-
tain even distribution.
5. Periodic maintenance must be per-
formed, such as lubrication, adjustment
and replacement. The best procedure is
to make a checklist of maintenance tasks
and frequency from the manufacturer's
instructions bulletins.
PLANT CHECKLIST
A checklist is a handy tool for the plant oper-
ator to schedule activities. Most of the items
are visual observations or maintenance needs
that take little time if performed according to
schedule. With regular attendance, the oper-
ator will develop ways to combine some of
the duties. In many installations that are
looked after regularly by a conscientious op-
erator, the scheduled items can be accom-
plished in one to two hours a day, allowing
the balance of the time for lab and other
duties.
The blank form in the Appendix may be used
as a guide.
3-2
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Following is a sample operation and main-
tenance checklist for a pond operation. Al-
though it is not a complete list of everything
the operator should be observing, it will serve
as a guide for setting up a schedule for his or
her own plant. The schedule will help the op-
erator organize work in a step-by-step fashion
and it will also help relief operators or new
personnel who are not familiar with the plant.
For the design engineer, a checklist should be
developed for the plant and included in the
operation and maintenance manual.
Operational and Preventive Maintenance
Plant Survey
Drive around perimeters of ponds taking note
of the following conditions:
1. Any buildup of scum on pond sur-
face and discharge outlet boxes.
2. Signs of burrowing animals.
3. Anaerobic conditions. Noted by
odor and black color.
4. Water grown weeds.
5. Evidence of dike erosion.
6. Dike leakage.
7. Fence damage.
8. Ice buildup in winter.
9. Evidence of short circuiting.
Plan, schedule, and correct problems found.
(Use troubleshooting section of this manual
for information.)
Pretreatment
1. Clean inlet, screens, and properly
dispose of trash.
2. Check inlet flowmeter and float well.
Frequency
Daily
X
X
X
X
X
X
X
X
X
X
Wk.
Mo.
3 Mo.
6 Mo.
Yearly
As
Necessary
X
X
3-3
-------
Frequency
Operational and Preventive Maintenance [Daily
If discharge is once or twice per year, the
discharge permit may require the following:
1. Odor
2. Aquatic plant coverage of pond
3. Pond depth
4. Dike condition
5. Ice cover
6. Flow (Influent)
7. Rainfall (or snowfall)
Note: Each state has requirements for data
collected prior to and during discharge
that is defined in the plant discharge
permit.
If discharge is continuous, the discharge permit
may require the following information:
1 . Weather
2. Flow
3. Condition of all cells
4. Depth of all cells
5. Lagoon effluent:
a. DO and pH grab sample
b. Chlorine residual
c. BOD and SS run on
composited samples
d. Fecal coliform
e. Record pounds of chlorine
remaining and used
Other tests and frequency information
will be defined in the individual permit
for the plant.
X
X
X
X
X
X
X
X
X
Wk.
X
X
X
X
X
Mo.
3 Mo.
6 Mo.
Yearly
As
Necessary
X
X
3-4
-------
Operational and Preventive Maintenance
Mechanical Equipment
Check mechanical equipment and perform
scheduled preventive maintenance on the
following pieces of equipment according
to the manufacturer's recommendations:
1. Pump stations:
a. Remove debris
b. Check pump operation
c. Run emergency generator
d. Log running times
e. Clean floats, bubblers, or
other control devices
f. Lubricate
2. Comminuting devices:
a. Check cutters
b. Lubricate
3. Aerators:
a. Log running time
b. Check amperage
4. Chlorinators:
a. Check feed rate
b. Change cylinders
5. Flow measuring devices:
a. Check and clean floats, etc.
b. Verify accuracy
6. Valves and gates:
a. Check to see if set correctly
b. Open and close to be sure
they operate
Frequency
Daily
X
X
X
X
X
X
X
Wk.
X
X
X
Mo.
X
3 Mo.
X
X
6 Mo.
'Yearly
As
Necessary
X
X
X
3-5
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HINTS TO IMPROVE OPERATION
Flow Regulation
Flow regulation is one of the most helpful op-
erational tools available to a lagoon operator.
Without the flexibility of being able to move
water around where it is needed the operator
would be severely handicapped.
In simple terms, an operator needs options.
For example:
Single Cell Ponds:
The only flexibility an operator has in
a single cell pond is depth control.
The water level may have to be varied
based on the season or to control
weeds and mosquitoes.
Multiple Cell Ponds:
1. May need to hold wastewater in
the primary cell, especially during
seasonal discharge operations.
2. May need to move water from cell
to cell to correct an oxygen defi-
ciency problem.
3. May need to control liquid depth
to get rid of weeds or mosquitoes.
4. May need to isolate a cell that has
turned anaerobic or to hold a
toxic waste.
5. May need to take advantage of
both series and parallel operation
to regulate loading.
6. May need to temporarily rest a
cell for recovery.
Baffles and Screens
Screens, often homemade, are used around
pond surface outlets to keep wind blown
weed and surface trash from entering a pipe.
Baffles are quite commonly used for a large
variety of purposes.
1. To direct the flow of water, especial-
ly around inlets. These may consist
of nothing more than pilings of 2" x
8" driven into the pond bottom.
2. To allow selection of depth for pond
draw-off and to keep surface scum
and trash from entering.
3. To provide a stilling area ahead of a
flow measuring device.
4. To reduce the force of a pump
discharge.
Dike erosion from wave action can be pre-
vented by using riprap in the form of rocks 3
to 8 inches (8 to 48 centimeters) laid along
the water's edge. One unusual method em-
ployed is to sink two by six's upright into the
lagoon floor extending above the water sur-
face to break up and dissipate the waves. In
another case, the lagoon operator had bags
filled with a dry mix of sand, gravel and ce-
ment. These were laid side by side and
stacked to form a system of neat functional
riprap protection. Riprap should extend one
foot above and below extreme operating lev-
els. Other forms of riprap or bank stabiliza-
tion include cribbing (snow fence) laid on the
bank and reed canary grass. The canary grass
is effective on ponds that are deep, have steep
slopes and a stable water level. Sodding
should be at least 3 inches (7.5 cm) square
and placed not more than 3 feet (1 meter)
apart.
3-6
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POND CLEANING
If it becomes necessary to clean a pond the
operator should have access to a suction
pump, a "mudcat" or other means of remov-
ing mud or sludge off the bottom to control
pond bottom levels and localized deposit
areas. This is seldom necessary except for sit-
uations where grit or sand gets into the sys-
tem. This occurred in a coastal city that had
high amounts of infiltration where sewers
were laid in sandy soil. Bottom solids can
normally be disposed of in the same manner
that digested solids are. Advice should be ob-
tained from the consulting engineer and the
regulatory agency.
STARTING A POND
Procedures
To Fill Primary Cell
1. Fill primary cell(s) with fresh water
from a river or municipal system, if
available, to the two-foot level.
(Spring or early summer is the best
time to startup to avoid low temper-
ature and possible freezing.)
2. Begin the addition of wastewater.
3. Keep pH above 7.5. See Trouble-
shooting Guide.
4. Check DO daily. See Trouble-
shooting Guide.
5. If started during warm weather:
a. Algal blooms usually will
appear from 7 to 14 days.
b. A good biological community
will be established in about 60
days. Color will be a definite
green as contrasted with blue or
yellow-green.
This procedure tends to avoid odorous
anaerobic conditions and weed growth
during the start-up phase. If it is neces-
sary to start in late fall or winter, level
should be brought to 21/2-3 feet (0.75-1
meter) and no discharge until late spring.
To Fill Successive Ponds
1. Begin filling when the water level in
the first pond reaches 3 feet (1
meter).
2. Add fresh water to a depth of 2 feet
(0.6 meters).
3. Begin adding water from previous
pond observing the following:
a. Use top draw-off to achieve
good transfer. Do not draw off
from a level below the bottom
18 inches (45cm).
b. Do not allow the water depth in
the previous pond(s) to fall be-
low 3 feet (1 meter).
c. Equalize water depths in all
ponds. This should be done by
the following:
(1) Hold the discharge until all
ponds are filled.
(2) Use effluent box with
gates or valves to allow
pumping the effluent to
any pond in the system if
system is designed with
this capability.
(3) Continuously recycle the
effluent to the ponds that
need the water level raised.
3-7
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4. Repeat the "3.c." operation using 6-
inch (15-cm) increments until ponds
are at their operating depth.
5. Finally, start continuous or intermit-
tent discharge, however the system is
designed. See the following section.
DISCHARGE CONTROL PROGRAM FOR
SEASONAL DISCHARGES
Preparation
1. Make a note of conditions in the stream
to receive discharge.
2. Estimate duration of discharge and ex-
pected volume.
3. Obtain State Regulation Agency
approval.
4. Isolate cell to be discharged. Allow to
rest for at least 1 month, if possible.
5. Arrange for daily sample analysis of
BOD5 , SS, pH, coliform and nutrients
(if required).
6. Plan other work so as to spend full time
on control of discharge throughout the
period.
7. Sample contents of cell and analyze for
DO; note and record turbidity, color and
any unusual conditions.
Discharge Procedures
Many northern states use a seasonal discharge.
