REMOVAL OF COLOUR AND SOLIDS FROM QAL SEA WATER NEUTRALISATION EFFLUENT USING VEOLIA ACTIFLO HIGH RATE CLARIFIER

Kane, A., Leong, T. and Jenner, R.

Colour, solids and pH are important parameters in seawater neutralised effluent discharge quality.

Coagulants such as ferric chloride, ferrous and ferric chloride, activated carbon, magnesium sulphate are known to remove colour and solids, however they exhibit poor settling rates resulting in ‘cloudy’ solutions. The addition of microsand in combination with coagulants and flocculants in the patented Veolia Actiflo process enhances flocculation and settling to give improved removal rates of colour and solids.

Laboratory simulations of the Veolia Actiflo system were performed on clarifier overflow and decant pond overflow using combinations of inorganic coagulants (ferric chloride, aluminium chlorohydrate (ACH), polyaluminium chloride (PAC)), organic coagulants including polyDADMAC (polydiallyldimethyl ammonium chloride) range of cationic polymers, together with a number of powder flocculants from different suppliers.

Removal rates of up to 96% of colour and 90% of solids have been achieved. Impacts were observed on pH, TIC and TOC. Based on the results of the laboratory tests, a trial of the Actiflo process has been performed at a pilot plant scale. Design data obtained from the laboratory and pilot plant trials resulted in a preliminary design for sizing and costing of a potential full scale plant.