Which is an important requirements for slow sand filters to function properly?
The key points and observations to make during a sanitary inspection of a slow sand filter are : The turbidity of the inlet water should be below 10 TU. The turbidity of the outlet water should be below 5 TU. The flow rate in the filter should be constant and in the range 0.1 to 0.3 metres per hour.
How do you make a slow sand filter?
Slow sand filters have traditionally been designed with a bed of sand initially about 1m in depth with about 1 m of super-natural water. The effective size of the filter sand ranges from about 0.15 – 0.35 mm  recommended that the uniformity co-efficient should be less than 5 and preferably less than 3.
What types of sand filters would you recommend for towns and villages?
169. Rpid sand filters are suitable for small towns and villages.
What are the components of slow sand filter?
Slow Sand Filter (Biological Filter)
- Supernatant or raw water.
- Bed of graded sand (on a support of gravel)
- Under – drainage system.
- A system of filter control valves.
Are Slow sand filters safe?
The drawbacks of slow sand filtration are: Not as effective against viruses. No chlorine residual protection – can lead to recontamination. Routine cleaning can harm the biolayer and decrease effectiveness. Difficult to transport due to weight – high initial cost.
What is slow sand filter and its layers?
Slow sand filters work through the formation of a gelatinous layer (or biofilm) called the hypogeal layer or Schmutzdecke in the top few millimetres of the fine sand layer. Slow sand filters slowly lose their performance as the biofilm thickens and thereby reduces the rate of flow through the filter.
What is loss of head in slow sand filter?
This energy in a rapid sand filter is usually in the form of head pressure—basically the weight of the water on top of the filter bed. As particles accumulate on the filter they begin to impede the flow of water through the filter. This loss of energy during the filtration process is known as head loss.
What is the difference between slow sand filter and rapid sand filter?
The difference between the two is not simply a matter of the filtration speed, but of the underlying concept of the treatment process. Slow sand filtration is essentially a biological process whereas rapid sand filtration is a physical treatment process (WHO n.y.).
What is the depth of base material of gravel in slow sand filter?
They are typically 1 to 2 metres deep, can be rectangular or cylindrical in cross section and are used primarily to treat surface water.
How long does a slow sand filter last?
One-time installation with low maintenance requirements. Long life (estimated >10 years) with no recurrent expenses.
What is the difference between slow sand filters and rapid sand filters?
What are the benefits of slow sand filter?
The benefits of slow sand filtration are:
- Proven reduction of protozoa and most bacteria.
- High flow rate of up to 0.6 liters per minute.
- Simplicity of use and acceptability.
- Visual improvement of the water.
- Production of sufficient quantities of water for all household uses.
What do you need to know about slow sand filters?
1.1 SSF Description A slow sand filter (SSF) is a means of treating water for drinking water purposes and involves filtering water through a bed of ‘media’ (usually sand). It is simple in design, construction and operation.
How is a rapid sand filter design example?
FILTER DESIGN EXAMPLE Dr. A. Saatci USA – Rapid Sand Filter Design Inputs Design a rapid sand filter to treat Q= 20000 m3/d Allowing filtered water for backwashing: Q_BW= 2% Time used for bakwashing per day = t_BW= 0.50 hours Assume the rate of filtration = 10 m/h Number of Filters 2.00 Length/ Width of Filters= 1.30
How is The Schmutzdecke layer of slow sand filter formed?
Schmutzdeckelayer formed due to the establishment of a microbial community on the top layers of the fine sand particles. These microbes usually came from the raw water and establish a community within a matter of a few days. The sand bed and slow filtration rate help to the establishment of this microbial community.
What is the effective filtration rate of sand?
This is so because much coarser sand is used with an effective grain size in the range 0.4-1.2 mm, and the filtration rate is much higher, generally between 5 and 15 m3/m2.h (120-360 m /m2.day).