Peat filters can also be used to treat septic tank effluent with a single-pass and bottomless method as a drainfield option. Prefabricated peat modules are typically placed on a prepared surface of washed stone or gravel. Wastewater is dosed to the top of the peat filter, trickles down through the media bed, and exits from the module through holes located in the filter base. Some peat filters can be installed without the bottom and installed directly on the soil surface. Other designs include stone or gravel at the module’s base that spread the effluent provided by the module’s holes.
Unlike sand media, peat tends to settle, decompose, and/or deteriorate over time and may need to be replenished or replaced entirely at some point during use. Replacement frequency is dependent upon the type of peat used and wastewater flow and characteristics, but typically peat needs to be completely replaced after 8 to 15 years of use. Additional peat material may need to be added to the module yearly to assure that distribution laterals are covered to prevent odor problems.