Views: 20 Author: Site Editor Publish Time: 2021-05-19 Origin: Site
What is MBR?
MBR, also known as membrane bioreactor, is a new water treatment technology combining activated sludge process with membrane separation technology. MBR membrane is mainly divided into four types: hollow fiber membrane, flat membrane, ceramic membrane and tubular membrane.
Hollow fiber membrane (also known as curtain membrane) and flat membrane are called "organic membrane". The main material is PVDF (polyvinylidene fluoride), which is the main material of all membranes on the market. But now there is a new one made of PTFE (polytetrafluoroethylene), which is said to be better than PVDF. When the membrane is pulled, the pore size distribution will be more uniform, known as the "king of plastics".
Ceramic membrane is a new product, and is also called "flat ceramic membrane". The chemical stability of ceramic membrane is very good, and it can resist acid, alkali, organic solvent and high temperature; The advantages of narrow pore size distribution and high separation efficiency are presented. The main materials of ceramic membrane are alumina, titanium oxide, and silicon oxide.
As a form of membrane element, organic tubular membrane is suitable for ultrafiltration, microfiltration, even nanofiltration, etc. its advantages are wide flow channel, turbulent flow of material liquid in the pipe, and low requirement for pretreatment precision of material liquid. The tube type membrane is easy to clean, besides the chemical reagent, it can also be cleaned by mechanical and physical scrubbing. The pressure loss of tubular membrane assembly is small, so its flow path is long (the longest can be connected with 48 meters), and the filtration efficiency is high.
Flat membrane is a plate (generally ABS) with a guide channel on it, lining cloth and PVDF material membrane are pasted on both sides, and a membrane is formed after seamless welding. There are also two kinds of membrane, also known as flat membrane, one is film membrane, the other is flexible membrane. Flat membrane module: the common shelf is made of 304 stainless steel. Insert the membrane into it one by one to fix, and install the aeration pipe fittings and water collection pipe fittings. It is called membrane module.
How to clean MBR membrane module?
The operating pressure of flat membrane is 0-35kpa. Under the action of self-priming pump (10 minutes as a working cycle, pumping for 8 minutes, stopping for 2 minutes), the mixed liquid passes through the microporous membrane in membrane tank. By using its uniform pore size, the particles and bacteria in water can be intercepted, so that they can not be removed through the membrane, and the sludge containing sewage can be filtered in biochemical reaction tank. Therefore, flat membrane plays the role of filtration
1. The membrane intercepts the microorganisms in the reaction tank and increases the concentration of activated sludge (about 6000-12000mg / L), which makes the biochemical reaction of wastewater degradation more rapid and thorough;
2. Due to the high filtration precision of the membrane, the effluent is clear and transparent, and the high-quality produced water is obtained. So here is to explain that the membrane is not omnipotent. It has pore size, and those that can pass through the pore size can not be filtered. Don't place all the hopes of upgrading on this link. If it can't be filtered, it will form a fouling plug near the membrane hole, that is to say, if the membrane is blocked, the water production is insufficient and the flux can't reach.
Simple operation of cleaning:
The method of online cleaning can be used when the membrane is slightly polluted, which is simple to operate, low in cost and obvious in effect; Generally, the advanced alkaline washing and pickling can be carried out. Gravity self flow or metering pump can be used for dosing.
Alkali washing: prepare the mixed water solution of 2000-5000mg/l sodium hypochlorite and 1000mg/l sodium hydroxide, and fill the suction pipe to membrane element by hydrostatic pressure of high liquid level cleaning water tank. The dosage of the drug solution is 3-5l/ tablet, and soaked for more than 5 hours.
Pickling: prepare 1000mg/l oxalic acid (or citric acid) solution, clean online, with the same water amount and soak for 3-5 hours.
Note: all the above reagents are calculated according to 100% purity. When the selected reagents contain impurities, the corresponding dosage shall be calculated according to the corresponding purity. The method of liquid gravity self flow is used to inject the liquid into the membrane through the charging port and reserved on the membrane suction pipe to clean the diaphragm.
Offline cleaning is also called maintenance cleaning. Usually, it is necessary to clean off-line for one year or when online cleaning cannot recover membrane flux. An off-line cleaning tank or membrane tank is set up for cleaning, that is, the whole tank is soaked in the whole tank, and the flux is recovered by aeration scouring.