Control of Calcium Sulfate (Gypsum) Scale in Nanofiltration of Saline Agricultural Drainage Water

Abstract

A methodology for calcium sulfate (gypsum) scale control in nanofiltration of saline waters is presented. The methodology involves the use of both theoretically and experimentally determined parameters. Pitzer's thermodynamic equations for electrolytes are used to determine the gypsum scaling potential of the feed water based on its ionic composition, whereas the extent of concentration polarization at the membrane surface is determined from the film model. A proportionality factor that relates the kinetic difference between the saturation predicted by the gypsum solubility model and the actual crystallization is determined using data from glassware crystallization experiments. The last step involves an experimentally developed parabolic equation relating antiscalant (polyacrylic acid) dose to the normalized concentration factors of the saline solution. These parameters are combined into a single model for predicting the required antiscalant dose to control calcium sulfate scale in nanofiltration membranes for any given saline solution. The model is tested by nanofiltration membrane experiments utilizing model solutions simulating saline agricultural drainage waters.

Desalination by ammonia–carbon dioxide forward osmosis: Influence of draw and feed solution concentrations on process performance

“…(2) for laminar flow and Eq. (3) for turbulent flow [22]. We have used this CP modulus for our calculations of the dilutive CP effects as the Reynolds number for the system based on the channel dimensions and flow rate is 2100.…”

Crystallization of calcium sulfate on polymeric surfaces

“…This leads to surface crystallization and as a consequence flux decline and potential membrane damage [6,7]. Membrane mineral salt crystallization is affected by various factors including fluid hydrodynamics in the membrane channel, membrane surface chemistry and topography as well as the supersaturation level of the solution with respect to the mineral salts [8][9][10]. Membrane scaling has been studied via permeate flux decline measurements [8][9][10], as well as acoustic detection [11,12] and direct surface observations [11,13] using commercial RO/NF membranes.…”

“…Membrane mineral salt crystallization is affected by various factors including fluid hydrodynamics in the membrane channel, membrane surface chemistry and topography as well as the supersaturation level of the solution with respect to the mineral salts [8][9][10]. Membrane scaling has been studied via permeate flux decline measurements [8][9][10], as well as acoustic detection [11,12] and direct surface observations [11,13] using commercial RO/NF membranes. The majority of commercial RO/NF membranes are thin-film polyamide membranes and thus studies of mineral scaling have been limited to polyamide surfaces [14,15], with a few studies also considering cellulose acetate surfaces [16,17].…”

Synthesis and evaluation of phosphate-free antiscalants to control CaSO 4 ·2H 2 O scale formation in reverse osmosis desalination plants

“…Effect of polyelectrolyte architecture on scale inhibition has been discussed by Oner et al [8]; it was found that polyacrylates imparting maximum surface charge density were more effective than polymethacrylates. Le Gouellec and Elimelech [9] reported the effect of hydrodynamics and dosage of additives on inhibition of gypsum scaling in a nanofiltration system. Effectiveness of several commercial antiscalants against gypsum scale formation was evaluated by Shih et al [10].…”