A trash screen is a type of fencing used to filter out debris in the path of a waterway. This is a helpful tool in keeping streams, rivers and lakes free of trash and unwanted elements. The basic design of all trash screens is similar, but internal, external and turbine-powered screens each serve different needs. Screens also can be made of different materials.
A basic waterway trash screen is made from any type of meshed material that allows water to pass through but holds back large pieces of debris. A trash screen usually is made from the same materials as many fences, such as metal or plastic. Depending on the waterway and the amount of pollution that passes through, screens often need to be cleaned regularly in order to avoid waterway blockage.
A trash screen normally is constructed from non-corrosive metal wire. Usually, it is a section of fencing made from aluminum. The size of the openings can be controlled by the type of fencing used, such as a backyard fence with larger holes or chicken wire fencing with smaller openings. In addition to metal fencing, plastic fencing, like the kind used for snow fences, also can be used. This method is less expensive than metal but runs the risk of deteriorating quicker because of the constant exposure to water and pressure.
The most common type of trash screen is the external screen. These screens are placed in the middle of a stream, usually at its narrowest point. The fence is anchored by metal posts that go deep into the ground. The screen spans the width of the waterway and normally goes under the waterline as well. Ideally, any piece of debris floating down this path will be captured by the screen in order to avoid further contamination.
Internal screens are popular for drainage systems. When it rains, most cities have water runoff on the street, and this water eventually is filtered into a nearby waterway. Many communities place trash screens within the drainage system to capture any debris that came through from the street level in order to keep it from reaching the waterway.
A more complex type of trash screen is the water-powered, turbine-driven trash screen. This self-sufficient piece of machinery has a water wheel that is turned by the stream's flow. This wheel powers a turbine that uses a screen to sweep the water and automatically remove trash.