Septic tanks and adsorption fields in Tasmania : matching environmental conditions with operating requirements

Septic tanks and soil adsorption fields are a commonly used wastewater treatment system in unsewered areas. The biological processes on which they rely were considered in detail and their operating requirements established along with the assumptions underlying the design of the treatment system. The principal regions in which septic tanks and adsorption fields are used in Tasmania were also established and the environmental conditions in these areas were compared with the operating and design conditions of septic tank and adsorption field systems. From this the suitability of septic tank wastewater treatment in the particular areas of use was predicted. In highland areas septic tank and adsorption field systems were considered to be unsuitable for wastewater treatment whilst in lowland areas their suitability is dependent upon site characteristics. No region of septic tank and adsorption field use in Tasmania was considered to be completely suitable for this form of wastewater treatment. The environmental conditions of two dissimilar sites, Mt. Mawson and Carlton, were characterised and the performance of septic tank and adsorption field systems under them assessed. The behaviour of the treatment systems was consistent with the predictions made earlier. Within this study several deficiencies in septic tank and adsorption field design and operation, both in Tasmania generally and specifically at the two study sites, were highlighted. Remedial action was suggested where appropriate.