PRESSURE SAND FILTER

Pressure sand Filter have commonly employed filtration units and largely found in the following sectors.

  • Secondary filtration treatment in Raw water treatment unit
  • Post biological treatment and/ or secondary clarifier in Effluent treatment units
  • Pre-treatment of water in a De-mineralization water plant
  • Pre-treatment step to tertiary treatment of water like Ultra filtration or Reverse Osmosis unit.

Pressure sand Filters are of steel construction with the system operating on the feed water pumping pressure. Filters are designed based on specific volumetric flow rate per unit cross sectional filtration area. Multiple sand filter vessels are installed to augment the treatment to the required capacity from a logistic point of view. The filter is complete with inlet distributors, bottom collector/ outlet pipe, vent arrangement, water inlet and outlet nozzles, drain and a pressure safety valve for vessel safety. The filter bed is made of selected layers of sand of various grain sizes.

The sand media filter bed can either be supported by a bed plate with nozzle arrangement or simply filled over a support gravel media. Both models are provided and the selection is done on client’s requirement. Ergonomically designed nozzles of poly propylene nozzles are selected and arranged in a specific fashion for equal distribution and at low pressure drops across the filter nozzles for sand filters having bed plate support arrangement.

Multi layered gravel with different sizes are used as support media where the sand filters are designed with header–lateral arrangement. The water flow from the top inlet distributor, downwards through the filter bed & goes out from the bottom outlet .The filter pump is sized to have adequate head to discharge filtered water to the filtered water tank or further process units.

 DUAL MEDIA FILTER / MULTI MEDIA FILTER

 Pressure sand filters are also referred as “Dual Media / Multimedia filters”. They are used to filters the water to remove the turbidity & suspended solids in water. They have commonly employed filtration units and largely found in the following sectors.

Dual Media sand filters are of steel construction with the system operating on the feed water pumping pressure. Filters are designed based on specific volumetric flow rate per unit cross sectional filtration area. Multiple sand filter vessels are installed to augment the treatment to the required capacity from a logistic point of view. The filter is complete with inlet distributors, bottom collector / outlet pipe, vent arrangement, water inlet and outlet nozzles, drain and a pressure safety valve for vessel safety.

ACTIVATED CARBON FILTER

Activated carbon filters are used for different purposes as pre-treatment to various process needs.

The high adsorptive capacity of activated carbon enables it to remove the test, odour causing compounds & other traces of organics from the water. However, not all organic compounds are removed with the same degree of efficiency.

Granular Activated Carbon filters are very effective as a de-chlorination agent. Hence, it is adopted as a pre-treatment filter before the resin based / RO based treatment plants. GAC filters employed for organic removal are similar to pressure sand filters with generally similar design, filtration rates & backwashing arrangements, with the flow rate adjusted to suit the lower density of GAC. The GAC is placed in the filter over the support gravel. Media depth is a function of the empty bed contact time (EBCT). GAC characteristics will very according to the material from which it is made whether wood, coconut shell or peat.

The carbon has to be replaced when the break through occurs. Activated carbon filters are of steel construction with the system operating on the feed water pumping pressure. The water flow from the top to the bottom across the filter bed with the filtered water discharged from the bottom. The filter pump is sized to have adequate head to discharge filtered water to the filtered water tank or further process units.

The filter bed is periodically back washed to loosen the bed to expose the compacted area. Back wash water is sourced from the filtered water tank and pumped counter current to the filtration mode operation. Dirty Backwash water from the filter is routed for further treatment before recycling back to the system. Hot water backwash is adopted in some cases where the volatile are removed for extending the life of the carbon. Air scouring blowers are provided to improve the cleaning of the filter bed during the filter back wash sequence. Special care is taken for sizing of the filter internals and frontal piping to facilitate filtration and back washing.