Nutrient loading on subsoils from on-site wastewater effluent, comparing septic tank and secondary treatment systems

Gill, Laurence; O'Luanaigh, Niall; Johnston, Paul; Misstear, Bruce; O'suilleabhain, C.

doi:10.1016/j.watres.2009.03.024

Cited by 107 publications

(78 citation statements)

References 30 publications

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“…A more detailed description of this procedure is provided in Gill et al (2009). After dilution factors were calculated at each depth plane a simple mass balance approach was adopted to estimate the zone of contribution of effective rainfall at each depth plane, the dimensions of which are shown on Table 5.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

The attenuation of microorganisms in on-site wastewater effluent discharged into highly permeable subsoils

O'Luanaigh

Gill

Misstear

et al. 2012

Journal of Contaminant Hydrology

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Please cite this article as: O'Luanaigh, N.D., Gill, L.W., Misstear, B.D.R., Johnston, P.M., The attenuation of microorganisms in on-site wastewater effluent discharged into highly permeable subsoils, Journal of Contaminant Hydrology (2012Hydrology ( ), doi: 10.1016Hydrology ( /j.jconhyd.2011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.The attenuation of microorganisms in on-site wastewater effluent discharged into highly permeable subsoils ABSTRACTAn extensive field study on percolation areas receiving both septic tank and secondary treated on-site effluents from single houses in Ireland was carried out to investigate the attenuation capacity of highly permeable subsoils with respect to E.coli bacteria and spiked bacteriophages (MS2, ΦX174 and PR772). The development of biomats across the percolation areas receiving the secondary effluent was restricted compared to the percolation area receiving septic tank effluent, promoting a much higher areal hydraulic loading which created significant differences in the potential microbiological loading to groundwater.Greatest E.coli removal in the subsoil occurred within the first 0.35 m of unsaturated subsoil for all effluent types. Analysis showed, however, that more evidence of faecal contamination occurred at depth in the subsoils receiving secondary treated effluents than that receiving A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT2 septic tank effluent, despite the lower bacterial influent load. All three bacteriophages were reduced to their minimum detection limit (< 10 PFU/mL) at a depth of 0.95 m below the percolation trenches receiving septic tank effluent, although isolated incidences of ΦX174 and PR772 were measured below one trench. However again, slightly higher breakthroughs of MS2 and PR772 contamination were detected at the same depth under the trenches receiving secondary treated effluent.

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Section: Accepted M Manuscriptmentioning

confidence: 99%

The attenuation of microorganisms in on-site wastewater effluent discharged into highly permeable subsoils

O'Luanaigh

Gill

Misstear

et al. 2012

Journal of Contaminant Hydrology

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“…The systems were designed (area and depth) based upon a modeled water balance between the typical wastewater effluent rates expected from the dwelling, the local rainfall and the estimated evapotranspiration from the basin over a four year period. Realistic time-varying fluctuations in flows (from basis of previous research carried out by Gill et al [15]), local meteorological conditions and estimated crop coefficients were input into the water balance model which then simulated willow evapotranspiration across a four year period. The crop coefficients were assumed to be 1 throughout the winter months, increasing up to maximum values of 2.65 across the summer months.…”

Section: Construction Of Full-scale Et Systemsmentioning

confidence: 99%

Upflow Evapotranspiration System for the Treatment of On-Site Wastewater Effluent

Curneen¹,

Gill²

2015

Water

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Full-scale willow evapotranspiration systems fed from the base with septic tank or secondary treated domestic effluent from single houses have been constructed and instrumented in Ireland in order to investigate whether the technology could provide a solution to the problem of on-site effluent disposal in areas with low permeability subsoils. Continuous monitoring of rainfall, reference evapotranspiration, effluent flows and water level in the sealed systems revealed varying evapotranspiration rates across the different seasons. No system managed to achieve zero discharge in any year remaining at maximum levels for much of the winter months, indicating some loss of water by lateral exfiltration at the surface. Water sampling and analysis however, showed that the quality of any surface overflow from the systems was similar to rainfall runoff. The performance results have then been used to formulate design guidelines for such systems in Ireland's temperate maritime climate. The effect of varying different combinations of design parameters (plan area, soil depth, etc.) has been evaluated with respect to the simulated number of overflow days over a five-year period using a water balance model. Design guidelines have then been based upon minimising the amount of runoff, in conjunction with other practical and financial considerations.

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“…In particular, Gill et al (2007Gill et al ( , 2009 observed that secondary treated effluent inputs to the percolation field can paradoxically lead to regions of higher contaminant concentration at depth in the soil than septic tank effluent inputs of higher contaminant content. They argued that the lower organic concentrations of the secondary treated inputs lead to a thinner, more permeable biomat, resulting in localization of wastewater flow in a shorter region at the upstream end of the percolation trench.…”

Section: Introductionmentioning

confidence: 99%

“…Gill et al (2009) suggested that reduced attenuation in freely draining soils may be due to a muted spread of biomat and a resulting concentration of hydraulic loading in the upstream region of the trench. Biomat in moderately percolating soils results in distribution of the flow over a greater area.…”

Section: Introductionmentioning

confidence: 99%

Biomat Development in Soil Treatment Units for On-site Wastewater Treatment

Winstanley

Fowler

2013

Bull Math Biol

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We provide a simple mathematical model of the bioremediation of contaminated wastewater leaching into the subsoil below a septic tank percolation system. The model comprises a description of the percolation system's flows, together with equations describing the growth of biomass and the uptake of an organic contaminant concentration. By first rendering the model dimensionless, it can be partially solved, to provide simple insights into the processes which control the efficacy of the system. In particular, we provide quantitative insight into the effect of a near surface biomat on subsoil permeability; this can lead to trench ponding, and thus propagation of effluent further down the trench. Using the computed vadose zone flow field, the model can be simply extended to include reactive transport of other contaminants of interest.

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Nutrient loading on subsoils from on-site wastewater effluent, comparing septic tank and secondary treatment systems

Cited by 107 publications

References 30 publications

The attenuation of microorganisms in on-site wastewater effluent discharged into highly permeable subsoils

The attenuation of microorganisms in on-site wastewater effluent discharged into highly permeable subsoils

Upflow Evapotranspiration System for the Treatment of On-Site Wastewater Effluent

Biomat Development in Soil Treatment Units for On-site Wastewater Treatment

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