For many surface waters, phosphorus (P) leaching is a serious problem that should be minimized to prevent eutrophication. In Sweden there is a demand for physical and technical development of high-performance P removal techniques to reduce phosphorus leaching from on-site wastewater treatment systems to the Baltic Sea. However, although these systems are designed to reduce eutrophication there are also other environmental impacts to be considered when implementing them in on-site systems; energy use and global warming potential are two examples. This study has investigated several bed filter materials (reactive media and natural soils) for their total environmental impact (in commercial applications) as well as for the predominating chemical phosphorus removal mechanisms. The use of life cycle assessment revealed that several reactive bed filters are relatively energy-consuming due to the material manufacturing process. Characterization of phosphorus compounds in used reactive media provided evidence for calcium phosphate precipitation as the predominating P removal mechanism in alkaline filter materials. However, in soil treatment systems with noncalcareous soils, batch experiments and extractions suggested that aluminium compounds were important for P removal. According to mass balance calculations that compared accumulated P with the estimated P load in a soil treatment system, the long term P removal capacity was very low; only 6.4 % of the applied phosphorus had been removed during 16 years of operation. / <p>QC 20110413</p>

L'assainissement non collectif concerne 12 à 15 millions de personnes en France. La filière classique de ce mode d’assainissement se compose généralement d'un prétraitement anaérobie par une fosse septique recevant l’ensemble des eaux usées domestiques suivi d’un système d’infiltration dans le sol ou d’un filtre à sable. Le filtre à sable vertical drainé met à profit le pourvoir épuratoire qui est principalement lié à la présence d’une biomasse sous forme d’un biofilm. Cette dynamique de la croissance de la biomasse ou du biofilm est soumise à l’impact de la nature de matériaux filtrants. L’écoulement insaturé dans ces systèmes conditionne également cette croissance du biofilm. Dans ce contexte, l'objectif du travail de la thèse est d’appréhender les mécanismes mis en jeu et particulièrement l’impact des matériaux dans le fonctionnement des filtres en comparant notamment deux types de matériaux: les sables de rivière et les agrégats concassés. Pour cela, une étude expérimental sur une unité pilote composé des réacteurs de filtration du diamètre de 30cm et différents épaisseurs de garnissage (15, 30 et 70cm) a été construite. Les réacteurs garnis de deux sables roulés et deux agrégats concassés, sont alimentés en effluent septique avec une charge volumique 12cm/jour par 10 bâchés par jour. Suite des matériaux, une étude de la performance épuratoire avec le suivi des composants biochimiques de la biomasse totale et de la matrice extracellulaire du biofilm est réalisée en comparant notamment les deux types de matériaux filtrants. / The onsite wastewater treatment systems concern 12 to 15 million of people in France. The treatment plant is generally composed by a septic tank as pretreatment, followed by soil infiltration field or sand filtration bed. The vertical drained sand filter provides the purification capacity thanks to the presence of a biomass in form of the biofilm. The dynamic of the biomass growth or the biofilm development is under the impact of filter materials’ nature. In this context, the objective of this work is to understand the mechanisms involved and especially the impact of medium in the functioning of the filtration reactor by comparing two types of packing materials: river sands and crushed aggregates. For this purpose, an experimental study is conducted with pilot unity composed by filtration reactors of 30cm of diameter and different packing thicknesses (15, 30 and 70cm). The reactors packed with two river sands and two crushed aggregates are fed with septic effluent with a volumic hydraulic charge of 12cm/day by 10 batches per day. Based on a characterization of materials, a study of purification performance with biochemical components monitoring of the total biomass and the extracellular matrix of the biofilm is realized by comparing two types of filter materials. The purification performance has presented similar efficiencies of particulates and organic matters removals by fine river sand and fine crushed aggregate. The nitrogen pollutants removals are more effective in the fine river sand which presents the finest granulometry with an alternative of aerobic and anoxic phases along the reactor depth and with a biomass more abundant. The distribution and the quality of the total biomass and the extracellular matrix differentiate between the river sand and the crushed aggregates. As the reference material, the fine river sand presented an earlier stabilization of total biomass growth with a less important production of extracellular exudates compared to the crushed aggregates. The origin of impacts brought by the crushed aggregates might be due to the higher fine particles content which created microenvironments poor in substrates or in oxygen and also due to a more heterogeneous mineralogy. The extracellular components of highest percentage in the biofilm of crushed aggregate are polysaccharides type substances.

Indiana University-Purdue University Indianapolis (IUPUI) / Underground septic systems thrive or fail based on the relationship with their local environment. This paper explores ways environmental variables such as soil type, tree roots, degree of slope, and impervious surfaces affect on-site wastewater treatment systems. It also discusses the effects each of these variables may have on a septic system, and the resulting impact a compromised system may have on the surrounding environment. This research focuses on an approximately 20 square mile area of central Washington Township in Marion County, Indiana. This area of central Indiana contains a large septic system owning population in a sampling of different environments such as wooded areas, hilly areas, and a variety of different soil types.