A m	effective area of forward osmosis membrane	[m2]
C t	concentration of Ca2+ in feed solution at time t	[kg/m2/s]
$C_{\mathrm{t}+{\mathrm{t}}_0}$	concentration of Ca2+ in feed solution at time (t + t0)	[kg/m2/s]
J Ca	reverse solute flux of Ca2+ without considering Ca2+ in Ca-Alg recovery production passing through the forward osmosis membrane per unit membrane area per unit time at time t	[kg/m2/s]
J Ca,av	total average reverse solute flux of Ca2+ with considering Ca2+ in Ca-Alg recovery production passing through the forward osmosis membrane per unit membrane area from time t = 0 to t	[kg/m2/s]
J w	volume of water passing through the forward osmosis membrane per unit membrane area per unit time at time t	[m/s]
J w,av	average volume of water passing through the forward osmosis membrane per unit membrane area from time t = 0 to t	[m/s]
t	forward osmosis time	[s]
t 0	time interval between two consecutive samplings	[s]
V DS	volume of draw solution at time t	[m3]
V t	volume of feed solution at time t	[m3]
$V_{\mathrm{t}+{\mathrm{t}}_0}$	volume of feed solution at time (t + t0)	[m3]
W Ca,r	content of Ca2+ in Ca-Alg recovery production formed on the forward osmosis membrane	[kg]
W Ca	total Ca2+ content of reverse osmosis containing Ca2+ in Ca-Alg recovery production formed on the forward osmosis membrane	[kg]
W SA	content of SA in the feed solution	[kg]