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Environmental systems analysis on enhanced phosphorus removal in onsite wastewater treatment
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
JTI - Swedish Institute of Agricultural and Environmental Engineering.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In order to minimize phosphorus (P) loads to surface waters, the regulatory pressure on onsite wastewater treatment systems has increased. However, the environmental side-effects of implementing secondary P treatment have not been seriously reviewed. In this study we hypothesized that local conditions will largely govern the overall environmental benefits and drawbacks of different options for onsite wastewater treatment from a regional perspective. To explore the validity of this hypothesis an environmental systems analysis (ESA) model was developed that could handle differences in local conditions. The model was applied for four different treatment options, two conventional and two enhanced P treatment options. In a sensitivity analysis three diverse local contexts (type cases) were configured to evaluate the overall environmental impacts from the local and the regional perspective. The evaluation indicated that the eutrophication impacts from onsite wastewater treatment systems are significant in relation to the mean per capita contributions. This statement was valid even at a regional perspective as long as the natural retention was not very strong. Thus, the environmental side effects (increased emissions of greenhouse gases (GHG) and acidifying substances) of implementation of enhanced treatment solutions might be justifiable in many situations. However, due to a low impact in most of the studied environmental aspects, groundwater discharging soil treatment systems (STS) seemed to be preferable in areas were hydrogeological conditions are satisfactory and the distance to surface water is sufficient.

Keyword [en]
Onsite wastewater treatment, Soil treatment system, Reactive filter, Eutrophication, Environmental impact, Environmental Systems Analysis, Life cycle assessment
National Category
Environmental Sciences
URN: urn:nbn:se:kth:diva-121048OAI: diva2:616563

QS 2013

Available from: 2013-04-17 Created: 2013-04-17 Last updated: 2013-04-19Bibliographically approved
In thesis
1. Sustainable phosphorus removal in onsite wastewater treatment
Open this publication in new window or tab >>Sustainable phosphorus removal in onsite wastewater treatment
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Aquatic eutrophication is a serious environmental problem that occurs all over the world. To protect surface waters (in particular the Baltic Sea), the regulatory pressure on onsite wastewater treatment (OWT) systems have increased in Sweden. Stringent requirements have led to uncertainties regarding the capability of conventional treatment techniques (soil treatment systems (STS)) to remove phosphorus (P), but they have also stimulated the development and introduction of enhanced P treatment techniques. In this thesis the accumulation and mobility of P as well as the chemical P removal mechanisms were studied in soils and reactive filter media. This knowledge was then used in environmental systems analysis. A model based on life cycle assessment (LCA) methodology was developed to evaluate the overall environmental performance of conventional and enhanced P treatment systems under various local conditions. The P accumulation in the studied STS varied (320-870 g m-3) and the accumulated P was rather mobile in some soils. Phosphorus compounds were identified in alkaline reactive filter media (calcium phosphates predominated) by means of X-ray Absorption Near Edge Structure (XANES). In sandy soils from STS aluminium was found to be a key element for P removal, as evidenced by a strong relationship between oxalate-extractable P and Al. The LCA studies indicated that enhanced P treatment systems may be beneficial from an eutrophication and P recycling perspective but causes increased impacts in terms of global warming and acidification. Despite the drawbacks, enhanced P treatment techniques should be considered suitable substitutes to surface water discharge STS under most conditions. This is because the latter systems have such a strong eutrophication impact. On the other hand, under appropriate conditions, STS with groundwater discharge may be advantageous. These systems generally caused low environmental impacts except for the dispersion of P resources. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xii, 34 p.
Trita-LWR. PHD, ISSN 1650-8602 ; 1070
Onsite wastewater treatment, Soil treatment system, Phosphorus, Removal mechanisms, Environmental impacts, Life cycle assessment
National Category
Earth and Related Environmental Sciences
urn:nbn:se:kth:diva-121049 (URN)978-91-7501-730-3 (ISBN)
Public defence
2013-05-13, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20130419

Available from: 2013-04-19 Created: 2013-04-17 Last updated: 2013-04-19Bibliographically approved

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