2. WASTEWATER
-Wastewater contains the waste products, excrement, or other
discharge from the bodies of human beings or animals, and other noxious or
poisonous substances that are harmful to the public health, or to animal or
aquatic life, or to the use of water for domestic water supply or for recreation.
- It is a combination of the liquid and water-
carried wastes from residences, commercial
buildings, Industrial plants, and institutions,
together with any groundwater, surface water and
Storm water that has infiltrated the public sewage
System.
4. Domestic Wastewater
-Wastewater from residences, apartments, motels, office buildings, and other
similar type of building. There are two types of domestic water: gray water
and black water.
Gray water is wastewater that typically
contains the residues of washing
processes. It is generated in the
bathtub, shower, sink, lavatory, and
clothes washing machine.
Black water is wastewater that
contains fecal matter and urine. It is
produced in water closets (toilets),
urinals, and bidets.
5. Commercial Wastewater
Commercial wastewater is nontoxic, nonhazardous wastewater from
commercial and institutional food service operations and beauty salons. It
is usually similar in composition to domestic wastewater, but may
occasionally have one or more of its constituents exceed typical domestic
ranges.
6. Industrial Wastewater
Industrial wastewater is process and nonprocess wastewater from
manufacturing, commercial, laboratory, and mining operations, including
the runoff from areas that receive pollutants associated with industrial or
commercial storage, handling, or processing.
7. Wastewater Constituents
Wastewater is mostly water by weight.
Wastewater released by residents, business, and industries is
approximately 99.94% water. Only about 0.06% of the wastewater is
dissolved and suspended solid.
The wastewater constituents of most concerns are those that have
the potential to cause disease or detrimental environmental effects.
These include the following:
•Organisms •Inorganics
• Pathogens • Nutients
• Organic Matter • Solids
• Oil and Grease • Gases
8. On-Site Sewage Treatment(OSST)
On-site sewage treatment (OSST) systems, traditionally called septic
systems, usually consist of the building sewer, which leads from the
building into a septic tank and then into a distribution box that feeds the
fluid (effluent) into a drainage field or disposal field.
OSST systems treat wastewater from
rural and suburban homes, mobile
home developments, apartments,
schools, retail facilities, and
businesses that do not have access
to a community wastewater
treatment and disposal system.
9. An OSST system consists of a primary treatment component, such as a
septic tank, and a disposal component, which is typically the drainage
field.
Household and human wastes flow
in a pipe from the building’s
sanitary drainage system to the
septic tank.
Inside the septic tank, anaerobic
and aerobic bacteria convert the
waste into minerals, gas and liquid
waste called the effluent
Clarified effluent leaves the septic
tank and flows in a pipe to a
drainage field.
10. Primary Treatment Equipment
Wastewater from a building is first treated in primary
treatment equipment such as tanks or filters. In the
primary treatment process, anaerobic digestion and
settlement of solids in wastewater takes place.
11. Septic Tank
The septic tank is a watertight, covered container designed to settle out and
hold solid wastes and partially treat wastewater with beneficial bacteria.
It allows heavier solids to settle
to the bottom of the tank and
lighter particles such as grease
and soap float to the top of the
tank.
The lighter particles form a
layer known as the scum
The remaining solids
accumulate as sludge in the
bottom of the tank
12. Aerobic Tank
Aerobic tanks are a substitute for a septic tank. They consist of a trash
tank, an aeration chamber, and a settling chamber.
Premanufactured aerobic tanks
use wastewater treatment
processes similar to municipal
wastewater treatment
processes. The clarified effluent
is then usually discharged into
a drainage field.
13. Pump Tank
A pump tank is a watertight container used to temporarily store clarified
effluent before it flows into a drainage field.
Wastewater is first treated in an aerobic
or septic tank. The effluent then flows by
gravity into the pump tank.
When the level of stored effluent reaches
a preset elevation, a float switch turns
on the pump. The pump discharges the
effluent to the drainage field several
times a day.
Pump tank materials are typically
concrete; plastic (fiberglass and
polyethylene) tanks are also used.
14. Sand Filters
A sand filter is a lined, impermeable container containing a bed of
granular material that provides additional treatment of effluent as it flows
from the primary treatment tank to the drainage field. They are usually
placed underground with the top surface covered with grass. At sites that
have near-surface bedrock or a high water table, sand filters are usually
constructed with aboveground concrete walls.
15. Trash/Grease Tank
A trash tank is occasionally used in conjunction with an aerobic tank. The
trash tank removes materials that treatment microorganisms are unable to
degrade.
Grease tanks are used with septic and aerobic tanks, usually in
commercial applications.
