Use of Peat for On‐Site Wastewater Treatment: I. Laboratory Evaluation

Abstract

AbstractPeat has been found to be an effective medium for the treatment of municipal and industrial wastewaters. Recent research has indicated that a peat filter can be utilized in the treatment of septic tank effluent (STE). Laboratory columns were used to determine the treatment capacity of sphagnum (Sphagnum spp.) peat at varying hydraulic and organic loadings.Thirty centimeters of peat compacted to a density of 0.12 Mg/m3 was found sufficient to treat STE at a hydraulic loading of 8.1 cm/d and an organic loading of 20.2 kg BOD5/1000 m2 per day (BOD5 = 5‐day biochemical oxygen demand). The BOD reduction exceeded 95% and suspended solids 90%. Chemical oxygen demand (COD) reduction was only 80% as the effluent COD exceeded 100 mg/L. The relatively high COD was attributed to the organic matter leached from the peat itself. This was reflected in a light yellow color and lowered pH in the effluent. The effect seemed to be temporary in nature and improved COD, color, and pH values were obtained with time. Excellent fecal coliform reduction was obtained, suggesting that a separate disinfection operation may not be necessary.Nutrient removal under aerobic conditions revealed < 10% P and N removal; however, nitrification was nearly complete. Significant denitrification was promoted under anaerobic conditions and a 62% reduction in total N was observed.Specifications for a full‐scale filter include a hydraulic loading of 4.1 cm/d for a typical strength STE (10 kg BOD5/1000 m2 per day) as 8.1 cm/d proved to be excessive at low temperature (5°C). The filter should have a minimum of 30 cm of lightly compacted peat (0.10–0.12 Mg/m3) below the distribution pipes. These recommended design criteria result in a much smaller filter than previously tested.