By Basavaraju Manu, on 22 December 2018.
Geogenic iron contamination can be explained by negative health effects caused by a high concentration of iron in water. Laterite is a major available soil type in coastal parts of Karnataka and Kerala. Laterite also contains 30-40 per cent of iron. Risks associated with this type of soil include leaching of iron into groundwater and contamination of drinking water sources. The orange stains in sinks, toilet or other areas of the bathroom can be an indicator of high iron presence. Iron can also leave stains on clothes through laundry equipment and cause discolouration of ceramic crockery. High iron content also imparts a metallic taste to water. Geogenic iron contamination can have adverse effects on human-health as well as damage buildings. When high concentration of iron is absorbed, it gets accumulated in the pancreas, liver, and heart eventually damaging the functionality of these vital organs.
Sea shells as adsorbents to treat geogenic iron: potentials in India
Iron contamination in water can be reduced with the help of a locally available seashell in the south-Indian peninsula. Meretrix casta, an edible mollusc, is a backwater clam (or bivalve) species. Along west coast, it occurs in Goa, Uppunda, Kundapur, Udyavara and Mulki estuaries in Karnataka and Ashtamudi, Chettuva, Beypore, Korapuzha, Moorad and Chaliyar estuaries inKerala. A reported experiment on Saigon river in Vietnam have shown that seashells hold potential of becoming an inexpensive medium for cleansing of water from heavy metals like iron.Notwithstanding that feasibility scenario given by researchers in Ho Chi Minh City, Vietnam was driven by a situation in Spain where seashells are in fact a waste product generated by the flourishing seafood canning industry.
A similar experiment was done in National Institute of Technology, Suratkal using adsorbents prepared from Meretrix casta. Up to 99 per cent removal of iron was obtained at neutral pH of water containing initial iron concentration of iron of 2.5 mg/Lof iron with corresponding residual concentration of < 0.1 mg/L. Hence it appears this seashell might be a potential solution to remove iron from water and in turn, also augment water with an essential nutrient, calcium.
Adsorption is an efficient and economic treatment technique to remove heavy metals from water. Other basic types of adsorbents include carbon based adsorbents (e.g. activated carbon, carbon nano-tubes, fullerens, carbonaceous nano materials etc.) and;mineral adsorbents (e.g. silica gel, activated alumina, oxides of metals,hydroxides of metals, zeolites, clay minerals, inorganic nano materials, pillared clay etc.). The seashell, Meretrix casta from Indian coasts contains high amount of calcium having higher affinity towards exchange of iron than compared to other heavy metals such as calcium, zinc or lead. The shells are easily available and hold potential of being used to prepare adsorbents that help decontaminate water.
Using sea shells as absorbents, good for water’s health – but is it good for the species?
However, beach cleaning activities and large scale sea-shell trade have also threatened several sea-shell species in various parts of the world. A section by N. V. Subba Rao in the report on Molluscs (PDF) by IUCN Species Survival Commission highlight exploitation of marine molluscs by Shell fishery industry in India. Particularly, Rao calls for judicious use of the bivalve Meretrix meretrix, noting its extensively used for manufacturing poultry feed as well as lime in regions of Orissa (now Odisha). Bearing in mind, a potential pressure on the species and little information available on population trends and life-cycle of Meretrix casta, a key question becomes – Should Sea Shells Be Used for Water Treatment, even though it is scientifically possible? I invite your views through a poll below. I also invite comments from our highly experienced commission members below.
Looking forward to hearing from you!
Disclaimer: the above poll is only an indicator of perceptions and should not be used as a scientific medium for decision making or consensus building.
Basavaraju Manu, PhD is Assistant Professor at Department of Civil Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore. Responsibility of information and views expressed lie with the author.