Improving chemical cleaning of fouled membranes in a drinking water treatment plant

Abstract Recently, membrane filtration systems have become increasingly common in drinking water treatment plants. In this industry, preventing membrane fouling is of utmost importance. Many studies on the relationship between raw water components and membrane fouling have been performed in laboratory conditions. However, very few studies have analyzed the components of foulants on the fouled membrane as operated in actual drinking water treatment plants. By analyzing these components in plant-conditions, membrane fouling will be more effectively prevented. In this study, we analyzed the components of foulants extracted with 0.1 N NaOH from a fouled membrane operated in a drinking water treatment plant in Japan. Our analysis revealed that the main foulants were humic substances. In order to dissolve the accumulated humic substances, additional chemical cleaning was attempted with 500 ppm sodium hypochlorite. As a result, it was found that humic substances were dissolved and filtration resistance significantly decreased. Additionally, the removal of inorganic foulants was also greater after chemical cleaning with 500 ppm sodium hypochlorite, as inorganic foulants trapped within humic substances were released to the membrane surface as hydroxides by the additional sodium hypochlorite cleaning and were dissolved by the periodic citric acid cleaning.

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Effectiveness of vertical subsurface wetlands for iron and manganese removal from wastewater in drinking water treatment plants

Universitas Scientiarum ◽

10.11144/javeriana.sc24-1.eovs ◽

2019 ◽

Vol 24 (1) ◽

pp. 135-163

Author(s):

Jader Martínez Girón ◽

Jenny Vanessa Marín-Rivera ◽

Mauricio Quintero-Angel

Keyword(s):

Drinking Water ◽

Wastewater Treatment ◽

Water Treatment ◽

Treatment Plant ◽

Drinking Water Treatment ◽

Water Treatment Plant ◽

Pilot Scale ◽

Treatment System ◽

Water Treatment Plants ◽

Significant Difference

Population growth and urbanization pose a greater pressure for the treatment of drinking water. Additionally, different treatment units, such as decanters and filters, accumulate high concentrations of iron (Fe) and manganese (Mn), which in many cases can be discharged into the environment without any treatment when maintenance is performed. Therefore, this paper evaluates the effectiveness of vertical subsurface wetlands for Fe and Mn removal from wastewater in drinking water treatment plants, taking a pilot scale wetland with an ascending gravel bed with two types of plants: C. esculenta and P. australis in El Hormiguero (Cali, Colombia), as an example. The pilot system had three upstream vertical wetlands, two of them planted and the third one without a plant used as a control. The wetlands were arranged in parallel and each formed by three gravel beds of different diameter. The results showed no significant difference for the percentage of removal in the three wetlands for turbidity (98 %), Fe (90 %), dissolved Fe (97 %) and Mn (98 %). The dissolved oxygen presented a significant difference between the planted wetlands and the control. C. esculenta had the highest concentration of Fe in the root with (103.5 ± 20.8) µg/g ; while P. australis had the highest average of Fe concentrations in leaves and stem with (45.7 ± 24) µg/g and (41.4 ± 9.1) µg/g, respectively. It is concluded that subsurface wetlands can be an interesting alternative for wastewater treatment in the maintenance of drinking water treatment plants. However, more research is needed for the use of vegetation or some technologies for the removal or reduction of the pollutant load in wetlands, since each drinking water treatment plant will require a treatment system for wastewater, which in turn requires a wastewater treatment system as well.

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Application of microfiltration for reuse of backwash water in a conventional water treatment plant - a case study

Water Science & Technology Water Supply ◽

10.2166/ws.2001.0115 ◽

2001 ◽

Vol 1 (5-6) ◽

pp. 199-206 ◽

Cited By ~ 3

Author(s):

H. Song ◽

X. Fan ◽

Y. Zhang ◽

T. Wang ◽

Y. Feng

Keyword(s):

