Tennessee Wastewater Operator Practice Exam

How can sand filters be cleaned effectively?

1. By applying high pressure

2. By backwashing at correct rates

3. By manual scrubbing

4. By spraying with disinfectants

The correct answer is: By backwashing at correct rates

Backwashing is an essential maintenance technique for sand filters that effectively cleans the filter media. During the backwashing process, water is directed in the opposite flow through the filter bed, which helps to dislodge and remove accumulated solids and debris that have built up in the sand. This process not only cleans the sand but also restores the filter's flow rate and efficiency. The efficiency of backwashing relies on applying the correct rates of water flow. If the flow is too slow, it may not adequately remove the trapped particles. Conversely, if the flow is too fast, it could disturb the sand bed excessively, leading to the loss of sand and potential damage to the filter system. Thus, backwashing at the correct rates is vital to ensure that the cleaning is thorough while maintaining the integrity of the filter. Effective cleaning of sand filters is necessary to ensure optimal performance and to prolong the lifespan of the filter system, making proper backwashing a fundamental practice. Other cleaning methods, such as manual scrubbing or high pressure, may not be practical or may damage the sand media, while the use of disinfectants is not suitable for cleaning the filter but rather for treating water.