Cationic coagulants are diluted to 10-40 times and added 2-10 kg of water solution to the printing and dyeing wastewater with PH value of 7-10.

The specific dosage and usage method should be adjusted according to the different wastewater from each factory through small-scale test, so as to achieve the best effect.

Thanks for your question, Julia. In fact, as Muhammed already pointed out, most companies do lab trials or field trials to estimate the optimum dosage for mine or wastewater treatment. You might be interested in reading this book (it is available online here www.kemira.com/aboutwatertreatment), where the principles are easily explained:

Valanko, R., Shestakova, M., Pekonen, P., Hesampour, M., Hansen, B., Halttunen, S., Hofmann, R., Pretorius, R., Penttinen, M., Recktenwald, M., Karpova, T., Rossum, R. v., Grönfors, O., Mattsson, E., Ahlgren, J., Nilsson, B., Leen, P., Havansi, H. & Abinet, R. (2020): About water treatment. – 287 p., Helsinki (Kemira Oyj).

You specific question might be answered in figure 5.20 – 21 of this publication ;-)

Aluminium salts will react with phosphate salts to form relatively insoluble poly aluminium phosphate complexes, usually in the mole ratio of one to one. Other substances present in the lake water will also react with the aluminium. Coagulant doses cannot be calculated but must be determined experimentally by simple jar tests. This calculation will provide you with a starting point to undertake jar tests to determine the optimum dose for that particular water.