Progrès dans le recyclage et la gestion des déchets

For efficient bioethanol production from maize stover, fermentation of glucose and xylose both was attempted using Saccharomyces cerevisiae and Pichia stipitis sequentially from enzymatic hydrolysate of mild alkali treated maize stover. Enzymatic saccharification of mild alkali treated maize stover at high substrate (30%) loading using 13.0 FPU/g commercial cellulase (MAPs 450) and 74.42 U/g crude β-xylosidase (Inhouse produced) after 36 h, yielded 161.32 mg ml-1 reducing sugars. Ethanol production was optimized employing response surface methodology. Under optimized conditions viz. 5% glucose, 14.55% inoculum and Time 35.51 h; 90.65% glucose was utilized and produced 18.93 g l-1 ethanol with 0.53 g l-1 h-1 productivity by Saccharomyces cerevisiae NCIM 3524. Further attempts were made to produce ethanol from xylose present in enzymatic hydrolysate using Pichia stipitis NCIM 3497. However, xylose conversion was not satisfactory as only 71% xylose was utilized.

The lands of Kalipur area are contaminated with industrial wastewater and dust particles. Anticipating a possible health hazard through contaminated food crops with toxic metals like chromium, nickel and cadmium was investigated. The mobilization of metal from rhizosphere soil to plant tissues was calculated to determine the enrichment factors of soil and plants. Scanning Electron Microscope and Fourier Transform Infrared Spectroscopy were used for comparative study of surface soil contamination. The Ni, Cr and Cd in soil varied from 24.5 to 44.5, 42.4 to 65.5 and 14.2 to 31.6 μg g-1 enriched by a factor of 3.81, 4.64 and 20.94. Their corresponding values in cultivated plants and weeds were 12.6 ± 1.04 to 44.5 ± 2.84, 26.3 ± 1.64 to 67.5 ± 4.82 and 6.6 ± 0.84 to 22.3 ± 1.46 μg g-1 dry wt. enriched by a factor of 7.49, 6.89 and 22.08 respectively. All these metals are causing toxicity of soil while in plant tissues exceed the phytotoxicity limit and fall in the critical range. The causes of wide variation in metal uptake and accumulation in above ground plant parts and how weeds are growing luxuriously in spite of pollution and metal stress condition through evolution are well explained. Thus our study suggests that there is a health risk due to consumption of plants containing higher amounts of toxic metals resulting in asymptomatic chronic disorders in humans and cattle.

Tire rubber has been found to adsorb pesticides and nitrate, and remove phosphorus by precipitation with iron released from steel wire. Golf courses are known to release pesticides and nutrients such as nitrogen and phosphorous. The feasibility of using tire rubber as an adsorbent for pesticides in golf courses was evaluated using statistical and mathematical methods. Empirical equations were proposed to predict the required tire rubber layer thickness to remove various pesticides under different conditions. It was found that a 20 cm thick tire rubber layer was capable of removing ≥ 90% for 37 out of 51 pesticides. Three of the 51 pesticides required a >200 cm thick tire rubber layer, yet had high solubility and short half-life. By using scrap tires for the mitigation of pesticides and fertilizers, golf courses may be able to realize the dual benefits of waste utilization and reduced environmental contamination.

Leather processing is an important economic activity around the world and uncontrolled release of tannery effluents to natural water bodies causes environmental degradation and increases health risks to human beings. The treatment of tannery effluent is a complex technological challenge because of the presence of high concentrations of organic and inorganic pollutants of both conservative and non conservative nature. In this review paper information relevant to tannery effluents and its prospective on biological treatment processes and other recent potential biological processes are discussed. Emphasis is laid on the removal of organic matter (COD/BOD), NH4-N and sulphide/sulphate from tannery effluent. Though the aerobic process is efficient in treating tannery effluent, it requires an extended aeration time at low organic loading rates and thereby increasing the overall treatment cost. Anaerobic process is not effective because of sulphide inhibition problems. Sulphide inhibition control is essential for successful anaerobic treatment of tannery effluent. Sequencing Batch Reactor (SBR) and membrane reactor technologies are found to be effective for removal of organic matter and ammonia, but they are having very high operational cost. A recent development is the employment of alternate electron acceptor/donor already present in tannery effluent for simultaneous removals of COD/BOD, NH4-N and sulphide/sulphate with possibility of elemental sulphur recovery at higher organic loading rates. The recent development shows possibility of high rate treatment of tannery effluent in an alternate and an effective way suitable to both developing and developed countries.

This study undertook an extensive overview of the state of recycling in Ontario, including detailed discussions on the types of material being generated and diverted and the economics of Blue Box recycling. Specifically, this study examined how Blue Box generation, recovery and costs have changed over time, and identified trends in the data to suggest that material management costs are increasing inordinately relative to the quantities of material being recovered. While it is difficult to specifically isolate the cause for rising system costs, there is evidence in the data to suggest that high cost "fringe" materials now comprise a larger share all material being generated in the province. Given that there is strong statistical support to suggest that this trend is likely to continue into the future, policy planners need to take a step back and identify not only how to reverse these trends, but develop policies that optimize the mix of materials being recovered.

This study examines the challenges and opportunities for increasing diversion in Ontario’s Industrial, Commercial and Institutional (IC&I) sector. The IC&I sector is responsible for more than 75% of all waste generated in the province, but manages to divert only 12% of end of life material from landfills. Using a system based cost model, focus is placed on analyzing 1) What are possible factors that contribute to poor IC&I diversion performance? 2) What would happen to provincial recycling costs if IC&I diversion increased? 3) What material types should policy planners prioritize when attempting to increase overall diversion? The results of this analysis show that Ontario’s poor diversion may be explained by low landfill disposal costs and high recycling costs relative to other jurisdictions. While there are significant opportunities to increase diversion in the IC&I sector, particularly for printed paper and packaging materials, the costs associated with doing so may prove prohibitive to businesses. Significant investments in collection and processing infrastructure may be necessary to accommodate for increases in diverted material from the IC&I sector. The findings of this study suggest that Ontario prioritize certain materials for increased diversion (due to high levels of recyclability and low cost), and support the sector through revised legislation that addresses who is legally mandated to divert material and who should pay for it.