Study of fouling in two-stage reverse osmosis desalination unit operating without an inlet pH adjustment: diagnosis and implications

2017 ◽  
Vol 17 (6) ◽  
pp. 1682-1693 ◽  
Author(s):  
Khaled Touati ◽  
Mehdi Hila ◽  
Kalthoum Makhlouf ◽  
Hamza Elfil
Keyword(s):  
Reverse Osmosis ◽  
Treatment Process ◽  
Membrane Surface ◽  
Periodic Acid ◽  
Feed Water ◽  
Kaolinite Clay ◽  
Ph Adjustment ◽  
Second Stage ◽  
Pre Treatment ◽  
Reverse Osmosis Desalination

Abstract In the current work, the diagnosis of a reverse osmosis desalination unit is reported. Over the two last decades, the studied desalination unit was supplying a 1,200 bed hotel. The feed water was driven from a well near the sea. The desalination unit has two stages giving an average recovery equal to 81%. The behaviour of all water streams with respect to aggressiveness and scaling tendency was assessed. The second stage reject water was shown to exhibit a very high scaling behaviour with an instantaneous precipitation in the absence of feed water pH adjustment. The analyses have shown that the produced water was very aggressive. The second stage module autopsy has revealed a sharp decrease in the membrane performances because of mineral as well as organic fouling. The inorganic scale was essentially made of coesite, calcite and kaolinite clay. The presence of silica and clay was attributed to an inadequate pre-treatment process, whereas the presence of calcite crystals at the membrane surface reveals that the chemical inhibition performed at the pre-treatment process without adjusting the pH was not able to prevent calcium carbonate precipitation. A periodic acid wash of the second stage membranes is then necessary to guarantee the desired objectives of this stage.

A Novel Dynamic Electromagnetic Heating-Magnetizing Device Used for Reverse Osmosis System

2012 ◽  
Vol 562-564 ◽  
pp. 913-916
Author(s):  
Hai Du ◽  
Yan Bin Qu ◽  
Shu Kang Cheng
Keyword(s):  
Reverse Osmosis ◽  
Mechanical Energy ◽  
Membrane Surface ◽  
Heat Energy ◽  
Feed Water ◽  
Reverse Osmosis Membrane ◽  
Operation Mechanism ◽  
Electromagnetic Heating ◽  
Electromagnetic Field Theory ◽  
The Mathematical Model

A novel, environmental friendly dynamic rotating electromagnetic heating-magnetizing device is proposed, which can heat up and magnetize the low temperature feed water of reverse osmosis system. The device converts input mechanical energy into heat energy completely. The structure and operation mechanism are discussed in detail, and the mathematical model of loss is established based on fundamental electromagnetic field theory. At last, the effects of water magnetization treated by the device are introduced, which inhibits scaling on the reverse osmosis membrane surface and slows down the corrosion of metal surface.

scholarly journals Improving performance of low pressure reverse osmosis systems by intermittent autoflushing

2018 ◽  
Vol 9 (1) ◽  
pp. 1
Author(s):  
I N Widiasa ◽  
N Sinaga ◽  
D Ariyanti
Keyword(s):  
Reverse Osmosis ◽  
Membrane Surface ◽  
Magnesium Silicate ◽  
Operating Mode ◽  
Low Pressure ◽  
Calcium Sulphate ◽  
Feed Water ◽  
Low Grade ◽  
Operating Pressure ◽  
Permeate Flux

