Ammoniacal Nitrogen Stripping From Landfill Leachate at Open Horizontal Flow Reactors.

The ammonia nitrogen stripping process at open horizontal flow reactors was evaluated and is described in this paper. The ammonia came from landfill leachate. Superficial loads of 650 kgN-.ha-1.day-1 (phase 1), 750 kgN-.ha-1.day-1 (phase 2), and 850 kgN-.ha-1.day-1 (phase 3) were applied with a hydraulic retention time of 51.2, 64.9, and 55.6 days, respectively. The experimental system setup was designed, built, and monitored at EXTRABES (Estação Experimental de Tratamentos Biológicos de Esgotos Sanitários) and consisted of a series of four open horizontal flow reactors fed with in natura leachate. The study was based on a stripping process with no alkaline chemical species addition, nor air flow for ammonium gas drag, and aimed to reduce the landfill leachate ammoniacal nitrogen concentration. The studied process showed a removal efficiency of 99.0% in the first phase, 99.3% in the second, and 99.5% in the third. Regarding the organic matter expressed in terms of CODtotal, the removal efficiency was 69.20% in phase 1, 40.12% in phase 2, and 29.23% in phase 3. It was noted that ammonia removal efficiency was directly proportional to the applied superficial load and the carbonaceous material removal was proportional to the organic matter applied in influent, since in phase 1 the CODtotal concentration removal efficiency was 1.7 times greater than that of phase 2, and 2.3 times that of phase 3. Briefly, the ammonia nitrogen stripping process by open horizontal flow reactor is a promising technological alternative for ammonia nitrogen reduction, mainly at regions with available area and temperature greater than 25°C. It is promising because it has no costs in terms of chemical reagents to raise the pH, nor does it require electric costs.

Fenton treatment of sanitary landfill leachate: optimization of operational parameters, characterization of sludge and toxicology.

This investigation aimed to refine the operational parameters of the Fenton process, to compare Fenton-treated and non-treated leachate with respect to physicochemical variables and toxicity towards Daphnia magna, and to characterize the sludge. The optimal conditions for the Fenton treatment involved the use of a reagent containing 12 g Fe2+ L-1, H2O2/Fe2+ molar ratio of 9 and pH 2.0, with oxidation, flocculation and sedimentation times of 30, 10 and 15 min, respectively. Under these conditions, the values of the majority of parameters, including chemical oxygen demand (COD), biochemical oxygen demand, dissolved organic carbon, true color (TC), carbohydrates, proteins, phosphorus, total solids, total volatile solids, dissolved volatile solids, Kjeldahl nitrogen, N-NH3 and iron, were reduced significantly after treatment. However, sludge production rate remained somewhat high (98 kg m-3 of treated leachate), although the specific resistance to filtration of the sludge was moderate (12 × 109 cm g-1). While the Fenton process achieved a satisfactory removal of COD (87%) and TC (91%), the treated leachate contained organic compounds that were resistant to oxidation and remained toxic towards D. magna. Hence we conclude that the Fenton process alone is not appropriate for treatment of leachate, because it could negatively affect the ecosystem in receiving water bodies, but it could represent a viable alternative for the pretreatment of landfill leachate.

Conversion of "Waste Plastic" into Photocatalytic Nanofoams for Environmental Remediation.

Plastic debris is a major environmental concern, and to find effective ways to reuse polystyrene (PS) presents major challenges. Here, it is demonstrated that polystyrene foams impregnated with SnO2 are easily generated from plastic debris and can be applied to photocatalytic degradation of dyes. SnO2 nanoparticles were synthesized by a polymeric precursor method, yielding specific surface areas of 15 m2/g after heat treatment to 700 °C. Crystallinity, size, and shape of the SnO2 particles were assessed by X-ray diffraction (XRD) and transmission electron microscopy (TEM), demonstrating the preparation of crystalline spherical nanoparticles with sizes around 20 nm. When incorporated into PS foams, which were generated using a thermally induced phase separation (TIPS) process, the specific surface area increased to 48 m2/g. These PS/SnO2 nanofoams showed very good efficiency for photodegradation of rhodamine B, under UV irradiation, achieving up to 98.2% removal. In addition the PS/SnO2 nanofoams are shown to retain photocatalytic activity for up to five reuse cycles.