Calcium sulphate scaling in membrane distillation process

2009 ◽  
Vol 63 (2) ◽  
Author(s):  
Marek Gryta
Keyword(s):  
Membrane Surface ◽  
Calcium Sulphate ◽  
Membrane Distillation ◽  
Water Recovery ◽  
Distillation Process ◽  
Recovery Coefficient ◽  
Aqueous Salt Solutions ◽  
Formed Precipitate ◽  
Co Precipitation ◽  
Hcl Solution

AbstractFormation of precipitates containing CaSO4 during membrane distillation, applied to the concentration of aqueous salt solutions, is discussed in this paper. It was found that the concentration of SO42− ions in such solutions should not exceed 600 mg L−1 when they are subjected to concentration. However, concentration of sulphates at the level of 800 mg L−1 in the feed is permissible provided that the excess of CaSO4 is removed in a crystallizer. Crystallisation of salts, mainly CaSO4 · 2H2O, on the surface and inside the membrane was observed at higher feed concentrations, causing damage of the module. Precipitation of calcium sulphate was also observed during the production of demineralised water when high values of the water recovery coefficient (above 90 %) were used. In this case, the formed precipitate also contained CaCO3, the co-precipitation of which significantly changed the properties of the scaling layer. The precipitate containing both CaSO4 and CaCO3 was formed mainly on the membrane surface and it could easily be removed by rinsing the module with a HCl solution.

Steady state evaluation with different operating times in the direct contact membrane distillation process applied to water recovery from dyeing wastewater

2020 ◽  
Vol 230 ◽  
pp. 115892 ◽  
Author(s):  
Regilene de Sousa Silva ◽  
Heloisa Ramlow ◽  
Carolina D' Ávila Kramer Cavalcanti ◽  
Rita de Cassia Siqueira Curto Valle ◽  
Ricardo Antonio Francisco Machado ◽  
...  
Keyword(s):  
Steady State ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Water Recovery ◽  
Distillation Process ◽  
Dyeing Wastewater ◽  
Direct Contact Membrane Distillation ◽  
State Evaluation

scholarly journals Long-Running Comparison of Feed-Water Scaling in Membrane Distillation

Membranes ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 173
Author(s):  
Mohammad Rezaei ◽  
Albraa Alsaati ◽  
David M. Warsinger ◽  
Florian Hell ◽  
Wolfgang M. Samhaber
Keyword(s):  
Tap Water ◽  
Saturation Index ◽  
Membrane Surface ◽  
Membrane Distillation ◽  
Salt Crystallization ◽  
Feed Water ◽  
Water Recovery ◽  
Permeate Flux ◽  
Salt Scaling ◽  
Precipitous Decline

Membrane distillation (MD) has shown promise for concentrating a wide variety of brines, but the knowledge is limited on how different brines impact salt scaling, flux decline, and subsequent wetting. Furthermore, past studies have lacked critical details and analysis to enable a physical understanding, including the length of experiments, the inclusion of salt kinetics, impact of antiscalants, and variability between feed-water types. To address this gap, we examined the system performance, water recovery, scale formation, and saturation index of a lab-scale vacuum membrane distillation (VMD) in long-running test runs approaching 200 h. The tests provided a comparison of a variety of relevant feed solutions, including a synthetic seawater reverse osmosis brine with a salinity of 8.0 g/L, tap water, and NaCl, and included an antiscalant. Saturation modeling indicated that calcite and aragonite were the main foulants contributing to permeate flux reduction. The longer operation times than typical studies revealed several insights. First, scaling could reduce permeate flux dramatically, seen here as 49% for the synthetic brine, when reaching a high recovery ratio of 91%. Second, salt crystallization on the membrane surface could have a long-delayed but subsequently significant impact, as the permeate flux experienced a precipitous decline only after 72 h of continuous operation. Several scaling-resistant impacts were observed as well. Although use of an antiscalant did not reduce the decrease in flux, it extended membrane operational time before surface foulants caused membrane wetting. Additionally, numerous calcium, magnesium, and carbonate salts, as well as silica, reached very high saturation indices (>1). Despite this, scaling without wetting was often observed, and scaling was consistently reversible and easily washed. Under heavy scaling conditions, many areas lacked deposits, which enabled continued operation; existing MD performance models lack this effect by assuming uniform layers. This work implies that longer times are needed for MD fouling experiments, and provides further scaling-resistant evidence for MD.

