Screening

Rotary drum screens are ideally suited for food manufacturers with large amounts of food solids in the wastewater.

Wastewater is screened by the rotating drum, the screened water flows through the screen openings and the screenings (solids) are scraped off the face of the rotating drum before dropping into a bin. The screen typically offers a high-pressure clean water wash to ensure the screen holes do not block.

Rotary screens are particularly effective at removing solids greater than 1mm in diameter.

Inline screens are typically used to remove fine solids in treated effluent for potable water or as pre-screening for membrane filtration systems (such as microfiltration, ultrafiltration or reverse osmosis). Inline screens can be used to remove solids down to 50 microns.

Inline screens are easy to remove, clean and replace. The screens can be backwashed automatically using a differential pressure detector.

Pressure screens are often described as a larger version of the inline screens and are normally used when the wastewater contains occasional larger solids. Pressure screens are often used as a pre-treatment to a DAF or biological system.

Pressure screens are also applicable where the wastewater contains mainly emulsified or colloidal solids (such as milk wastewater), and are present to remove the occasional bottle top or other solid particles.

All wastewater containing low amounts of larger solids can benefit from a simple safeguard screening system.

A sieve bend offers pre-treatment screening for industrial wastewater treatment plants. It is a simple solution with no moving parts where the solids are screened out via wedge wire and captured in screening bins below.

Wastewater is pumped into a chamber at the top of the screen and water overflows the inlet chamber via a distribution level weir at the top. Wastewater flows down the face and screened wastewater flows through the screen openings. Screenings fall down the outside face of the parabolic screen into a collection bin.

The sieve bend is typically a more affordable option than a rotating screen. It does not require mechanical or electrical equipment during operation. A sieve bend is an extremely robust option and is simple to install. It requires water supply for manual cleaning of the screen openings if blocked by fat or other particles.

A sieve bend is sometimes used as a standalone screening device if the standards for sewer discharge are not too stringent.

Vibrating screens are ideal for filtering solids of varying sizes. For example, Aerofloat often installs a vibrating screen in plastics recycling plants to recover product and remove grit ahead of the AeroMBBR and AeroDAF.

The inline mechanical screen is suited to when the available height prevents the use of a rotary screen. The wastewater flows through the inline screen and flows out through the screen outlet,with the solids collected inside the filter chamber. A brush and valve arrangement discharges screenings. It is a great solution for minimising odours.