Three or four weeks after ice break-up, the
ponds generally return to normal operating
conditions. The wastewater in the cells is
tested and results are reported to the state. If
the wastewater is of a quality suitable for dis-
charging, the operator then follows state
guidelines in discharging. The NPDES permit
states the discharge quality the operator must
maintain.
The quality of the receiving stream is usually
determined by the State Pollution Control
Agency as part of the discharge approval
program. When discharge approval is ob-
tained, proceed as follows:
1. Begin the discharge program with the
last cell in series.
2. Draw off the discharge from the best
level at a time when the discharge is
acceptable. Stop the discharge when
ponds are upset.
3. Follow testing procedures outlined
by your State Regulatory Agency.
3-8
-------
4. Troubleshooting for Ponds
How to control water weeds
How to control burrowing
animals
How to control dike vegetation
How to control scum
How to control odors
How to control blue-green algae
How to control insects
How to obtain best algae
removal in the effluent
How to correct lightly
loaded ponds
How to correct a low
dissolved oxygen (DO)
How to correct overloading
How to correct a decreasing
trend in pH
How to correct short-circuiting
How to correct anaerobic
conditions
How to correct a high BOD
in the effluent
How to correct problems in
aerated ponds
How to correct problems in
anaerobic ponds
-------
4. Troubleshooting
for Ponds
HOW TO CONTROL WATER WEEDS
INDICATORS/OBSERVATIONS
Weeds provide food for burrowing animals.
cause short-circuiting problems, stop wave ac-
tion so that scurri can collect and make a nice
home for mosquitoes, and odors develop in
the still area. Duckweed stops sunlight pene-
tration and prevents wind action thus reduc-
ing the oxygen in the pond. Root penetration
causes leaks in pond seal.
PROBABLE CAUSE
Poor circulation, maintenance, insufficient
water depth.
SOLUTIONS
1. Pull weeds by hand if new growth.
2. Mow weeds with a sickle bar mower.
3. Lower water level to expose weeds, then
burn with gas burner.
4. Allow the surface to freeze at a low
water level, raise the water level and the
floating ice will pull the weeds as it rises.
(Large clumps of roots will leave holes in
pond bottom, best results are obtained
when weeds are young.)
5. Increase water depth to above tops of
weeds.
6. Use riprap. Caution: 1 f weeds get start-
ed in the riprap, they wilt be difficult to
remove but can be sprayed with accept-
able herbicides.
7. To control duckweed, use rakes or push
a board with a boat, then physically re-
move duckweed from pond.
HOW TO CONTROL BURROWING ANIMALS
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
Burrowing animals must be controlled be-
cause of the damage they do to dikes. Ro-
dents such as musk rats and nutria dig partially
submerged tunnels into dikes. If the water
level is raised, they will burrow further and
may go on out the top thus weakening the
dike.
Bank conditions that attract animals. High
population in area adjacent to ponds.
Remove food supply such as cattails and
burr reed from ponds and adjacent areas.
Muskrats prefer a partially submerged
tunnel, if the water level is raised it will
extend the tunnel upward and if lowered
sufficiently, it may abandon the tunnel
completely. They may be discouraged
by raising and lowering the level 6-8
inches over several weeks.
If problem persists, check with local
game commission officer for approved
methods of removal, such as live
trapping, etc.
4-1
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HOW TO CONTROL DIKE VEGETATION
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
High weed growth, brush, trees and other
vegetation provide nesting places for animals,
can cause weakening of the dike and presents
an unsightly appearance. Also may reduce
wind action on the pond.
Poor maintenance.
1. Periodic mowing is the best method.
2. Sow dikes with a mixture of fescue and
blue grasses on the shore and short na-
tive grasses elsewhere. It is desirable to
select a grass that will form a good sod
and drive out tall weeds by binding the
soil and "out compete" undesirable
growth.
3. Spray with approved weed control chem-
icals. Note: Be sure to check with au-
thorities. Some states do not allow
chemical usage. All others require that
chemicals be bio-degradable. Examples
of some herbicides that are used are:
Dow Dalapon for cattails
Dow Silvex for willows and emergent
weeds
Ortho Endo-thal for suspended weeds
Copper sulfate for filamentous algae
Simazine for weeds
4. Some small animals, such as sheep, have
been used. May increase fecal coliform,
especially to the discharge cell. Practice
"rotation grazing" to prevent destroying
individual species of grasses. An exam-
ple schedule for rotation grazing in a 3-
pond system would be: Graze each
pond area for 2 months over a 6-month
grazing season.
HOW TO CONTROL SCUM
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
It is necessary to control scum formations
to prevent odor problems and to eliminate
breeding spots for mosquitoes. Also, sizeable
floating rafts will reduce sunlight.
Pond bottom is turning over with sludge float-
ing to the surface. Poor circulation and wind
action. High amounts of grease and oil in in-
fluent will also cause scum.
1. Use rakes, a portable pump to get a wa-
ter jet or motor boats to break up scum
formations. Broken scum usually sinks.
2. Any remaining scum should be skimmed
and disposed of by burial or hauled to
landfill with approval of regulatory
agency.
4-2
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HOW TO CONTROL ODORS
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
Odors are a general nuisance to the public.
The odors are generally the result of over-
loading, long periods of cloudy weather, poor
pond circulation, industrial wastes or ice melt.
1. Use parallel feeding to primary cells to
reduce loading.
2. Apply chemicals such as sodium nitrate,
Dibrom or Micro-Aid to introduce oxy-
gen. Application rate: 5-15 percent of
sodium nitrate per pound of BOD on a
pound-for-pound basis. Or apply 200
pounds sodium nitrate per million gal-
lons. See literature for commercial prod-
ucts. Repeat at a reduced rate on suc-
ceeding days. Or use 100 pounds sodi-
um nitrate per acre {112 kg/hectare) for
first day, then 50 pounds per acre (56
kg/hectare) per day thereafter if odors
persist. Apply in the wake of a motor
boat.
3. Install supplementary aeration such as
floating aerators, caged aerators, or dif-
fused aeration to provide mixing and
oxygen. Daily trips over the lagoon area
in a motor boat also helps. Note: Stir-
ring the pond may cause odors to be
worse for short periods but will reduce
total length of odorous period.
4. Recirculate pond effluent to the pond
influent to provide additional oxygen
and to distribute the solids concentra-
tion. Recirculate on a 1 to 6 ratio.
5. Eliminate septic or high-strength indus-
trial wastes.
HOW TO CONTROL BLUE-GREEN ALGAE
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
Low pH (less than 6.5} and dissolved oxygen
(less than 1 mg/L). Foul odors develop when
algae die off.
Blue-green algae is an indication of incom-
plete treatment, overloading and/or poor
nutrient balance.
Apply 3 applications of a solution of
copper sulfate.
a. If the total alkalinity is above 50
mg/L apply 10 pounds of copper
sulfate per million gallons in cell
{1200 kg/m3}.
b. If alkalinity is below 50 mg/L reduce
the amount of copper sulfate to 5
pounds per million gallons (600
kg/m3}.
Note: Some states do not approve the
use of copper sulfate since in
concentrations greater than 1
mg/L it is toxic to certain
organisms and fish.
Break up algal blooms by motor boat or
a portable pump and hose. Motor boat
motors should be air cooled as algae may
plug up water cooled motors.
4-3
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HOW TO CONTROL INSECTS
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
Insects present in area and larvae or insects
present in pond water.
Poor circulation and maintenance.
Solution for Mosquito Control
1. Keep pond clear of weeds and allow
wave action on bank to prevent mos-
quitoes from hatching out.
2. Keep pond free from scum.
3. Stock pond with Gambusia (Mosquito
Fish).
4. Spray with larvacide as a last resort.
Check with state regulatory officials for
approved chemicals. (Some that have
been used are Dursban, Naled, Fenthion
and Abate in dosages of 1 mg/L.)
Solution for Controlling Midges
1. Stock pond with Gambusia.
2. Spray with approved insecticide.
(Fenthion, Abate and Sursban have been
used based on directions on the
package.)
HOW TO OBTAIN BEST ALGAE REMOVAL IN THE EFFLUENT
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
Most of the suspended solids present in a
pond effluent are due to algae. Because many
single-celled algae are motile and are also very
small they are difficult to remove.
Weather or temperature conditions that favor
particular population of algae.
1. Draw off effluent from below the sur-
face by use of a good baffling arrange-
ment.
2. Use multiple ponds in series.
3. The use of intermittent sand filters and
submerged rock filters may also be used
but will require modification and the
services of a consulting engineer.
4. In some cases, alum dosages of 20 mg/L
has been used in final cells used for inter-
mittent discharge to improve effluent
quality. Dosages at or below this level
are not toxic.
HOW TO CORRECT LIGHTLY LOADED PONDS
INDICATORS/OBSERVATIONS
Lightly loaded ponds may produce filamen-
tous algae and moss which limits sunlight
penetration. These forms also tend to clog
pond outlets.
PROBABLE CAUSE
Overdesign, low seasonal flow.
SOLUTIONS
1. Correct by increasing the loading by
reducing the number of cells in use.
2. Use series operation.
4-4
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HOW TO CORRECT A LOW DISSOLVED OXYGEN (DO)
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
A low, continued downward trend in DO is
indicative of possible impending anaerobic
conditions and the cause of unpleasant odors.
