Stable barium sulphate supersaturation in reverse osmosis

A study of CaCO3 scale formation and inhibition in RO and NF membrane processes

“…The most widely applied method in membrane water-treatment plants is based on estimates of supersaturation ratio (or degree of supersaturation), which is defined as the ion activity product of the salt divided by its solubility product. In certain cases, however, with several sparingly soluble salts (CaCO 3 , BaSO 4 , CaF 2 ) supersaturation with respect to a mineral salt does not necessarily indicate that scaling would occur [9,10]. Indeed, a "threshold" supersaturation ratio, much higher than one, must be usually exceeded before scale formation occurs.…”

“…Indeed, a "threshold" supersaturation ratio, much higher than one, must be usually exceeded before scale formation occurs. For instance, this trend in BaSO 4 scale formation is believed to be associated with either slow nucleation kinetics or long induction period [9].…”

Dielectric measurements of fouling of nanofiltration membranes by sparingly soluble salts

“…However, it is important to note that the concentration polarization in this work is from the dissociation of insoluble salts, which is different from the original concentration polarization layer when there is a flux. According to the report [35] that the capacitance value of the membrane/solution system is proportional to the insoluble salt concentration near the membrane pore, and the fact that dielectric increment ( C Δ ) is proportional to the capacitance value of the system in this work, we infer that initial increment of the capacitance (stage�) was mainly due to the CP, which was caused by the partial dissociation of insoluble salt nuclei near the membrane pore; the reason for the subsequent decrease of the capacitance (stage�) was that salt nuclei grown beyond the critical size and became more stable and can hardly to redissolve [36], which leads to the decline of the CP. The relaxation before 4 h was the result of cooperation of CP (near the membrane surface) and the interfacial polarization (between the membrane and deionized water); the relaxation before 2 h was mainly controlled by the CP.…”

“…7a, the value of the membrane capacitance reaches the minimum at the initial stage (t¼ 2 h) of fouling process. This was because that: on one hand, the membrane pore had been partially blocked by crystal particles and the permittivity of the membrane phase decreased after 2 h; on the other hand, most of the insoluble salt molecules existed in the form of crystal nuclei, which are very small [36] and can easily attach to membrane surface to block the membrane pore. When conducting dielectric measurement, the small crystal nuclei can redissolve into water, leading to concentration polarization.…”

Coal Seam Gas Water Quality and Impacts on Downstream Treatment Technologies

“…Consequently, the application of a suitable anti-scalant may be recommended [91,109]. The anti-scalant used should be carefully investigated as further problems can arise such as biofouling [136,137]. A study by Alternative options include effective cleaners for scale which remove mineral scaling, colloidal particles or bio-foulants [62].…”