Mixing System for the Clarifier

At one of the drinking water treatment plants, we have 4 longitudinal gravity soil clarifiers with a trapezoidal cross-section with a base width of 18 m and a water mirror of 30 m. The length is 750 m. The depth of the basins varies between 2.5 and 4 m, depending on the degree of clogging. The water passes from one clarifier to the other. The dosage of the coagulant is done in several points without mixing, only at one decanter with driving water under pressure (at decanter number 1). Does anyone know if there are mixing systems for this type of clarifier?