Treatment becomes less efficient.
Poor light penetration, low detention time,
high BOD loading or toxic industrial wastes.
(Daytime DO should not drop below 3.0
mg/L during warm months.)
1. Remove weeds such as duckweed if
covering greater than 40 percent of the
pond.
2. Reduce organic loading to primary
cell(s) by going to parallel operation.
3. Add supplemental aeration (surface
aerators, diffusers and/or daily operation
of a motor boat).
4. Add recirculation by using a portable
pump to return final effluent to the head
works.
5. Apply sodium nitrate (see How to
Control Odors for rate).
6. Determine if overload is due to industrial
source and remove it.
HOW TO CORRECT OVERLOADING
INDICATORS/OBSERVATIONS
Overloading which results in incomplete treat-
ment of the waste.
Overloading problems can be detected by of-
fensive odors, a yellow green or gray color.
Lab tests showing low pH, DO, and excessive
BOD loading per unit area should also be
considered.
PROBABLE CAUSE
Short-circuiting, industrial wastes, poor de-
sign, infiltration, new construction (service
area expansion), inadequate treatment and
weather conditions.
SOLUTIONS
1 . Bypass the cell and let it rest.
2. Use parallel operation.
3. Apply recirculation of pond effluent.
4. Look at possible short-circuiting.
5. Install supplementary aeration equip-
ment.
HOW TO CORRECT A DECREASING TREND IN pH
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
pH controls the environment for algae types,
as an example, the green chlorella needs a pH
from 8.0 to 8.4.
pH should be on the alkaline side, preferably
about 8.0 to 8.4.
Both pH and DO will vary throughout the day
with lowest reading at sunrise and highest
reading in late afternoon.
Measure pH same time each day and plot on a
graph.
A decreasing pH is followed by a drop in DO
as the green algae die off. This is most often
caused by overloading, long periods of adverse
weather or higher animals, such as Daphnia,
feeding on the algae.
1. Bypass the cell and let it rest.
2. Use parallel operation.
3. Apply recirculation of pond effluent.
4. Check for possible short-circuiting.
5. Install supplementary aeration equip-
ment if problem is persistent and due to
overloading.
6. Look for possible toxic or external
causes of algae die-off and correct at
source.
4-5
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HOW TO CORRECT SHORT-CIRCUITING
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
Odor problems, low DO in parts of the pond,
anaerobic conditions and tow pH found by
checking values from various parts of the
pond and noting on a plan of the pond. Dif-
ferences of 100 percent to 200 percent may
indicate short-circuiting.
After recording the readings for each location,
the areas that are not receiving good circula-
tion become evident. These areas are char-
acterized by a low DO and pH.
Poor wind action due to trees or poor arrange-
ment of inlet and outlet locations. May also
be due to shape of pond, weed growth or
irregular bottom.
1. Cut trees and growth at least 500 feet
{150 m} away from pond if in direction
of prevailing wind.
2. Install baffling around inlet location to
improve distribution.
3. Add recirculation to improve mixing.
4. Provide new inlet-outlet locations,
including multiple inlets.
5. Clean out weeds.
6. Fill in irregular bottoms.
HOW TO CORRECT ANAEROBIC CONDITIONS
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
Facultative pond that turned anaerobic result-
ing in high BOD, suspended solids and scum
in the effluent in continuous discharge ponds.
Uhpleasant odors, the presence of filamentous
bacteria and yellowish-green or gray color and
placid surface indicate anaerobic conditions.
Overloading, short circuiting, poor operation
or toxic discharges.
1. Change from a series to parallel opera-
tion to divide load. Helpful if conditions
exist at a certain time each year and are
not persistent.
2. Add supplemental aeration if pond is
continuously overloaded.
3. Change inlets and outlets to eliminate
short-circuiting. See How to Correct
Short-Circuiting.
4. Add recirculation (temporary-use porta-
ble pumps) to provide oxygen and
mixing.
5. In some cases temporary help can be ob-
tained by adding sodium nitrate at rates
described elsewhere in this manual.
6. Eliminate sources of toxic discharges.
4-6
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HOW TO CORRECT A HIGH BOD IN THE EFFLUENT
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
High BOD concentrations that are in violation
of NPDES or other regulatory agency permit
requirements. Visible dead algae.
Short detention times, poor inlet and outlet
placement, high organic or hydraulic loads
and possible toxic compounds.
1. Check for collection system infiltration
and eliminate at source.
2. Use portable pumps to recirculate the
water.
3. Add new inlet and outlet locations.
A. Reduce loads due to industrial sources if
above design level.
5. Prevent toxic discharges.
HOW TO CORRECT PROBLEMS IN AERATED PONDS
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
SOLUTIONS
Fluctuating DO, fine pin floe in final cell ef-
fluent, frothing and foaming, ice interfering
with operation.
Shock loading, overaeration, industrial wastes,
floating ice.
Control aeration system by using time
clock to allow operation during high
load periods, monitor DO to set up
schedule for even operation, holding
approximately 1 mg/L or more.
Vary operation of aeration system to
obtain solids that flocculate or "clump"
together in the secondary cell but are
not torn apart by excessive aeration.
Locate industrial wastes that may cause
foaming or frothing and eliminate or pre-
treat wastes. Examples are slaughter
house, milk or some vegetable wastes.
Operate units continuously during cold
weather to prevent freezing damage or
remove completely if not a type that will
prevent freeze-up.
HOW TO CORRECT PROBLEMS IN ANAEROBIC PONDS
INDICATORS/OBSERVATIONS
Odors
Hydrogen sulfide, (rotten egg) odors or other
disagreeable conditions due to sludge in a
septic condition.
LowpH
pH below 6.5 accompanied by odors are the
result of acid bacteria working in the
anaerobic condition.
PROBABLE CAUSE
Lack of cover over water surface and insuf-
ficient load to have complete activity which
eventually forms scum blanket.
Acid formers working faster than methane
formers in an acid condition.
SOLUTIONS
Use straw cast ver the surface or polystyrene
planks as a ter i torary cover until a good sur-
face sludge bla'.ke'. has formed.
The pH can be raised by adding a lime slurry
of 100 pounds of hydrated lime to 50 gallons
(580 kg/200 liters) of water at a dosage rate
of 1 pound of lime for every 10,000 gallons
(120 g/10,000 liters) in the pond. The slurry
should be mixed while being adde I. The best
place to put the lime in is at the e. 'ranee to
the lagoon so that it is well mixed .- j it enters
the pond.
4-7
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5. Safety Around Ponds
;.
Public health aspects
-------
5. Safety
Around Ponds
PUBLIC HEALTH ASPECTS
Stabilization ponds, like other wastewater
treatment facilities, must be treated with cau-
tion and respect from a safety and public
health standpoint by operators and the gen-
eral public alike. This means that stabiliza-
tion ponds must be utilized for their de-
signed purpose only, and not for public
recreation.
The relative amount of water surface of sta-
bilization ponds is insignificant in comparison
to the many natural bodies of open water in
most localities. In some areas, however, sta-
bilization ponds represent the only sizeable
body of water and have been sources of at-
traction to children as well as adults for rec-
reation purposes. Incidents of boating, ice-
skating, extensive waterfowl hunting and even
swimming in ponds have been reported. Rec-
reational use should be discouraged and safety
practices encouraged for several important
reasons.
First, even though the efficiency of bacterial
removal as measured by the MPN method is
very high, the possibility of contamination or
infection from pathogenic organisms does ex-
ist when one comes in contact with waste-
water in a stabilization pond.
Second, although most stabilization ponds at-
tain a depth of only 5 feet, there is still suf-
ficient depth to drown a person. Also, clay
liners used in sealing ponds become very
sticky when water is added. Should anyone
fall in the pond, this clay liner would make it
extremely difficult for anyone to get out.
Another factor to be considered is the exis-
tence of mosquitos. However, on a well-
maintained pond system, mosquitoes usually
are not a nuisance.
According to studies made by the U.S. Public
Health Service, the density of the mosquito
population is directly proportional to the ex-
tent of weed growth in the ponds. Where
weed growth in the ponds and along the water
line of the dikes is negligible and where wind
action on the pond is not unduly restricted,
the production of mosquitoes in stabilization
ponds is low.
To discourage use of the ponds for recreation
the entire area should be fenced and warning
signs displayed.
Personal Hygiene
It is in the interest of your health and the
health of your family that this list of Do's and
Don'ts for personal hygiene is made. Use it,
don't abuse it!
1.
2.
3.
Never eat your lunch or put anything
into your mouth without first washing
your hands.
Refrain from smoking while working in
manholes, on pumps or other parts of
the operation where hands may become
contaminated.
Don't wear your coveralls or rubber
boots in your car or home.
5-1
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4. Always clean any equipment such as
safety belts, harness, face masks, gloves,
etc., after using. You or someone else
may want to use it again.
5. Keep your fingernails cut short and clean
as they are excellent carriers of dirt and
germs.
Safety
Sewer Maintenance Safety Precautions
1. Remove and replace heavy manhole
covers carefully and only with the
proper tools.
2. Descend into any manhole cautious-
ly to guard against defective steps or
rungs.
3. See part regarding noxious gases that
may be found in sewers.
