Depending on their principle of operation, the proposed screens (grids) can be divided into static and rotary. In the first type the water is filtered through a static sieve, which separates solids from the treated water, which collects at the base of the equipment naturally due to the inclination of the grid itself. In the second type the sieve rotates assisted by a reducer, there is an installed barrier and a chute, which help the separation of the retained substances, and the nozzles installed in this type of equipment additionally protect from clogging. Another type of grille offered allows installation in open channels, in which case an auger installed in the equipment removes and compacts the captured solids.
The Defender® static screens are made of fiberglass reinforced plastic, they include a stainless steel filter mesh that removes solids in water by straining through a static sieve. The equipment is provided with drainage pipes and outlets for clean water.
The Defender® rotary screens are designed to remove solids transported by the water which must be treated so it can be avoided the obstruction and mechanical problems in the aftercoming equipment. These devices are self-cleaning, automatic propelled and they filter the wastewater through a filtration drum made of a grid or perforated mesh with different apertures of 3.0 to 0.15 mm depending on the type and amount of solids. Their installation in wastewater treatment plants of settlements can allow the replacement of primary sedimentation tanks, ensuring the elimination of coarse sands and up to 30% of the fats. The offered equipment is easy to operate due to the fact that the treatment stream enters through a flange located on the outside of the drum and is distributed evenly by an overflow over the drum filter. The solids are retained on the surface of the drum as it rotates and the inflow water passing the drum in both upper and bottom sides performs as cleaning function. When passing through the external scraper, the solids are separated from the net and fall off by gravity. The Defender rotary screens are divided into several models depending on the diameter of the filter drum and the flow rate:
Defender® channel screen conveyors are versatile equipment that is used in the straining, compaction and transportation processes for mechanical sewage treatment. The installation of these facilities prevents various in type and dimension solids from entering the wastewater and prevent causing the sewers, reservoirs and pipelines clog, and protects the rest of the equipment at the plant from overloading, blocking and wear. The lattice structure in form of bent half-pipe is made of stainless steel with perforations from 1 to 10 mm in size. The characteristic design of the equipment is specially designed for its easy installation in cannals, the implementation can be tailored to the specific needs at different angles and can be offered in two versions with and without compacting bathtub. As advantages of the offered equipment can be emphasized its high transport capacity and easy cleaning (brushes mounted on the outside of the screw keep the grille constantly clean). In the presence of a sealing bathtub for the grid cleaning system are provided water jets. The installed screws are resistant to friction due to the reinforced inner surface of the conveyor tube.
