Sedimentation is a physical water treatment process that uses gravity to remove suspended solids from water. Contact beds, intermittent sand filters, trickling filters, and miscellaneous filters are types of biological wastewater treatment processes that use microorganisms to break down organic matter. Contact beds have fallen out of use due to inefficiencies when the tank is full, while intermittent sand filters and trickling filters remain common.

1. Building Services
Sedimentation
Submitted By:
Group C

2. Sedimentation:
Sedimentation is the tendency for particles in suspension to settle out
of the fluid in which they are entrained and come to rest against a
barrier. This is due to their motion through the fluid in response to the
forces acting on them: these forces can be due to gravity, centrifugal
acceleration, or electromagnetism.
Sedimentation is a physical water treatment process using gravity to
remove suspended solids from water. Solid particles entrained by the
turbulence of moving water may be removed naturally by
sedimentation in the still water of lakes and oceans.

3. Sedimentation
-Contact Bed
-Intermittent Sand Filters
-Trickling Filter
-Miscellaneous Filter

4. 1. Contact Bed
In this type of wastewater filtration, the sewage applied on the contact
material is allowed to stand undisturbed for some time before, being
emptied and an interval is allowed before recharging the contact beds.
During the 'contact period', when the filter is standing full, the fine
suspended particles of sewage are deposited on the contact material
and worked over by the anaerobic organisms. During the 'empty
period' that follows next, the deposited matter is oxidized by the
aerobic bacteria. It is then washed off the contact material and carried
out with the sludge effluent on the next emptying of the tank.

5. Construction
Contact beds are watertight tanks with masonry walls and very much similar in
construction to an intermittent sand filter. The contact material is made of broken
stone called ballast and is of 2.5 - 7.5 cm gauge. The tank is filled with the
sewage over a period of an hour; allowed to stand full over a period of two hours,
then emptied through underdrains. This process takes another hour. The tank is
now left empty for 3 to 4 hours before admitting the next charge. (Thus with a
total working period in a shift of 8 hours, the contact bed can be worked in three
shifts daily). The organic loading in this case is about the same i.e., 1.1 million
liters per hectare per day.
Use
The contact beds method is now only of historical interest and not commonly
used. This is mainly because of the loss of efficiency brought about by the
exclusion of air when the tank is standing full. For an efficient biological action, it
is imperative that the aeration should be through the mass of sewage. It has
therefore, been superseded by more efficient biological wastewater treatment
process, as in the case of trickling filter wastewater treatment method and
activated sludge plants. However, the contact beds have some merit when
compared to the trickling filters as:
(i) Lesser operating head required

6. Intermittent Sand Filter
• They are a viable alternative to conventional methods when soil
conditions are not conducive for proper treatment and disposal of
wastewater through percolative beds/trenches.
• Sand filters can be used in sites that have shallow soil cover,
inadequate permeability, high groundwater, and limited land area.
• Treatment is accomplished through physical and chemical
means, but mainly by microorganisms attached to the filter media.
• The treated wastewater is collected in under drains at the bottom
of the sand filter and is then transported to a line for further
treatment or disposal.

7. Types of Intermittent Sand
Filter
Gravity Discharge ISFs
• The gravity discharge ISF, is usually located on a hillside with the long axis
perpendicular to the slope to minimize the excavation required.
• The effluent leaving the sand filter flows out by gravity, the bottom of the sand
filter must be several feet higher than the drain field area.
• To achieve that difference in elevations, a sand filter may be constructed partially
above ground.

8. Bottomless ISFs
• A third type of buried sand filter has no impermeable liner and does not discharge to
a drain field, but rather directly to the soil below the sand.
Pumped Discharge ISFs
• The pumped discharge sand filter, is usually sited on level ground.
• Its location in relation to the drain field is not critical since a pump located within the
sand filter bed allows effluent to be pumped to a drain field at any location or
elevation.
• Discharge piping goes over—not through—the sand filter liner, so the integrity of the
liner is protected.