Pumping Station and Stabilization Pond
Safety Precautions
1. Maintain a high level of good house-
keeping. This involves keeping
floors, walls and equipment free
from dirt, grease and debris. Keep
tools properly stored when not in
use.
2. Keep walkways clean and free from
slippery substances. If ice forms on
walks, apply salt or sand or cover
with earth or ashes than can be
removed later.
3. Be especially cautious when working
with an electrical distribution system
and related facilities. Never work on
electrical equipment and wire with
wet hands or when clothes or shoes
are wet. Always wear appropriate
safety gloves for electrical work.
Never use a switchbox for anything
other than a switchbox.
4. Keep all personnel safety conscious
by reminding them of specific safety
instructions. Such instructions
should include information on how
to contact the nearest medical center
and fire station, rescue techniques,
resuscitation and first aid techniques.
5. Make certain that a sufficient num-
ber of capable personnel with proper
equipment are assigned and present
whenever it is necessary to perform
any hazardous work.
6. A life preserver must be used when
using a boat on stabilization ponds.
Also, never work alone around the
ponds because of the danger of
drowning and other accidents. One
of the requirements for a pond op-
erator should be that he can swim at
least 100 feet in normal work
clothing.
7. Sufficient fire extinguishers (Under-
writer's Laboratories approved)
should be placed in readily accessible
locations.
Body Infection and Disease Safety
Precautions
1. Treat all cuts, skin abrasions and sim-
ilar injuries promptly. When work-
ing with wastewater, the smallest cut
or scratch is potentially dangerous
and should be cleaned and treated
immediately with a 2 percent
solution of tincture of iodine.
2. See a doctor for all injuries.
3. Provide first aid training for all
personnel.
4. Be innoculated for waterborne di-
seases, particularly typhoid and para-
5-2
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typhoid fever. Keep a record of all
immunizations in an employee
health record to assure yourself of
receiving up-to-date boosters, etc.
5. In laboratory work, use pipet bulbs
rather than the mouth so as not to
introduce contamination to the
mouth. Don't drink water from lab-
oratory glassware. Paper cups should
be provided in laboratories for drink-
ing purposes. Never prepare food in
a laboratory.
Noxious Gases, Explosive Mixtures and
Oxygen Deficiency
1. The principal gas hazards associated
with wastewater treatment are ac-
cumulations of sewer gas and its mix-
ture with other gases or air which
may cause death or injury through
explosion or by asphyxiation as a re-
sult of oxygen deficiency. The term
sewer gas is generally applied to the
mixture of gases in sewers and man-
holes containing high percentages of
carbon dioxide, varying amounts of
methane, hydrogen, hydrogen sulfide
and low percentages of oxygen.
Such mixtures sometimes accumu-
late in sewers and manholes where
organic matter has been deposited
and has undergone decomposition.
The actual hazards from sewer gas
exist in the explosive amount of
methane, hydrogen sulfide or in oxy-
gen deficiency. Hydrogen sulfide is
toxic at very low concentrations and
one's sensitivity to the odor is
quickly deadened.
2. Chlorine gas, which is irritating to
the eyes, respiratory tract and other
mucous membranes, may settle in
low, still areas. The gas forms an
acid in the presence of moisture.
The gas escapes by leakage from cyl-
inders and feed lines and finds its
way to these places.
Safety Equipment
The types of safety equipment which a waste-
water facility should have are as follows:
1. Detection equipment (for gases and
oxygen deficiencies).
2. Masks (self-contained air packs for
oxygen deficiencies).
3. Safety harnesses, lines and hoists.
4. Proper protective clothing, foot-
wear and head gear.
5. Ventilating equipment.
6. Nonsparking tools.
7. Communications equipment.
8. Portable air blower.
9. Explosion-proof lantern and other
safe illumination.
10. Warning signs and barriers.
11. Emergency first aid kits.
12. Proper fire extinguishers.
13. Eye wash and shower stations in
laboratory areas.
14. Safety goggles for work in labora-
tories and other dangerous areas.
Additional Sources of Information
New York Manual, Ch. 14
WPCF, MOP No. 1, Safety in Wastewater Works
Texas Manual, Ch. 35
Sacramento State Home-Study Course, Ch. 12
5-3
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Appendices
Glossary of terms
B Formulas and problems
C Flow measuring devices
D Design considerations
from an operation and
maintenance viewpoint
E Case histories
F Metric equivalents
G References and suggested
resource material
H Plants visited
J Checklist form
-------
A Glossary of terms
ACRE-FOOT A volume term referring to
that amount of liquid, 1 acre in area, 1 foot
deep. (43,560 cubic feet)
AERATED POND - A wastewater treatment
pond in which mechanical or diffused-air
aeration is used to supplement the oxygen
supply.
AEROBIC A condition characterized by
the presence of free dissolved oxygen in the
aquatic environment.
AEROBIC BACTERIA - Bacteria that
require free dissolved oxygen for growth.
AEROBIC STABILIZATION - The stabiliza-
tion of organic matter through metabolism
into more complex matter by bacteria in the
presence of dissolved oxygen.
ALGAE Primitive one- or many-celled
plants, usually aquatic, that produce their
food by photosynthesis.
ALGICIDE Any substance or chemical
applied to kill or control algal growths.
ANAEROBIC BACTERIA - Bacteria which
grow in the absence of free dissolved oxygen
and must obtain their oxygen by chemically
breaking down organic compounds which
contain combined oxygen.
ANAEROBIC DECOMPOSITION -The
breakdown of complex organic matter by
bacteria in the absence of dissolved oxygen.
AQUATIC VEGETATION - That vegetation
which will grow in or near water.
BACTERIA A group of microscopic organ-
isms lacking chlorophyll and organic nutrients
as a food source.
COLIFORM GROUP - A group of bacteria
that inhabit the intestinal tract of man, warm
blooded animals and may be found in plants,
soil and air and the aquatic environment.
DISSOLVED OXYGEN (DO) - Dissolved
molecular oxygen usually expressed in mg/L,
ppm or percent saturation.
DIURNAL Having a daily cycle.
EFFLUENT A liquid flowing out of a
chamber, treatment unit or basin.
FACULTATIVE BACTERIA - Those bac-
teria that can adapt to aerobic or anaerobic
conditions. Can utilize dissolved or combined
oxygen (oxygen bound in a compound by a
chemical action).
FUNGI Simple or complex organisms with-
out chlorophyll. The simpler forms are one-
celled; higher forms have branched filaments
and complicated life cycles. Examples are
molds, yeasts and mushrooms.
GRAB SAMPLE - A single sample not nec-
essarily taken at a set time or flow. An
instantaneous sample.
HYDRAULIC LOADING - The volume of
flow per day per unit area.
INFLUENT That liquid entering a process
unit or operation.
A-1
-------
INORGANIC MATTER - Chemical
substances of mineral origin.
MILLI An expression used to indicate
1/1000 of a standard unit of weight, length or
capacity (metric system).
milliliter (ml) - 1/1000 liter (L)
milligram (mg) - 1/1000 gram (g)
millimeter (mm) - 1/1000 meter (m)
MILLIGRAMS PER LITER (mg/L) - A unit
of concentration on weight/volume basis,
milligrams per liter. Equivalent to ppm when
speaking of water or wastewater.
ORGANIC LOADING - The number of
pounds of BOD added to treatment unit per
day.
OXYGEN AVAILABLE - That part of the
oxygen available for aerobic stabilization of
organic matter. Includes dissolved oxygen
and that available in nitrites or nitrates, per-
oxides, ozone and certain other forms of
oxygen.
OXYGEN DEPLETION - The loss of oxygen
from water or wastewater due to biological,
chemical or physical action.
pH Expresses the intensity of acidity or
alkalinity of a liquid.
PHOTOSYNTHESIS - A process in which
chlorophyll-containing plants produce com-
plex organic (living) materials from carbon
dioxide, water and inorganic salts, with sun-
light as the source of energy. Oxygen is pro-
duced in this process as a waste product.
POPULATION EQUIVALENT - The calcu-
lated population which would normally con-
tribute the same amount of biochemical oxy-
gen demand as the wastewater. A common
base is 0.2 Ib. (0.09 kg) of 5-day BOD per
capita per day.
SETTLEABLE SOLIDS - Those solids which
will settle out when a sample of sewage is al-
lowed to stand quietly for a one-hour period.
SHORT-CIRCUITING - The hydraulic condi-
tions in a tank, chamber or basin where time
of passage is less than that of the normal flow-
through period.
SLUDGE BANKS - The accumulation of
solids including silt, mineral, organic and cell
mass material that is produced in an aquatic
system.
STABILIZATION - The process of reducing
a material using a biological and chemical
means to a form that does not readily
decompose.
STANDARD METHODS - Methods of analy-
sis prescribed by joint action of the American
Public Health Association (APHA), American
Water Works Association (AWWA) and Water
Pollution Control Federation (WPCF).
SUPERSATURATION - The situation in
which water holds more oxygen at a specified
temperature than normally required for
saturation.
SUSPENDED SOLIDS - The concentration
of insoluble materials suspended or dispersed
in waste or used water. Generally expressed
in mg/L on a dry weight basis. Usually
determined by filtration methods.
TOTAL SOLIDS Refers to the solids con-
tained in dissolved and suspended form in
water. Determined on weighing after drying
at 103 degrees Celsius.
