Debasis Roy

Limited availability of simple yet adequately validated tools for estimating the deformation potential of municipal solid waste (MSW) material poses difficulty in planning and managing landfill operations. Estimation of settlement of MSW landfills has remained a challenge because of heterogeneity and time-varying mechanical behavior of MSW materials and difficulty of extracting representative samples and reconstituting them for laboratory testing. An empirical correlation is proposed here for estimating the short-term settlement of landfill materials. The relationship was developed by calibrating laboratory data from axial (1D) compression and consolidated drained triaxial tests against field-measured shear wave velocities from five landfill sites with varied waste compositions. The correlation was validated against three full scale load tests; one obtained in this research and two reported by others, and a field compaction study from a fourth landfill. Although the proposed correlation was more accurate than an alternative developed earlier, overall it underestimated settlements by about 12%. The proposed relationship could therefore provide a conservative guidance in MSW landfill design and operation.

Chitin is a linear homo-polymer of N-acetyl-d-glucosamine (GlcNAc) and the second most abundant biopolymer after cellulose. Several industries rely on the bioprocesses for waste chitin recycle and hydrolysis by chitinase (EC 3.2.1.14) for potential healthcare applications through the production of its monomeric subunit, GlcNAc. In the present study, a chitinase-producing fungus (named as MFSRK-S42) was isolated from the marine water sample of North Bay of the Andaman and Nicobar Islands. It was identified as Aspergillus terreus by morphological and molecular characterization methods leveraging the internal transcribed spacer between 18S rRNA and 5.8S rRNA. Chitinase that was isolated from the fermentation broth of marine Aspergillus terreus was used to carry out biotransformation of chitineaceous wastes. Prior to the enzymatic hydrolysis step, chitins from different sources were characterized for the presence of characteristic functional groups, grain size distribution, and surface morphology. Enzymatic hydrolysis of 50 mg/ml substrate with six units of enzyme incubated for 5 days revealed 15, 36.5, 40, and 46 mg/ml GlcNAc production from ground prawn shell, chitin flakes, colloidal prawn shell, and swollen chitin respectively under standardized conditions, as determined by HPLC. In this study, 30, 73, 80, and 92% GlcNAc yields were observed from ground prawn shell, chitin flakes, colloidal prawn shell, and swollen chitin conversion respectively. The HPLC-eluted product was confirmed as GlcNAc by the presence of characteristic functional groups in FTIR and 244 Da molecular weight peak in HRMS analyses.

Skempton’s pore pressure parameter B_w,, often used as a proxy for the degree of saturation of soil, depends strongly on the pore fluid compressibility. Presence of dissolved gas in pore fluid or free gas within soil void space has a remarkable influence on pore fluid compressibility. Gas generated through natural bioprocesses often increases pore fluid compressibility leading to a reduction in pore pressure development for soils under undrained loading. Loose sand samples inoculated with two aerobic soil bacteria sustained with a single dose of minimal nutrient media were monitored for bacterial growth, calcite and CO₂ production, and pore fluid compressibility. A simple analytical model was developed to explain these observations based on biogenic gas production by these bacteria through different bioprocesses. Observed B_w-values were in excellent agreement with the estimated values. Biogas was found to increase pore fluid compressibility and is therefore expected to enhance liquefaction resistance of loose soil.

Excessive fluoride (above 1.5 mg/L) containing water consumption for prolonged periods could pose health hazards, for example, dental fluorosis. Longer exposure could also cause skeletal fluorosis leading to the permanent deformity to skeleton. In the current context, use of biomasses for defluoridation would be a most economic and sustainable option for water defluoridation over the available alternatives. This article presents a brief summary of processes used biomasses for fluoride removal from aqueous solutions. This article also discusses the theoretical and instrumental approaches used by the researchers till date to understand the defluoridation mechanisms. The literature survey pointed that theoretical models such as Langmuir and Freundlich isotherms, pseudo‐first‐order and second‐order kinetic models, and different thermodynamic equations were also used to define the defluoridation by biomasses. Apart from the theoretical modeling, several researchers have also tried to understand the biomass‐based defluoridation by applying advanced instruments, for example, FTIR, XPS, NMR, TG, FESEM, and Raman spectroscopic analysis. © 2018 American Institute of Chemical Engineers Environ Prog, 37: 1560–1572, 2018