Membrane Fouling and Chemical Cleaning in Three Full-Scale Reverse Osmosis Plants Producing Demineralized Water

Membrane fouling and cleaning were studied in three reverse osmosis (RO) plants. Feed water was secondary wastewater effluent, river water, and surface water. Membrane autopsies were used for fouling characterization. Fouling layer measurements included total organic carbon (TOC), adenosine triphosphate, polysaccharides, proteins, and heterotrophic plate counts. In all locations, membrane and spacer fouling was (bio)organic. Plant chemical cleaning efficiencies were evaluated from full-scale operational data and cleaning trials in a laboratory setup. Standard cleaning procedures were compared to two cleaning procedures specifically adapted to treat (bio)organic fouling using commercial blend cleaners (mixtures of active substances). The three RO plants were impacted by irreversible foulants causing permanently decreased performance in normalized pressure drop and water permeability even after thorough chemical cleaning. The standard plant and adapted cleaning procedures reduced the TOC by 45% on average, with a maximum of ~80%. In general, around 20% higher biomass removal could be achieved with adapted procedure I compared to adapted procedure II. TOC measurements and SEM showed that none of cleaning procedures applied could remove foulants completely from the membrane elements. This study underlines the need for novel cleaning approaches targeting resistant foulants, as none of the procedures applied resulted in highly effective membrane regeneration.

Download Full-text

Effect of dead cells on biofouling in the reverse osmosis process

Water Science & Technology Water Supply ◽

10.2166/ws.2013.120 ◽

2013 ◽

Vol 13 (5) ◽

pp. 1396-1401

Author(s):

Myung Seop Shin ◽

Lan Hee Kim ◽

Sung-Jo Kim ◽

Chang-Min Kim ◽

Kyu-Jung Chae ◽

...

Keyword(s):

Reverse Osmosis ◽

Biofilm Formation ◽

Extracellular Polymeric Substances ◽

Live Cells ◽

Feed Water ◽

Fouling Control ◽

Flux Decline ◽

Low Concentrations ◽

Plate Counts ◽

Heterotrophic Plate Counts

Biofilm formation in membrane processes causes a flux decline, pressure drop increase, and other adverse effects. Understanding the mechanisms of fouling, control, and cleaning are important in order to resolve fouling problems. In this paper, the effect of cell viability on biofouling was studied via a feed water analysis and membrane autopsy. Pseudomonas aeruginosa PAO1 was used as the model bacteria. Biofouling tests were divided into two parts: live cells and dead cells (autoclaved cells). The feed water was periodically collected every 3 h to analyze the total direct counts (TDCs), heterotrophic plate counts (HPCs), and extracellular polymeric substances (EPS). A membrane autopsy was performed to characterize the fouled membrane through TDCs and EPS. When dead cells were inoculated into the feed water, low concentrations of TDCs and EPS were measured in both the feed water and fouled membrane. As a result, it was determined that initial flux decline by biofouling can be reduced if feedwater is disinfected before the reverse osmosis process.

Download Full-text

A feasibility study on UV pretreatment for microfiltration and reverse osmosis membrane processes in wastewater reclamation

Journal of Water Reuse and Desalination ◽

10.2166/wrd.2013.002 ◽

2013 ◽

Vol 3 (3) ◽

pp. 260-267

Author(s):

Ho-Young Jeong ◽

Yoon-Jin Kim ◽

Ji-Hee Han ◽

Dong-Ha Kim ◽

Jinsik Sohn ◽

...

Keyword(s):

Reverse Osmosis ◽

Membrane Fouling ◽

Treatment Options ◽

Human Consumption ◽

Feed Water ◽

Reverse Osmosis Membrane ◽

Wastewater Reclamation ◽

Important Place ◽

Quality Water ◽

Small Footprint

Wastewater reclamation is where wastewater from various sources is purified so the water can be used by human consumption. Among many treatment options, membranes have gained an important place in wastewater reclamation. It allows the production of high quality water from wastewater, with a small footprint and affordable energy consumption. Nevertheless, membrane fouling is regarded as a serious problem due to the high fouling potential of wastewater. In this study, we applied ultraviolet (UV) processes as a pretreatment for membrane systems that are used for wastewater reclamation. Low pressure UV (LUV) and pulsed UV (PUV) were used to decompose or alter the organics in the feed water of the membranes. Effluent organic matter was characterized by total organic carbon (TOC) and UV absorbance (UVA). Also the effect of UV pretreatment on membrane fouling was investigated for microfiltration (MF) and reverse osmosis (RO) processes. The pretreatment of membranes using LUV or PUV was effective to control fouling of hollow fiber MF membranes. This is probably because of the reduction and modification of organics after UV treatments. However, the effect of UV pretreatment on RO flux was less significant, which is attributed to low fouling prophecy after MF treatment.

