Large scale phycoremediation of acidic effluent from an alginate industry

The present study deals with the Successful commissioning of a phycoremediation plant to treat the acidic effluent from an alginate industry. The liquid effluent is highly acidic. Conventionally, sodium hydroxide has been used for the neutralization of the acidic effluent which results in an increase in total dissolved solids and the generation of solid waste. The study was conducted in three stages. In the first stage, the solar ponds used for evaporating the effluent were converted into high rate algal ponds with Chroococcus turgidus, a blue green alga. Algal growth increased the pH and fresh untreated acidic effluent was introduced until the pH of the effluent was reduced to the desired level depending on the amount of effluent already in the tank. When allowed to stand, the pH of the effluent increased from 6.0 to 8.2 in 4 days. In stage 2, pilot plant Studies were undertaken in a sloping tank to reduce the time taken for the pH to increase. The pH increased within hours and enhanced evaporation also Occurred. The sludge formation was negligible. In the final stage, based on the results of pilot plant Studies, a full scaling Lip of the slope tank was made. With the addition of around 30 kl of acidic effluent every day, the pH of the effluent remained constant around 7.02 and total dissolved salts stabilized at 49 g/l. There was no Sludge formation even after 2 years of operation. With just one circulation of the effluent at a pumping rate of 80 kl/h on the slopes, the desired evaporation of 30 kl was achieved.