An effective commercial sewage lift station design has to match your industry’s needs. Often, it’s a pump system put in to move sewage to the sewers, but there’s a problem. The sewer line is at a higher elevation than the pipes leaving the business. For example, a hotel may have dozens of bathrooms with wastewater going to the lowest elevation, often a basement wet well, and then out to the nearby sewer.
When you have wastewater at a lower elevation that needs to travel to a higher elevation, the best solution is a sewage lift station. The lift station needs to be designed to meet needs and efficiently move the sewage along its route. You don’t want clogs to create issues. How do you determine what is the most effective commercial sewage lift station design?
Factors to Consider
When choosing your commercial sewage lift station design, what should you consider? These are the key points to consider when designing the lift station.
#1- Flow Capacity
Start with the flow capacity. You’re going to have peaks where more wastewater is leaving than usual. If you own an office building, toilets and sinks will get more use during office hours. At night, the flow decreases. You have to play your sewage lift station to match the peak flow rates. Leaving some extra room for the unexpected is a smart idea.
Flow capacity is calculated by going over all of the fixtures in the commercial building or area. You have to look at the max load for each of those fixtures. If you have 20 toilets and each toilet flush sends five gallons of water to the sewage lift station, there’s the chance that you’ll get 100 gallons of wastewater hitting the lift station at once. Add sinks, dishwashers, washing machines, etc. to that figure. While it’s unlikely they’d all run simultaneously, it’s better to plan accordingly than have a lift station that isn’t prepared for the peak flow rate.
#2 – Force Main
You now have the peak flow rate. You have to take that and consider the velocity of the force main, which is the pressurized pipe that handles the sewer pump’s discharge. You want to keep that velocity to two to five feet per second. This is important as it keeps solids from settling without creating head loss. It also helps you decide the minimum pipe size to prevent clogging of the force main.
Force main pressure may have the velocity change rapidly. If that happens, you end up with a rapid increase in water pressure known as water hammer. Water hammer can damage valves and lead to costly repairs. Making sure the water pressure on valves and other components is within the correct psi range is essential for force main pressure.
#3 – System Head
Head loss occurs when there is friction in pipes or components like the elbows. Friction can make it harder for a pump to cool down, resulting in unnecessary wear and tear. You want to avoid head loss. To do this, you want to plan for the system head curve. If you make the pipe length and elbows too small, it can lead to head loss. If you consider the vertical lift that the wastewater must be able to travel, you keep wear and tear to a minimum and reduce the need for unexpected maintenance.
#4 – Wet Well
All of the commercial wastewater may collect in a covered wet well. That wet well collects the wastewater that needs to be pumped to the sewer lines. Knowing the right size for this wet well is also essential. In the Water Pollution Control Federation’s manual, rules state sewer pumps shouldn’t run less than 5 minutes or more than 30 minutes. Your wet well needs to be large enough so that the pump falls within these discharge rates.
#5 – Area Regulations
Towns, cities, and municipalities all have regulations you must follow. These regulations are in place to prevent wastewater from overloading a wastewater treatment plant, which increases the risk of raw sewage going into bodies of water before there is enough time to treat it. You don’t want to design a lift station that increases flow so much that it impacts the effectiveness of downstream lift stations.
You may be required to design a sewage lift station that accommodates several decades of use. That means planning for growth and expansion, which also benefits you because you have a system that will not need replacing in a few years. You save money on future expansions and improvements.
#6 – The Site
You have to choose a site that considers the impact on the environment. If you’re building a commercial sewage lift station near a wetland, you could cause harm. Any flooding would also impact your lift station. You need to be near a power supply, have a site that drains well, and be located in an area where the odors won’t cause issues with residents. If there may be issues with the smell, you need to consider odor control in your design.
Types of Sewage Lift Stations
A typical sewage lift station has a wet well with a pump and piping. The pump pushes wastewater uphill to the gravity sewer manhole. Wastewater travels into the wet well for the pump to push out when the water level is high enough.
Submersible pumps are one option. The pump sits on the floor of the wet well. The impellers draw the wastewater through the pump and into the piping, heading to the sewer. A screw pump is an alternative that suits many commercial facilities’ needs due to the lift, low maintenance requirements, and efficiency.
Why Choose Screw Pumps?
Screw pumps are the best choice for moving large volumes of sewage from a commercial area, while keeping an eye on maintenance costs, downtime, and efficiency. You have two choices for screw pumps: enclosed or open.
An enclosed screw pump sits within a tube. Lakeside Equipment has two types: Type C or Type S. Type C screw pumps use a rotating tube, while Type S has a stationary tube. Here are the benefits of enclosed screw pumps.
- Designed for drop-in replacement
- No grouting or trough is required, shortening the time needed for installation and lowering costs
- Type C inclines up to 45 degrees and is up to 10% more efficient than an open screw pump
- Type S inclines range from 22 to 40 degrees and is able to pivot
An open screw pump is the opposite. The exposed screws sit in a concrete or steel trough and can be installed at angles of 22 to 40 degrees. Here are a few facts to know about open screw pumps:
- Hydraulic lift of up to 50 feet
- Move as little as 90 gallons per minute to as much as 55,000 gallons per minute
- Permanently lubricated roller bearings to reduce maintenance
- Pre-screening is not necessary thanks to the non-clogging design
- Slow operating speeds with variable pumping capacities
- Up to 75% efficient
- Wet well is not required
What’s most important when it comes to a commercial sewage lift station? You want a practical design that gets the job done without requiring a lot of maintenance or wear. A lot goes into a commercial sewage lift station, and it’s not always something you can design on your own. It’s best to call an expert.
Lakeside Equipment’s screw pumps meet and exceed your goals. We’ve been designing screw pumps since the 1960s and have the experience you need for fuss-free operation and extreme efficiency. Call our experts at 630-837-5640.