Archive:
ARI sets up an integrated process for Removal of Arsenic from Groundwater
A scaling-up of groundwater arsenic treatment plant has been trailed to treat 1000 L water per day, by the researchers of Agarker Research Institute(ARI), which is a follow up of their earlier research outcome.
The pilot plant was found functioning with very high efficiency through a year long monitoring schedule. The economics of this pilot scale treatment plant have been estimated to be highly favourable, with groundwater treatment costs worked out to be approximately 20 paise per liter. In the follow up, the applicability of this Integrated Arsenic Treatment Process (IATP) was tested in field scale studies. For this, five sites (arsenic contaminated tubewells) from two villages have been identified in the state of Chhattisgarh. In order to make the plants more versatile and easy to operate under field conditions, certain modifications have been made. A 100 L equilibration tank with a separate pump (0.25 HP) is now placed in between the bio-oxidation column and the alumina adsorption column for proper and independent flow regulation through the alumina and activated carbon columns. A flow meter-cum-regulator with additional pump is placed before the biofilm column for maintaining stringent flow control over. One additional column each of alumina and activated carbon are placed as stand-by columns for uninterrupted operation. Valves at the back of the columns offer the facility of backwashing the columns for maintaining high efficiency continuously.
Source: ARI Annual Report, 2004-05
It is a routine practice to use treated effluent of pulp and paper mill for irrigation. As the treated effluent always has some adsorbable organically bound halogens (AOX) content the soil irrigated with such effluents are contaminated with AOX. From environmental point it is essential to remove AOX from such soil. Bioremediation is good alternative to do this. It is true for the disposal of sludge, which gathers during aerobic treatment of the effluent.
At the ARI the scientists have intervened the issue and tried experiments with soil irrigated by true effluents from pulp and paper industries, and unearthed a few soil micro-flora capable of bioremediation of the toxic soil. As a prerequisite for bioremediation studies characterization of soil is necessary. Accordingly soil samples were collected from land irrigated with the effluent at different PAP. As sludge is normally disposed off by land filling, samples of sludge were also collected. These samples were analyzed for pH, organic carbon, and water holding capacity using methods described for ISO-14000 and AOX content on AOX analyzer.
Results show that soil of Mill-1 and Mill-3 were slightly acidic and had low content of organic carbon, poor water holding capacity and low AOX content in comparison to the rest of the samples. Bioremediation of soil with respect to organochlorines is better if soil pH is neutral or near neutral and poor in organic carbon content. In these terms soil from Mill-3 appeared more suitable than other soil samples and hence selected for further experiments. To find out extent of bioremediation by the indigenous microflora an experiment was performed using soil from Mill-3. Soil from Mill-3 was spiked with 2,4-DCP as AOX standard. All the sets were kept in triplicate. Samples, in triplicate, from each treatment taken on day 0 and then after every 30 days were analyzed for AOX. The results show that percent degradation of AOX in sterile and unsterile soil, both without any external addition of 2,4-DCP is of biogenic nature degradation. Degradation of AOX content in sterile soil spiked with 2,4-DCP indicates possibility of auto oxidation, irrespective of air (oxygen) limitation. Moreover, the soil microflora caused better degradation of AOX in unsterile soil spiked with 2,4- DCP. Further biodegradation was better when ample oxygen was available.
Source: ARI Annual Report, 2004-05
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