VOLATILE SOLIDS - The quantity of solids
in water that represent a loss in weight upon
ignition at 550 degrees Celsius.
A-2
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B Formulas and problems
SYMBOLS
A = Area L = Length V = Volume
B = Base (length of) P = Perimeter Vel = Velocity
C = Circumference Q = Flow W = Width (length of)
D = Diameter R = Radius TT = Pi = (3.14)
H = Height (length of) S = Side (length of) / = Per (as gallons/day)
LENGTH CONVERSION FACTORS
1 foot = 12 inches
1 yard (yd) = 3 feet (ft)
1 rod = 51/2 yards = 161/2ft
1 chain = 4 rods = 66 ft
1 mile = 5,280 feet = 1,760yds
1 nautical mile = 6,076 feet
.001 kilometer = 1 meter = 100 centimeters =
1,000 millimeters
AREA CONVERSION FACTORS
1 square foot (ft2 ) = 144 sq inches (inch2 )
1 square yard (yd2 ) = 9 sq ft (ft2 )
1 square rod (rd2 ) = 272% sq ft (ft2 )
1 acre = 43,560 sq ft (ft2 )
= 4,840 sq yds
1 square mile = 640 acres or 1 section
1 hectare = 10,000 square meters =
0.1 square kilometers
CALCULATION OF AREAS
1. Square of Rectangle = L x W
2. Triangle = 1/2 B x H
o -r -_j (Bl + 62 ) X H
o. Trapezoid «
4. Circle: a. A = TT R2
h A 7r°2
A
c. A = 0.785 D2
B-1
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CALCULATION OF VOLUMES
VOLUME CONVERSION FACTORS
1 cubic foot (ft3) - 1,728 cu in (in3)
7.5 gallons
1 cubic yard (yd3) - 27 cu ft (ft3)
1 acre- foot = 43,560 cu ft (ft3)
= 325.851 gallons
1 gallon (gal) = 231 cu in (in3)
4 quarts
0.001 cubic meters =1 liter =1,000 cubic
centimeters ^=1,000 milliliters
1. Rectangular Solids V =L x W x H
2. Cylinders: a. V = 7rR2 x H
b. V = 0.785 D2 x H
TrD2 x H
c.
3. Cones
v=-
7TR2 X H
4. Pyramids V = A* H (A = Area of Base)
O
WEIGHT CONVERSION FACTORS
1 gal = 8.34 Ibs of water
1 cu ft = 62.4 Ibs of water
1 ft of water = 0.434 psi
0.001 kilograms (kg) = 1.0 g= 1,000mg
1 ton (metric) = 1,000kg
1 psi
1
ft
0.433
= 2.31 ft of water
VELOCITY
1. Velocity
Distance
Time
i u mile
a. mile per hour =7-
b.
c.
ft per min =
ft per sec =
feet
minute
feet
second
Velocity (ft per sec)
Flow Rate (ft3 per sec)
Cross Sectional Area (ft2)
2. Gal per min (gpm)
= cu ft per sec x 60 sec per min
x 7.5 gal per ft3
OR
gpm =ft3 per sec x 60 sec per min
x 7.5 gal per ft3
VELOCITY CONVERSION FACTORS
1 cu ft per sec (cfs) = 7.5.gal per sec (gps).
- 450 gal permin (gpm)
1 gal per sec =0.133 cu ft per sec (cfs)
= 7.98ft3 permin
B-2
-------
COMMONLY USED FORMULAS
1. Gal/day (gpd) = gal/min (gpm)
x 1,440m in/day
= gal/hr (gph)
x 24 hrs/day
2. Million Gal/Day (mgd) = 1
4.
gpd
1,000,000
3. Pounds/Day (Ibs/day)
(BOD,TSS,SVS,CI2,etc.)
Ibs/day = milligrams/liter
x million gal/day
x 8.34 Ibs/gal
OR
Ibs/day = mg/L x mgd
x 8.34 Ibs/gal
OR
Ibs/day = population equivalent
x population equivalent
factor
Population Equivalent
(BODorTSS)
_ Daily Loading in Pounds
Population Equivalent Factor
5. Volume in Gallons
a. Rectangular Tank
V=LxWxHx7.5 gal/ft3
b. Circular Tank
V = 7rR2 xHx7.5 gal/ft3
V = 0.785D2 x H x 7.5 gal/ft3
9.
(influent - effluent)
fp ,
of Removal)
x 100
Organic Loading on Primary Cell
_ influent Ibs of BQD/day
acres (primary)
Storage Volume of a Pond
= avg surface area (ft2 )
x design operation depth (ft)
x 7.5 gal/ft3
Daily Rise in Inches
total flow/day (gal)
= x design operating depth (inches)
volume of pond (gal)
B-3
-------
SAMPLE PROBLEM
CALCULATIONS
A. Find the Operating Surface Area of Pond
(Acres)
Surface Area in Sq Ft (SF)
= Lx W
= 424' x 624' = 264,576 SF
One Acre
= 43,560 SF
Area
= 264,576 SF -4- 43,560 SF/Acre
= 6.07 Acres
Answer
= 6.07 Acres
Rounded Off
= 6.1 Acres
(SLOPE 3:1)
rr! _ J
PROFILE
Essential Data:
Avg Influent Flow Rate
Avg Influent BODs
Avg Effluent BODs
Population Served
Industry Served
= 250,000 gpd
380 mg/L
190mg/L
2,000 persons
= One
(BOD unknown)
B. Find the Volume of Pond (Gallons)
Volume = L x W x d
Since the pond has sloped sides, the
cross-horizontal area decreases with
depth. To calculate the volume of the
pond, the average horizontal area is
required.
Average Horizontal Area
_ Surface (area) + Bottom (area)
2
Surface A = 264,576 SF
Bottom A = 600 x 400 = 240,000 SF
A A 264,576 SF + 240,000 SF
Avg Area = ' = '
= 252,288 SF
V = h
-------
C.
D.
E.
F.
Calculate the Pounds of BODs /Day
(Influent)
Ibs BOD/day
= 8.34 x concentration (ppm)
x flow (mgd)
= 8.34 x 380 x 0.25
= 792 Ibs/day
Calculate the Removal Efficiency
(Based on BOD Reduction)
P«. . _ BOD in - BOD out
Eff.c.ency - - -
x 100%
_ 380mg/L- 190mg/L
380 mg/L
x 1 00%
= 50%
Calculate the Organic (BOD) Loading
(Ibs BOD/Acre/Day)
Loading = Ibs BOD/day
-T- Surface Area (Acres)
= 792- 6.1 = 130
= 130 Ibs BOD/Acre/Day
Note: Most stabilization ponds are
designed for an organic loading of
15-30 Ibs BOD/acre/day-this pond
is overloaded at 130 Ibs BOD/acre/day.
Calculate the Population Loading
(Number of Persons/Acre)
Population Loading
= 2,000 persons -=- 6.1
= 328 persons/acre
G. Find the Population Equivalent
Because industry increases the strength
of the waste by adding organic materials,
it is sometimes desirable to determine
the equivalent population served, or the
number of people that would be equal
to the industry's effect.
Assume equivalent organic loading
= 0.2 Ibs BOD/day/person
Total number Ibs BOD arriving at pond
= 792 Ibs/day
Equivalent population
= 792 Ibs BOD/day
-7- 0.2 Ibs BOD/person/day
= 3,960 persons
There are only 2,000 persons being
served by this pond but because of the
industry, the bond is being loaded as if
there were 3,960 persons contributing
waste. In essence, the industry load is
equivalent to 3,960 minus 2,000 = 1,960
persons.
H. Theoretical Retention Time (Days)
Time
= Volume of Pond
-i- Average Daily Flow
= 7.6 mg H- .25 mgd
= 30.4 days
Note: Most stabilization ponds are
designed for a population loading of 100
persons per acre. The population lo ad-
ing in this example does not indicate as
severe an overload condition as does the
BOD loading figure. This is due to the
fact that industry is adding organic
material, thus increasing the BOD load-
ing, but the contributing population
remains the same.
B-5
-------
C Flow measuring devices
RUNNING TIME OF PUMPS IN A
LI FT STATION
Flow is calculated by multiplying the total
minutes logged on each pump by the volume
the pump will pump in one minute. The vol-
ume that the pump can pump in one minute
can be computed as shown below.
(in sq ft)
(in ft)
area of tank x change in level x 7.5
: 3 -: = gpm
minutes pumped
Example:
(25 sq ft) x (3 ft) x 7.5 =
41 minutes ^
Measure Change in Level of a Tank (Wet Well)
Being Pumped in a Measured Time
Knowing the pumping rate in gallons per
minute, records can be maintained as in the
following table in order to calculate the
daily flow.
PUMP RUNNING TIME AND FLOW RECORD
DATE
Date
Start
1
2
3
4
5
6
PUMP NO. 1
Reading
(Hours)
00.0
12.2
25.7
39.7
50.9
Minutes
(Hours x 60)
0
732
1,542
2,382
3,054
Minutes/
Day
-
732
810
840
672
PUMP NO. 2
Reading
(Hours)
0.0
17.5
33.5
51.5
68.1
Minutes
(Hours x 60)
0
1,050
2,010
3,090
4,086
Minutes/
Day
-
1,050
960
1,080
996
Total
Mins.