16. Cesspool
A cesspool is a covered underground container that receives untreated
sewage directly from a building and discharges it into soil. Openings in
the cesspool walls allow untreated sewage to pass through and seep into
the surrounding soil.
Because of health concerns tied to the
discharge of raw sewage, use of a
cesspool is considered unacceptable
today in most applications in developed
countries.
17. Types of On-Site Sewage Treatment
1) Septic Tank Systems
This is the most common type of
on-site sewage system. It
consists of a septic tank, which
is a large underground container
where wastewater from the
building is stored and partially
treated. Heavy solids settle to
the bottom of the tank while
greases and lighter solids float to
the top. The solids stay in the
tank while the wastewater is
discharged to the drainfield for
further treatment and dispersal.
18. 2) Aerobic Treatment Unit(ATU)
Aerobic Treatment Unit use many
of the same processes as a
municipal sewage plant, but on a
smaller scale. An aerobic system
injects oxygen into the treatment
tank. The additional oxygen
increases natural bacteria
activity within the system that
then provides additional
treatment for nutrients in the
effluent. Some aerobic systems
may also have a pretreatment
tank and a final treatment tank
including disinfection to further
reduce pathogen levels.
19. 3) Mound System
Mound systems are an option in areas
of shallow soil depth, high
groundwater, or shallow bedrock. The
constructed sand mounds contains a
drainfield trench. Effluent from the
septic tank flows to a pump chamber
where it is pumped to the mound in
prescribed doses. Treatment of the
effluent occurs as it discharges to the
trench and filters trough the sand, and
then disperses into the native soil.
20. 4) Drip Disribution System
The drip distribution system is a type
of effluent dispersal that can be used
in many types of drainfields. The main
advantage of this system is that no
large mound of soil is needed as the
drip laterals are inserted into the top 6
to 12 inches of soil. The disadvantage
of the drip distribution system is that
it requires a large dose tank after the
septic tank to accommodate the timed
dose delivery of wastewater to the drip
absorption area.
21. 5) Conventional System
A decentralized wastewater treatment
system consisting of a septic tank and a
trench or bed surface wastewater
infiltration system(drainfield). A
conventional septic system is typically
installed at a single-family home or
small business.
The gravel/stone drainfield is a design
that has existed for decades. The effluent
is piped from the septic tank to a
shallow underground trench of stone or
gravel. A geofabric or similar material is
then placed on top of the trench so sand,
dirt, and other contaminants do not
enter the clean stone.
22. 6) Chamber System
This type of system consist of a series
of connected chambers. The area
around and above the chambers is
filled with soil. Pipes carry wastewater
form the septic tank to the chambers.
Inside the chambers, the wastewater
comes into contact with the soil.
Microbes on or near the soil treat the
effluent.
23. 7) Recirculating Sand Filter System
Sand filter systems can be constructed
above or below ground. Effluent flows
from the septic tank to a pump
chamber. It is then pumped to the sand
filter. The sand filter is often PVC-lined
or a concrete box filled with a sand
material. Effluent is pumped under low
pressure through the pipes at the top
of the filter. The effluent leaves the
pipes and is treated as it filters though
the sand. The treated wastewater is
then discharged to the drainfield.
24. 8) Evapotranspiration System
Evapotranspiration systems have
unique drainfields. The base of the
evapotranspiration system drainfield
is lined with a watertight material.
After the effluent enters the
drainfield, it evaporates into the air.
Unlike other septic systems designs,
the effluent never filters to the soil
and never reaches groundwater.
25. 9) Constructed Wetland System
A constructed wetland mimics the
treatment processes that occur in
natural wetlands. Wastewater flows
from the septic tank and enters the
wetland cell. The wastewater then
passes through the media and is
treated by microbes, plants, and
other media that remove pathogens
and nutrients. The wetland cell
typically consists of an
impermeable liner, and gravel and
sand fill, along the with the
appropriate wetland plants, which
must be able to survive in a
perpetually saturated environment.
26. 10) Cluster/ Community System
A cluster decentralized wastewater
treatment system is under some
form of common ownership and
collects wastewater from two or
more dwellings or buildings. It
conveys the wastewater to a
treatment and dispersal system
located on a suitable site near the
dwelling or buildings. It is common
to find cluster systems in places like
rural subdivisions.
27. SEPTIC TANK
Septic tank is a receptacle or vault used to collect organic waste
discharged from the house sewer. The main function of a septic tank is to
liquefy and precipitate solid waste purifying odorous materials.
Septic tanks are constructed of concrete, metal, fiberglass, or plastic
(fiberglass and polyethylene) and are commonly placed underground with
the top surface covered with grass. An access cover built into the top of
the tank allows periodic inspection and removal of sludge and scum that
collects in the tank.
