Dynamic sorption of ammonium by sandy soil in fixed bed columns: Evaluation of equilibrium and non-equilibrium transport processes.

The release of excess nitrogen-containing compounds into groundwater is a major concern in aquifer recharge by the Soil Aquifer Treatment (SAT) process. Ammonium (NH(4)(+)) is one of the most nocive and common nitrogen compounds in wastewaters. In order to assess the risk of wastewater use for aquifer recharge, NH(4)(+)adsorption onto Souhil wadi soil sampled from the SAT pilot plant (Nabeul, Tunisia) was studied using laboratory columns experiments. Several experiments were conducted using aqueous synthetic solutions under different aqueous ammonium concentrations and flow rates. Furthermore, a real wastewater solution was used to test the effect of competitive cations contents on NH(4)(+) adsorption. Afterwards, the Hydrus-1D model was used in inverse mode to simulate the ammonium transport through the Souhil wadi soil. For the synthetic solutions, the adsorbed ammonium amount varied from 1 to 30.7 mg kg(-1) for aqueous ammonium concentrations between 4.9 and 36.4 mg L(-1). The linear isotherm model was found to be the most suitable for describing this adsorption. The flow rate decrease from 45 to 15 mL min(-1) induced an increase in the ammonium adsorption capacity by 49%. Indeed, the lesser the flow rate is, the longer the residence time and the higher the exchange between the aqueous solution and soil matrix. The use of wastewater instead of aqueous synthetic solution decreased about 7 times the Souhil wadi adsorption capacity of ammonium because of its relatively high concentrations of competitive ions such as calcium and magnesium. The use of the Hydrus-1D model showed that the chemical non-equilibrium model was the best to simulate the ammonium transport through the laboratory soil columns.

Protection of the lingual nerve during operations on the mandibular third molar: a simple method.

The object of the study was to assess the incidence of lingual nerve sensory loss during removal of impacted mandibular third molar teeth, and the effect of retention of the lingual plate on the incidence. The subjects were 395 patients, of whom 362 completed the study. Removal of 504 impacted wisdom teeth with retention of the lingual plate was performed. Results showed that 381 (76%) of the teeth were partially erupted and the remaining 123 were unerupted. In 497 (99%) bone had to be removed, and of these 376 (76%) required division of the tooth before removal (75% of the entire series). The only complication was transient paraesthesia in one patient which settled within a month. The study concludes that retention of the lingual plate gives optimum protection to the lingual nerve during removal of impacted wisdom teeth.