What is effective size of slow sand filter?

What is effective size of slow sand filter?

Slow sand filter Rapid sand filter
Effective Size 0.2 mm to 0.4 mm 0.35 to 0.55 mm
Uniformity coefficient 1.8 to 2.5 1.2 to 1.8

What are the elements 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.

How does slow sand filters work?

Slow sand filtration is a simple and reliable process. They are relatively inexpensive to build, but do require highly skilled operators. The process percolates untreated water slowly through a bed of porous sand, with the influent water introduced over the surface of the filter, and then drained from the bottom.

What is vital layer in slow sand filter?

The vital layer is the “heart” of the slow sand filter. It removes organic matter, holds back bacteria and oxidizes ammoniacal nitrogen into nitrates and helps in yielding a bacteria-free water. Until the vital layer is fully formed, the filtrate is wasted.

How much is the capacity of slow sand filter to remove the bacteria?

Slow sand filters can reduce water turbidity to less than 1 NTU, total organic content by 10%, remove 95% of coliform bacteria, improve a water’s color, taste, and odor, and do not result in significant sludge production.

What is vital layer of slow sand filter?

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.

What is the sand size used in slow sand filter?

Most literature recommends that the effective size of sand used for continually operated slow sand filters (COSSFs) should be in the range of 0.15 – 0.35mm, and that the uniformity coefficient should be in the range of 1.5 – 3, although a coefficient of less than 2 is desirable (Schulz and Okun, 1984 [ref.

How long do slow sand filters last?

Local production (if clean, appropriate sand is available) One-time installation with low maintenance requirements. Long life (estimated >10 years) with no recurrent expenses.

What is the design period of slow sand filter?

The frequency of cleaning is 1 to 3 months. Rate of filtration is 100-200 l/hr/m2 of filter area. It is used for smaller plants in villages.

What is the capacity of a sand filter?

A sand filter has a dirt holding capacity of 3 to 6 kg TSS / m2 of sand surface. When the filters are loaded with particles, the flow direction is reversed and the flow is increased to clean the filter again.

What are the advantages 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.

How many feet of sand do you need to purify water?

Slow Sand Filters This depth should ideally be about 2-3 meters (7-10 feet) even if 1.5 meters (4 feet) should also allow the filter to work properly. This depth will depend on the sand properties and the porosity of the schmutzdecke.

Which sand is best for water filtration?

Crushed rock is the best type of filtration sand since it has less chance of being contaminated with pathogens or organic material. Grains of sand that have been shaped by water (i.e., river sand and beach sand) are rounded and uniform in size.

What are the difference between slow sand filter and rapid sand filter?

Filter media Rapid filters typically have an effective size of greater than 0.55mm and a Uniformity Coefficient of less than 1.5. Slow sand filters, on the other hand, should have an effective size of 0.15–0.35mm and a Uniformity Coefficient of 1.5–3, with a preference for less than 2.

What is the minimum TDS for water?

What is the best TDS level for drinking water? Ans: Generally, the TDS level between 50-150 is considered as the most suitable and acceptable. Ans: If the TDS level is about 1000 PPM, it is unsafe and unfit for human consumption.