Tennessee Wastewater Operator Practice Exam

How can a drier cake be obtained on a belt press?

1. By increasing the temperature of the feed

2. By decreasing the speed of the belt

3. By adding more polymer to the mixture

4. By increasing the pressure on the press

The correct answer is: By decreasing the speed of the belt

A drier cake from a belt press can be obtained by optimizing the operational parameters of the equipment, particularly through an increase in pressure on the press. Applying higher pressure forces more water out of the sludge being processed. This mechanism enhances the dewatering process by compacting the material and pushing out the liquid, resulting in a drier final product. While increasing the temperature of the feed can also facilitate the dewatering process by reducing the viscosity of water and promoting faster drainage, it does not directly correlate to the pressure applied during pressing, which is a more effective method for achieving a lower moisture content in the cake. Decreasing the speed of the belt could lead to more extended exposure time, which might allow for some additional gravity drainage but would not necessarily lead to a consistent reduction in moisture content. Adding more polymer to the mixture is a common practice to improve flocculation and enhance the dewatering process; however, it is more about enhancing the efficiency and effectiveness of the solid-liquid separation rather than directly producing a drier cake. Therefore, increasing the pressure is the most effective means to achieve a drier cake on a belt press, as it directly influences the expulsion of water from the solids.