Filter Underdrain Water and Air Distribution System

Monolithically Cast Filter Plate and Adjustable Filter Head

In the filter structure of a water treatment plant, the water and air distribution system of the filter is critical. Air-water backwash processes in particular place higher demands on this system: the uniformity of air and water distribution directly affects not only the backwash performance of the filter, but also the distribution and cleanliness of the filter bed and the quality of the filtered water, and ultimately the operating efficiency and operating cost of the filter.

This monolithically cast filter plate and adjustable filter head have been widely used in the construction of both new and existing filters, including V-type air-water backwash filters, conventional backwash filters, siphon backwash filters, BAF aerated biological filters and ozone-activated carbon filters.

Structure of the Monolithically Cast Filter Plate and Adjustable Filter Head

• The bottom formwork of the concrete filter plate uses a purpose-made, high-strength, food-grade plastic ribbed panel produced in a single operation; circular holes fitted with neck sleeves are provided to fix the embedded sockets of the long-stem filter heads.

• The adjustable filter head consists of an embedded socket, a filter stem and a filter cap. The stem has an adjusting thread for raising and lowering, and an adjusting lug that engages the anti-release strip inside the embedded socket, so that the adjustment precision of the stem is controlled and its position locked.

Performance of the Monolithically Cast Filter Plate and Adjustable Filter Head

• The formwork surface shall be flat and free from cracking, sink marks, air bubbles and flash.

• When renovating a filter, the filter plate supports shall be arranged according to the plan dimensions of a single filter cell and the formwork module, and cutting of the formwork shall be minimised.

• The filter plate must be cast as a single monolith, uniformly vibrated and compacted. The surface levelness error within a single filter cell shall be less than ±5 mm.

• The filter stem has an adjustment range of 0 to 50 mm. The horizontal plane of the air inlet holes is set by adjusting the stem, with a flatness error of ±0.4 mm.

Features of the Monolithically Cast Filter Plate and Adjustable Filter Head

• The seamless monolithic cast concrete filter plate eliminates the air and water leakage caused by poorly sealed plate joints, removing a hidden risk that the filter cannot operate normally.

• The levelness of the filter head air inlet holes is set by the adjustable filter head, so the levelness error of the filter beams within a cell need only be controlled to ±10 mm. This simplifies construction, raises the degree of mechanisation, shortens the construction period and reduces project cost.

• Adjusting the stem up or down sets the horizontal plane of the air inlet holes and guarantees uniform air and water distribution. Filter caps with different slot areas can also be exchanged, so the open area ratio can be adjusted with the same filter head layout.

• For wastewater treatment and reclaimed water reuse under ozone conditions, the stainless steel adjustable filter head used with the monolithic cast plate is made of grade 316L material and offers strong oxidation resistance, resistance to damage, wear resistance, freedom from clogging and a long service life.