Drinking Water ◽

Water Treatment ◽

Treatment Plant ◽

Drinking Water Treatment ◽

Water Treatment Plant ◽

Transmembrane Pressure ◽

Total Production ◽

Chemical Cleaning ◽

Direct Filtration ◽

Filter Backwash Water

In conventional drinking water treatment processes, the amount of the filter backwash water covers nearly 3% of the total production. To reduce the water loss and waste discharge in the conventional drinking water treatment process, the Macao Water Supply Co. Ltd (SAAM) plans to recover the backwash water by Microfiltration (MF) membrane process as water resources are scarce and new environmental regulations are mandated in Macao. Generally, the filter backwash water from the conventional water treatment plant with sedimentation process is recycled to the source water to be treated again under certain conditions, and the sedimentation tank discharges most of the sludge. However, it is possible to recycle the backwash water directly to the inlet for direct filtration process due to the limitation of inlet turbidity. This paper describes how to apply MF technology to treat the backwash water of the direct filtration plant and to optimize MF operation. Without pre-treatment of the settling basin for backwash water, the operation of the MF pilot plant is proved to be stable and the permeate quality can meet EU drinking water standards. The pilot study shows that it is both economically and technically feasible to adopt MF technology in backwash water treatment. The main parameters to test MF process include flux, chemical cleaning duration and transmembrane pressure (TMP). They are 150-200 L/m2.h, 20 days and <1 bar respectively. The estimated cost including O&M and investment for a 1320-1760 m3/d backwash water treatment plant is USD 0.126-0.168/m3.

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Drinking-Water Supply for CKDu Affected Areas of Sri Lanka, Using Nanofiltration Membrane Technology: From Laboratory to Practice

Water ◽

10.3390/w11122512 ◽

2019 ◽

Vol 11 (12) ◽

pp. 2512 ◽

Cited By ~ 1

Author(s):

Titus Cooray ◽

Yuansong Wei ◽

Junya Zhang ◽

Libing Zheng ◽

Hui Zhong ◽

...

Keyword(s):

Drinking Water ◽

Water Treatment ◽

Sri Lanka ◽

Treatment Plant ◽

Drinking Water Treatment ◽

Water Treatment Plant ◽

Membrane Technology ◽

Safe Drinking Water ◽

Drinking Water Treatment Plant ◽

Water Treatment Plants

Installation of decentralized water-treatment plants is an ideal option to supply safe drinking water for rural communities. Presently in Sri Lanka, over 3.6 million villagers face acute water-quality problems, and chronic kidney disease of unknown etiology (CKDu) is also prevalent among this community. Most of the drinking water in these villages is unpalatable due to high hardness and salinity. As an interim measure, reverse-osmosis (RO) water-treatment plants are introduced to provide safe water. However, due to deficient electrolytes, RO-treated water tastes unpleasant to some consumers; hence, people refuse it after prolonged use. The operation, maintenance, and management of RO plants are other major problems. Aimed at providing safe drinking water to the rural sector in a cost-effective manner, in this study, we fabricated an automated drinking-water purification system based on nanofiltration (NF) membrane technology, which can remove divalent cations, dissolved organic carbon (DOC) and pathogens efficiently, and monovalent ions partially, and thus keep electrolytes to some degree. Ten commercial NF membranes were tested in a laboratory, for solute and DOC removal efficiency and robustness. The DF-90 membrane showed the highest removal of DOC and hardness, and it was therefore selected, to design a pilot NF drinking-water treatment plant. The adhered DOC by the membrane can be cleaned by NaOH solution (pH = 12). The pilot NF drinking-water treatment plant has been in use since September 2018, and it shows excellent performance of removing DOC, TDS, hardness, fluoride, and pathogens in groundwater, and the permeate water of the NF plant has been well-accepted by the stakeholders of the society. The dominant genus of source water, and throughout the two processes (NF and RO), is Pseudomonas, and their difference is significant in the concentrates of the NF and RO processes.

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Modifications of unit processes for finished water quality improvement at the Kueui water treatment plant in Seoul

Water Science & Technology Water Supply ◽

10.2166/ws.2002.0169 ◽

2002 ◽

Vol 2 (5-6) ◽

pp. 193-199

Author(s):

M.J. Yu ◽

H.M. Cho ◽

J.Y. Koo ◽

I.S. Han ◽

E.M. Gwon ◽

...

