Question

Provide a detailed overview of the wastewater treament pump (any mid-sized pump will work) including its horsepower, system head curves, and pump curve.

Answer 1

I will start by describing the main parts of a pump and system curve and what it represents followed by a simple example for illustration. The system curve impacts from valves and control valves will be addressed. I will discuss a more complicated system where there are multiple branch points in a system to illustrate additional system curve complexities that can exist and show how the system curve can change over time. Multiple system curves can exist in a system, especially when there are multiple pumps present and I will demonstrate these aspects as well. I will focus on how pump and system curves are generated for multiplepumps in parallel or series. Sometimes, adding multiple pumps in parallel will not result in producing more flow and I will discuss how to understand your system curve in order to know when addtional parallel pumps will be beneficial or not.

In general, a pump is used to overcome frictional head loss in piping systems as well as system elevation changes between system boundaries (i.e., static head). The term "Static Head" is represented by changes in elevation between supply and discharge reservoirs, like the system shown in Figure 1, and/or pressure differences for the case where system supply and discharge tanks may be pressurized. A system curve, as shown in Figure 2, is a graphical representation of the pump head that is required to move fluid through a piping system at various flow rates. The system curve helps quantify the resistance in a system due to friction and elevation change over the range of flows. When there are no control features in the system, such as flow control valves, then the pump and system curves will intersect at the operating flow rate.

I want to point out that a system curve is developed with reference to a specific location in a system. Therefore, multiple system curves can exist for a system and this is something that can lead to potential system curve confusion. Typically, a system curve is going to be developed with reference to a pump in a system because the pump is what will generate the necessary pressure required to overcome the system resistance at various flow rates.

Common Modifications
The two most commonly used types of pump
stations are the dry-pit or dry-well and submersible
pump stations. In dry-well pump stations the
pumps and valves are housed in a pump room (dry
pit or dry-well), that can be easily accessed. The
wet well is a separate isolated chamber attached or
located adjacent to the dry-well (pump room)
structure.
The submersible pump stations do not have a
separate pump room, however, the pump station
header piping, associated valves, and flow meters
are located in a separate dry vault on the surface for
easy access. Submersible pump stations include
sealed pumps that operate submerged in the wet
well. These submerged pumps are not intended for
frequent inspection, but can be removed
periodically to the surface and re-installed using
guide rails and a hoist. Key advantages of the dry-
well pump stations are that they allow an easy
access for routine visual inspection and
maintenance, and in general they are easier to repair
than submersible pumps. Key advantages of the
submersible pump station include lower costs than
the dry-well stations and an ability to operate
without frequent pump maintenance. In addition,
submersible pump stations usually do not require
large aboveground structures and are easier to blend-in with the surrounding environment in
residential areas. They require less space and
typically are easier and less expensive to construct
for wastewater flow capacities of 38,000 lpm
(10,000 gpm) or less. Figures 1 and 2 illustrate the
two types of pumps.

With horsepower ranges up to 500 HP and capacities to 35,000 GPM,