How Filter Plates and Cloths Contribute to Primary Wastewater Treatment

Filter plates and cloths are the primary components of a machine called a filter press. These versatile pieces of equipment have been in use since the 1800s, but were mostly used to make clay. Presently, they serve the purpose of separating liquids from solids for the mining, food, and pharmaceutical industries, but their principal use is within wastewater treatment plants. Here we will describe the treatment of wastewater and then break down the specific role that filter plates and cloths play in that process.Wastewater is defined as any type of fluid, which contains dissolved and suspended solids that is expelled from farms, factories, and residences. Wastewater may even be considered polluted if it carries chemicals, industrial waste, or toxins. Because of the potential harm wastewater can cause, it must be treated before being released back into the environment to take part in the water cycle. Sometimes, wastewater may even be treated for the express purpose of reuse.

There are three steps to overall treatment that most wastewater treatment plants perform on liquids before allowing their re-release or reuse. These steps are primary treatment, secondary treatment, and tertiary treatment. While the latter steps involve the use of biological organisms or chemicals breaking down matter that cannot be strained from the water, primary treatment involves the removal of solid sediments in the wastewater through the filter press.In operation, slurry (the combination of liquids and solids) is pumped under pressure into the machine. A moving component grips several filter plates together using a hydraulic system. The filter plates contain cloth centers that act as sieves.

As the slurry runs through the plates, the liquid portion passes through these sieves and the solids are left behind to form what are known as “cakes.” Depending on their composition, wastewater cakes are then discarded, or they move onto further processing that incorporate wash liquors, heating, vacuum, and air, so they are able to be safely disposed of in landfills.Among different types of presses that are capable of handling the treatment process, the design using filter plates and cloths remains the most fundamental and efficient. The capability of the equipment is undisputed, as these machines can remove as much as 99% of solid waste products and sludge from fluid. The use of these presses speeds up the overall treatment process, and also reduces the “biochemical oxygen demand” or “BOD” of the fluid, meaning the amount of oxygen consumed by microorganisms breaking down the organic waste in the water (secondary treatment). For all these reasons and more, the nearly 200-year-old technology is now a mainstay of the wastewater treatment industry.