Keyword(s):

Water Quality ◽

Drinking Water ◽

Water Treatment ◽

Treatment Plant ◽

Drinking Water Treatment ◽

Water Treatment Plant ◽

Pilot Scale ◽

Sand Filters ◽

Water Treatment Plants ◽

Sedimentation Basins

Recently, Seoul city has tried to modify and upgrade the existing facilities and utilities and to improve the established water treatment plants, instead of application of a new treatment process. These efforts have finally lowered the turbidity of finished water below 0.1NTU. Small lab-scale and pilot-scale experiments have been conducted and they have provided optimum parameters for the design and operation of drinking water treatment plants. In addition, quantitative and/or trace analysis technologies developed for monitoring water quality of effluent from unit processes and automization of facilities, have contributed to the improvement of turbidity in drinking water. The Kueui water treatment plant, one of the drinking water treatment plants in Seoul, produces finished water with 0.08 NTU. It results from the operators' continuous endeavor to lower the turbidity in a scale of 0.01 NTU. The data for 12 months indicated that turbidity of settled water was less than 1.16 NTU and that of filtered water was less than 0.12 NTU for 95% of the period. Sedimentation basins and sand filters satisfy the recommended turbidity criteria, 2 NTU and 0.3 NTU, respectively. Also Kueui water treatment plant has focused on the control of organic matters to decrease in DBPs and on the removal of microorganisms.

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Modeling of full-scale drinking water treatment plants with embedded plant control

Water Science & Technology Water Supply ◽

10.2166/ws.2009.355 ◽

2009 ◽

Vol 9 (3) ◽

pp. 253-261 ◽

Cited By ~ 6

Author(s):

A. W. C. van der Helm ◽

L. T. J. van der Aa ◽

K. M. van Schagen ◽

L. C. Rietveld

Keyword(s):

Water Quality ◽

Drinking Water ◽

Water Treatment ◽

Treatment Plant ◽

Drinking Water Treatment ◽

Water Treatment Plant ◽

Pid Controllers ◽

Direct Control ◽

Water Treatment Plants ◽

Plant Control

In general, the available control actions in drinking water treatment plants are not directly related to the process objectives for water quality. Model based optimization of operation of a drinking water treatment plant by direct control of water quality objectives is discussed. Plant control with PID controllers is embedded in the model of a drinking water treatment plant and the ozonation process in the plant is used as a case study. It is concluded that direct control of water quality objectives, e.g. Giardia inactivation for ozonation, can largely reduce uncertainty and variation in process performance and leads to improvements of drinking water quality. In the discussed case it led to less bromate formation at the same disinfection capacity. Embedded plant control with PID controllers in the model of drinking water treatment plants through the use of code for writing control functionality has a large potential for model based optimization of operation.

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Assessment of a wastewater stabilization pond system for removal of arsenic, iron, and ammonia from reverse osmosis water treatment plant residual wastewater

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2021-0306 ◽

2021 ◽

Author(s):

Harrison Bull ◽

Ali Ekhlasi Nia ◽

Mohsen Asadi ◽

Kerry McPhedran

Keyword(s):

Heavy Metals ◽

Drinking Water ◽

Water Treatment ◽

Treatment Plant ◽

Drinking Water Treatment ◽

Water Treatment Plant ◽

Depth Data ◽

Water Treatment Plants ◽

Removal Of Arsenic ◽

Wastewater Stabilization Ponds

Drinking water treatment plants (DWTPs) produce wastewaters with elevated concentrations of heavy metals, metalloids, ammonia, and other contaminants. These wastewaters require treatment via processes including wastewater stabilization ponds (WSPs). This study assessed the arsenic (As), iron (Fe), and ammonia (NH3) concentrations in a Saskatchewan DWTP WSP system of five sequential ponds. Drone imaging combined with flow and depth data was used to estimate retention times which increased from 7-9 to 8-10 days after the DWTP upgrade. Concentration trends showed Fe decreased from Pond 1 to 3 and increased in Ponds 3 and 5, while As decreased from Pond 1 to 5. Average effluent As concentrations of 10.6 µg/L were over the 5.0 µg/L guideline, while both Fe and NH3 concentrations guidelines were easily met post-upgrade in 2020. Several actions are recommended to ensure adequate WSP operation including dredging, aeration, and installing macrophytes capable of As uptake.

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