1+2
0
1,782
1,770
1,920
1,668
(Gal)
Minutes
-
13.9
13.9
13.9
13.9
Flow
(Gal)
-
24,769
24,603
26,668
23,185
C-1
-------
2.5 H
H (HEAD)
2.5 H
CREST
NAPPE
\
3" MIN
AIR SPACE
DOWNSTREAM
V-NOTCHWEIR 1.
The weir has the advantage of simplicity. To
determine flow it is only necessary to measure 2.
the head of water above the crest of the weir.
The sharp-crested weir may be a metal plate
up to 1/4" (6 mm) in thickness. V-notch
flow measurement weirs are usually construct-
ed with either a 60-degree or 90-degree notch.
The 60-degree V-notch weir is generally in-
stalled for measuring flows in the lower
ranges. 3-
The V-notch beveled weir is usually installed
in a concrete flow structure which allows grit
and heavy organic solids to settle out. This
creates a condition that requires frequent
cleaning and flushing of the flow channel.
The V-notch of the weir catches and holds 4.
trash and debris. This requires frequent clean-
ing. The edges of the notch of the weir
should be beveled on the downstream side to
form a "sharp" crest or edge of about a 45-
degree or more angle on the upstream side. 5.
Confirm angle of "V" notch.
The measurement of head on the weir
should be taken as the difference in ele-
vation between the notch and the water
surface at a point upstream from the
weir a distance of at least 2 times and
preferably 4 times the maximum head
on the crest.
Liquid depth below crest should be at
least 2.5 x head. The distance from the
sides of the weir to the sides of the ap-
proach channel should never be less than
2H, where "H" is the head of the water
above the notch.
Liquid downstream of weir plate should
be no higher than 3" below crest of weir.
Air should circulate freely both under
and on the sides of the nappe.
Flow over weir is related to head (H)
reading.
Example: 90-degree V-Notch Weir
1-1/2" head
From table flow would be
6.05 gpm.
C-2
-------
DISCHARGE FROM TRIANGULAR V-NOTCH WEIRS
Head
(H)
in
Inches
1
1-1/4
1-1/2
1-3/4
2
2-1/4
2-1/2
2-3/4
3
3-1/4
3-1/2
3-3/4
4
4-1/4
4-1/2
4-3/4
5
5-1/4
5-1/2
5-3/4
6
6-1/4
6-1/2
Flow
Per
90°
Notch
2.19
3.83
6.05
8.89
12.4
16.7
21.7
27.5
34.2
41.8
50.3
59.7
70.2
81.7
94.2
108
123
139
156
174
193
214
236
in Gallons
Minute
60°
Notch
1.27
2.21
3.49
5.13
7..16
9.62
12.5
15.9
19.7
24.1
29.0
34.5
40.5
47.2
54.4
62.3
70.8
80.0
89.9
100
112
124
136
Head
(H)
in
Inches
6-3/4
7
7-1/4
7-1/2
7-3/4
8
8-1/4
8-1/2
8-3/4
9
9-1/4
9-1/2
9-3/4
10
10-1/2
11
11-1/2
12
12-1/2
13
13-1/2
14
14-1/2
Flow
Per
90°
Notch
260
284
310
338
367
397
429
462
498
533
571
610
651
694
784
880
984
1,094
1,212
1,337
1,469
1,609
1,756
in Gallons
Minute
60°
Notch
150
164
179
195
212
229
248
267
287
308
330
352
376
401
452
508
568
632
700
772
848
929
1,014
C-3
-------
DISCHARGE OVER RECTANGULAR WEIR WITH STANDARD END CONTRACTIONS
DISCHARGE -- GALLONS PER MINUTE (gpm)
Head
(H)
Inches 2
1/4
1/2
3/4
1
1/4
1/2
3/4
2
1/4
1/2
3/4
3
1/4
1/2
3/4
4
1/4
1/2
3/4
5
1/4
1/2
3/4
6
1/4
1/2
3/4
7
1/4
1/2
3/4
8
1/4
1/2
3/4
9
1/4
1/2
3/4
10
1/2
Length of Weir (L)
Inches
10 12 15 18
24
36
60
2
4
8
12
17
22
28
34
2
6
12
18
25
33
42
51
61
71
82
93
3
9
16
24
33
44
55
68
81
95
109
124
140
157
174
190
4
11
19
30
42
55
69
85
101
118
136
155
176
197
218
239
262
285
310
334
5
13
23
36
50
66
83
101
121
142
164
187
210
235
261
287
314
343
374
403
433
464
496
528
6
16
29
45
63
83
104
127
152
178
205
233
264
294
326
358
392
429
465
500
540
580
620
660
701
743
785
830
875
920
7
19
35
54
76
99
124
152
183
213
246
280
316
353
392
431
472
515
559
605
650
695
745
791
842
893
934
1,000
1,050
1,100
1,160
1,210
1,270
1,340
1,400
1,460
10
26
46
72
100
132
166
202
242
284
328
374
420
470
522
574
628
686
748
806
866
928
992
1,050
1,120
1,190
1,260
1,330
1,400
1,470
1,540
1,620
1,700
1,780
1,860
1,940
2,020
2,100
2,180
2,270
2,450
108
150
197
248
303
363
426
492
561
630.
705
783
861
942
1,030
1,120
1,210
1,300
1,390
1,480
1,850
1,680
1,790
1,890
1,990
2,100
2,200
2,310
2,430
2,550
2,670
2,790
2,910
3,030
3,150
3,270
3,400
3,680
180
250
330
415
505
605
710
820
935
1,050
1,180
1,310
1,430
1,570
1,710
1,860
2,010
2,160
2,320
2,480
2,640
2,800
2,980
3,150
3,320
3,500
3,680
3,850
4,050
4,250
4,450
4,650
4,850
5,050
5,250
5,450
5,670
6,120
C-4
-------
PARSHALL FLUME
The parshall measuring flume is widely used
to measure sewage flows because of its sim-
plicity and its freedom from difficulties with
sand or suspended solids.
The head over the crest of a Parshall Flume
can be measured by placing a gauge stick in
the sewage at the float in the flow channel or
at the pipe leading to the float well and then
taking a reading off the free-flow discharge
chart.
,WELL
ij/
L
GAUGE
DIRECTION OF FLOW
4
GAUGE
LEVEL FLOOR
SECTION
FREE FLOW DISCHARGE - PARSHALL FLUME GALLONS PER MINUTE
Head in
Inches
1-3/16
1-13/16
2-3/8
3
3-5/8
4-3/16
4-13/16
5-3/8
6
6-5/8
7-3/16
7-13/16
8-3/8
9
9-5/8
10-3/16
10-13/16
11-3/8
12
13-3/16
14-3/8
15-5/8
3 Inches
10.3
22.4
36.7
51.6
69.0
68.0
104.0
130.0
152.0
180.0
202.0
233.0
257.0
294.0
315.0
357.0
378.0
420.0
448.0
6 Inches
22.4
44.9
71.6
103.3
139.2
175.1
215.5
260.0
310.0
359.0
413.0
467.0
525.0
588.0
651.0
714.0
781.0
853.0
925.0
1,077.0
1,234.0
1,400.0
9 Inches
40.0
76.3
116.9
166.1
219.9
278.0
341.1
404.0
476.0
552.0
628.0
714.0
799.0
889.0
978.0
1,073.0
1,171.0
1,274.0
1,377.0
1,594.0
1,822.0
2,060.0
12 Inches
157.1
219.9
287.3
359.0
444.3
534.0
624.0
727.0
826.0
934.0
1,046.0
1,158.0
1,280.0
1,400.0
1,530.0
1,661.0
1,795.0
2,074.0
2,370.0
2,675.0
18 Inches
229.0
318.7
422.0
534.0
659.0
790.0
925.0
1,073.0
1,225.0
1,387.0
1,553.0
1,728.0
1,912.0
2,096.0
2,289.0
2,491.0
2,692.0
3,119.0
3,564.0
4,035.0
If readings are to be recorded in gallons per day, multiply the answer in gpm by 1440.
C-5
-------
Sample Calculations for Compositing
If the average flow rate is 50,000 gpd, the
flow in gpm is:
50,000 gpd _ -,,
1,440min/day = 35 gpm
Size of composite sample needed = 2,500 to
3,000 ml (sample size is dependent on type
of test run).
A.
B.
Average size of sample for 24-hour
composite (24 samples, each taken on
the hour):
2 500 to 3,000 ml =105to125m|
24 hourly samples
Sizing an individual sample based on the
rate of flow at that instant:
105 to 125ml
35 gpm
= approx. 3 to 4 ml/gpm
Example: Flow rate = 30 gpm;
Sample size = 4 x 30 = 120 ml
Note: It is safer to take too much than
not enough, 504 ml/gpm is used. After
thoroughly mixing the total combined
sample, the excess amount can be
discarded.
Average size of sample for NPDES com-
posite (four 2-hour samples for an 8-hour
composite, samples taken at 10 a.m.,
12 noon, 2 p.m., and 4 p.m.):
2,500 to 3,000 ml
Four 2-Hour Samples
= 625 to 750 ml
Sizing an individual sample based on the
rate of flow at that instant. Consider
that daytime flow rates will usually be
greater than the average daily flow rate.
