In order to fulfil the requirements in the EURO VI standard, regulating emissions from heavy duty vehicles, the exhaust aftertreatment system needs to maintain its efficiency for at least seven years or 700 000 km. In diesel applications the diesel oxidation catalyst (DOC) is located closest to the engine and is thus the most vulnerable to poisoning contaminants, such as phosphorus originating from fuel and oil additives, which deactivates the catalyst. An idea to reduce the impact from phosphorus impurities (recently patented by Scania CV) is to place a low-cost sacrificial substrate, consisting of one or more pillared clay mineral (PILC) with high affinity for phosphorus, upstream the aftertreatment system in order to protect and thus increase the lifetime of the catalytic components which contain platinum group metals. In this work one commercially available and four custom made PILCs, comprising of two conventional type PILCs and two of the type porous clay heterostructures (PCH), were evaluated. The PILCs were exposed to a phosphorus-containing gaseous mixture using a lab-scale experimental setup in order to determine their phosphorus sorption potential. The PILC materials exhibit potential to function as sacrificial substrates for phosphorus in the intended application. It was indicated to be a correlation between increasing iron content (wt%) and increasing phosphorus sorption capability. The most promising material was the custom made Al,Fe-pillared saponite, which was up to twice as effective in trapping phosphorus as the DOC. The commercial sample, the Al-pillared montmorillonite, was only about as efficient as the DOC.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Phosphorus (P) is an essential plant nutrient and is one of the most critical elements influencing crop production throughout the world. Phosphorus deficiency is widespread in most soils of northern Ghana, and ferruginous nodules contained in some soils in the region accentuate the deficiency problem because they act as P sinks. This research focuses on P fertility status of soils in landscapes common to northern Ghana. Three sites were selected for the study and were referred to as sites 1, 2 and 3. Soils in a catenary sequence from site 1 were sampled for detailed P distributions in profiles, and surface soils from the upper, mid and lower slope positions of the other landscapes (sites 2 and 3) were used. The nature of P in the soil fines and ferruginous nodules was investigated using a modified Hedley fractionation procedure. The objective was to quantify the labile and non-labile inorganic P (Pi) and organic P (Po) in relation to pedogenic weathering processes at different slope positions at site 1. A secondary objective was to assess the P distribution in the landscapes at sites 2 and 3. The largest P fraction in both soil fines and nodules at each site was resistant non-labile P forms. Primary P (Ca-P) decreased with depth in the profile at the upper slope position but it occurred in greater quantities in C horizons of the lower slope soils. Phosphorus sorption capacity of the soil fines and nodules was determined to predict the behaviour of P fertilizers in the soils. Phosphorus sorption by the soil fines increased to a maximum in the B horizon of each profile and a t-test showed that P sorption was similar in profiles at each slope position. The P sorption capacities of uncrushed ferruginous nodules varied according to their sizes. The small nodules were more reactive and sorbed more P than the larger sizes. Fractionation of P from the nonfertilized and fertilized soils at the end of cropping and anion exchange resin (AER) extraction, revealed that there had been redistribution of P into different fractions. A comparison of P fractions of the nonfertilized soils after the AER extraction with those of the native soil P showed decreases in some native labile and non-labile P fractions. This suggested that these P fractions could be available for plant uptake. Both 50% PAPR and SSP fertilizations increased the labile Pi and NaOH extractable Pi levels in the soils. (Abstract shortened by UMI.)

A new modeling method for estimation of the longevity of infiltration system was suggested in this study. The model was one-dimensional, based on results from long-term infiltration sites in Sweden, taking some physical and chemical parameters as controlling factors. It defines the longevity of infiltration systems as the time during which the P solution in effulent is under national criteria (1 mg/L in this study), and it aims at providing the longevity for any given point of the infiltration system. The soil in the model was assumed to be totally homogenous and isotropic and water flow was assumed to be unsaturated flow and constant continuous inflow. The flow rate was calculated from the Swedish criteria for infiltration systems. The dominant process in the model would be the solute transport process; however, retardation controlled by sorption would play a more important role than advection and dispersion in determining the longevity in the model. By using the definition of longevity in this study, the longevity of the three soil columns at 1 m depth (Knivingaryd, Ringamåla and Luvehult) were 1703 days, 1674 days and 2575 days. The exhaustion time of the three soil columns under inflow of 5 mg/L were 2531 days, 2709 days and 3673 days. The calculated sorbed phosphorus quantity for soil from sites Kn, Lu and Ri when they reach estimated longevity were 0.177, 0.288 and 0.168 mg/g, while the maximum sorption of Kn, Lu and Ri were 0.182, 0.293 and 0.176 mg/g separately. From the result of sensitivity study of the model, the sorption capacity and flow velocity were most important to the longevity of the infiltration system. Lower flow velocity and higher P sorption capacity extend the longevity of an infiltration bed. Due to the sorption isotherm selected in this study and the assumption of instant equilibrium, the sorption rate of the soil column was quite linear, although the estimated longevity was much shorter than the real exhaustion time of the soil column. In fact the soil has almost reached its sorption maximum when the system reaches its longevity.