Download Full-text

Removal Characteristics of N-Nitrosamines and Their Precursors by Pilot-Scale Integrated Membrane Systems for Water Reuse

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph15091960 ◽

2018 ◽

Vol 15 (9) ◽

pp. 1960 ◽

Cited By ~ 11

Author(s):

Haruka Takeuchi ◽

Naoyuki Yamashita ◽

Norihide Nakada ◽

Hiroaki Tanaka

Keyword(s):

Membrane Fouling ◽

Water Reuse ◽

Pilot Scale ◽

Feed Water ◽

Water Reclamation ◽

Size Distributions ◽

Membrane Systems ◽

Chemical Cleaning ◽

Ro Membrane ◽

Feed Water Temperature

This study investigated the removal characteristics of N-Nitrosamines and their precursors at three pilot-scale water reclamation plants. These plants applies different integrated membrane systems: (1) microfiltration (MF)/nanofiltration (NF)/reverse osmosis (RO) membrane; (2) sand filtration/three-stage RO; and (3) ultrafiltration (UF)/NF and UF/RO. Variable removal of N-Nitrosodimethylamine (NDMA) by the RO processes could be attributed to membrane fouling and the feed water temperature. The effect of membrane fouling on N-Nitrosamine removal was extensively evaluated at one of the plants by conducting one month of operation and chemical cleaning of the RO element. Membrane fouling enhanced N-Nitrosamine removal by the pilot-scale RO process. This finding contributes to better understanding of the variable removal of NDMA by RO processes. This study also investigated the removal characteristics of N-Nitrosamine precursors. The NF and RO processes greatly reduced NDMA formation potential (FP), but the UF process had little effect. The contributions of MF, NF, and RO processes for reducing FPs of NDMA, N-Nitrosopyrrolidine and N-Nitrosodiethylamine were different, suggesting different size distributions of their precursors.

Download Full-text

Coliforms and other microbial indicators occurrence in water and biofilm in full-scale distribution systems

Water Science & Technology ◽

10.2166/wst.2006.446 ◽

2006 ◽

Vol 54 (3) ◽

pp. 41-48 ◽

Cited By ~ 7

Author(s):

M. Batté ◽

C. Féliers ◽

P. Servais ◽

V. Gauthier ◽

J.-C. Joret ◽

...

Keyword(s):

Water Quality ◽

Residence Time ◽

Distribution Systems ◽

Full Scale ◽

Bacterial Indicators ◽

Total Coliforms ◽

E Coli ◽

Plate Counts ◽

Microbiological Water Quality ◽

Heterotrophic Plate Counts

Biofilm and microbial water quality were studied in four middle size full-scale distribution systems (DS) in France serving 5,000–30,000 inhabitants (maximum residence time 23–160 h) through three sampling campaigns over 1 year. Three of these DSs were chosen because of a quite high occurrence of bacterial indicators (i.e. total coliforms), the last DS was considered as a reference. Biofilm was studied on cast iron coupons incubated for more than 1 month in devices continuously fed with water from the DS in conditions imitating those met in DS. The devices were located at different points (4–6) along each DS. The abundance of bacteria in biofilm was estimated by heterotrophic plate counts (HPC) after detachment of the biofilm from the support by sonication. Microbiological water quality was estimated in parallel; analysis of total coliforms, E. coli, enterococci and anaerobic sulphide-reducing bacteria spores (ASRB spores) was carried out in biofilm and water. Over the period of the study, 171 water samples and 57 biofilm samples were collected. Over these 171 waters, 19 (11%) were positive for at least one of the measured indicators while two biofilm samples were positive (3.5%). Significant differences were observed in the levels of contamination between the DSs. High residence time in the DS, low disinfectant residual and high temperature increased the risk of indicator occurrence in the water phase. Due to the low number of biofilm samples positive for bacterial indicators, the data collected in the present study did not allow observation of a direct association between biofilm and water contaminations, even if the occurrence of indicators in water appeared on DSs with the highest density of biofilm (HPC).

Download Full-text

Reverse Osmosis Technology for Wastewater Reuse

Water Science & Technology ◽

10.2166/wst.1991.0251 ◽

1991 ◽

Vol 24 (9) ◽

pp. 215-227 ◽

Cited By ~ 16

Author(s):

B. J. Mariñas

Keyword(s):

