Mechanism of pH sensitive flocculation for organic load and colour reduction in landfill leachate.

Landfill leachate has an important fraction of humic substances, mainly humic acids (HAs), which often represent more than half value of COD, specially in liquids proceeded from composting processes of organic fraction of solid wastes. We propose in this article a new method of pH sensitive flocculation for COD and colour reduction in landfill leachate based on the chemical properties of HAs. Landfill leachate with a high content of humic acids can be efficiently treated by pH sensitive flocculation at pH 2.0, reducing COD value in 86.1% and colour in 84.7%. Mechanism of pH sensitive flocculation is based in protonation first of phenolic groups and later of carboxylic acid groups in the HAs molecules, resulting in a reduction of Zeta potential value. For pH over neutrality, carboxylic acid and phenolic groups are ionized and Zeta potential increases in absolute value, maintaining HAs in suspension as colloids and conducting flocculation to be obstructed. Ionized anionic groups (carboxylates) can interact electrostatically with cations abundant in leachate (site binding) aiding to maintain HAs in suspension. Simulation of this situation and ideal visualization of Zeta potential behavior is described in the paper and aggregation of molecules by H-bonds is proposed as the main step in separation of HAs from leachate and reduction of COD value in this complex liquid. CHNS analysis, FT-IR spectrometry and UV-VIS spectrophotometry show chemical elements content in the range of natural and commercial HAs, clear aromaticity and carboxylic acids and phenolic groups presence in the precipitate from landfill leachate.

Intestinal obstruction secundary to gallstone ileus: case report.

Gallstone ileus is an intestinal obstruction that is secondary to the presence of gallstones in the small intestine. It is a rare complication of cholelithiasis, which represents 1-3% of the causes of intestinal obstruction. The diagnosis is difficult given that the symptoms are nonspecific with intermittent intestinal obstruction, Rigler's triad (pneumobilia, stone and abdominal distention) is pathognomonic. Among the diagnostic aids are abdominal radiography, ultrasound and abdominal tomography. Treatment should be individualized depending on the patient's conditions, with laparotomy with enterotomy being the treatment of choice.

El íleo biliar es una obstrucción intestinal secundaria a la presencia de cálculos biliares en el intestino delgado. Es una complicación rara de la colelitiasis y representa el 1-3% de las causas de obstrucción intestinal. El diagnóstico es difícil dado que la clínica es inespecífica, con un cuadro de oclusión intestinal intermitente; la tríada de Rigler (neumobilia, lito y distensión abdominal) es patognomónica. Dentro de los auxiliares diagnósticos se encuentran la radiografía de abdomen, el ultrasonido y la tomografía computarizada abdominal. El tratamiento debe individualizarse dependiendo de las condiciones del paciente, siendo de elección la laparotomía con enterotomía.

Landfill leachate treatment by sorption in magnetic particles: preliminary study.

Leachates are still an open issue in environmental protection. Many of the applied methods for their treatment present low efficiency and thus need to be used collectively. In practice reverse osmosis is mostly used, as it is the most effective option, regardless of its cost. Magnetic methods to treat effluents have been used for water and wastewater treatment by the use of magnetic particles together with magnetic separation for the removal of contaminants. However, large-scale applications are few or even non-existent when we deal with complex contaminated media such as landfill leachates, for which not even research studies at laboratorial scale with real samples have been done yet. In this work, we apply for the first time magnetic sorption for the treatment of leachates, and close the full cycle by studying the regeneration and re-use of the magnetic particles; we also study the influence of the concentration of magnetic particles, the use of several pre-treatment methodologies and the type of particle used in the process, in real landfill samples from the waste treatment plant of Salamanca (Spain), for the removal of COD, NO3-, NO2-, NH4+, Total-N, PO43-, SO42- and Cl-. Regeneration of the magnetic particles after being used in the sorption stage is also studied, as well as their efficiency regarding their re-use. It is also determined the optimum number of batches for complete desorption and for regeneration of the particles, the effect of successive regeneration and re-use cycles, the use of two different regeneration methods, the efficiency of the desorption, the effect of the quantity of solvent and the influence of the time of sorption. Due to its innovative character and the complexity of the media, this work represents a first preliminary approach and, although some promising results have been obtained, further studies are required to completely understand and evaluate the proposed treatment process.