<div>Excessive phosphorus (P) is a threat to water quality and aquatic life, and one of the governing causes of eutrophication in water systems. It has been the object of much research that led to the implementation of P best management practices, aimed at curbing P export from agricultural and urban landscapes. However, these efforts are somewhat insufficient to mitigate and control dissolved P transport, a P pool 100% bioavailable for aquatic biota. Recent developments in nutrient management research highlight the ability of P removal structures to sequester dissolved P from flowing water, e.g., runoff and subsurface drainage, before it reaches water bodies. Phosphorus removal is accomplished through the use of reactive filter media, which are either manufactured, mined, or industrial by-products. These media, also referred to as P sorption materials (PSMs), vary in P removal ability, due to their origin, chemical and physical properties, or the conditions under which they operate. Consequently, there is a need to fully distinguish the characteristics of PSMs and their behavior in P removal structures that result in a superior P removal performance. In this study, six different types of PSMs were characterized according to their chemical and physical nature, and PSM-P interactions. To evaluate the variability of P removal capacity of steel slag, a series of flow-through experiments were conducted, using 18 different samples from different origins and generation processes. Phosphorus removal was evaluated on uncoated and aluminum(Al)-coated steel slag samples under two residence times. After chemically characterizing the samples, we found that, for the uncoated steel slags, electrical conductivity (EC), bulk density, particle density and magnesium (Mg) content could explain around 70% of the variability of P removal. Steel slags showed a high variability in their P removal ability, but such variability could be considerably decreased when coating the slags with Aluminum (Al). The Al-coating also allowed a significantly better P removal performance under shorter residence times. Flow-through experiments were also conducted to evaluate the ability to regenerate the P removal capacity of iron(Fe)- and Al-rich PSMs across two cycles of sorption-desorption with potassium hydroxide (KOH). This study found an average P recovery of 81%, 79% and 7% for Alcan, Biomax and PhosRedeem, Fe/Al-rich PSMs commercialized for contaminant removal. The most effective regeneration treatment was characterized by the largest KOH volume (20 pore volumes) and no recirculation, with up to 100\% reported P recovery, although a more economical/feasible use of 5 pore volumes of 1M KOH with recirculation was also found to perform well. The results suggested that the use of Al/Fe-dominated PSMs in P removal structures can be extended through the demonstrated regeneration technique. Iron-rich PSMs were further evaluated in regards to their behavior under anoxic conditions, a scenario that can be found in P removal structures with bottom-upward flow regimes. To evaluate the interference of redox-induced changes on P removal, PSM samples were incubated in a biogeochemical reactor in the presence of tile drainage water. Measurements of Eh throughout the incubation period indicated that PSMs, similar to soils, developed anoxic conditions. After incubation, the dissolved P concentrations in P-loaded and original PSMs were equally low, demonstrating the stability of P retention of PSMs under anoxic conditions. Additionally, the P removal ability of the original PSMs was not significantly altered by undergoing anoxic conditions, as determined from flow-through experiments following incubation. Anoxic-induced changes did not result in any limitations to the implementation of P removal structures with bottom-upward flow. These studies demonstrated the variability in P removal capacity of PSMs as a function of chemical and physical properties, the dominant P removal mechanism, and the operational characteristics of the P removal structure. The experimental data suggests that P removal structures are an effective and environmentally safe best management practice (BMP) that, in conjunction with traditional BMPs, are critical for the mitigation of dissolved P export to water systems. </div>