Estimate that the daytime flow rate is
approximately 40 gpm:
625 to 750 ml
40 gpm
= approx. 16 to 19 ml/gpm
Note: In this case, you might want to
take 20 ml/gpm since this is an easier
number to multiply by.
Example: Flow rate = 50 gpm;
Sample size = 20 x 50 = 1,000 ml
C-6
-------
D Design considerations
from an operation and
maintenance viewpoint
Operating experience at many pond installa-
tions shows the need to pay attention to
several important areas when designing ponds
for optimum operational control.
Conservative design in this instance should re-
flect operational flexibility above that re-
quired at the moment. These considerations
should include:
1. The capability to move water around
within the system. The advantages
of this provision include premixing
the pond's contents with the incom-
ing wastewater which provides oxy-
gen to the incoming waste and as-
sures a more completely mixed
environment in the feed zone area.
Two methods are available; using
portable pumps or pond recircula-
tion. The latter has been success-
fully used in California.
2. The use of multiple inlets and outlets
to improve pond circulation.
3. The use of interpond transfer pipes
with valves or gates to permit indi-
vidual pond level control and to re-
distribute loading. This interpond
flexibility will permit the operator
to operate cells at those water levels
which will give the best treatment.
Operators with this capability will
need to experiment with pond levels
until the best plant effluent is ob-
tained. For example, a primary cell
might operate best at an 8-foot water
depth, while the final cell is 3 feet.
4. A well-designed outlet structure
which will permit control of pond
depths and also the rate of discharge.
5. The use of reliable continuous-flow
measuring devices such as V-notch or
Cipoleti weirs or float-actuated
electrically-timed recorders.
D-1
-------
E Case histories
CASE 1 - COLORADO
This plant in Colorado was visited because of
rock filter built for algae removal. Filter will
be discontinued because it does not work.
General impression of plant was that it was
poorly-attended, if at all. Although a new
facility, it had a goodly start on water weed
growth but no cover on dikes. Dikes were
showing signs of erosion. Algae growth in
ponds OK.
Plant was designed for continuous discharge
but had not needed to do so yet.
The filter will be abandoned because of plug-
ging. Rock size too small, ranging from 2" to
sand. Filter was uncovered and odorous.
Evidence of spiders and midges.
SCUM 3".6"
DARK
ANAEROBIC
IN SERIES
\\
O\ 0
0 0
\
\
AERATED
POND
\
X
A;.
&'
.-$
<
SUBMERGED
ROCK ,, _
FILTER \ /7^r\ /
1 CHLORINE
MLSS 3500 4000
> CONTACT
FINAL
POLISHING
CELL
E-1
-------
CASE 2 - COLORADO
Another plant in Colorado also has a different
rock filter following the last cell and prior to
chlorination.
This filter has an air blower used to keep the
filter aerobic. However, the filter is not work-
ing, again due to plugging problems.
General comment on both filters would be to
use larger rock (5 to 6" in diameter) as deter-
mined by O'Brian. Reference No. 6.
FORCE MAIN
1 1
>*
i i
OFFICE &
LAB
-°°H
CARBON &
GRAVEL
FILTER
NON-AERATED
CASE 3 - COLORADO
This system shows evidence of being well run
by a Certified IV Operator. Good algal
growth in both ponds. Cells do not have the
capability to control or vary the water level.
Plant is continuous discharge into a nearby
river. The lagoon receives both domestic sew-
age and pretreated industrial waste from a
Kodak plant.
Domestic waste is discharged into the primary
aerated cell, then into the secondary cell. The
secondary cell also receives Kodak waste. Ef-
fluent is chlorinated prior to discharge. The
effluent shows evdience of a high solids carry-
over (algae).
CASE 4 - COLORADO
Although this is a larger plant combining ex-
tended aeration and an oxidation pond sys-
tem, it deserves a discussion because it is a
well-run facility meeting its NPDES discharge
requirements. Undoubtedly, its reason for
success is that the operator knows the basics
of the process and it is well attended. Daily
operation and maintenance schedules are in
force and carefully adhered to. An estab-
lished wasting and lab testing program is also
followed.
CASE 5 - COLORADO
(Anaerobic/Aerobic Lagoon)
This complex treats animal wastes from a live-
stock feed lot and the treated effluent is used
for field irrigation. The raw waste enters an
influent diversion structure, then flows
through two anaerobic lagoons in series. The
effluent is discharged into a complete-mix
activated sludge process consisting of two
aerated basins and two final clarifiers. Ef-
fluent from the clarifiers is discharged into a
E-2
-------
polishing lagoon. Return sludge is about
10,000 to 12,000 mg/l_: Excess sludge rang-
ing from 20,000 to 40,000 mg/L is pumped
to a sludge holding basin. The solids level
in the aerator is held between 3,500 and
4,000 mg/L.
A good scum blanket existed on both anaero-
bic ponds and there was an absence of bad
odors. Operators said, however, that severe
odors developed when starting a new pond.
This condition held until a scum blanket was
formed, usually about 1 month.
CASE 6 - COLORADO
The operator of this plant has an operational
checklist that is worth mentioning. The treat-
ment system is an oxidation ditch followed
by lagoons as shown in the figure.
Daily Operational Checklist
1. Checks comminutor for operation to
make sure nothing is clogged.
2. Reads flowmeter, checks press and re-
winds (sets totalizer to 76,000) at 11:00
a.m. each day.
3. Checks second bar screen and cleans.
Takes screenings to small landfill.
4. Checks and lubricates each cage aerator.
5. Checks sludge blanket.
6. Inspects cells.
7. Takes samples at outfall manhole and
influent structure. Performs tests.
8. Checks CI2 feed rate. Keeps it between
7 and 12lbs/day.
Other Duties
1. Wastes (2 times per week).
2. Isolates comminutor, greases, flushes
comminutor and channel return to
service.
3. Mows dike grass, pulls weeds.
4. Counts number of threads on valve stem
when changing flow pattern.
FLOWMETER
(STEVENS)
WORTHINGTON
COMM.
r BY-PASS
CASE 7 - KANSAS
An overload in the primary cell was corrected
by diverting all flow into Cell No. 2 and rout-
ing water from Cell No. 3 back to the primary
cell for additional oxygen and dilution.
Low DO, following melting of the ice cover,
was corrected by adding 50 to 100 pounds of
sodium nitrate per acre.
E-3
-------
CASE 8 - KANSAS
Anaerobic conditions in the primary cell were
corrected by diverting part of influent flow
into the second cell and adding water to keep
both cells above a 3' level. Duckweed growth
is controlled by applying 2-4D in oil solution.
CASE 9 - KANSAS
Excessive foam in aerated pond, which was
corrected by adding 1 quart of coconut oil.
CASE 10-CALIFORNIA
Algae Control Using Phase Isolation
The facility at Woodland, California, has suc-
cessfully shown that algae can be removed
from the final discharge cell by starving it.
The following represents their conclusions
and observations.
Summary and Conclusions
Based upon 15 months of successful field
scale operation, during which an average of
1.2 mgd has been treated to exceed the 1977
discharge requirements for BOD and suspend-
ed solids, it can be justifiably stated that the
concept of "phase isolation" works under
Woodland conditions.
It was not the scope of this investigation to
ascertain why it works, but only if it does
work. It appears that the reasons as to why it
works are quite complex and is a fit subject
for investigation by someone with sufficient
technical resources.
Observations
1. Spectrophotometer determinations for
suspended solids correlates reasonably
well with "Standard Methods" in the
upper range, but gives an "optimistic"
low reading in the low range. However,
a low reading on the Spectrophotometer
shows that it is the proper time to start
testing by "Standard Methods." A plant
operator, by viewing the phase isolation
effluent in a glass jar, can rapidly learn
when it is time to start laboratory tests
because of its clarity.
Low suspended solids measurements and
low BOD measurements generally ac-
company each other and when they do
not, it was always proved to be a lab-
oratory error.
During periods of rainfall or high wind,
the colloidal silt of the unlined ponds
would give a "high" reading on the sus-
pended solids. A large population of
waterfowl would also cloud the contents
of the pond because of their bottom
feeding habits.
Waterfowl and shorebirds preferred the
phase isolation pond and the pond into
which it discharged over the adjacent
four 12-acre facultative ponds.
Attached filamentous algae at times ob-
scured as much as 85 percent of the sur-
face of the phase isolation pond, but
caused no difficulty - in fact, the pond
appeared to clear up quicker under these
conditions. Filamentous algae and sus-
pended algae do not appear to be com-
patible and generally it was observed
that one excludes the other.
The algae precipitate out more rapidly
on some occasions than on others. The
fastest clearing up time was 2 days after
shut-off of influent. At times the algae
would not mix with the residual con-
tents of the phase isolation pond, but
would precipitate in the vicinity of the
influent discharge pipe.
E-4
-------
7. During the phase isolation period, inflow
must be absolutely and totally shut off.
A small leak can sustain the algae bloom
in the pond and in every instance when
the pond did not seem to be clearing as
rapidly as was expected, it was found
that leaking influent was the cause.
Once the leak was stopped, the pond
then got back on schedule.
