Distributed mathematical model for simulating temperature profile in landfill.

Elevated Landfill temperatures have an undesirable effect on landfill cover, stability, slope and leachate migration pattern. Thus, to predict the temperature profile in the landfill a distributed numerical model using MacCormack finite difference method is developed. The developed model considers stratification of the upper and lower layers of the waste as new and old waste by assigning different values of heat generation for aerobic and anaerobic processes. Further, as the new layers of the waste get accumulated over the older layers, the density, moisture content and hydraulic conductivity of the underlying waste layers get modified. The mathematical model utilizes a predictor-corrector approach with a Dirichlet boundary at the surface and no flow condition at the bottom. The developed model is applied to the Gazipur site located in Delhi in India. A correlation coefficient of 0.8 and 0.73 is obtained between the simulated and observed temperatures in calibration and validation respectively. The result shows that the temperature at all the depths and in all the seasons was found to be higher than the atmospheric temperature. The maximum difference of 333 °C was observed in December, and the minimum difference of 22 °Cs was observed in June. The temperature rise is higher in the upper waste layers as it undergoes aerobic degradation. The locus of the maximum temperature gets modified with moisture movement. Since the developed model shows a good agreement with the field observation, it can be used to predict the temperature variation within the landfill under different climatic conditions.

Assessing efficiency and economic viability in treating leachates emanating from the municipal landfill site at Gazipur, India.

The leachates emanating from the landfills are high in organic loads and thus become potential sources of contamination for both surface and groundwater. As the landfill ages, the nature of leachate changes from acidic to alkaline. The change in pH level affects the chemical oxygen demand (COD)/biochemical oxygen demand (BOD) ratio and when it is less than 0.63, chemical treatments are more effective over the biological treatment methods such as upflow anaerobic sludge blankets (UASB). The existing literature suggests coagulation-flocculation and advanced oxidation process (Fenton) as effective methods for treating wastewater but no comparison of the two are available. Thus, the present study attempts to identify the most efficient coagulants out of ferric chloride (FeCl3), ferrous sulphate (FeSO4) and alum [Al2(SO4)3]. Ferric chloride leading to 99% colour removal, 98% COD removal, 99% decrease in total organic carbon, 94.3% removal in NH3-N and 91.4% removal in total Kjeldahl nitrogen is observed to be the most efficient coagulant and surprisingly, proves to be even better than Fenton. To understand the field applicability of the two treatment procedures, coagulation with FeCl3 and Fenton are compared with the UASB method which is currently employed at Gazipur landfill site, Delhi. With lesser operational cost than UASB, both FeCl3 and Fenton perform better on cost-efficiency scale. Switching from in-suit UASB method to the FeCl3 method of treatment may result in decreasing the operational cost by 71.9% and to conventional Fenton may result in decreasing the operational cost by 76.8%.

N-Heterocyclic-based adsorbents for antibody purification-effect of ligand structure.

A new set of ligands based on substituted pyridine and other N-heterocyclic structures, possessing an aliphatic primary amino group tether and an exocyclic sulphur atom, has been prepared and immobilized onto epoxy-activated matrices such as Sepharose 6 Fast Flow®. The derived adsorbents have been evaluated for their utility to capture and purify humanized monoclonal antibodies. Favourable binding properties were assessed from screening assays to determine optimal conditions for the capture and elution of the monoclonal antibodies. Static and dynamic binding experiments were employed to derive the equilibrium dissociation constants KD 's and binding capacities Qmax 's. Typically, the KD values were in the range of 2-5 µM and the Qmax values between 20 and 75 mg mAb/ml resin, depending on the stereo-electronic properties of the substituent in the N-heterocyclic ring structure. The effect of ligand structure on the selectivity of these adsorbents was also investigated, and criteria for their use in the purification of monoclonal antibodies from cell culture supernatants established.