Bisan Chemicals And Engineers Private Limited

Owing to the expertise of professionals, we are able to provide Automatic Pressure Sand Filter. This sand filter available in various specifications to suit the individual needs of customers. Automatic Pressure Sand Filter is used for iron and manganese removal from groundwater. Apart from that, this filter is also used in swimming pool for recirculation water treatment. 

A Pressure Sand Filter consists of a closed, cylindrical vessel, typically made of corrosion-resistant materials like mild steel (MS) with internal epoxy coating, Fiberglass Reinforced Plastic (FRP), or stainless steel (SS). Inside this vessel, layers of specially graded filter media are arranged, usually with coarser, heavier media at the bottom (like gravel) and finer, lighter media (like filter sand or sometimes anthracite) at the top.

The filtration process in a pressure sand filter involves the following steps:

1. Inlet (Raw Water) Flow: Untreated water, containing suspended solids and turbidity, enters the filter vessel, usually from the top.

2. Downward Flow Through Media: The water flows downwards through the layers of filter media. As it passes through the media bed, the suspended particles are physically trapped within the interstitial spaces of the sand and gravel.

   • The top, finer layers of sand are primarily responsible for capturing the smaller, finer particles.

   • The coarser layers below provide support for the finer media and act as a pre-filter for larger particles, preventing clogging of the finer layers.

3. Filtered Water Collection: Clean, filtered water, now significantly reduced in turbidity and suspended solids, collects at the bottom of the filter in an underdrain system.

4. Outlet (Filtered Water) Flow: The filtered water is then directed out of the filter vessel to the next stage of treatment or directly to consumption/use.

Over time, as particles accumulate within the filter media, the filter bed becomes clogged, leading to:

• Increased Differential Pressure: The pressure difference between the inlet and outlet of the filter increases, indicating resistance to flow.

• Reduced Flow Rate: The amount of filtered water produced decreases.

• Deterioration of Effluent Quality: If not backwashed, eventually some particles might start passing through.

To restore the filter's efficiency, a backwash cycle is performed:

1. Reverse Flow: The flow of raw water is stopped. Clean water (or sometimes a combination of water and air) is introduced into the filter from the bottom, flowing upwards through the filter media.

2. Fluidization: This upward flow expands and fluidizes the filter bed, dislodging the trapped suspended solids and dirt particles from the media.

3. Waste Discharge: The dirty water, carrying the dislodged particles, is then discharged from the top of the filter to a drain or a separate backwash water treatment system.

4. Rinse: After backwashing, a short rinse cycle is often performed, where water flows downwards (or a combination of flows) to resettle and compact the media layers correctly before returning the filter to service.