8. Inflow and discharge should be accom-
plished in as short a time as practical to
minimize pond area needs and to hasten
the clearing of the pond.
Summary
Extremely good effluent has been obtained
from the pond receiving overflow from the
facultative ponds even though algae content
of the influent has been high. The secret
seems to be in taking advantage of a cycle the
final pond goes through when the algae settles
out leaving effluent with a quality that is well
within the regulatory limits of 30/30,
BOD/SS.
The facultative ponds with approximately 60
days detention time discharge into the final
pond until the level is 3 to 4 feet deep. Flow
is stopped and the condition of the contents
are observed until maximum clarity is reached
then the pond is drawn down to a level about
2 feet deep and the cycle is repeated.
By using this system, effluent quality has
been measured at 4 mg/L BOD and 12 mg/L
SS for sustained periods. The cycle for dis-
charging has varied from a minimum of 4 days
to approximately 20 days. More information
on this project is given in an article in Water
and Sewage Works, December 1975, p. 42.
E-5
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F Metric equivalents
METRIC CONVERSION TABLES
Recommended Units
Description
Length
Arta
Volume
Man
Time
Force
Unit
meter
kilometer
millimeter
centimeter
micrometer
square meter
tquere kilometer
square centimeter
square millimeter
hectare
cubic meter
cubic tint, meter
liter
kilogram
gram
milligram
tonne
cond
day
year
newton
Symbol
m
km
mm
cm
Mm.
m*
km2
cm'
mm'
ha
m3
cm3
1
kg
g
mg
t
s
dey
yr or
N
Comments
Basic SI unit
The hectere (10.000
m2) is e recognised
multiple unit end
will remain in inter-
national use.
The liter is now
recognised as the
special name for
the cubic decimeter
Basic SI unit
1 tonne- 1.000kg
Basic SI unit
Neither the day nor
the year is an SI unit
but both are impor-
tant.
The newton is that
force the! produces
en ecceleretion of
1 m/$2 in e mess
of 1 kg.
English
Equivalents
39.37 in. > 3.28 II-
1.09yd
0.62 mi
0.03937 in.
0.3937 in.
3337 X 103-103A
10.744 sq ft
= 1.196 to. yd
6.384 sq mi
247 ecres
0.155 sq in.
0.00155 sq in.
2.471 acres
35.314 cu ft
1.3079 cu yd
0.061 cu in.
1.057 ql 0.264 gal
0.81 XlO-'acre-
ft
2.205 Ib
0.035 os> 15.43 gr
0.01543 gr
0384 ton (long)
1.1023 ton (short)
0.22481 Ib (weight)
7.5 poundals
Rrcummrndrd Units
Description Unit
Velocity
linear meter per
second
millimeter
per second
kilometers
per second
engutar radians per
second
Flow (volumetric) cubic meter
per second
liter per second
Viscosity poise
Pressure newton per
square meter
kilonewton per
square meter
kilogram (force)
per square
centimeter
Temperature degree Kelvin
degree Celsius
Work, energy, joule
quantity of heat
kilo joule
Power well
kilowatt
joule per second
Symbol
m/s
mm/s
km/t
rad/t
m3/t
l/s
poise
N/m>
kN/m2
kgf'«»J
K
C
J
U
W
kW
J/s
Comments
Commonly called
Ihecumec
The newton is not
yet well-known as
the unit of force
and kgl cm2 will
dearly be used for
some time. In this
field the hydreulic
heerj eMpressad in
meters is en accept-
able ellernelive.
Bask- HI unit
The Kelvin end
Celsius degrees
are identical.
The use of the
Celsius scale is
recommended es
it is the former
centigrede scale.
1 joule 1 N-m
1 watt - 1 J/s
English
Equivalents
3.26 Ips
0.00328 fps
2.230 mph
15.650 gpm
2.120 cfm
15.85 gpm
O.OC72/lb'
tec ft
0.00014 psi
0.145 psi
14.223 psi
9F - »"
2.778 X lO'7
kwhr
3.725 X 10-'
hp-hr 0.73756
h-lb 9.48 X
10-« Blu
2.778 kw-rtr
F-1
-------
Application of Units
Application of Units
Description
Precipitation,
run off.
evaporation
River flow
Flow in pipes.
conduit t.crtan
nels. over weirs.
pumping
Discharges or
abstractions.
yields
Usage of water
Density
Unit
millimeter
cubic meter
per second
cubic meter per
second
liter per second
cubic meter
per day
cubic meter
par year
liter per person
per day
kilogram per
cubic meter
Symbol
mm
m3/s
m3/s
l/s
m3/day
m3/yr
I/person
day
kg/m3
English
Comments Equivalents
For meteorological
purposes it may be
convenient to meas-
ure precipitation in
terms of mass/unit
area (kg/m3).
1 mm of rain *
1 kg/sq m
Commonly called 35.314 cfs
the cumec
15.85gpm
1 l/i - 86.4 m3/day 1.83X10-3gpm
0.264 gcpd
The density of 0.0624 Ib/cu ft
water under stand-
ard conditions is
1,000 kg/m3 or
1,000g/l
Description
Concentration
BOO loading
Hydraulic load
pet unit area;
e.g. filtration
rates
Hydraulic load
per unit volume;
e.g. biological
filters, lagoons
Air supply
Pipes
diameter
length
Optical units
Unit
milligram per
liter
kilogrem per
cubic meter
per day
cubic meter
per square miter
per day
cubic meter
per cubic meter
per day
cubic mater or
liter of free air
par second
millimeter
meter
lumen per
square meter
Symbol Comments
mg/l
kg/m3 day
m3/m3 day If this is con-
verted to e
vatocity.it
should be ex-
pressed in mm/s
(1 mm/i » 86.4
m3/m2 day).
m3/m3day
m3/i
l/s
mm
m
lumen/m^
English
Equivalents
1 ppm
0.0624 Ib/cu It
day
3.28 cu ft/sq ft
0.03937 in.
39.37 in. «
3.28 ft
0.092 ft
candle/sq f I
ft U.S. GOVERNMENT PRINTING OFFICE: 1975-630-902
F-2
-------
G References and suggested
resource material
1. Stabilization Pond Operation and
Maintenance Manual
Minnesota Pollution Control Agency
1935 West County Road B2
Roseville, Minnesota 55113
2. Operating Waste Stabilization Ponds -
Course Manual for Operator Training
EPA No. T0077046-01
Iowa Department of Environmental
Quality
Kirkwood Community College
Cedar Rapids, Iowa
3. Palmer, C. Mervin, Algae in Water Sup-
plies: An Illustrated Manual on the
Identification, Significance, and Control
of Algae in Water Supplies, PHS Pub.
657, Robert A. Taft Sanitary Engineer-
ing Center, Cincinnati, Ohio, reprinted
1962, 93 pp. National Technical Infor-
mation Service Number PB 216 459.
4. Operation of Wastewater Treatment
Plants (Chapters 9, 13 and 14)
Department of Civil Engineering
Sacramento State College
6000 Jay Street
Sacramento, California 95819
5. Wastewater Treatment Ponds
EPA 430/9-74-011
6. Upgrading Waste wa ter Stabiliza tion
Ponds to Meet New Discharge Standards
(Pages 15, 21, 31 and 8)
7.
8.
Proceedings of a Symposium at Utah
State University, 1974
Utah Water Research Laboratory
College of Engineering
Utah State University
Logan, Utah 84322
Standard Methods for the Examination
of Water and Wastewater, 14 Edition
(Note algae plates in color.)
Water Pollution Control Federation
2626 Pennsylvania Avenue, Northwest
Washington, D. C. 20037
Manual of Wastewater Operations
(Chapters 16 and 21)
Texas State Department of Health
Austin, Texas
G-1
-------
H Plants visited
Lafayette, Oregon
Dundee, Oregon
Bay City, Oregon
Greeley, Colorado
Windsor, Colorado
Louisville, Colorado
Sunnyvale, California
Woodland, California
Modesto, California
Polishing ponds
following a pack-
age plant.
Two-cell stabiliza-
tion pond.
Two-cell stabiliza-
tion pond.
Two-cell anaerobic
pond followed by
a complete-mix
activated sludge
plant, plus a sludge
lagoon and a pol-
ishing pond.
Two-cell stabiliza-
tion pond.
Four-cell polishing
pond following an
extended aeration
facility.
Waste stabilization
pond followed by
an algae removal
system which in-
cludes air flotation
and multi-media
filters.
Oxidation ponds
utilizing phase iso-
lation for algae
removal.
Oxidation ponds.
Turlock, California
Eudora, Kansas
Shawnee County, Kansas
Topeka Truck Plaza,
Kansas
Shawnee County Sewer
Dist. No. 8, Kansas
City of Topeka, Kansas
(Pauline Plant)
Oxidation ponds.
Three-cell stabiliza-
tion pond.
Two-cell stabiliza-
tion pond.
Aerated lagoon
ahead of stabiliza-
tion pond.
Two-cell aerated
pond.
Three-cell stabiliza-
tion pond.
H-1
-------
\~ S
»Cv (/^-\ C-Cv
VW**'
C OL.
-------
J Checklist form
Frequency
Operational and Preventive Maintenance
Daily
Wk.
Mo.
3 Mo.
6 Mo.
Yearly
As
Necessary
J-1
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