The use of filtration membrane devices do not need to flocculation chemical treatment, there is no need for evaporation separation effect, only the pressure to make the solid-liquid separation in water, which is a major feature of the filtration membrane treatment. There are two types of filtration mode:
(1) the flow of liquid all perpendicular through the membrane holes, the liquid impurities within the retention of full-volume filtration mode;
(2) the flow direction of the liquid flow and the membrane surface is equal to the formation of the liquid and the membrane surface at a right angle through the membrane holes, the liquid impurities within the retention of cross-flow filtration mode. The full-volume filtration method is applicable to microfiltration and part of ultrafiltration. Cross-flow filtration is suitable for ultrafiltration, nanofiltration, and reverse osmosis filtration, which are prone to scale buildup, because the liquid flows on the membrane surface, generating shear force and reducing the accumulation of slime on the membrane surface due to the concentration of impurities. During the passage of fluid through the membrane, it contains impurities that clog the membrane pores, making it difficult for the fluid to pass through the membrane pores. In order to restore the efficiency of water filtration, the following methods can be used:
(1) backwash
and filtration in the opposite direction through the water, so that the inhibition of staying in the membrane pore impurities flushed away. There are also air flushing method instead.
(2)Sponge ball flushing
Only used alone for the internal pressure type tubular membrane, it is the sponge ball through the internal membrane, so that the sponge ball and the inner wall of the membrane friction, the inhibition of retention of the method of flushing away.
(3)Air bubble rinsing
It is a method of removing the retained material attached to the membrane wall with the stirring force of air bubbles. Air bubble stirring soft synthetic resin hollow system of the membrane wall, received the effect of flushing.
(4) pharmaceutical flushing
Membrane after long-term use, impurities into the membrane holes, with the general flushing method can not be resolved, the use of chemical cleaning. Chemicals are caustic soda, hydrochloric acid, sodium hypochlorite, citric acid and hydrogen peroxide. (1) without coagulant
From the past experience of using the membrane, drinking water use of raw water (river water, reservoir water and nutrient-rich lake water), with no coagulant MF membrane treatment, and coagulant coagulation, precipitation, filtration of the conventional treatment compared to the former and the latter treated water quality is comparable to or more than.
(2) automation is simple to manipulate, easy to unmanaged
The use of membrane separation technology only for the supply of raw water to provide the necessary operating pressure, and only need to run for a long time before rinsing the membrane, and no other processes. The current coagulation, precipitation, filtration and water purification processes are numerous, in the dosing can not yet set the dosage rate. In this case, the manipulation of the membrane device is easy to automate, unmanaged, while the conventional treatment to automate is not easy.
(3) filter membrane water plant occupies less space
Using a filter membrane water plant, membrane device occupies a small area, it is easy to the same amount of water produced by the conventional treatment of the area occupied by the plant reduced by half. The remaining place can be set up activated carbon treatment device. Because the filter membrane water plant can be unmanned, staff living in the building and supporting facilities can be cut.
(4) maintenance and management costs are small
Currently, the service life of the filter membrane and the price is still unknown, the full cost is not good. However, from the point of view of the membrane treatment of electricity and pharmaceutical costs are less than the conventional treatment of the situation of high maintenance and management costs have great advantages.
(5) easy drainage treatment
For the requirements of the effluent turbidity ≤ 5mg / L can meet the drinking water quality standards for industrial water, domestic water and municipal water supply system;
(6) industrial wastewater in the removal of suspended solids, solids removal; 3 can be used as a softening of the ion exchange method, desalination system in the pre-treatment equipment, the quality of water quality requirements for the industrial water supply of the coarse Filtration equipment;
And used in swimming pool circulating treatment system, cooling circulating water purification system and so on.
Because of the use of membrane treatment without dosing, the amount of sludge is reduced, so it is easy to deal with. Whether or not this is still in the research stage, no clear results. (1)Membrane life
Membrane holes are blocked by impurities in the water, so that the fluid through the membrane holes when the head loss increases, the fluid flow rate decreases. This can usually be flushed with water to make the membrane hole to restore the original permeability. Can not achieve the purpose, should be appropriate to clean with chemicals, so that the membrane can continue to use the hole. But should consider the service life of the membrane. Because even according to the above approach, the membrane will be due to excessive scale accumulation, cleaning with chemicals is not ideal. In this case, add coagulant, to extend the service life, can also reduce the permeate flow rate, so that the life of the membrane to extend, but to increase the use of the membrane area.
(2) filtration membrane water plant construction management
Membrane tube itself is quite high strength, there is a certain *. But more or less part of the construction membrane tube damage. Of course, due to one or two membrane pipe damage, will not affect the membrane pipe permeate water quality. But a medium water plant has tens of thousands of membrane tube, it is not one or two membrane tube damage, so it is necessary to strengthen the membrane device parts management and construction management, can not be treated in the same way as conventional treatment in the past.
(3) the use of new technology of filtration membrane remedies
Generally the use of new technology will encounter unexpected conditions, especially the use of filtration membrane separation occasions, which the entire change in the past conventional treatment system, so there will be a certain amount of concern. Since there is no practical experience with membrane technology, additional facilities should be added in case of abnormalities in the membrane device. For example, whether or not to install additional bio-activated carbon facilities after the membrane treatment to remove odor measures, as well as the addition of other equipment to consider.