Water consumption backwash pressure

Water consumption of the jets as a percentage of process effluent decreases from 5% at 15 psi to 2% at 50 psi. In general, backwash systems are operated at as low a pressure as possible consistent with successful cleaning. High-pressure operation incurs added system maintenance, particularly jet replacement, and is used only as needed. 

Increasing the backwash duration from 0.5 to 1 min had almost negligible effect on flux restoration. However, when the backwash duration was increased to 2 min, a significant effect on flux restoration was observed for aU backwash pressures tested. Increasing the backwash pressure increases the water consumption, which reduces the system recovery. It is, therefore, important to optimize the backwash pressure and duration to achieve as high a degree of flux restoration and system recovery as possible. 

Net flux serves as a tool to determine the optimal backwashing conditions since it reflects the operation efficiency by taking into account water production and consumption, including the time spent for backwashing. Kennedy et al. (1998) observed that, for all backwash pressures and durations tested, the net flux increased up to a pressure ratio of 2.5, then decreased, even though flux restoration increased (Fig. 6.15, right). The reason is that above a pressure ratio of 2.5, the flux decline that was recovered by backwashing was small compared to the quantity of water consumed to realize the flux restoration. 

Figure 6.15 (a) Effect of backwash pressure on flux restoration and water consumption, and (b)... 

---