S.K. Adhikary

Defluoridation during desalination of brackish water by electrodialysis

Studies have been conducted to defluoridate brackish water containing 2120, 3020, 4260 and 4800 ppm total dissolved solids (TDS) and 5, 10, 15 and 20 ppm fluoride by means of electrodialysis. A Laboratory electrodialysis stack containing 15 cell pairs of cation-and anion-exchange membranes of 80 cm2 effective cross-sectional area is used. Data have been collected under different flow rates and current densities. Optimum operational conditions have been determined for obtaining product water containing ⩽600 ppm TDS and ⩽1.5 ppm fluoride, which is acceptable for use as potable water. Brackish waters up to 5000 ppm TDS containing fluoride up to 15 ppm can be reduced to ca. 600 ppm TDS and ⩽1.5 ppm fluoride. This approach is found suitable for desalination and defluoridation of water having TDS up to 5000 ppm and fluoride up to 10 ppm with an energy requirement of <1 kWh/kg of salt removed.

Performance analysis of photovoltaic electrodialysis desalination plant at Tanote in Thar desert

The 450 peak watts photovoltaic panel coupled electrodialysis(PV-ED) plant of size 30 × 60 cms with 42 cell pairs operating at about 80 volts gives about 1000 litres per day of product water with salinity less than 1000 ppm from feed water having total dissolved solids(tds) of about 5000 ppm. The flow is fixed at 120 litres per hour for 8 hours operation per day between 8.30 a.m. to 4.30 pm.

Desalination of brackish water by electrodialysis

Abstract The performance of an electrodialysis unit comprising interpolymer type cation and anion-exchange membranes developed in this institute in single-stage and two-stage operation for desalting of brackish waters having different total dissolved solids has been studied highlighting the energy requirement and pressure drop under different conditions. For higher salinity waters, a two-stage reduction is advantageous with lower power requirements and power index. The results will be useful for design and installation of ED plants in brackish water sectors.

Separation of inorganic and organic acids from glyoxal by electrodialysis

Abstract The electrodialysis (ED) processemploying ion-exchange membranes has been used mainly for the desalination of brackish water and concentration of seawater. Of late ED has become a unique process for the separation of ionic and non-ionic substances from chemical mixtures. In such manufacturing processes, glyoxal is produced by the oxidation of acetaldehyde with nitric acid. After the reaction, the product contains nitric acid, acetic acid, glycolic acid, etc., which are to be separated from the mixture. Attempts were made to make use of ED to separate electrolytes from non-electrolytes and to separate nitric acid and weak organic acids from glyoxal. The experimental results obtained from the separation of nitric acid, organic acids and glyoxal under different experimental conditions are presented and discussed.

Desalination of brackish water of higher salinity by electrodialysis

Abstract A laboratory model electrodialysis(ED) stack containing 35 cell pairs of cation and anion exchange membranes of 80 cm 2 effective cross-sectional area is used to study the desalination of brackish water having total dissolved solids (TDS) of 6000 – 10250 ppm. For brackish water containing TDS of 12000 – 27170 ppm, two ED stacks and for TDS of 27100 – 36000 ppm, three ED stacks containing different cell pairs of membranes having same effective cross-sectional area are used. Parallel-cum-series flow system is employed in all the stacks. The reduction in anions like Cl − , NO 3 − along with total hardness and TDS have been reported. The energy requirements and current efficiencies are also given based on the experimental data. Optimum flow rates and energy consumptions are reported for obtaining potable water having TDS of ⋍ 800 ppm from different brackish water. The results will be useful for design and operation of different capacity of electrodialysis plants for desalting brackish water of different salinity.

Performance of an electrodialysis desalination plant in rural area

Abstract The provision of potable water in problem villages of Gujarat, Rajasthan, Tamil Nadu and Andhra Pradesh has been given high priority by the Government of India. To meet the demands of these villages having population of about one thousand, desalination by membrane techniques, eloectrodialysis plant of 1.25 m3/h capacity built and commissioned by the institute in Adalsar village of Gujara tSate to desalt a brackish well water of ⋍ 4000 ppm tds and hardness of ⋍ 1200 ppm CaCO3 is described. The cost of treatment and economics of desalination in a rural set up are presented

Studies on interpolymer membranes. Part III. Cation-exchange membranes

Abstract Studies have been conducted without use of solvents in the preparation of interpolymer bases for cation-exchange membranes using blends of high and low density polyethylenes with styrene-divinylbenzene copolymers. The blending ratios of polymer and copolymer with different degrees of crosslinking and their effects on the properties of the films, such as tearing, bursting and tensile strength, were studied. The properties of cation-exchange membranes from different base films in relation to their physicochemical characteristics were also evaluated. It has been observed that the properties of the membranes are equally good or better than could be obtained from solvent-based systems and at reduced processing cost.

Performance of the first sea water electrodialysis desalination plant in India

Abstract The problem of potable Water shortage in some of the islands and coastal areas of India has led to consider sea water desalination for potable purposes. One of the membrane processes, namely, the electrodialysis(ED) has been designed and fabricated to meet the demand of a section of the population of Kavaratti island (Lakshad weep, Union Territory). The plant having a capacity of 5.5 m 3 /day is based on two stage reduction of salt wherein the first stage reduction upto 85% is achieved by recirculation of sea water. The plant commissioned in February, 1989 is running satisfactorily to its rated capacity. Useful information obtained during the period of first one year is reported here. A novel method of preventing scale formation and other salient features are brought about. An awareness is being created to go in for such plants in near future based on the performance of the above first experimental unit.