Potable water recovery from As, U, and F contaminated ground waters by direct contact membrane distillation process

2011 ◽  
Vol 192 (3) ◽  
pp. 1388-1394 ◽  
Author(s):  
Saketa Yarlagadda ◽  
Veera Gnaneswar Gude ◽  
Lucy Mar Camacho ◽  
Saireddy Pinappu ◽  
Shuguang Deng
Keyword(s):  
Direct Contact ◽  
Potable Water ◽  
Membrane Distillation ◽  
Water Recovery ◽  
Distillation Process ◽  
Ground Waters ◽  
Direct Contact Membrane Distillation

Thermodynamic modelling of a membrane distillation crystallisation process for the treatment of mining wastewater

2015 ◽  
Vol 73 (3) ◽  
pp. 557-563 ◽  
Author(s):  
Jeeten Nathoo ◽  
Dyllon Garth Randall
Keyword(s):  
Membrane Fouling ◽  
Mining Industry ◽  
Calcium Sulphate ◽  
Membrane Distillation ◽  
Thermodynamic Modelling ◽  
Water Recovery ◽  
Liquid Discharge ◽  
Different Temperatures ◽  
Mining Wastewater ◽  
Crystallisation Process

Membrane distillation (MD) could be applicable in zero liquid discharge applications. This is due to the fact that MD is applicable at high salinity ranges which are generally outside the scope of reverse osmosis (RO) applications, although this requires proper management of precipitating salts to avoid membrane fouling. One way of managing these salts is with MD crystallisation (MDC). This paper focuses on the applicability of MDC for the treatment of mining wastewater by thermodynamically modelling the aqueous chemistry of the process at different temperatures. The paper is based on the typical brine generated from an RO process in the South African coal mining industry and investigates the effect water recovery and operating temperature have on the salts that are predicted to crystallise out, the sequence in which they will crystallise out and purities as a function of the water recovery. The study confirmed the efficacy of using thermodynamic modelling as a tool for investigating and predicting the crystallisation aspects of the MDC process. The key finding from this work was that, for an MDC process, a purer product can be obtained at higher operating temperatures and recoveries because of the inverse solubility of calcium sulphate.

scholarly journals Desalination of brackish groundwater by direct contact membrane distillation

2010 ◽  
Vol 61 (8) ◽  
pp. 2013-2020 ◽  
Author(s):  
D. Y. Hou ◽  
J. Wang ◽  
D. Qu ◽  
Z. K. Luan ◽  
C. W. Zhao ◽  
...  
Keyword(s):  
Direct Contact ◽  
Polyvinylidene Fluoride ◽  
Membrane Surface ◽  
Negative Influence ◽  
Membrane Distillation ◽  
Rapid Decline ◽  
Water Recovery ◽  
Permeate Flux ◽  
Feed Concentration ◽  
Direct Contact Membrane Distillation

The direct contact membrane distillation (DCMD) applied for desalination of brackish groundwater with self-made polyvinylidene fluoride (PVDF) membranes was presented in the paper. The PVDF membrane exhibited high rejection of non-volatile inorganic salt solutes and a maximum permeate flux 24.5 kg m−2 h−1 was obtained with feed temperature at 70°C. The DCMD experimental results indicated that the feed concentration had no significant influence on the permeate flux and the rejection of solute. When natural groundwater was used directly as the feed, the precipitation of CaCO3 would be formed and clog the hollow fibre inlets with gradual concentration of the feed, which resulted in a rapid decline of the module efficiency. The negative influence of scaling could be eliminated by acidification of the feed. Finally, a 250 h DCMD continuous desalination experiment of acidified groundwater with the concentration factor at constant 4.0 was carried out. The permeate flux kept stable and the permeate conductivity was less than 7.0 μS cm−1 during this process. Furthermore, there was no deposit observed on the membrane surface. All of these demonstrated that DCMD could be efficiently used for production of high-quality potable water from brackish groundwater with water recovery as high as 75%.

scholarly journals Membrane Distillation Process

Membranes ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 144
Author(s):  
Alessandra Criscuoli
Keyword(s):  
Water Stress ◽  
New Technologies ◽  
Membrane Distillation ◽  
Distillation Process

The water stress that we have been experiencing in the last few years is driving the development of new technologies for the purification and recovery of water [...]

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