Screening is the primary treatment station for both surface and wastewater and it is purposely done for protecting the structure from the downstream against large objects which can create obstructions in some of the facility's units, they can easily separate and remove the large matter which that are carried along by the raw water that might negatively affect the efficiency of the further treatment processes or make the implication complicated. Commonly the fine screening is followed by a preliminary screening operation for protection purposes. The screening is done by a manually cleaned bar screen or preferable by an automatically cleaned bar screen. The automatic bar screen is mainly protected by a study preliminary bar screen that must come with an automatic cleaning system in large facilities and in case of raw water containing a high volume of coarse matter. For reducing the manual operation as much as possible, screening procedures have become more and more automated even in smaller facilities. Automation plays an essential part in situations where water carries large amounts of plant matter and arrives all at once at the bar screen, which tends to mat the bars and clog the screen completely in a few minutes. Fine screens must be automated.
Wastewater comprises large solids and grit which can interfere with treatment processes or cause undue mechanical wear and increased maintenance on wastewater treatment equipment. For minimizing the potential problems, these materials need a separate handling process. Preliminary treatment is done for removing these constituents from the influent wastewater. Preliminary treatment comprises grit removal, screening, septage handling, flow equalization, and odor control. The automatic cleaning for bar screens, SGM type, that are equipped with grab buckets represents an advanced technical solution between the systems of automatic cleaning of bar screens which are installed in big channels for intaking water from rivers, sea, lakes, and also large water treatment plants. Particularly it is composed of a supporting frame in steel, composed of a set of pillars that supports a sliding monorail, a trolley, that moves on the above-mentioned monorail and is equipped with four wheels which are mounted on bearings with the motorised gearbox. The electrical feed of internal components of the trolley is assured by a line festoon having multipolar cable or, on-demand, by an electrical cable reel. An electric hoist is also installed inside the trolley which by means of two strong steel ropes are wrapped up in a drum, bears the grab bucket during its upwards run, and down the channel. A grab bucket for screening material collection is also present. The bucket consists of a fixed rake scraping type that is made of strong plates having the same wheelbase of bars, that always stays in contact with screen bars and drags the screening material on channel bottom during its downward run and of upper rotating pliers.