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Introduction to the application of filter membranes in the field of drinking water
Date: 2015-11-04Read: 18
1、 Application of drinking waterfilter membranefacility
Among MF, UF, NF, and RO, except for the application of RO in seawater desalination, RO has not been used yet. RO almost completely removes all the salts, and the treated water becomes pure water without any salts, even purer than distilled water. Such water cannot be used as drinking water. If it is used, beneficial salts for human health must be added, and there are currently no conditions to achieve this requirement. NF is second only to RO in removing salts, but its removal rate is also very high. It is generally used as soft water and is not suitable for drinking water due to the above reasons. Therefore, the membranes used for water purification treatment should be MF and UF membranes. This type of membrane can mainly remove colloids and plankton, insoluble iron and manganese, and bacteria. But in order to prevent bacteria from not regenerating in the clean water tank, the sterilization process cannot be omitted. Considering the molecular weight of substances removed by UF, it does not have the ability to remove ozone substances and organic solvents such as trihalomethanes. These solvents will form a thin film on the membrane surface, which may be removed in the future and can be studied in the future. In terms of membrane types, external pressure hollow systems or tubular membranes are suitable for use. If an external pressure membrane is used, the raw water passing through the sedimentation tank can be directly connected to the membrane for treatment. The raw water directly connected to the plate frame and spiral membranes should be free of floating substances before flowing into the membrane in order to prevent the membrane pores from being blocked.
2、 Application of drinking waterfilter membraneprogram
The conventional treatment procedures for water treatment plants are coagulation, sedimentation, and filtration. For membrane separation plants, the treatment procedure is simple and only requires the use of a filtration membrane device when the raw water meets the conditions for filtration membrane treatment. (When the quality of the raw water deteriorates, conventional treatment or micro sieve treatment may need to be added). In terms of energy consumption, the full filtration method using a filter membrane is necessary. As the pressure is increased through the filter membrane, the raw water pump still needs to consider enhancing the pressure.
3、 The advantages of using filter membranes for drinking water treatment
(1) No need for coagulant
Based on past experience using membranes, the water quality of drinking water treated with MF membranes without coagulants (river water, reservoir water, and nutrient rich lake water) is comparable to or exceeds that of conventional treatments such as coagulation, sedimentation, and filtration with coagulants.
(2) Automated operation is simple and easy to manage without human intervention
The use of membrane separation technology only provides the necessary operating pressure for supplying raw water, and only requires running for a long time to flush the filter membrane, with no other processes. At present, there are numerous processes involved in coagulation, precipitation, and filtration water treatment, and the dosage rate cannot be set yet. In such a situation, it is easy to automate the membrane device and achieve unmanned management, while it is not easy to automate conventional processing.
(3) Filter membrane water plant occupies less land
Adopting a filtration membrane water plant, the membrane device occupies a small area, making it easy to reduce the plant area occupied by conventional treatment with the same water production by half. Activated carbon treatment devices can be installed in the remaining areas. Due to the unmanned nature of the filtration membrane water plant, the buildings and supporting facilities where employees reside can be reduced.
(4) Low maintenance and management costs
The current service life and price of the filter membrane are still unknown, and the total cost is difficult to calculate. However, from the perspective of lower electricity and medication costs for membrane treatment, it has significant advantages over the higher maintenance and management costs of conventional treatment.
(5) Easy to drain and treat
Used for industrial water, domestic water, and municipal water supply systems that require effluent turbidity ≤ 5mg/L to meet drinking water quality standards;
(6) Removal of suspended solids and solid substances in industrial wastewater;
4、 Can be used as pre-treatment equipment in ion exchange softening and desalination systems, as well as coarse filtration equipment for industrial water supply with low water quality requirements;
And used in swimming pool circulation treatment systems, cooling circulation water purification systems, etc.
Due to the fact that membrane treatment does not require medication and reduces the amount of sludge processed, it is easy to handle. Whether this is the case is still in the research stage and no clear results have been obtained.
5、 Problems with filter membrane treatment
(1) The service life of the membrane
The membrane pores are blocked by impurities in the water, causing an increase in head loss and a decrease in fluid velocity when the fluid passes through the membrane pores. At this point, it is usually possible to rinse the membrane pores with water to restore their original permeability. When the goal cannot be achieved, appropriate medication should be used to clean the membrane pores so that they can continue to be used. But the service life of the membrane should be considered. Even if treated according to the above method, the membrane will still have poor cleaning effect due to excessive fouling caused by medication. In this case, adding coagulants can prolong the service life and reduce the permeation flow rate, which can extend the lifespan of the membrane, but it is necessary to increase the usage area of the membrane.
(2) Construction Management of Filter Membrane Water Plant
The membrane tube itself has a relatively high strength and some flexibility. But some of the membrane pipes were damaged to some extent during construction. Of course, due to damage to one or two membrane tubes, it will not affect the quality of the permeate water from the membrane tubes. But if a medium-sized water plant has tens of thousands of membrane tubes, it is not a problem of one or two membrane tubes being damaged. Therefore, it is necessary to strengthen component management and construction management of membrane devices, and they cannot be treated the same as conventional treatment methods in the past.
(3) Remedial measures using new filtration membrane technology
Generally, unexpected situations may arise when using new technologies, especially when using filter membrane separation, which completely changes the conventional treatment system of the past, so there may be some concerns. Due to the lack of practical experience in membrane technology, additional facilities should be added to remedy any abnormal situations in the membrane device. For example, whether to add biological activated carbon facilities to remove odors after membrane treatment, and consider adding other equipment.
