One of the most common applications for Kemflo’s Kempac plastic random media is biological filtration. Kemflo’s Tri-Pack style, Plastic Pall Ring or Plastic Saddle packing are ideal for use is biological filtration applications. From small systems to large systems Kemflo has a plastic random media for you.

Most modern biological filters have a bed of plastic random media over which wastewater is continuously distributed. The plastic random media bed can range in depth from one to more than ten meters deep. Wastewater is applied uniformly over the plastic random media by filter feeds and distribution systems. An underdrain system is provided to collect filter effluent for transport to a clarifier for solids separation. A biological filter does not actually purify wastewater by any filtering or straining action, but by absorption and biological oxidation of the soluble. Organic matter in the wastewater.

Wastewater applied to a biological filter usually has undergone primary treatment to remove suspended solids that can plug the filter, and to remove suspended biochemical oxygen demand or BOD that reduces filter organic loading. The function of the filter is to convert soluble and colloidal organics to settleable solids. These solids are then separated from the wastewater in a postfilter clarifier. The conversion of the soluble and colloidal organics to settleable solids is accomplished biochemically. As wastewater is applied, a biological film develops on the plastic random media. The biological film is responsible for the decomposition of the organic matter in wastewater. The film is a jelly-like slime composed of a very large and diverse population of living organisms including bacteria, protozoa, algae, worms, and insect larvae. The microorganisms that comprise the biological film use the organic matter in wastewater as their food source and the oxygen in the wastewater to metabolize this food. Oxygen is dissolved into the wastewater from the air that circulates through the filter. Metabolism of the organic matter entails numerous complex biochemical reactions within the cells of the microorganisms. Some filer organisms feed on complex substances in the wastewater and produce new cell material and compounds as waste byproducts. The process continues until the final waste products can no longer be used as food by any of the filter microorganisms.

To ensure fast, odor free decomposition of wastewater organics, the filter must remain aerobic. Sufficiently dissolved oxygen must be present in the wastewater at it trickles through the plastic random media. Although dissolved oxygen is only slightly soluble in wastewater, it is constantly being consumed by the microorganisms. Therefore, Oxygen must constantly be available for dissolution into the wastewater. This oxygen comes from the air that circulates through the filter. If there is insufficient air circulation, odorous anaerobic conditions will develop and treatment efficiency will decrease. Filters are classified as low or standard, intermediate rate, high rate or super high rate. Further designations such as single stage, two stage, series and parallel describe the hydraulic flow patterns. Super high rate filters involve plastic random media. Super high rate filters are loaded at hydraulic rates between 140,000 and 840,000 meters squared and organic loadings up to 4.5 kg/m. The major differences between super high and high rate filters are greater hydraulic loadings and greater filter depths. The greater depths are possible because lighter plastic random media is used.

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