Emerging Green Technologies for Combating Environmental Pollution and their Usefulness in Sustainability Education
By: Dr. U. N. Rai*
Green technologies are eco–friendly technologies and no risk is involved in their application, they use renewable things, conserve natural resources and the environment, thus help in sustainable development. There are no side-effects while cleaning/ ameliorating pollutants from environmental components (water, air & soil) and are environment conscious and can change radical thinking. Application of green technology provides a multiple achievements by reducing disaster vulnerability, risk and impacts, and tackling climate change by reducing GHG emissions, changing waste generation pattern and safeguarding environment, economic growth and development. Low carbon and ecologically sound developmental strategies will help relive the impacts of disaster and climate change. Emerging Green Technologies are: environmental green clean technologies (phytoremediation, rhizofiltration, constructed wetlands, bioremediation); green energy (wind, water, solar, bio-fuels, wastewater); green buildings (environment conscious for water, energy and wastes); green chemistry (safe, environment-benign substances, energy efficient process, waste disposal); green purchasing (green products, organic clothing, green chemicals, low volatile compounds) and green nanotechnology for enhancing environmental sustainability of process.
Green Clean is the direct use of living green plants for in situ, or in place, risks reduction by removal of pollutants from soil, sludge, sediments and ground water through contaminant removal, degradation, or containment to render them harmless. It is emerging as the new eco-ally that can cut the cost of cleanup, non – intrusive and restore much larger sites than has been possible with traditional remediation methods. Is an aesthetically-pleasing, passive, solar energy driven clean up technique. It improves contaminated site aesthetics and potential for ecosystem restoration. Sub-sets of green clean (phytoremediation) technology are; phytoextraction, rhizofiltration, phytostabilization , phytodegradation and phytovolatilization. Rhizofiltration refers to the approach of using hydroponically cultivated plant roots to remediate contaminated groundwater, surface water and wastewater through absorption, concentration, precipitation and filtering contaminants through a mass of roots to remove toxic substances or excess nutrients. Besides, engineered bed reed system (horizontal flow system and down flow system) and constructed wetlands in which role of rhizospheric microbes mediated bioremediation is important.
Phytoremediation of toxic metal contaminated industrial wastes like; tannery effluent, sludge and fly-ash etc vis a vis utilization of treated phytomass by composting is an important advance step to enhance the success of the technology. Bio-gas plant is the best way to digest or compost treated plants and other organic material. The fertilizer which comes from a bio-gas plant contains three times more nitrogen. Bio-compost is natural and organic fertilizer, thus better establishment and growth of plants. Biogas, a promising substitute for natural gas, is the collective term for the mixture of methane and carbon dioxide produced by the biological breakdown of organic matter in the absence of oxygen. It consists of about 60% methane, a non-toxic and effective fuel gas and 40% is mainly inert carbon dioxide with traces of hydrogen, hydrogen sulphide, etc. Biogas can replace the wood as an energy source to save standing forest cover. This shadow price of afforestation/deforestation will minimize resource depletion. In addition, biogas could potentially help reduce global warming by less emission of nitrous dioxide and methane, which warms atmosphere three hundred and ten times and twenty-one times more than carbon dioxide, respectively.
Constructed wetlands for wastewater treatment have been proven to be effective, low-cost and sustainable alternative for conventional wastewater treatment technologies. Different types of wastewater can be treated with constructed wetlands as: domestic wastewater, storm water runoff from parking lots or farmland, wastewater from livestock operations, wastewater from mining and oil operations and landfill leachate. For the most common current use, treating domestic wastewater, the wetland is usually used in conjunction with a pretreatment process such as a standard septic tank. Different types of constructed wetlands are developed and applied at treatment sites epending upon demographic, topographic factors and the nature of waste to be treated. Surface flow constructed wetlands characterized by the horizontal flow of wastewater across the roots of the plants while subsurface flow constructed wetlands in which the flow of wastewater occurs between the roots of the plants and there is no water surfacing (kept below gravel). As a result the system is more efficient, doesn't attract mosquitoes and is less odorous and less sensitive to winter conditions. For large applications, they are often used in combination with vertical flow constructed wetlands and third vertical flow constructed wetlands, which are similar to subsurface flow constructed wetlands but the flow of water is vertical instead of horizontal and the water goes through a mixture of media, it requires less space than surface flow but is dependent on an external energy source. Intake of oxygen into the water is better (thus bacteria activity increased), and pumping is pulsed to reduce obstructions within the intakes. Basic understanding of environmental factor and their interactions is important for the design and construction of a wetland. The wetland needs to be designed according to nature of contaminant, absorption, sedimentation and chemical process, etc. In addition design principles need to address based on hydraulic load rate, residence time, plant density and inlet concentration. CSIR-NBRI has developed a horizontal flow constructed wetland at Shantikunj, Haridwar for onsite treatment of untreated drained wasters emerging from domestic sources, which may be helpful in treatment of wastewater before discharged in Ganga to conserve the river ecosystem. The results of the research on plant- based management of Ganga water pollution have immense applied value. Monitoring results of operation of wetland revealed a significant improvement in sewage water quality as reflected by a marked reduction in BOD (90%), TSS (65%), TDS (78%), NO3–N (84%), P (76%) and NH4–N (86%) and concomitant increase in dissolved oxygen content after 36 h retention time under established condition. Further, constructed wetland also resulted in the reduction of metal contents which was 35, 87, 49, 39, 95, 55, 85 and 92% for Cr, Mn, Co, Ni, Cu, Zn, As and Pb, respectively. Such pollution loaded plants could be harvested from the wetland from time to time and could be digested in a bio-composter for production of biogas and organic manure, thus facilitating the green economy. Sustainable development is a confluence of four constituent parts; environmental, economic, socio-political and cultural sustainability. Drivers of changes for sustainable development are technology, financial mechanisms, policy, legal enforcement and the systems in which communication and education are crucial. The goal of sustainability education is to develop a world population that is aware and concerned about the total environmental, economical and social issue its associated problems, and which has the knowledge, attitudes, skills, motivation, and commitment to work individually and collectively towards sustainable development and for prevention of global issues; climate change, greenhouse effects and biodiversity loss by facilitating use of green technologies. To protect children living in polluted regions, environmental education represents a relevant means of prevention. It is need for the hour to propose the sustainability education where teaching and learning to be designed in a participatory, learner-centered way. Need for sustainability education is to acquire the skills for identifying and solving environmental problems by using green technologies and lastly, the participation to encourage citizens to be actively involved at all levels in working toward for resolution of environmental problems for sustainable development.
Various global issues as climate change, global warming, bio-resource degradation, biodiversity loss, sustainable development must be included in their curriculum. Sustainability education goals are to produce confident and independent students, create equality, healthy social relations, priority for self-activity, thinking about other development i.e., permanent type of development and people should do their basic development and peace for human security.
*Director, Green Clean, Former Senior Principal Scientist & Professor AcSIR,, CSIR-National Botanical Research Institute, Lucknow – 226 001, India, Email: [email protected]