Application of a laboratory screw decanter to evaluate sludge behaviour in mechanical thickening and dewatering: Preliminary results

Screw decanters are widely applied for sludge concentration, usually assisted by chemical conditioning. Performances and optimal operating parameters are difficult to predict because of non-quantified high shear stresses applied to flocs in industrial devices. Existing laboratory indicators are not able to reproduce all those conditions. This paper presents an evaluation of a new mini screw decanter that should reproduce more accurately the shearing action of the screw on the particles during bowl rotation. The effect of acceleration, relative velocity and feeding conditions on separation performances is investigated, demonstrating a good sensitivity of the method and consistent trends. The separation obtained at lab-scale with the optimal operating parameters is compared for five sludge to full-scale performances, highlighting a good correspondence between both scales results. Finally, the five sludge are compared based on their behavior in relation to their physico-chemical characteristics. The results demonstrated the applicability and consistency of the method.

Automated summary

This study evaluated a new mini screw decanter and investigated the impact of acceleration, relative velocity, and feeding conditions on separation performance. The results demonstrated good sensitivity and consistent trends of the method, as well as a good correspondence between lab-scale and full-scale performances. Additionally, the behavior of five sludges based on their physico-chemical characteristics was compared, showing the applicability and consistency of the method.