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INSTRUCTOR: 
Mark Peterson, P.E.

Purpose and Background

Low pressure sewer systems can be used in areas where gravity sewer systems are not economical due to long distances or uneven terrain. Two types of low pressure sewer systems are in common use. One type uses grinder pumps at each building and the other type uses a septic tank and a septic tank effluent pump at each building. This course will focus primarily on grinder pump applications. The course will address the basic reasons for using a low pressure sewer system, discuss some of the characteristics of grinder pumps (including advantages and disadvantages), and discuss the force main design parameters. It will also cover how to estimate the minimum and maximum flows in a force main that serves residential units, and how these values might change when commercial facilities are part of the system. It will also cover in general terms the hydraulic design of low pressure sewer systems and some of the challenges associated with these types of systems, including maintenance responsibilities.

Benefits and Learning Outcomes

Upon completion of this course, you will be able to:

• Explain the reasons for using a low pressure sewer system
• Estimate the minimum and maximum flows in a force main that serves residential units
• Explain the challenges associated with these types of systems, including maintenance responsibilities

Assessment of Learning Outcomes

Students' achievement of the learning outcomes will be assessed via a short post-assessment (true-false, multiple choice and fill in the blank questions).

Who Should Attend?

• Water Resource Engineers
• Hydraulic Engineers
• Hydrology Engineers
• Utility Engineers
• Designers
• Project Managers

Outline

Basis concepts of Low Pressure sewers

• What is the general configuration
• Where and why are they used (rocky soil, hilly terrain, shallow bedrock, high groundwater, long flat terrain, areas of slow growth)
• Grinder pumps vs. STEP (septic tank effluent pumps)

Grinder pump characteristics

• Typical pump curves
• Basin details
• Storage requirements
• Controls

Pipe characteristics

• Material options
• Pipe sizing
• Alignment parameters (horizontal and vertical alignment, depth)
• Installation parameters (open trench, boring, directional drilling)
• Construction time and surface restoration

Commercial vs. residential uses

• Flows – magnitude and different diurnal curves
• Wastewater quality (especially FOG)

Design considerations

• Flow estimates
• Average day
• Instantaneous peak
• Inflow/infiltration (sump pumps)
• Desired velocities
• Air management (odor and air/vacuum valves)
• Reliability of electrical system (frequent outages result in frequent periods of very high flows)
• Hydraulic design – how many pumps will run at one time; what happens if more pumps run than have been estimated – requires careful selection of pump, so it can run at shutoff head for potentially an extended time period.

Maintenance considerations

• Who owns the pump, basin and controls? Who is responsible for maintenance? Is it better for the municipality to own and maintain the system, to insure that proper maintenance is done? Who is responsible for system failure and associated damages?

How to Earn your CEUs/PDHs

This course is worth .8 CEU /8 PDHs. To receive your certificate of completion, you will need to complete a short post-test and receive a passing score of 70% or higher within 30 days of the course.

How do I convert CEUs to PDHs?

1.0 CEU = 10 PDHs [Example: 0.1 CEU = 1 PDH]