Design of High-Rate Settlers

The result of a comparison indicates that downflow settlers may have better performance provided the effluent collection system presents no problem. If the design criteria on overflow rate for conventional settling tanks are used for designing high-rate settlers, the latter will give better performance within the normal range of practical design. It appears that a high-rate settler system can handle considerable overloading without serious reduction in its turbidity removal efficiency. A settler with its flow through velocity less than 0.6 fpm (18.3 cm/min) tends to perform better than that with a higher flow through velocity even though the design overflow rate is kept the same. The theoretical design equation is found to incorporate the effects of angle of inclination and relative settler length reasonably well.