Six kinds of sewage treatment technology

(6) Chemical precipitation method to add a chemical agent to the sewage, so that it reacts with some dissolved substances, resulting in insoluble salt precipitation. It is mainly used to treat industrial wastewater containing heavy metal ions. 

⑺ ion exchange method ionization exchange method is widely used in sewage treatment. The ion exchanger used is divided into inorganic ion exchange method (natural zeolite and synthetic zeolite), organic ion exchange resin (strong acid cation resin, weak acid cation resin, strong basic anion resin, weak basic anion resin, chelate and resin, etc.). When ion exchange method is used to treat sewage, the selectivity of resin must be considered. The exchange ability of the resin for various ions is different, which mainly depends on the size of the affinity of each ion for the resin, also known as the size of the selectivity, and also takes into account the regeneration method of the resin.

(8) Membrane separation percolation, electrodialysis, ultrafiltration, microfiltration, reverse osmosis and other technologies for separating ions and molecules in water through a special semi-permeable membrane, collectively known as membrane separation method. Electrodialysis is mainly used for desalting water, recovering some metal ions and so on. Reverse osmosis is mainly a function of the chemical nature of the membrane surface. The particle size of the solute separated by it is small, the salt removal rate is high, and the required working pressure is large. The material used in ultrafiltration is the same as reverse osmosis, but ultrafiltration is a screening effect, the separation of solute particle size is large, the water permeability is high, the salt removal rate is low, and the working pressure is small.

3. Biological law

The biofilm method of sewage is to take certain artificial measures to create an environment conducive to the growth and reproduction of microorganisms, so that microorganisms proliferate in large numbers, so that microbial oxidation and decomposition of organic pollutants are degraded and converted into harmless substances, so that sewage can be purified. Biological treatment can be divided into two categories: aerobic treatment and anaerobic treatment. The former has high efficiency, good effect and wide use, and is the main method of biological treatment. There are several processes that belong to biological treatment.

(1) Activated sludge method is the most widely used biological treatment technology. The air is continuously pumped into the sewage containing a large number of dissolved organic pollutants, and after a period of time, the water not only forms a flocculant with a large number of aerobic microorganisms - active sludge, the activated sludge can adsorb the organic matter in the water, the microorganisms in the activated sewage on the activated sludge take the organic matter as food, obtain energy, and constantly multiply, and the organic matter is decomposed and removed. To purify the sewage. Generally, the effluent treated by the aeration tank is the sewage mixed liquid containing a large amount of activated sludge, which is separated by precipitation, and the water is purified and discharged. The sludge after precipitation and separation is used as seed mud, and part of it is returned to the aeration tank. Since the emergence of activated sludge method, after more than 80 years of evolution, there have been various variations of activated sludge method, but its principle and process have not fundamentally changed.

(2) Ordinary activated sludge method This method has been widely used and is a common process in many sewage treatment plants. The traditional activated sludge method is to introduce sewage and return sludge from the first section of the aeration tank and flow out in a push flow to the end of the aeration tank. This method is suitable for treating sewage with high requirements and stable water quality, but it is weak in adaptability to load changes. Later on, some improved forms have been produced on this basis.

(3) In order to make the organic load in the tank close to a certain value, the sewage is divided into several points, which is conducive to solving the overload problem.

(4) The activated activated sludge in the contact tank adsorbed polluting substances, and after the separation of sludge and water, the adsorbed polluting substances were oxidized in the aeration tank. This method is beneficial to increase the amount of sewage treatment and has a certain ability to resist the impact load.

(5) Delayed aeration method Sewage in the aeration tank to extend the aeration time, is conducive to complete oxidation, less sludge, this method is suitable for small sewage treatment plants.

(6) Anaerobic - anoxic - aerobic activated sludge method in the conventional activated sludge method to remove organic pollutants at the same time, in order to effectively remove nitrogen and phosphorus and other nutrients, people combine anaerobic, anoxic, aerobic conditions into the activated sludge method, so that anaerobic - anoxic - aerobic conditions exist at the same time in the reaction aeration tank or repeated cycles to achieve the formation of anaerobic - anoxic - aerobic activated sludge method. There are also processes using anaerobic-aerobic activated sludge method.