Efffluent flux prediction in variably saturated soil zones within a septic tank-soil absorption trench

被引:3
作者
Beal, Cara D. [1 ]
Gardner, Ted
Rassam, David W.
Vieritz, Alison M.
Menzies, Neal W.
机构
[1] Univ Queensland, Sch Land & Food Sci, Indooroopilly, Qld 4068, Australia
[2] Coastal CRC, Indooroopilly, Qld 4068, Australia
[3] Qld Dept Nat Resources Mines & Water, Indooroopilly, Qld 4068, Australia
[4] CSIRO Land & Water, Indooroopilly, Qld 4068, Australia
来源
AUSTRALIAN JOURNAL OF SOIL RESEARCH | 2006年 / 44卷 / 07期
关键词
biomat zone; septic system; unsaturated flow; HYDRUS-2D; modelling; on-site wastewater;
D O I
10.1071/SR06007
中图分类号
S15 [土壤学];
学科分类号
0903 ; 090301 ;
摘要
The treatment and hydraulic mechanisms in a septic tank-soil absorption system ( SAS) are highly influenced by the clogging layer or biomat zone which develops on bottom and lower sidewall surfaces within the trench. Flow rates through the biomat and sub-biomat zones are governed largely by the biomat hydraulic properties (resistance and hydraulic conductivity) and the unsaturated hydraulic conductivity of the underlying soil. One- and 2-dimensional models were used to investigate the relative importance of sidewall and vertical flow rates and pathways in SAS. Results of 1-dimensional modelling show that several orders of magnitude variation in saturated hydraulic conductivity (Ks) reduce to a 1 order of magnitude variation in long-term flow rates. To increase the reliability of prediction of septic trench hydrology, HYDRUS-2D was used to model 2-dimensional flow. In the permeable soils, under high trench loading, effluent preferentially flowed in the upper region of the trench where no resistant biomat was present (the exfiltration zone). By comparison, flow was more evenly partitioned between the biomat zones and the exfiltration zones of the low permeability soil. An increase in effluent infiltration corresponded with a greater availability of exfiltration zone, rather than a lower resistance of biomat. Results of modelling simulations demonstrated the important role that a permeable A horizon may play in limiting surface surcharge of effluent under high trench hydraulic loading.
引用
收藏
页码:677 / 686
页数:10
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