Surface characterization of natural apatites used to remove phosphates from wastewater in constructed wetlands: which techniques to use?

Phosphorus is an essential element for all life forms. However, an excessive concentration of phosphates is the most common cause of water bodies eutrophication as phosphorous is usually the limiting nutrient involved in plant growth. In constructed wetlands (CWs) treating domestic wastewaters, good treatment performances are obtained on main pollutants except with phosphates. In order to improve phosphate removal by CWs, different experiments were performed considering a series of reactive substrates. Among those, natural apatitic materials showed a high sorption capacity for phosphates. This paper presents the various analytical techniques that were used to characterize five natural apatitic materials which were tested in experiments performed at different scales (laboratory, pilot plant and full-scale experiments). These apatitic materials have been studied using X-ray powder diffraction, Raman spectroscopy and scanning electron microscopy. In addition, chemical compositions were obtained from X-ray fluorescence and ICP-MS analyses. The results suggest that the studied apatitic materials present a wide spectrum of physical, mineralogical and chemical characteristics. This variety is related to the presence of impurities in the natural materials (5–60% w/w). Therefore, the characterization of the natural apatitic materials available is necessary in order to select the ones that would lead to the best performances in terms of phosphate removal. Moreover, the observation of the surface of the grains before and after the percolation of phosphate containing solutions showed that the primary apatitic peloids were progressively covered with a carbonate hydroxyapatite precipitate layer formed with the phosphates removed from the treated solution

Rétention du phosphore par apatite en filtres plantés de roseaux : recommandations de dimensionnement

International audiencePhosphorus (P) removal in constructed wetlands (CWs) has received particular attention during the last decades by using specific materials which promote P adsorption/precipitation phenomena. Recent studies have shown an interest in using apatite materials to promote P precipitation onto their surface. About ten years of experiments at different scales (laboratory, pilot, full scale) have passed. The process is now open in France. This paper presents the first design recommendations according to the apatite mineral quality and treatment outlet requirements. Kinetics and their evolution with the material saturation degree are presented based on the k-C* model. The process can achieve 1 mgP.l-1 for long term while using surface P removal filter area of 0.5 m².p.e.-1. With a low land footprint and high P removal efficiency, the interest of the process also result in the orthophosphates accumulation on a phosphate mineral which makes easier to reuse phosphorus from wastewater once saturated

Rétention du phosphore par apatite en filtres plantés de roseaux : recommandations de dimensionnement

International audiencePhosphorus (P) removal in constructed wetlands (CWs) has received particular attention during the last decades by using specific materials which promote P adsorption/precipitation phenomena. Recent studies have shown an interest in using apatite materials to promote P precipitation onto their surface. About ten years of experiments at different scales (laboratory, pilot, full scale) have passed. The process is now open in France. This paper presents the first design recommendations according to the apatite mineral quality and treatment outlet requirements. Kinetics and their evolution with the material saturation degree are presented based on the k-C* model. The process can achieve 1 mgP.l-1 for long term while using surface P removal filter area of 0.5 m².p.e.-1. With a low land footprint and high P removal efficiency, the interest of the process also result in the orthophosphates accumulation on a phosphate mineral which makes easier to reuse phosphorus from wastewater once saturated

Phosphorus removal by the use of apatite in constructed wetlands: Design recommendations

cited By 6International audiencePhosphorus (P) removal in constructed wetlands (CWs) has received particular attention during the last decades by using specific materials which promote P adsorption/precipitation phenomena. Recent studies have shown an interest in using apatite materials to promote P precipitation onto their surface. About ten years of experiments at different scales (laboratory, pilot, full scale) have passed. The process is now open in France. This paper presents the first design recommendations according to the apatite mineral quality and treatment outlet requirements. Kinetics and their evolution with the material saturation degree are presented based on the k-C* model. The process can achieve 1 mgP.l-1 for long term while using surface P removal filter area of 0.5 m2.p.e.-1. With a low land footprint and high P removal efficiency, the interest of the process also result in the orthophosphates accumulation on a phosphate mineral which makes easier to reuse phosphorus from wastewater once saturated. © IWA Publishing 2011

Performances evaluation of phosphorus removal by apatite in constructed wetlands treating domestic wastewater: Column and pilot experiments

International audienceIn constructed wetlands (CWs) treating domestic wastewater, good treatment performances are obtained on mains parameters except phosphorus (P) which can cause eutrophication problems. In order to improve P removal from wastewater with a low specific filter surface per people equivalent (p. e.), different materials have been tested: man-made and natural materials, industrial by-products, and a mixture of these materials. The P removal by natural apatite have been studied by a very few works. Despite apatite materials appears to possess high and long-term retention capacity, a better knowledge is needed to precise the quality of apatite to be used and the P removal evolution with time and water quality. In this work the P retention kinetics have been studied in two different scales (lab-experiments and pilots) on different apatite qualities. Retention rate in pilots is smaller than the one found in lab-experiments and the results suggested that a security coefficient might be applied while designing apatite filter