In this round, the original tank agitator was replaced by a longer one with a helical design, more suitable for stirring higher viscosity fluids.

<p style="text-align: justify;">With this modification, the adsorption of all the heavy metals in the sludge was increased, reaching percentages of reduction similar to the pilot tests and homogeneity in the results in each cycle for a given metal.</p> <p style="text-align: justify;"><br /> The treated sludge and the conditioned ashes used in this round were treated as in the previous ones: in the manufacture of compost fertilizer and building material, respectively.</p>