Phytoremediation of heavy metals: Recent techniques

The current remediation technique of heavy metal from contaminated soil-water are expensive, time consuming and environmentally destructive. Unlike organic compounds, metals cannot degrade, andtherefore effective cleanup requires their immobilization to reduce or remove toxicity. In recent years, scientists and engineers have started to generate cost effective technologies that include use ofmicroorganisms/biomass or live plants to clean polluted areas. Phytoremediation is an emerging technology for cleaning up contaminated sites, which is cost effective, and has aesthetic advantages and long term applicability. It is best applied at sites with shallow contamination of organic, nutrient or metal pollutants that are amenable to one of the five applications; phytotransformation, rhizosphere bioremediation, phytostabilization, phytoextraction and rhizofiltration. The technology involves efficient use of plants to remove, detoxify or immobilize environmental contaminants in a growth matrix (soil, water or sediments) through the natural, biological, chemical or physical activities or processes of the plants. A brief review on phytoremediation of heavy metals and its effect on plants have been compiled to provide a wide applicability of phytoremediation

Vermicomposting of vegetable waste: A biophysicochemical process based on hydro-operating bioreactor

The increasing waste generation rate, high collection cost and dwindling financial resources are the major problems faced by most of the developing countries for efficient solid waste management. Insome cities, the organic waste (market, municipal, household) are dumped indiscriminately or littered on the streets causing environmental deterioration. Biological processes such as composting followed by vermicomposting to convert vegetables waste (as valuable nutrient source) in agriculturally useful organic fertilizer would be of great benefit. Therefore this technique is studied in the present research work. A simple and potentially inexpensive Hydro Based Operating Bioreactor (HBOB) was developed for aeration and turning of plant biomass for efficient aerobic composting process. The compostingprocess was done viz ambient, mesophilic, thermophilic and cooling down stages for a period of two weeks. After cooling stage, the partially decomposed material was used further as bedding forearthworms for vermicomposting. Experiments were conducted to determine the changes in the physicochemical parameters (pH, temperature, moisture content and C/N ratio). The dominant speciesof microorganisms at different temperatures during entire process of composting and vermicomposting were investigated. Self heating of the ingredients due to microbial activity occurred within thebioreactor at the thermophilic stage of the composting process. The vermicompost developed in the HBOB was found to have comparatively high value of nutrients such as calcium, sodium, magnesium,iron, zinc, manganese and copper which can serve as a natural fertilizer giving high yield of plants. The vermicomposting has proved very effective and efficient for developing compost from vegetable waste