28. Construction of Septic Tank
Septic Tank is constructed from either of the following materials:
1. Reinforced concrete
2. Plastered concrete hollow blocks
3. Prefabricated asbestos
4. Thin metal and plastic
The most popular and widely used material for construction of septic tank
is plastered hollow blocks or reinforced concrete. Others have not gained
acceptance due to cost and durability.
29. General Conditions in Constructing a Septic Tank
1. The concrete or masonry septic tank is usually constructed in rectangular
form. The reason is to retard the even flow of the waste, which is necessary,
to avoid disturbing the decomposition processes inside the tank.
2. The minimum inside dimension of a septic tank is 90 cm wide by 150 cm
long.
3. For effective decomposition of the organic materials inside the septic tank, a
120 cm depth of the liquid content is necessary. It is not impractical though,
to construct a tank of greater depth, provided that the depth should not be
deeper than the natural ground water table.
4. The inlet and outlet inverts of the septic tank shall be long turn sanitary tee.
The inverts are installed in the wall of the tank at least 120 cm from its
bottom floor equally spaced from both sides.
5. The invert is extended down the liquid of the tank not more than 30 cm. this
is to assure smooth delivery of the incoming sewage below the scum line.
Scum refers to the lighter organic materials that rises to the surface of the
water.
30. 6. The bottom of the digestion chamber should be sloped to one low point. The
purpose is to gather the settles organic materials into one mass to favor the
propagation of the anaerobic bacteria.
7. The septic tank, should be provided with a manhole, extended a few centimeters
above the surface of the soil to overcome infiltration of surface water. This
manhole will serve the purpose of cleaning, inspection and repair of the tank.
8. Septic tank for large plumbing installations are provided with suspended
compartment attached to the ceiling slab of the tank. The baffle plate is extended
down the bottom of the tank about 40 centimeters below the scum line. Each
compartment of the tank separated by baffle plate is provided with manhole.
9. The Septic Tank, should be constructed near the surface of the ground, because
the correction of the waste depends upon the extent of oxidation and the existence of
anaerobic bacteria. Another kind of bacteria that split and digest the effluent is the
aerobic bacteria. A kind of bacteria that survive only in the subsoil not more than
150 centimeters below the surface. Oxidation of the effluent deeper than 150 cm
would become extremely difficult.
31. • SIZE OF SEPTIC TANK
So far, there is no mathematic formula ever formulated to arrive in determining a
definite size of a septic tank. However, sanitary authorities agreed in principles
that:
1. For a family of 6 persons, the minimum tank capacity should be approximately
1.3 cubic meters with a minimum size of 90 centimeters wide by 150 centimeters
long and 120 centimeters depth.
2. A very large tank is not advisable, because the bacterial activities would be
retarded. The size of the tank is proportionally based on the number of persons
expected to be served. In other words, the volume of the tank has a rational
proportion with the volume of incoming waste for bacterial activities to be in
favorable condition.
3. For residential installation, the practice is to allow 5 to 6 cubic feet of tank
volume per person. Thus, a septic tank that will serve a family of 12 persons
must have a liquid capacity of 6 x 12 = 72 cubic feet or 538 gallons. (one cubic
foot is 748 gallons)
32. LOCATION OF SEPTIC TANK
Location of the septic tank shall observe the following considerations:
1. The septic tank may be located closer to the building it will serve, providing a
minimum distance of 2 meters from the outside wall.
2. As much as possible, the septic tank should not be located closer to the doors
or windows.
3. Septic tank should be at least 15 meters away from any source of water supply.
The farther the better.
33. REQUIREMENTS FOR A SATISFACTORY DISPOSAL OF HUMAN WASTE
1. There should be no contamination of ground surface that may enter into the
spring or wells.
2. There should be no contamination of surface water.
3. The surface soil should not be contaminated.
4. Excreta should not be accessible to animals, flies, cockroaches, vermin and
the like.
5. There should be no odor and unsightly conditions.
34. SAFETY PRECAUTIONS
In most cases septic tanks are poorly aerated or ventilated. It lacks free oxygen.
Under this condition, an individual entering into septic tank for making repairs or
cleaning purposes, may meet almost instant death.
Septic tank may contain harmful and dangerous gases
When repair work or cleaning is to be made, be sure that the septic tank is well
ventilated, by removing the manhole cover few days in advance of the work.
Another precaution is to supply fresh air inside the tank, while work is being done.
Remember that the tank may contain inflammable gases that might be ignited to
cause a terrific explosion. If light is needed to work in the dark, an electric
emergency light with properly insulated cord should be used. In the absence of
electric supply, a flashlight powered by dry cell battery is equally safe.
