<b>Calcium-free and low-calcium water production for aquaculture research</b> - doi: 10.4025/actascianimsci.v33i1.10686

Abstract

The present work aimed to obtain a mathematical expression to calculate the amount of EDTA required to produce calcium-free and low-calcium water ([Ca²⁺] < 5 mg L^-1). Initially, a pilot test was carried out to confirm the effectiveness of EDTA as a chelating agent of waterborne calcium and to evaluate its effect on water pH. Five application rates of Na-EDTA (25, 50, 75, 100 and 125 mg L^-1) were tested. The concentration of calcium in water was determined initially (before the application of EDTA) and after one hour. Linear regression analysis was performed to find out the relationship between the desired calcium concentration in water and the required EDTA: initial calcium hardness ratio. The expression ŷ = -0.0911x + 3.3628 (R^² = 0.933) was derived from the linear regression analysis carried out, in which x represents the desired calcium concentration in water and y the required EDTA: initial calcium hardness ratio.