Abstract
Peat is an alternative filter medium for the treatment of various waste streams including septic tank effluent. The water holding capacity and adsorption capacity of peat make it a favorable filter medium over sand or gravel which are commonly used as the filter medium for the drainage field of septic systems. This paper presents the results of a field study to evaluate the hydraulics of a peat filter used to treat the septic tank effluent from a public school west of Ottawa, Canada. An experimental box was placed within the filter during its construction to provide access to the vertical profile of the peat layer. The filter is periodically pulsed with septic tank effluent, which is distributed over the top of the filter and flows vertically through the peat. The filter was instrumented with tensiometers and transducers to monitor the pore water pressures in response to a pulse of septic tank effluent. An in-depth study of the hydraulics of the system was completed. The soil moisture retention curve and the hydraulic conductivity as a function of density were determined in laboratory experiments. A one-dimensional unsaturated flow model was used to predict the pressure response due to a pulse. A comparison of the field and model results illustrates the impact of the density variations, and the corresponding hydraulic conductivity variations, on the model predictions. The compaction of the peat is an important design consideration for the filter since it directly impacts the flow characteristics and the hydraulic retention time within the filter.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Bedient, P. B., Rifai, H. S. and Newell, C. J.: 1994, Ground Water Contamination, PTR Prentice Hall, Englewood Cliffs, New Jersey, pp. 38-39.
Boelter, D. H.: 1969, Physical properties of peats as related to degree of decomposition, Soil Sci. Soc. Am. Proc. 33, 606-609.
Brooks, L. L., Rock, C. A. and Struchtemeyer, R. A.: 1984, Use of peat for on-site wastewater treatment: II, J. Environ. Quality 13(4), 524-530.
Butler, D. and Payne, J.: 1995, Septic tanks: problems and practice, Building and Environ. 30(3), 419-425.
Celia, M. A. and Binning, P.: 1992, A mass conservative numerical solution for two-phase flow in porous media with application to unsaturated flow, Water Resour. Res. 28(10), 2819-2828.
Couillard, D.: 1994, The use of peat in wastewater treatment, Water Res. 28(6), 1261-1274.
da Silva, F. F., Wallach, R. and Chen, Y.: 1993, Hydraulic properties of sphagnum peat moss and tuff (Scoria) and their potential effects on water availability, Plant and Soil 154, 119-126.
Farnham, R. S. and Brown, J. L.: 1972, Advanced wastewater treatment using organic and inorganic material, Proc. 4th International Peat Congress 4, 271-285.
Guntenspergen, G., Kappel, W. and Stearns, F.: 1980, Response of a bog to application of laggon sewage: the Drummond project - an operational trial, Proc. 6th International Peat Congress, 559-562.
Hagedorn, C., McCoy, E. L. and Rahe, T. M.: 1981, The potential for ground water contamination from septic effluents, J. Environ. Quality 10(1), 1-7.
Jowett, E. C. and McMaster, M. L.: 1995, On-site wastewater treatment using unsaturated absorbent biofilters, J. Environ. Quality 24, 86-95.
Kaluarachchi, J. and Parker, J. C.: 1987, Effects of hysteresis with air entrapment on the water flow in the unsaturated zone, Water Resour. Res. 23(10), 1967-1976.
Lenhard, R. J.: 1992, Measurement and modeling of three-phase saturation pressure hysteresis, J. Contaminant Hydrol. 9, 243-269.
Loxham, M. and Burghardt, W.: 1983, Theoretical considerations of transport of pollutants in peats, Proc. 6th International Peat Congress, 600-606.
Mualem, Y.: 1976, A new model for predicting the hydraulic conductivity of unsaturated porous media, Water Resour. Res. 12(3), 513-522.
Nichols, D. S. and Boelter, D. H.: 1982, Treatment of secondary sewage effluent with a peat-sand filter bed, J. Environ. Quality 11(1), 86-92.
Schaub, S. A. and Sorber, C. A.: 1977, Virus and bacteria removal from wastewater by rapid infiltration through soil, Applied and Environ. Microbiol. 33(3), 609-614.
Touma, J. and Vauclin, M.: 1986, Experimental and numerical analysis of two-phase infiltration in a partially saturated soil, Transport in Porous Media 1, 22-55.
van Genuchten, M. T.: 1980, A close-form equation for predicting the hydraulic conductivity of unsaturated soils, Soil Sci. Soc. Am. J. 44, 892-898.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Kennedy, P., Geel, P.J.v. Hydraulics of Peat Filters Treating Septic Tank Effluent. Transport in Porous Media 41, 47–60 (2000). https://doi.org/10.1023/A:1006796827147
Issue Date:
DOI: https://doi.org/10.1023/A:1006796827147