9. Advantages of Using Intermittent Sand Filter
• ISFs produce a high quality effluent that can be used for drip irrigation or can be
surface discharged after disinfection.
• Drain fields can be small and shallow.
• ISFs have low energy requirements.
• ISFs are easily accessible for monitoring and do not require skilled personnel to
operate.
• No chemicals are required.
• If sand is not feasible, other suitable media could be substituted that may be
found locally.
• Construction costs for ISFs are moderately low, and the labour is mostly manual.
• The treatment capacity can be expanded through modular design.
• ISFs can be installed to blend into the surrounding landscape.
• The soil cover prevents odours.

10. Disadvantages of Using Intermittent Sand Filter
• The land area required may be a limiting factor.
• Regular (but minimal) maintenance is required.
• Odour problems could result from open filter configurations and may
require buffer zones from inhabited areas.
• If appropriate filter media are not available locally, costs could be higher.
• Clogging of the filter media is possible.
• ISFs could be sensitive to extremely cold temperatures.
• ISFs may require an NPDES Permit when the effluent is surface
discharged.

11. Trickling Filter
A trickling filter, also called trickling biofilter, biofilter,
biological filter and biological trickling filter, is a fixed-bed,
biological reactor that operates under (mostly) aerobic
conditions. Pre-settled wastewater is continuously
‘trickled’ or sprayed over the filter. As the water migrates
through the pores of the filter, organics are aerobically
degraded by the biofilm covering the filter material.

12. It is used in the secondary
treatment. A trickling filter
consists of a fixed bed of rocks,
lava, gravel, polyurethane foam,
sphagnum peat moss, ceramic,
or plastic media over which
sewage or other wastewater
flows downward and causes a
layer of microbial slime (biofilm)
to grow, covering the bed of
media.
12

13. Aerobic conditions are
maintained by splashing,
diffusion, and either by forced air
flowing through the bed or
natural convection of air if the
filter medium is porous.

14. 14

15. Miscellaneous Filters

16. Water Distillation (Water Distillers)-
Water Distillation involves heating
the water to boiling point and
condensing the steam. Pollutants
with a boiling point near that of
water are hard to remove, but
generally the distilled water is of
very high quality. The major
drawback to this method is that it
requires a large amount of energy.
Some people will also complain
that the distilled water tastes flat
(this is due to less dissolved
oxygen).
Water Distillers

17. Reverse Osmosis (Hyper-filtration)- In water filter terms,
reverse osmosis (or hyper-filtration) is the process of
filtering water under pressure through a semi-permeable
membrane, allowing water to pass through but rejecting
other particles such as bacteria, toxins, salts, and
anything bigger than around 150 Daltons.

18. Activated Carbon (AC) Water Filters- Activated Carbon
Filtration is an established technology that works through
absorption of the problematic compounds, primarily to
remove taste and odour but systems will also remove
some harmful contaminants. AC is a highly porous
material with a very large surface area. Chemical
pollutants are attracted to and held by AC's surface.
These water filters are best suited for the removal of
organic compounds.

19. UV Filters- UV filters are able to kill the majority of
bacteria and viruses in the water which passes through
them, However, they won't remove chemical pollutants
from the water. Since the treatment is ineffective outside
the treatment area, water should be used immediately
after it is treated.

20. Eaton's BECO INTEGRA® PLATE system offers an enclosed filter
system for sophisticated filtration tasks. The product channels of
the filter elements are sealed via the depth filter sheet and
ensures that only the filter element and the filter sheet are in
contact with the product. For added protection, an additional
circumferential gasket hermetically seals the filter packet. Eaton's
BECO INTEGRA PLATE system can be used for sheet filtration,
precoat filtration or step filtration
Enclosed Filtration

21. BIOFILTRATION-Biological
filters can be used in the
treatment of screened raw
sewage or settled
wastewater from primary
settlement (sedimentation)
tanks. The filter plant
consists of a bed of random
or modular plastic media
through which the effluent
percolates.