Frequently Asked Questions

Q. What is a Storm King^® Overflow?

A. A Storm King^® Overflow is a hydrodynamic separator used for removing settleable solids from wastewater. As the flow within the unit is dynamic (moving) the unit requires far less volume than a conventional passive device to obtain the same removal performance. This is because of drag forces set up within the unit due to the flow patterns set up which are themselves dictated by the unit geometry.

Q. Does a Storm King^® Overflow control the flow rate as well as providing solids removal?

A. No, it doesn’t. Hydro-Brake^® Flow Controls are typically used to control the pass-on flow rate to treatment. If a gravitational system is unobtainable then a pump can be used to control the pass-on flow to treatment as an alternative to the Hydro-Brake^®.

Q. What performance can a hydrodynamic separator achieve?

A. The performance efficiency of a hydrodynamic separator depends on the physical size of the unit itself (and consequently retention time) and on the settleability of the incoming sewage. Purely neutrally buoyant material cannot be removed by gravitational forces alone. A hydrodynamic separator typically achieves the same removal performance as a primary sedimentation tank in a quarter of the plan area. Higher loading rates can be used when less efficient performance is required, eg. at a treatment works where grits and silts are desired to be removed but where it is beneficial for finer faecal material to pass forward to further downstream treatment processes. Conversely, chemicals can be added to enhance solids separation.

Q. What dictates the size of a Storm King^® Overflow?

A. The required diameter of a Storm King^® Overflow is a function of the peak design inflow rate, design removal performance and the available depth. Within defined design limits, unit diameter can be increased to counter-act the effect of limited available depth.