ABCO highly recommends screening of waste water prior to the treatment process. Large matter can cause major problems in pumps and smaller filtration units, as well as causing pipe blockage, if it is not screened off initially. There are a number of screening options available; drum screening and bar screening.
Drum (Trommel) Screen
Drum screens are capable of filtering solids as small as 5-20mm in size. They are designed to rotate slowly in order to prevent solids blocked by the mesh stopping the flow of water through the screen. These screens often incorporate a self cleaning function, which utilize a fresh water source to spray clean the mesh and deposit the collected solids in a waste basket.
Bar screens are best suited for filtering waste water with a high content of stringy solids, such as paper, rags and plastics. These screens typically filter solids of the size of 10-60mm. The bar screen arrangement is typically equipped with an automatic mechanical cleaner, which scrapes the bars clean and deposits the collected solids into a waste basket.
Screenings should be disposed of by burial or incineration after removing residual faecal matter, or can also be fed into a macerator and returned to the wastewater plant influent flow.
Grit removal is typically incorporated into the wastewater treatment plant design, either through an initial balance tank or clarifier or through other means.