Improving performance of low pressure reverse osmosis systems by intermittent autoflushing Scaling formation on the membrane surface in the form of calcium carbonate, calcium sulphate, silica, and/or magnesium silicate is a main problem of the reverse osmosis (RO) application for upgrading low grade water. Scaling in RO system is generally controlled by softening the feed water, limiting the recovery and/or the addition of antiscalants which is impractical for household RO system. In this work, the feasibility of intermittent autoflushing to prevent scale formation in household RO systems was investigated. All experiments were carried out using commercially available RO membrane (CSM RE-1812LP) which operated for 6 hours under operating pressure 5 kg/cm2 and total recycle operating mode. Model solution of feed water contain CaCl2 and NaHCO3 were prepared to meet various LSI values in the range of 0 to 1.5. Duration and interval time of autoflush were in the range of 60 to 15 s and 5 to 60 min respectively. The results shown that the permeate flux of the system which operated using intermittent autoflushing relatively stable. It is emphasized that intermittent autoflushing may improve the performance of household reverse osmosis systems.Keywords: Autoflushing, scaling, physical cleaning, reverse osmosis  Abstrak Pembentukan kerak (scaling) pada permukaan membran berupa kerak kalsium karbonat, kalsium sulfat, silika dan atau magnesium silikat merupakan permasalahan utama pada aplikasi sistem membran reverse osmosis (RO) pada proses pemurnian air. Scaling pada sistem RO umumnya dikontrol dengan melakukan pretreatment terhadap air umpan seperti softening, menambahkan zat antiscalant pada saat proses pemisahan serta membatasi tingkat recovery, dimana proses-proses tersebut tidak praktis apabila diaplikasikan pada sistem RO skala rumah tangga. Penelitian ini bertujuan untuk melihat kemungkinan metode intermittent autoflush dapat diaplikasikan untuk menghambat terjadinya scaling pada sistem RO skala rumah tangga. Penelitian ini dilakukan dengan menggunakan satu unit membran spiral wound jenis CSM RE-1812LP yang dioperasikan dengan tekanan operasi 5 kg/cm2 dan waktu operasi ± 6 jam. Larutan umpan sintesis dibuat dengan melarutkan CaCl2 dan NaHCO3 hingga nilai LSI mencapai kisaran 0-1,5. Durasi dan interval dari metode intermittent autoflush divariasikan pada kisaran 60-15 detik dan 5-60 menit. Hasil penelitian menunjukkan bahwa fluks permeat relatif stabil pada sistem RO yang menggunakan metode intermittent autoflush. Hal ini menandakan bahwa metode intermittent autoflush ini dimungkinkan untuk meningkatkan kinerja dari sistem RO skala rumah tangga.Kata Kunci: Autoflushing, scaling, physical cleaning, reverse osmosis

Design considerations for wastewater treatment by reverse osmosis

2005 ◽  
Vol 51 (6-7) ◽  
pp. 473-482 ◽  
Author(s):  
C.R. Bartels ◽  
M. Wilf ◽  
K. Andes ◽  
J. Iong
Keyword(s):  
Wastewater Treatment ◽  
Calcium Phosphate ◽  
Reverse Osmosis ◽  
Membrane Fouling ◽  
Urban Areas ◽  
Large Scale ◽  
Membrane Surface ◽  
Feed Water ◽  
High Quality ◽  
Quality Water

Reverse Osmosis is finding increasing use for the treatment of municipal and industrial wastewaters due to the growing demand for high quality water in large urban areas. The growing success of membranes in this application is related to improved process designs and improved membrane products. Key factors which have been determined to result in successful operation of large-scale plants will be discussed. Factors which play a key role in the use of RO membranes include ultra or microfiltration pretreatment, low fouling membranes, flux rate, recovery and control of fouling and scaling. In particular, high flux rates can be used when UF or MF pretreatment is used. These technologies remove most of the suspended particles that would normally cause heavy fouling of lead elements. Typically, fluxes in the range of 17–21 lmh lead to cleaning frequencies in the range of 3–4 months. By combining the use of membrane pretreatment and chloramination of the feed water through chlorine addition, two of the primary sources of RO membrane fouling can be controlled. The use of chloramine has become a proven means to control biofouling in a membrane for wastewater applications. The other significant problems for RO membranes result from organics fouling by dissolved organics and scaling due to saturation of marginally soluble salts. The former can be a significant problem for membranes, due to the strong attraction forces. To some extent, these can be mitigated by making the membrane surface more hydrophilic or changing the charge of the membrane surface. To minimize fouling, many plants are turning to low fouling membranes. Extensive studies have demonstrated that the membrane surface is hydrophilic, neutrally charged over a broad pH range, and more resistant to organic adsorption. Also, an analysis of the potential scaling issues will be reviewed. In particular, calcium phosphate has been found to be one of the key scalants that will limit RO system recovery rate. Calcium phosphate concentrations can reach high values in many wastewaters, and scaling of this compound is not often modeled in most RO projection software. Various process options will be presented to evaluate the most economic means of avoiding phosphate scaling. Finally, data from major RO wastewater treatment plants will be presented to show how the RO membranes operate under actual conditions, utilizing many of these design features. Long term data from the 2.6 mgd Bedok demonstration Plant demonstrate that the RO membranes operate consistently on wastewater. Experiences from the 8.5 mgd (32,000 m3/day) Bedok and 10.5 mgd (40,000 m3/day) Kranji plants will also be presented. These large plants started operation in the fall of 2002 and have demonstrated an effective means to reclaim high quality water from difficult source waters, such as municipal wastewaters.

