Deacidification through calcium carbonate dosing in combination with ultrafiltration

Abstract

Soft acidic waters are often treated for drinking water purposes by using limestone filters to attain chemical equilibrium. The present study investigated the process parameters of a relatively new process combination in which powdered calcium carbonate (CaCO3) was added prior to an ultrafiltration (UF). In order to reach the targeted pH value (≥7.8), dosing concentration, type of material and retention time were evaluated in pilot-scale experiments. The deacidification followed the same kinetics as for limestone filtration and yielded similar filtrate characteristics with dosing concentrations of 20 and 40 g/L CaCO3. No significant increase in transmembrane pressure was observed during the operation of a pilot-scale UF module at low flux (34 L m−2 h−1). Critical flux was determined in a lab scale to evaluate the potential impact of CaCO3 particles on the UF operation. Stepping-flux experiments revealed the presence of fouling only at high-dosing concentrations, resulting in a critical flux of 55 L m−2 h−1. At a higher flux, a CaCO3-fouling layer was formed, which decreased the membrane's permeability by 20% over 5 h. Considering that effective air-enhanced backwash and acidic chemical cleanings will be implemented in large-scale applications, the investigated process combination promises to be an appropriate treatment technology for turbid and soft acidic waters.

Effects of an inoculation dose of Issatchenkia terricola WJL‐G4 on physicochemical properties, active substances, and antioxidant capacity of black, red, and white currant juice

“…However, chemical deacidification can affect the taste, color, aroma, and stability of the fruit wine when used excessively. 17 Biological deacidification, involves the decomposition of organic acids in fruit juice or fruit wine through microorganisms. This method can not only reduce the total acidity but also change the juice's flavor and taste.…”

“…Chemical reagents, such as calcium carbonate, potassium bicarbonate, potassium tartrate, and double calcium salts are used to reduce the tartaric acid in fruit juice. However, chemical deacidification can affect the taste, color, aroma, and stability of the fruit wine when used excessively 17 . Biological deacidification, involves the decomposition of organic acids in fruit juice or fruit wine through microorganisms.…”