A trial on solid-liquid extractions has been carried out by means of a maceration of sealed fly ash into sewage sludge previously characterized in fertilizing elements and heavy metals contents (Ratio fly ash/sewage sludge: 1/10), in order to avoid the mixture of the two solids.

<p style="text-align: justify;"> After different agitation periods, it was assessed:</p> <p style="text-align: justify;"> &bull;<span class="Apple-tab-span" style="white-space:pre"> </span>percentage of fertilizing fractions in sewage sludge, and</p> <p style="text-align: justify;"> &bull;<span class="Apple-tab-span" style="white-space:pre"> </span>percentage of heavy metals in fly ash</p> <p style="text-align: justify;"> &nbsp;</p> <p style="text-align: center;"> <img alt="" src="http://www.ctaex.com/icirbus/ficheros/imagenes/2017_02/grafico1.png" style="text-align: center; width: 300px; height: 196px;" /><span style="text-align: center;">&nbsp;&nbsp;</span><img alt="" src="http://www.ctaex.com/icirbus/ficheros/imagenes/2017_02/grafico2.png" style="text-align: center; width: 300px; height: 196px;" /></p> <p style="text-align: justify;"> &nbsp;</p> <p style="text-align: justify;"> Even a trial on fly ash pellets manufacturing is being considered to increase ratio sewage sludge / fly ash.</p> <p style="text-align: justify;"> &nbsp;</p> <p style="text-align: justify;"> Promising results show that Fertilizing Fraction kept in the sewage sludge reached 80-100% for N. P and K, while heavy metals quelated in fly ash ranged 52 &ndash; 88% of initial values, depending on the very metal.</p> <p style="text-align: justify;"> &nbsp;</p> <p style="text-align: justify;"> With this final solution, the main technical problem, separation of fertilizing fraction from heavy metals one, affixing this last one in the fly ass, has been overcome.&nbsp;</p> <div> &nbsp;</div>