Microbial Treated Waste Foundry Sand and its Metal Leachate Analysis
Abstract
As the quantity of Waste Foundry Sand (WFS) is generated in huge amount, only a part of WFS is considered as the hazardous waste and the rest of the part is considered as non-hazardous industrial waste foundry sand. The leachate from WFS may contain hazardous compounds, which may probably effect the environment. The random release of heavy metals into the soil and waters is a major health alarm worldwide, as they cannot be broken down to non-toxic forms and therefore have long-lasting effects on the ecosystem. Leaching characteristics are essential in understanding the environmental impact or toxicity, dumping and potential development of beneficial applications of WFS. This study investigates that a trial was done to find out a fungal species from dumped site of a local foundry located at Coimbatore (Tamilnadu, India). Isolation of different fungal species from soil sample was carried out. All the isolated fungal species were then screened for their organic acid production by using HPLC. The molecular characterization of 18S rRNA for the isolated fungus was matched with R. oryzae. Physiochemical Characterization of WFS was done. Assessment of impacts of using fungal treated WFS its leachate quality was done using atomic absorption spectroscopy.
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Introduction
Increasing awareness on the environment has dramatically contributed to the concerns related with disposal of the wastes generated and discharged. Industrialization is considered to be a significant factor for the development of a country’s economy. But the plants and factories from this industrialization process which discharges wastes and byproducts causes severe disastrous to the environment contaminating the surface water, ground water and soil. There are a number of reasons the waste are not safely treated [1]. Waste foundry sand (WFS) is one of such industrial by-product or considered as waste discarded material coming from ferrous and nonferrous metal-casting industry. It contains high content of silica sand with uniform physical characteristics which is used by the foundry industry to create metal casting molds [2]. WFS contain different heavy metal-leachate which needs to be treated before discharged. The leachate from such materials may contain dangerous compounds, which may possibly affect the atmosphere [3]. But with the scarcity of space for land filling and due to its ever increasing cost, waste utilization from these industries has become an attractive alternative to disposal. Research is being carried out on the utilization of waste products in concrete as a replacement of natural sand. Discarded tyres, plastic, glass, burnt foundry sand, and coal combustion byproducts were considered to be as such waste products, provides specific effect on the properties of fresh and hardened concrete. The use of waste products in concrete not only makes it economical, but also helps in reducing disposal problems. Thus the reuse of bulky wastes is considered as the best environmental alternative for solving the problem of disposal [1]. The high cost of land-filling and the potential uses of WFS in construction purposes have driven research into their beneficial reuse [2].
Bhat and Lovell [4] estimated that for every ton of metal castings produced and shipped that a typical foundry generates approximately one ton of waste sand. After molding is completed, the sand is discarded and generally land-filled. The rate of land-filling may vary from country to country. These costs are generally more in developed countries in measurement to developing and under-developed countries. According to Winkler and Bol’shakov [2] metal casting foundries in US, disposed of approximately 9 million metric tons of waste foundry sand in landfills. The annual cost of WFS disposal was around US$ 135–675 million which inclusive of storage, transportation and labor costs. This issue is gradually more addressed by alternate scenarios of beneficially reusing WFS. Thus WFS was considered to be a potential alternative in a range of applications including construction materials such as Controlled Low-Strength Material (CLSM) and concrete. According to Bhat and Lovell [4] foundry sand has become a viable candidate for use in Controlled Low Strength Materials because of cost effective, increasing availability, and satisfactory performance.
Conclusion
Waste foundry sand is waste material from foundries which exhibits lower unit weight, higher water absorption and higher percentage of void compared to regular sand. This study aimed to present the utilization of fungal treated WFS in concrete (eco-friendly). The ability of producing organic acid from the fungi R.oryzae was selected by HPLC. From the previous optimization study concludes 6% of fungal inoculum, 3% 0f waste foundry sand and 0.6% of additional nutrient (glucose) gives maximum organic acid production in 7 days of incubation. Study also included leachate analysis obtained from the concrete mixes made with fungal treated WFS and untreated WFS. Results showed the metal concentration of Cu, Co, Fe, Mg, Ni and Zn were reduced to significant levels. Reduction of metal leaching is attributed due to the uptake or absorption of metals by fungal mycelium for its metabolic activity. Its shows the reduction in the metal concentration in leachate obtained from fungal treated concrete. The beneficial use of such by-products in construction materials results in reducing the cost of construction materials’ ingredients and also helps in reducing disposal problem. It could be conveniently used in making good quality concrete, white ware bodies, construction materials, soil amendments, flowable fills and embankment. Strength properties of concrete mixtures increase with the increase in foundry sand content.