scholarly journals Novel Hole-Pillar Spacer Design for Improved Hydrodynamics and Biofouling Mitigation in Membrane Filtration

2020 ◽  
Author(s):  
Adnan Qamar ◽  
Sarah Kerdi ◽  
Syed Muztuza Ali ◽  
Ho Kyong Shon ◽  
Johannes Vrouwenvelder ◽  
...  
Keyword(s):  
Shear Stress ◽  
Membrane Filtration ◽  
Membrane Surface ◽  
Applied Pressure ◽  
Feed Water ◽  
Permeate Flux ◽  
Biofilm Thickness ◽  
Feed Pressure ◽  
Pre Treatment ◽  
Critical Components

Abstract Feed spacers are the critical components of any spiral-wound filtration module, dictating the filtration performance. Three spacer designs, namely a non-woven commercial spacer (varying filament cross-section), a symmetric pillar spacer, and a novel hole-pillar spacer (constant filament diameter) were studied using Direct Numerical Simulations (DNS), 3-D printed and subsequently experimentally tested in a lab-scale ultrafiltration set-up with high biofouling potential feed water at various feed pressures. Independent of the applied pressure, the novel hole-pillar spacer showed initially the lowest feed channel pressure drop, the lowest shear stress, and the highest permeate flux compared to the commercial and pillar spacers. Furthermore, less biofilm thickness development on membrane surface was visualized by Optical Coherent Tomography (OCT) imaging for the proposed hole-pillar spacer. At higher feed pressure, a thicker biofilm developed on membrane surface for all spacer designs explaining the stronger decrease in permeate flux at high pressure. The findings systematically demonstrated the role of various spacer designs and applied pressure on the performance of pre-treatment process, while identifying specific shear stress distribution guidelines for engineering a new spacer design in different filtration techniques.

scholarly journals Managing the reverse osmosis concentrate from the Western Corridor Recycled Water Scheme

2010 ◽  
Vol 5 (1) ◽  
Author(s):  
David Solley ◽  
Claire Gronow ◽  
Stephan Tait ◽  
Jon Bates ◽  
Alison Buchanan
Keyword(s):  
Reverse Osmosis ◽  
Environmental Risks ◽  
Feed Water ◽  
Nutrient Reduction ◽  
Recycled Water ◽  
Reduction Strategies ◽  
Feasible Option ◽  
Full Capacity ◽  
Pre Treatment ◽  
Nitrogen Phosphorus

The Western Corridor Recycled Water Scheme consists of three advanced water treatment plants (AWTPs), with the combined capacity to recycle 232 ML/d. Each AWTP process consists of pre-treatment, microfiltration (MF), reverse osmosis (RO), UV/peroxide advanced oxidation and chlorination. A key objective of the project is to improve the environmental health of regional waterways, particularly in relation to nutrient discharges. Reverse osmosis processes produce a concentrate stream (ROC), which is the main reject stream of the AWTPs. Options for management of ROC were assessed, and ultimate disposal to nearby waterways was the only feasible option identified. ROC flows for the scheme total 41 ML/d at full capacity, divided between the three AWTPs. The contaminants in this stream are generally 6 to 7 times more concentrated than in the feed water. Environmental risks were identified due to potential increased toxicity associated with these higher concentrations, which were exacerbated due to chlorine and ammonia dosed in the AWTP process. Target ROC contaminants have been identified as nitrogen, phosphorus, ammonia, metals and chlorine. The paper presents the selected toxicity management and nutrient reduction strategies for each AWTP, and the results of full-scale operation to date are also summarised.

Case study on the effects of feed water temperature on the performance of a reverse osmosis desalination system

2020 ◽  
Vol 205 ◽  
pp. 46-52
Author(s):  
Abdulrahim Kalendar ◽  
Aboelyazied Kulaib ◽  
Shafqat Hussain ◽  
Yousuf Alhendal
Keyword(s):  
Water Temperature ◽  
Reverse Osmosis ◽  
Feed Water ◽  
Feed Water Temperature ◽  
Reverse Osmosis Desalination
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