Wastewater treatment agent: Conditioner

2021-03-19

Wastewater treatment agent: Conditioner

Conditioning agent: also known as dehydrating agent, used for conditioning the remaining sludge before dehydration. Its varieties include the above-mentioned partial flocculants and coagulant aids.


Types of commonly used sludge conditioners


Conditioners, also known as dehydrating agents, can be divided into two categories: inorganic conditioners and organic conditioners. Inorganic conditioners are generally suitable for vacuum filtration and plate and frame filtration of sludge, while organic conditioners are suitable for centrifugal dewatering and belt filter dewatering of sludge.


(1) Inorganic conditioning agents The most effective, cheapest and most commonly used inorganic conditioning agents are mainly iron salts and aluminum salts. Iron salt conditioning agents mainly include iron chloride (FeCl3∙6H2O), iron sulfate (Fe2(SO4)3∙4H2O), ferrous sulfate (FeSO4∙7H2O) and polymeric ferric sulfate (PFS) ([Fe2(OH)n( SO4)3-n/2]m) etc. The aluminum salt conditioning agents mainly include aluminum sulfate (Al2(SO4)3∙18H2O), aluminum trichloride (AlCl3), and basic aluminum chloride (Al(OH)2Cl) , Polyaluminum chloride (PAC) ([Al2(OH)n∙Cl6-n]m), etc.

After adding the inorganic conditioning agent, it can greatly accelerate the sludge concentration process and improve the filtering and dewatering effect. Moreover, the combined use of iron salt and lime can further improve the conditioning effect. The disadvantage of adding inorganic conditioning agents is that the dosage is large. Generally speaking, the dosage should reach 5% to 20% of the dry solids weight of the sludge, resulting in an increase in the volume of the filter cake; second, the inorganic conditioning agent itself is corrosive (Especially iron salt), the dosing system must have anti-corrosion performance.

It should be noted that when ferric chloride is used as a conditioning agent, it will increase the corrosiveness of the metal components of the dewatered sludge treatment equipment, so the anti-corrosion level of the dewatered sludge treatment equipment should be appropriately increased.

polyaluminium chloride PAC

polymeric ferric sulfate


(2) Organic conditioning agents. There are many types of organic synthetic polymer conditioning agents. According to the degree of polymerization, they can be divided into low polymerization degree (molecular weight of about 1,000 to tens of thousands) and high degree of polymerization (molecular weight of about hundreds of thousands to several million) Two types; divided into cationic, anionic, non-ionic, anionic and cationic according to ionic type. Compared with inorganic conditioners, the dosage of organic conditioners is less, generally 0.1% to 0.5% of the dry solid weight of the sludge, and it is not corrosive.

Polyacrylamide flocculant

The organic conditioning agents used for sludge conditioning are mainly polyacrylamide flocculant products with high degree of polymerization, including cationic polyacrylamide, anionic polyacrylamide and non-ionic polyacrylamide.

Among them, the cationic polyacrylamide can neutralize the negative charge on the surface of the sludge particles and produce a bridging effect between the particles to show strong cohesion, and the conditioning effect is significant, but the cost is relatively high. In order to reduce the cost, the cheaper anionic polyacrylamide-lime combination method can be used, and the positively charged Ca(OH)2 flocs are used to adsorb the negatively charged flocculant and the sludge particles together to form a Complex cohesion system.


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