Removal of iron, arsenic and coliform bacteria from water by novel constructed soil filter system Pravin D. Nemade , Avinash M. Kadam, H.S. Shankar Department of Chemical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, Maharashtra, India Keywords: Arsenic Iron Coliform bacteria Constructed soil filter Drinking water abstract The present paper presents results of the study in removal of iron, arsenic and total coliform from drinking water using single-pass constructed soil filter (CSF). Results indicated that arsenic levels ranged from 0.5 to less than 10 gl -1 levels; iron from 5 to less than 0.3 mg l -1 and coliform from 10 -5 to less than 5 CFU/100 ml. The results revealed very high removal efficiency, i.e., over 99% and water quality as per WHO standard. 1. Introduction About 80% of communicable diseases in the world are water- borne. Among the various undesirable and naturally occurring pollutants in water, coliform bacteria, iron, fluoride and arsenic are very important as these pose severe health problems (Joshi and Chaudhuri, 1996). Iron is a troublesome element in water supplies. Making up at least 5% of the earth’s crust, iron is one of the earth’s most plentiful resources. Rainwater, as it infiltrates soil, the underlying geologic formations, dissolves iron, causing it to seep into aquifers that serve as sources of groundwater for wells. Iron is seldom found at con- centrations greater than 10 milligrams per liter (mg l -1 ) or 10 parts per million. However, as little as 0.3 mg l -1 can cause water to turn a reddish brown color (Das et al., 2007). Thus, the removal of iron is necessary. Iron is mainly present in water in two forms: either soluble ferrous iron or insoluble ferric iron. Water containing fer- rous iron is clear and colorless because iron is completely dissolved. When exposed to air in the pressure tank or atmosphere, the water turns cloudy and a reddish brown substance begins to form. This sediment is the oxidized or ferric form of iron that will not dis- solve in water. There are several methods for removal of iron from drinking water like ion exchange and water softening (Vaaramaa and Lehto, 2003), activated carbon and other filtration materials (Munter et al., 2005), bioremediation (Berbenni et al., 2000), oxi- dation by aeration, chlorination, ozonation followed by filtration (Ellis et al., 2000), by ash (Das et al., 2007), by aerated granular filter (Cho, 2005) and by adsorption (Tahir and Rauf, 2004). Arsenic is a brittle-natured and gray or white-colored toxic metalloid that cannot be found as a free element in the earth’s crust. There are more than 245 species of arsenic-bearing miner- als, mostly ores containing sulphide along with copper, nickel, lead, cobalt and other metals as well as some oxides that exist in nature. There are also anthropogenic sources of arsenic such as insecticides, pesticides and wastes from mine, smelter and tannery industries. Both organic and inorganic compounds of arsenic are present in the environment. The inorganic arsenic is highly toxic (Rahaman et al., 2008). In high concentrations, arsenic poisoning can also lead to an acute condition called arsenicosis (Hering et al., 1997; Gregor, 2001; Saha et al., 1999). Coliform bacteria is the indicator of water contaminated with human or animal wastes and if these are absent, only then can water be considered safe for drinking purpose. Generally not all bacte- ria are harmful but other microbes along with these bacteria can cause short-term effects like diarrhoea, cramps, nausea, headaches, or other symptoms (Jerzy et al., 1999). Many methods have been used to remove iron, arsenic and coliforms from water. Conventional methods for removal of iron, arsenic and coliform bacteria involve coagulation followed by sep- aration of the produced insoluble settling or by direct filtration through sand beds. Arsenic removal by various methods includes reverse osmosis, ion exchange, lime softening, flotation and adsorp- tion on iron oxides or activated alumina (Kartinen and Martin, 1995); waste materials (Rahaman et al., 2008); iron oxide fungal