Phosphorus recovery as struvite and hydroxyapatite from the liquid fraction of municipal sewage sludge with limited magnesium addition.

Phosphorus (P) is an essential element to produce feed and fertilizers but also a nonrenewable resource. Both the predicted exhaustion of phosphatic rocks and the risk of eutrophication lead to an increasing necessity for P recovery methodologies to be applied in municipal wastewater treatment plants (WWTPs). One of the most promising solutions involves the precipitation of P-based minerals reusable as slow-release fertilizers. In this study, P recovery as struvite and hydroxyapatite from a municipal WWTP digestate liquid fraction (centrate) was investigated at varying pH (8-10), reagent typologies (MgCl2 , NaOH, Ca(OH)2 , and CaCl2 ), and concentrations under limiting magnesium doses through liquid- and solid-phase analyses and thermodynamical modeling. A maximum P recovery of 87.3% was achieved at pH 9 by adding NaOH and MgCl2 at a dose of 656 mg/L (the higher tested). According to these data, it was estimated that 92.0 tons/year of struvite and 33.2 tons/year of hydroxyapatite could be recovered from the WWTP centrate with a cost for reagent consumption being almost 50% of the mean P market value. An increase in P precipitation was observed while comparing experiments with the same pH values but with a higher Mg2+ dose. Ca2+ addition led to extensive P precipitation but mainly as amorphous phases that interfere with struvite formation.

Binders alternative to Portland cement and waste management for sustainable construction - Part 2.

The paper represents the "state of the art" on sustainability in construction materials. In Part 1 of the paper, issues related to production, microstructures, chemical nature, engineering properties, and durability of mixtures based on binders alternative to Portland cement were presented. This second part of the paper concerns the use of traditional and innovative Portland-free lime-based mortars in the conservation of cultural heritage, and the recycling and management of wastes to reduce consumption of natural resources in the production of construction materials. The latter is one of the main concerns in terms of sustainability since nowadays more than 75% of wastes are disposed of in landfills.

Role of exercise evaluation in restrictive lung disease: new insights between March 2001 and February 2003.

Restrictive lung disease is often first detected when patients complain of dyspnea on exertion. Many forms of exercise testing are available, from simple hallway oximetry to the more formal and more complex cardiopulmonary exercise test. Although the use of exercise for diagnosis, treatment, and predicting outcomes is largely understudied in this population, it has recently been shown to be of value in some settings. Exercise testing may be a valuable diagnostic tool in determining the extent of lung disease in sarcoidosis. Medinger et al. reported that the symptom-limited exercise test detected pulmonary dysfunction earlier than history, physical examination, chest radiography, and spirometry alone. Furthermore, Delobbe et al. noted that in patients with biopsy-proved sarcoidosis, cardiopulmonary exercise testing was a more sensitive indicator of early lung disease than pulmonary function tests. The American College of Chest Physicians/American Thoracic Society have published an updated consensus statement for cardiopulmonary exercise testing. Christensen et al. reported that patients with restrictive lung disease may be at risk for hypoxemia with light exercise while on an airplane, and suggest that these patients be considered for in-flight oxygen therapy. Lastly, Herridge and the Canadian Critical Care Trial Group used the 6-minute walk test to prove that survivors of acute respiratory distress syndrome have significant functional limitation 1 year after discharge from the intensive care unit largely secondary to neuromuscular sequelae. Exercise testing appears to be a valuable tool in evaluating, treating, and predicting outcomes in patients with restrictive lung disease. Further study will help to support its use in other restrictive lung diseases.