Water Quality ◽

Reverse Osmosis ◽

Membrane Fouling ◽

Quality Parameters ◽

Operating Conditions ◽

Water Quality Parameters ◽

Feed Water ◽

Hydraulic Pressure ◽

Predominant Component ◽

Percent Removal

Reverse osmosis technology has a great potential in the field of wastewater reclamation. A reverse osmosis plant includes the following processes: (1) feed water microfiltration and chemical conditioning, (2) membrane treatment, (3) permeate aeration, neutralization and disinfection, and (4) concentrate (liquid residue) treatment and disposal. The performance of reverse osmosis membranes depends on operating conditions and water quality parameters. Permeate productivity and contaminant removals increase with applied hydraulic pressure. Water quality parameters such as concentration, composition and pH also affect contaminant removal efficiencies. For example, the treatment of a simulated wastewater containing 10 mg/L of nitrate with a commercial polyamide-type reverse osmosis membrane resulted in membrane permeates containing approximately 0.05 mg/L of nitrate (or 99.5 percent removal) when sodium chloride was the major dissolved solid present in the feed water, and 1 mg/L (or 90 percent removal) when sodium sulfate was the predominant component. The removals of weak electrolyte contaminants are affected by feed water pH. For example, the removal of boron by a cellulose acetate-type membrane was reported to be greater than 99 percent at a pH of approximately 11, and less than 30 percent at a pH of 7. The practice of pre-treatment processes such as microfiltration and chemical conditioning can minimize performance deterioration resulting from membrane fouling by inorganic precipitates, organic macromolecules and microorganisms (biofouling).

Download Full-text

Critical design considerations for harnessing reverse osmosis processes in water/wastewater treatment

Water Science & Technology Water Supply ◽

10.2166/ws.2006.950 ◽

2006 ◽

Vol 6 (6) ◽

pp. 61-70 ◽

Cited By ~ 1

Author(s):

L.F. Song ◽

K.G. Tay ◽

G. Singh

Keyword(s):

Mass Transfer ◽

Membrane Fouling ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Full Scale ◽

Driving Pressure ◽

Feed Water ◽

Permeate Flux ◽

Membrane Channel ◽

Permeable Membrane

In this paper, the performance of the full-scale RO process with highly permeable membranes and the governing mechanisms were carefully studied. It was found that the performance of a full-scale RO process could be controlled by two possible mechanisms, namely mass transfer rate and thermodynamic limitations. Under relatively low driving pressure, it was controlled by mass transfer rate (water flux) of the membrane. However, with the highly permeable membrane, it is possible that the performance is limited by the thermodynamic limitation, in which the osmotic pressure becomes equal to the driving pressure inside of the membrane channel. A process controlled by thermodynamic limitation is an extremely case of the hydraulic imbalance problem. When it occurs, it means part of the membranes in the processes do not contribute to permeate production. More complicated are situations in the intermediate pressure range, in which both mechanisms contribute to, but none of them can dominate, the performance of the process. Some innovative concepts and theories on the performance of the full-scale RO processes were developed. These concepts and theories may provide better qualitative explanations for the behaviors often observed in the full-scale RO processes. A better quantitative simulations or predictions of the performance of the process were developed upon these concepts and theories. Experiments were carried out on a pilot membrane process of 6 m membrane channel to imitate the performance of the full-scale RO under various conditions. The experimental performance data were compared with theoretical simulations and excellent agreement was obtained. Another focus of this current study was on characterization and modeling of membrane fouling in the full-scale RO process. Colloidal fouling experiments were conducted to study the fouling potential of feed water and a new fouling indicator was proposed. The indicator can be directly used in the mathematical model to simulate fouling development in the full-scale RO processes. Model simulations showed that under certain condition (thermodynamic restriction), the recovery or average permeate flux of a full-scale RO process would maintain a constant value even membrane fouling was taking place. Experimental verification of the simulation results is currently under way. With the new developments and findings in this area, methods or protocols for optimization of full-scale processes of the highly permeable RO membranes were suggested.

Download Full-text

Production of process water using integrated membrane processes

Chemical Papers ◽

10.2478/s11696-006-0076-y ◽

2006 ◽

Vol 60 (6) ◽

Cited By ~ 7

Author(s):

K. Karakulski ◽

M. Gryta ◽

M. Sasim

Keyword(s):

Reverse Osmosis ◽

Membrane Fouling ◽

Tap Water ◽

Industrial Effluents ◽

Membrane Distillation ◽

Process Water ◽

Feed Water ◽

Reverse Osmosis Membrane ◽

Permeate Flux ◽

Membrane Processes

AbstractApplication of ultrafiltration, nanofiltration, reverse osmosis, membrane distillation, and integrated membrane processes for the preparation of process water from natural water or industrial effluents was investigated. A two-stage reverse osmosis plant enabled almost complete removal of solutes from the feed water. High-purity water was prepared using the membrane distillation. However, during this process a rapid membrane fouling and permeate flux decline was observed when the tap water was used as a feed. The precipitation of deposit in the modules was limited by the separation of sparingly soluble salts from the feed water in the nanofiltration. The combined reverse osmosis—membrane distillation process prevented the formation of salt deposits on the membranes employed for the membrane distillation. Ultrafiltration was found to be very effective removing trace amounts of oil from the feed water. Then the ultrafiltration permeate was used for feeding of the remaining membrane modules resulting in the total removal of oil residue contamination. The ultrafiltration allowed producing process water directly from the industrial effluents containing petroleum derivatives.

Download Full-text