Three full‐size sphagnum (Sphagnum spp.) peat filter fields were monitored to determine the treatment levels after application of septic tank effluent (STE). Systems I and II were designed with a liner and had overboard discharges, whereas system III was constructed with a subsurface discharge. Gravity‐feed, dosed‐feed, and pressure distribution systems all provided excellent organic and 99% fecal coliform removal without additional disinfection.The 5‐day biochemical oxygen demand (BOD5) reduction exceeded 90% and chemical oxygen demand (COD) reduction exceeded 80% in all three systems. Total suspended solids (TSS) measured 16 and 9 mg/L in the effluent from systems I and II, respectively. Systems I and II showed 58 and 62% total P reduction, respectively, while a total P reduction of 96% was obtained in system III. Nitrate‐N in the effluent from all three systems was < 4.5 mg/L, well below the recommended limit of 10 mg/L. The pH of the effluents ranged from 5.3 to 6.5 and color averaged 330 standard units. In Maine, or other areas where the natural waters tend to be both colored and slightly acidic, neither parameter would be problematic when using an overboard discharge. Effluent from the well‐aerated fields contained dissolved O2 averages of 4.6 and 6.7 mg/L for systems I and II.Annual variation in weather conditions, including prolonged cold, with and without snow cover, and extreme short‐term precipitation, had no adverse effects on the performance of the peat filter fields. The use of sphagnum peat for on‐site wastewater treatment seems to be an acceptable alternative for areas where conventional systems cannot be installed.
Peat 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.
The goal of this study was to evaluate the effect of effluents from conventional activated sludge (CAS) and biological nutrient removal (BNR) processes on algal bloom in receiving waters. We made multiple effluent sampling from one CAS and two BNR facilities, characterized their effluents, and conducted bioassay using river and ocean water. The bioassay results showed that CAS effluents brought similar productivity in both river and ocean water, while BNR effluents were more reactive and productive in ocean water. Unexpectedly, nitrogen-based biomass yields in ocean water were up to six times larger for BNR effluents than CAS effluent. These results indicated that nitrogen in BNR effluents, although its total concentration is lower than that of CAS effluent, is more reactive and productive in ocean water. The ocean water bioassay further revealed that effluents of BNR and CAS led to considerably different phytoplankton community, indicating that different characteristics of effluents could also result in different types of algal bloom in receiving waters. The present study suggests that effects of upgrading CAS to BNR processes on algal bloom in receiving waters, especially in estuary and ocean, should be further examined.
Stantec Consulting Ltd. (Stantec) was retained by Williams Operating Corporation (WOC, Marathon, ON, Canada) in July 2008 to conduct bench-scale tests for the destruction of cyanide (CN) using hydrogen peroxide (H 2 O 2 ) and copper sulphate (CuSO 4 ) at the mine effluent treatment plant (ETP). Based on a 2 4 factorial analysis, the following preliminary recommendations could be drawn: i) CN oxidization with H 2 O 2 and CuSO 4 is an effective approach for CN destruction at WOC, ii) Practice CN oxidization in warm season; iii) H 2 O 2 and CuSO 4 could be dosed based on mass ratios of H 2 O 2 /CN of 5-10/1 and Cu 2+ /CN of 5/1; and iv) a reaction time of 40 min would be sufficient.
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