With the current shortage of hydrochloric acid in Europe, wastewater treatment facilities are turning to Sodium aluminate as an alternative to PAC, to fulfill their wastewater treatment needs.
PAC and functional aluminates
Historically, acidic metal salt coagulants, such as poly aluminium chloride (PAC) or ferric chloride (FeCl3) has been the flocculants of choice for many wastewater treatment facilities. PAC offers a performance per price ratio, with better 20% Phosphor removal, lower chemical dosing and thereby also lower sludge amounts compared to ferric chloride.
While other acidic aluminates such as Aluminium Chlorohydrate finds limited use in municipal wastewater treatment due to higher price and lower Phosphor removal effect, caustic Sodium Aluminate offer many advantages over ferric chloride and even PAC.
Current PAC situation sep 2022
Europe is currently experiencing an unprecedented hydrochloric acid shortage, causing shortage on anything made from hydrochloric acid. Recent weeks and months have seen the price of hydrochloric acid (HCl) more than double, and price increases does not seem to stop any time soon. This greatly affects the prices of Ferric Chloride and PAC.
PAC and Ferric Chloride are produced using a high content of HCl, and the effects of high prices and short supply of HCl are now also seen for Ferric Chloride and PAC.
Sodium Aluminate an attractive alternative to PAC
At Alumichem, we have been working with coagulation, flocculation, polymers and functional aluminates for more than 20 years. Our focus has always been to help our customers optimize their performance at the lowest total cost of operation.
At the current PAC and Ferric Chloride price levels, Sodium Aluminate has become a very attractive PAC alternative. The Alumichem Sodium Aluminate, AluSAL is produced using Sodium Hydroxide rather than HCl. Sodium Hydroxide have seen increases in pricing, but not to the extend that hydrochloric acid have – and there is no shortage in the market. Our unique manufacturing process produces a material that is free of precipitates. Additionally, Sodium Aluminate AluSAL has a very low content of heavy metals.
Sodium Aluminate AluSAL is available in a technical grade used for general water and waste water treatment and a PWG grade which is produced according to EN 882 (Chemicals used for the treatment of water intended for human consumption).
The best choice for Phoshor removal
Sodium Aluminate is the best choice for Phosphor removal, with 60% more efficient removal compared to ferric chloride. Also, the caustic nature of the product makes is less aggressive to the structures and provides better environment for the biology. Due to the efficient P removal, the product can be used at reduced dosage compared to ferric chloride and PAC.
What does it take to switch from PAC to Sodium Aluminate
Sodium Aluminate may see slight precipitation when exposed to oxygen. Therefore it is recommended to use an hosepump for dosing rather than e.g. membrane pumps.
As Sodium Aluminate is caustic, tanks that has been used for acidic chemicals must be thoroughly cleaned and dried before they can be used for Sodium Aluminate storage. Similarly, the tank should be evaluated for resistance against caustic.
Pro’s and con’s of switching from PAC/Ferric Chloride to Sodium Aluminate
- Gives high purity and quality of water
- Excellent coagulation, flotation and sedimentation
- The high content of AI in aluminates facilitates lowered transport costs.
- FeCl3 will be reduced to FeCl2 in digester, thus releasing P from sludge to water phase*
- Increases alkalinity – no need for lime and hydroxides
- Excellent removal of phosphor (+60% compared to Ferric Chloride)
- Minimal chemical sludge
- Low transportation cost
*This basically mean that Phospor precipitated and caught in the sludge, will be redissolved and be returned to the plant with reject water in dewatering step. This creates an internal recirculation of Phosphor, again increasing the need for chemicals. This is eliminated when using Al based coagulants like PAC and Sodium Aluminate.
- Aluminate is more prone for precipitation, so care must be taken for correct storage and dosing equipment
Contact our experts
Do you want to know more about making the switch from Poly Aluminium Chloride PAC to Sodium Aluminate AluSAL? Go to our AluSAL product page or Talk to one of our experts expert.
PAC & Sodium aluminate versus iron salts
Using aluminium salt, such as AluPAC (poly aluminiumchloride) or AluSAL (sodiumaluminate) instead of iron salts has a lot of advantages, such as:
- Lower dosage of aluminum products are needed to precipitate phosphorus
- Less dosage - less chemical sludge production
- Less impact on the pH in the biology
- Aluminum products reduce phosphorous release in the digester
- Helps with removing filamentous bacteria
- Limited struvite formation
